Lands of the Isaac-Comet Area, Queensland

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LANDS OF THE ISAAC-COMET AREA,

QUEENSLAND

LAND RESEARCH SERIES NO. 19 COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANIZATION, AUSTRALIA 1967

REGISTERED IN AUSTRALIA FOR TRANSMISSION BY POST AS A PERIODICAL Lands of the Isaac-Comet Area, Queensland

Comprising papers by R. Story, R. W. Galloway, R. H. Gunn, and E. A. Fitzpatrick

Land Research Series No. 19

Commonwealth Scientific and Industrial Research Organization, Australia Melbourne 1967 Printed by CSIRO, Melbourne The Isaac-Comet area. CONTENTS PAGE PART I. INTRODUCTION. By R. Story ...... 9 I. GENERAL ...... 9 II. SURVEY TECHNIQUE ...... 10 III. SIZE AND LOCATION OF THE AREA ...... 11 IV. EXPLORATION AND EARLY SETTLEMENT ...... 11 V. COMMUNICATIONS ...... 13 VI. POPULATION AND ACTIVITIES ...... 15 VII. ACKNOWLEDGMENTS ...... 15 VIII. REFERENCES ...... 16

PART II. SUMMARY DESCRIPTION OF THE ISAAC-COMET AREA. By R. W. Galloway ...... 17

I. INTRODUCTION ...... 17

II. MAJOR FEATURES OF THE ENVIRONMENT ...... 17 (a) Climate ...... 17 (b) Geology ...... 17 (c) Geomorphology ...... 18 (d) Soils ...... 18 (e) Vegetation ...... 19 III. TYPES OF COUNTRY ...... 20 (a) Mountains ...... 20 (6) Hills with Woodlands ...... 20 (c) Hills with Softwood Scrub ...... 20 (rf) Hills with Lancewood Scrub ...... 20 (e) Tablelands and Lowlands with Red and Yellow Earths ...... 20 (/) Lowlands with Woodlands ...... 21 (g) Lowlands with Brigalow Scrub ...... 21 (h) Lowlands with Softwood Scrub ...... 21 (0 Grassland ...... 21 (j) Alluvium ...... 21

IV. LAND USE ...... 22 (a) Natural Pastures ...... 22 (b) Improved Pastures ...... 22 (c) Cultivation ...... 22 (d) Irrigation ...... 23

PART III. LAND SYSTEMS OF THE ISAAC-COMET AREA. By R. Story, R. W. Galloway, and R. H. Gunn ...... 24

PART IV. CLIMATE OF THE ISAAC-COMET AREA. By E. A. Fitzpatrick .. .. 53 I. INTRODUCTION ...... 53 (a) Principal Climatic Features ...... 53 (b) Principal Climatic Controls ...... 53 5 CONTENTS

PAGE II. GENERAL CLIMATIC CHARACTERISTICS ...... 55 (a) Rainfall ...... 55 (b) Temperature ...... 61 (c) Humidity ...... 64 (d) Cloudiness, Sunshine, and Radiation ...... 65 (e) Evaporation ...... 65

III. AGROCLIMATOLOGY ...... 67

IV. REFERENCES ...... 67

PART V. GEOLOGY OF THE ISAAC-COMET AREA. By R. W. Galloway . . .. 68

I. INTRODUCTION ...... • - - 68

II. GENERAL GEOLOGY ...... • • .. 68 (a) Permian ...... 68 (b) Triassic ...... 70 (c) Jurassic and Cretaceous ...... - . . 70 {d) Tertiary ...... - . • 70 0) Post-Tertiary ...... 71

III. STRUCTURE ...... 71

IV. GEOLOGY AND THE LAND SYSTEMS ...... 72 (a) Non-quartzose Pre-Tertiary Sedimentary Rocks ...... 72 (b) Quartzose Sedimentary Rocks ...... 74 (c) Quartz Sandstone ...... 74 (d) Basalt and Volcanics ...... 75 (e) Tertiary Sandstone ...... 75 (/) Tertiary Clay ...... 75 (g) Post-Tertiary Alluvium ...... 76

V. REFERENCES ...... 76

PART VI. GEOMORPHOLOGY OF THE ISAAC-COMET AREA. By R. W. Galloway 77

I. GENERAL DESCRIPTION ...... 77 (a) Isaac-Connors Catchment ...... 77 (b) Comet Catchment ...... 78 (c) Central Area Draining to the Nogoa-Mackenzie ...... 78

II. EVOLUTION OF THE LAND FORMS ...... 79 (a) Late Mesozoic Erosion ...... 79 (b) Lower Tertiary Basalt ...... 80 (c) Post-basalt Erosion ...... 80 (rf) Tertiary Deposition ...... 80 (e) Tertiary Deep Weathering ...... 81 (/) Late Tertiary Erosion ...... 82 (g) Late Tertiary Deposition ...... 83 (h) Quaternary Alluviation ...... 84

III. GEOMORPHOLOGY AND THE LAND SYSTEMS ...... 84 (a) Land Systems on Intact or Slightly Denuded Tertiary Land Surface .. .. 85 (b) Land Systems on Erosional Areas within the Tertiary Weathered Zone . . 86 (c) Land Systems on Depositional Areas within the Tertiary Weathered Zone .. 86 (d) Land Systems on Erosional Areas cut below the Tertiary Weathered Zone .. 86 (e) Land Systems on Post-Tertiary Alluvium ...... 87 CONTENTS 7

PAGE PART VII. SOILS OF THE ISAAC-COMET AREA. By R. H. Gunn .. .. 89

I. INTRODUCTION ...... 89

II. SOIL GROUPS AND FAMILIES ...... 89

III. DESCRIPTIONS OF THE SOIL GROUPS AND FAMILIES ...... 92 (a) Alluvial Soils ...... 92 (b) Cracking Clay Soils ...... 93 (c) Texture-contrast Soils ...... 97 (d) Red and Yellow Earths ...... 100 (e) Dark Brown and Grey-brown Soils ...... 101 (/) Uniform Coarse-textured Soils ...... 102 (g) Shallow Rocky Soils ...... 102 IV. ORIGIN AND OCCURRENCE OF THE SOILS ...... 103 (a) Occurrence of the Soils ...... 103 (b) Past Climate and Geomorphic Influences ...... 103 (c) Lithology and Relief ...... 106 (d) Halomorphic Influences ...... 106

V. REFERENCES ...... 107

PART VIII. VEGETATION OF THE ISAAC-COMET AREA. By R. Story .. .. 108

I. INTRODUCTION ...... 108

II. DESCRIPTION OF THE VEGETATION TYPES ...... 110 (a) Shrub Woodland, Sandstone Form ...... 110 (U) Mixed Shrub Woodland ...... 113 (c) Savannah Woodland ...... 118 (d) Downs ...... 122 (e) Brigalow Scrub {Acacia harpophylla) ...... 123 (/) Softwood Scrub ...... 126 (g) Lancewood Scrub (Acacia shirleyi) ...... 127 (h) Bendee Scrub (Acacia calenulata) ...... 127 (0 Blackwood Scrub (Acacia sp.) ...... 127

III. REFERENCES ...... 128

PART IX. GRASSES OF THE ISAAC-COMET AREA AND THEIR UTILIZATION. By R. Story ...... 129

I. THE MAIN GRASS COMMUNITIES ...... 129 (a) Sparse Mixed Grasses of Shrub Woodland, Sandstone Form ...... 129 (b) Eastern Mid-height Grass Community ...... 129 (c) Downs Community ...... 131 (d) Scrub Grasses ...... 131

II. THE PASTURE LANDS ...... 131 (a) Pasture Land 1 ..131 (b) Pasture Land 2 ..132 (c) Pasture Land 3 132 (d) Pasture Land 4 ..132 (e) Pasture Land 5 ..133 (/) Pasture Land 6 ..133 (g) Pasture Land 7 ..133 (A) Pasture Land 8 133 (0 Pasture Land 9 134 0) Pasture Land 10 ..134 (k) Pasture Land 11 ..134 8 CONTENTS

PAGE III. THE BROAD ASPECTS OF UTILIZATION ...... 135 (a) General ...... 135 (b) Herbage and Browse ...... 136 (c) Pasture Quality ...... 136 (rf) Stocking Rate and Grazing Management ...... 136 (e) Research and its Application ...... 137

IV. REFERENCES ...... 138

PARTX. LAND USE IN THE ISAAC-COMET AREA. By R. H. Gunn .. .. 139

I. INTRODUCTION ...... 139

II. CLIMATE AND LAND USE ...... 141 (a) Pasture Growth ...... 141 (b) Dryland Crops ...... 142

III. SOILS AND LAND USE ...... 143 (a) Soil-Water Relationships ...... 143 (b) Erosion ...... 144 (c) Fertility ...... 144 (d) Salinity ...... , . 145 (e) Other Aspects ...... 145

IV. IRRIGATION ...... 145

V. REFERENCES ...... 146 APPENDIX I. LAND CAPABILITY CLASSES AND SUBCLASSES .. .. 147 APPENDIX II. AVAILABLE COMMON PLANT NAMES ...... 150

MAPS Land Systems Geology and Geomorphology^| Soils I _ , .. . )=On one sheet Vegetation Pasture Lands f PART I. INTRODUCTION

By R. STORY*

I. GENERAL The survey was requested by the Queensland Government to cover part of an area of new activity in pastoral and agricultural pursuits and in prospecting for oil and minerals, one known to have considerable natural resources of which more knowledge was required. Large holdings in this part of Queensland are being subdivided

TABLE 1 SIMILAR LAND SYSTEMS IN THE NOGOA-BELYANDO, ISAAC-COMET, AND DAWSON-FITZROY AREAS

Nogoa-Belyando Isaac-Comet Dawson-Fitzroy

Wharton Arcadia — Barwon Barwon Kareela Bedourie Womblebank Blackwater Blackwater Wandoan Carborough Carborough Carborough Comet Comet Coreen Alpha Connors Dingo Hope Cotherstone — Durrandella Durrandella Funnel Funnel Coolibah Hillalong Hillalong — Humboldt Humboldt Thomby Lennox (in part) Junee Kaiuroo Monteagle Monteagle — Oxford Oxford — Percy Percy — — Planet Nathan (in part) — Racecourse Eurombah Somerby Somerby Highworth Waterford Waterford — Skye — Woleebee as the leases expire, closer settlement is being encouraged and assisted, brigalow is being cleared, new roads are being constructed, the possibilities of irrigation are being examined, and investigations by private companies and Government departments are in progress. Most of the brigalow lands investigated by the Bureau of Agricultural Economics (1962) are in the Isaac-Comet catchment. * Division of Land Research, CSIRO, Canberra. 10 R. STORY

The survey is one of a series done by the Division of Land Research, CSIRO. The aim is to provide a .first-stage broad inventory of the natural features of an area by subdividing it into land systems, each with its characteristic arrangement of topography, soils, and vegetation, and consequently with its own capacity for agricultural use. The size of the area, the time available, and the scale of the published map set the limits on the amount of detail presented.

Fig. 1.—Location of the Isaac-Comet area in relation to other survey areas in Queensland.

The Isaac-Comet area was the first of three adjacent and similar areas to be surveyed by the Division of Land Research. The survey was completed in draft form in mid 1964, and was then held over for comparison with the adjacent surveys and for coordination with them through the revision of the land systems and mapping. This was done with the cooperation of the survey teams concerned and of other interested members of the Division of Land Research, the land systems being linked with those of the Nogoa-Belyando area immediately to the west (Gunn et al. 1967) and with those of the Dawson-Fitzroy area immediately to the east (Speck et al. 1967). Land systems that are closely similar in the three areas have a common name, and they, and those with points of similarity, are listed in Table 1 and annotated accordingly on the tabular descriptions. The location of the areas is shown in Figure 1.

II. SURVEY TECHNIQUE The method of survey is that of Christian and Stewart (1953). As it has been described in various publications and reports since then, only a short account is given here. The surveys are carried out by a geomorphologist, a pedologist, and an ecologist, working in close cooperation; their technique is based on the observation INTRODUCTION 11

that areas with a repeating pattern of land forms, soils, and vegetation have a distinctive pattern on aerial photographs (Plate 1, Fig. 1). Mappable areas thus distinguished are known as land systems and are subdivided into land units which are relatively more uniform in their land characteristics, and mostly correspond to the distinctive components of the air-photo patterns. The degree of subdivision of land systems into land units is largely determined by the scale of working, by the complexity of the land system, and by the outlook of the team members. After the literature had been consulted as a first step to this survey, mosaics of the photographs were laid out in sequence, and their different patterns roughly delineated. A reconnaissance route, covering as many types of country as possible, was then chosen for a preliminary survey of four weeks in the spring of 1961. From this reconnaissance and from more thorough study of the aerial photographs, future traverse routes and sample areas were selected. Further field work consisted of two five-week periods in the winter and spring of 1962, with an interval of six weeks at base during which the material was reviewed and put in order. Routes traversed are shown in Figure 2. Field work consisted in checking that each photographic pattern did in fact represent a certain type of country, and in describing the country in terms of land forms, soils, and vegetation. The position of the survey party was continually kept under review on the aerial photographs so that notes could be correlated on the spot with the photographic pattern and among team members. More detailed work was done in preselected areas. After the final five weeks of field work and after some independent work and team discussions, the mapping and description of the land systems were begun as a team project. Mapping was done by stereoscope directly onto the aerial photographs. Because of the scale of working only areas wider than half a mile could be mapped. Geomorphology, soils, vegetation, and pasture lands have been mapped separately and at a smaller scale by grouping land systems in which these features are similar. III. SIZE AND LOCATION OF THE AREA The area covers 16,500 sq miles. It is about 300 miles from south to north and 60 from east to west, lying between lat. 21°15'S. and 25°30'S., and long. 147°45'E. and 149°30'E., bisected by the Tropic of Capricorn and with the centre of the eastern boundary about 100 miles inland from Rockhampton. The area is drained by the Mackenzie River but does not include the whole catchment—the tributaries east of the Bruce highway and most of the Nogoa basin lie outside the boundary. The location is shown on the land system map that accompanies this report.

IV. EXPLORATION AND EARLY SETTLEMENT Some information on the history of the southern part of the area is to be found in a booklet published for the Springsure centenary (Anon. 1959), which has provided much of the material for the following three paragraphs. The first European explorer in the area was Leichhardt, who entered the southern part in 1844 and named, among other features, the Expedition and Christmas Ranges, 12 R. STORY

Fig. 2.—Routes traversed on survey. INTRODUCTION 13

Albinia Downs, and the Comet River. He was followed in 1846 by Mitchell, who entered from the west and named the Nogoa River. The first European settlers, presumably sheep graziers, settled on Springsure Creek in 1854. Settlement thereafter was from the south and east, "runs" being taken up on the Comet River in 1857, and on Carnarvon, Clematis, Consuelo, Planet, Meteor, and Orion Creeks between 1858 and 1860. Conflict soon arose between the settlers and the aborigines, beginning with massacres by both sides and ending when the aborigines were reduced to detribalized remnants of their former strength. They are settled today in groups in the towns and on the properties. Springsure arose as a depot for carriers plying their trade from Rockhampton to the Gulf country and the Barcoo, and in the early days of settlement was linked to Rockhampton by a direct coach road that crossed the northern end of the Expedition Range about 10 miles south of where the railway is today. It was probably the building of this railway that caused the direct road to fall into disuse. The railhead was at Comet until 1882, when the line was extended west and south to link with Springsure in 1886 or 1887. Exploration in the northern half of the area took place a little later than in the south. Mt. Nebo and Mt. Fort Cooper were discovered by William Landsborough in 1859, and settlement must have followed rapidly because Lotus Creek, Kemmis, Bovey, Nebo Creek, and Leichhardt Downs were settled by 1863 or 1864 (Cilento and Lack 1959). This settlement probably took place not from Mackay but from Rockhampton, which was founded in 1856 as a port eventually to serve the pastoral interests of the hinterland (Clark 1918). Mackay was founded only after 1860, when the Pioneer River was discovered by John Mackay.

V. COMMUNICATIONS

The area is served by one railway which runs from Rockhampton westwards through the middle of the area to Emerald and beyond, with a branch to Springsure. The North Coast railway is accessible by way of the Bruce and Clermont-Coast highways. The main roads are shown in Figure 3. Five of them are highways. Those running east-west are the Clermont-Coast highway in the north, which connects with Mackay, the Northern Inland highway in the centre, which follows the railway, and the Springsure-Bauhinia-Duaringa highway in the south, which joins the Northern Inland highway to the east of the area. Those running north-south are the Bruce highway, which connects Mackay and Rockhampton and forms part of the north- eastern boundary of the area, and the Carnarvon highway, which provides an outlet to the south and connects with Brisbane. The Bruce and the Northern Inland highways are bituminized, the rest are not, except for sections between Springsure and Emerald. Secondary roads and tracks provide access to the intervening parts in good weather but many are unmapped and little known, and trackless areas may cover as much as 300 sq miles. 14 R. STORY

Fig. 3.—Railways and more important roads. INTRODUCTION 15

VI. POPULATION AND ACTIVITIES Of the towns and villages Emerald, with a population of over 2000, lies just outside the area but for all practical purposes may be considered part of it. The rest are Springsure, with a population of about 800, and Blackwater, Comet, Nebo, and Rolleston, all with postal facilities and hotel accommodation. When this report was drafted they were dependent on primary industry, and the last four each had a population of only about 80. Since then, supplies of natural gas have been struck near Rolleston and in the extreme south of the area near Warrinilla, and what used to be a small amount of coal-mining near Blackwater has greatly increased, a company having contracted to supply 13J million tons of coal, valued at $122,000,000, from the Blackwater coalfields by 1978. Properties vary greatly in size. The largest are of the order of 400 sq miles, but in the agricultural holdings towards the west they are much smaller. The farming community numbers roughly 1800. Most properties are connected by telephone, and about 30 have airfields. The environment is well suited to beef production. This is the main industry, and Hereford cattle are those most commonly used. The stocking rate varies from 11 acres to a beast on the downs {Dichanthium or Heteropogon grasslands) to more than 100 in dense scrub. Over most of the area it is roughly 30 or 40. Improvements vary widely according to the property, and include the provision of water, fencing, clearing, and the establishment of improved pastures. Some wheat is grown on the basalt country in the west, and a little sorghum, but apart from this there is no significant agriculture, nor is there any significant industrial activity apart from that connected with the coal and gas.

VII. ACKNOWLEDGMENTS

The assistance of the following institutions and individuals is acknowledged with many thanks: officers of the Queensland Department of Primary Industries, particularly Mr. W. J. Bisset and the staff of the Botanic Museum and Herbarium for their constructive criticism and for many additions and amendments to the typescript of Part VIII, and the staff of the Botanic Museum and Herbarium for determining the botanical collections also; the Queensland Department of Forestry for permission to collect plants in the Carnarvon National Park; the staff of the Surveyor-General's Office, Queensland Department of Public Lands, for supplying revised maps of the area; Mr. R. F. Isbell, of the Division of Soils, CSIRO, and Mr. M. Lazarides, of the Division of Land Research, CSIRO, for cooperation and assistance with pedology and with field and taxonomic botany respectively; Mr. G. D. Hubble, of the Division of Soils, CSIRO, for criticism of the soils chapter; officers of the Commonwealth Bureau of Mineral Resources, Geology and Geophysics, the Queensland Department of Mines, and Mines Administration Pty. Ltd. for supplying geological information and maps and for helpful comments on parts of the text; Mr. Y. Takehisa, of the Japanese Geographical Survey Institute, for assistance in geomorphic observations and photographic interpretation; the Bureau of Meteorology and the Department of National Development for generous cooperation in providing climatic data. 16 R. STORY

While acknowledging these contributions, the authors nevertheless accept responsibility for the statements made in the report.

VIII. REFERENCES ANON. (1959).—Springsure centenary 1859-1959 booklet. A short history of Springsure and district. (City Printing Works: Rockhampton.) BUREAU OF AGRICULTURAL ECONOMICS (1962).—The economics of brigalow land development in the Fitzroy basin, Queensland. (Commonw. Govt. Printer: Canberra.) CHRISTIAN, C. S., and STEWART, G. A. (1953).—General report on survey of Katherine-Darwin region, 1946. CSIRO Aust. Land Res. Ser. No. 1. CILENTO, R., and LACK, C, Eds. (1959).—"Triumph in the Tropics." (Smith and Paterson Pty. Ltd.: Brisbane.) CLARK, W. (1918).—The founding of Rockhampton and the Archer brothers. J. Qd hist. Soc. 1, 327-37. GUNN, R. H., GALLOWAY, R. W., PEDLEY, L., and FITZPATRICK, E. A. (1967).—Lands of the Nogoa- Belyando area, Queensland. CSIRO Aust. Land Res. Ser. No. 18. SPECK, N. H., WRIGHT, R. L., SWEENEY, F., PERRY, R. A., FITZPATRICK, E. A., GUNN, R. H., NIX, H. A., and WILSON, I. B. (1967).—Lands of the Dawson-Fitzroy area, Queensland. CSIRO Aust. Land Res. Ser. No. 21.

PART II. SUMMARY DESCRIPTION OF THE ISAAC-COMET AREA

By R. W. GALLOWAY*

I. INTRODUCTION This Part outlines the major features of the environment, describes the major types of country, and summarizes aspects of the land use. It has been written with reference to the small-scale coloured maps, text figures, plates, and the land system map.

II. MAJOR FEATURES OF THE ENVIRONMENT (a) Climate The area has a subhumid tropical to subtropical climate with only gradual transitions across the area. The mean annual rainfall ranges from 22 to 30 in., the wetter parts lying in the north-east and south of the area. About three-quarters of the precipitation falls between November and April but there is a rather higher proportion of winter rainfall in the south. February, with 4-6 in., is the wettest month and August and September are the driest (less than 1 in.). Variability from year to year is high. Mean maximum temperatures range from just over 70°F during June and July to about 95°F in December and January. Temperatures can exceed 100°F during the hottest months and on the other hand frosts are common from June to August. The diurnal temperature range is considerable, especially in winter. The "drying power" of the air as measured by the 9 a.m. saturation deficit is high from October to January and moderate for the rest of the year with lowest values in June and July. Calculated pan evaporation ranges from about 3 in. in June to 9 in. in December for the Springsure-Emerald area. Rather lower evaporation probably occurs in the more humid north-eastern and southern parts of the area. (b) Geology The area occupies much of the Bowen Basin synclinorium of east-central Queensland. It contains rocks ranging from lower Permian to Recent in age, many of which have been deeply weathered. The oldest rocks are the resistant Lower Bowen Volcanics which crop out over a limited area in the north-east. The overlying marine shales and sandstones of the Middle Bowen beds extend over much of the northern half of the area, around Comet in the centre, and in the long NNW.-SSE. Springsure-Serocold anticline in the south-west. The unresistant terrestrial sandstone, siltstone, shale, and coal of the * Division of Land Research, CSIRO, Canberra. 18 R. W. GALLOWAY

Upper Bowen Coal Measures occupy much of the centre of the area. The Triassic rocks consist partly of resistant quartz sandstone giving rise to rugged ranges. In the southern half of the area, shaly, weak formations overlie and underlie this sandstone and give rise to lowlands. Resistant Jurassic quartz sandstone rims the southern part of the Comet catchment. Tertiary basalt is widespread on the western margin of the area, in the south round Rolleston, and in the north-east while Tertiary intrusive rocks occur in the Peak Range in the north-west. Tertiary sediments, ranging from conglomerate through sandstone to clay, occupy more than half the area. Post-Tertiary alluvium is widespread along all major rivers. On fresh rock lithologic variations affect the soils and vegetation (Plate 1, Fig. 2). Where the effects of Tertiary deep weathering are preserved, on the other hand, it is the horizon of the weathered zone which is now exposed that largely determines the character of the country. (c) Geomorphology The major features of the relief are illustrated in the frontispiece. The area is a lowland between 400 and 1000 ft above sea level from which limited hill and mountain areas rise, mainly on the margins, to from 1500 to 3500 ft. Prolonged erosion in Mesozoic and lower Tertiary times resulted in the formation of a level to gently undulating landscape formed mainly on deeply weathered Tertiary rocks above which rose low residuals on more resistant pre-Tertiary rocks (Fig. 8). The subsequent survival, partial removal, or complete removal of the Tertiary land surface and deep weathered zone determine the major characteristics of the country. The geomorphology map shows the distribution of these three situations. The old surface with its low gradients and generally sandy or loamy surface survives in extensive remnants along the central axis and in the north-west of the area. Partial removal is widespread in the north and centre where soil and vegetation are determined largely by the various zones of the deep weathered profile now exposed at the surface. There has been extensive redeposition of weathered rock in this situation helping to form widespread clay sheets which support brigalow on cracking clay soils. Complete removal is commonest in the south and north-east and here soils and vegetation reflect the lithology of the unweathered pre-Tertiary rocks that are now exposed. Post-Tertiary alluvium has accumulated in terraces and flood-plains along the major streams. id) Soils The distribution of major soil types is shown on the soils map. Four major groups can be recognized and in addition there are areas of alluvial soils and uniform coarse-textured soils too small to map separately. (i) Cracking Clay Soils.—These soils have medium to high clay content and pronounced swelling and shrinking properties (Plate 2, Fig. 1). They are generally fertile but often difficult to work and their properties tend to vary with the parent material. Deep clays, generally alkaline at depth, have formed on alluvium. Gilgaied, SUMMARY DESCRIPTION 19 deep, medium to heavy clays, generally with alkaline or neutral surface layers over acid material below 3 ft, occur in low-lying areas on truncated deep weathering profiles. Non-gilgaied clay soils of rather similar properties occur on slightly higher sites on the same material. Moderately shallow to deep medium clays with generally alkaline reaction at depth have formed on shales. Sedentary cracking clay soils, usually strongly alkaline and of moderate to considerable depth, occur on basalt lowlands while shallow light clays occur on hilly basalt areas. (ii) Texture-contrast Soils.—These widespread soils occur on a variety of parent materials including igneous and sedimentary rocks, alluvium, and the lower zones of deep weathering profiles (Plate 2, Fig. 2). They are usually alkaline at depth and often show solonetzic or solodic features while stony surface horizons are common. They usually have poor physical properties and show a high susceptibility to erosion (Plate 3, Fig. 1). They have been subdivided into those with shallow sandy or loamy surface soils, deep sandy surface soils, and shallow total depth. (iii) Red and Yellow Earths.—These soils are found on more or less intact remnants of the Tertiary land surface. Sandy- and loamy-textured varieties are present. Fertility and water-retaining capacity are low. (iv) Shallow Rocky Soils.—Mountains and hills have shallow rocky soils of negligible economic value.

(e) Vegetation Five major types of vegetation are shown on the vegetation map but these are, of course, gross simplifications of the complex natural distributions. (i) Shrub Woodland, Sandstone Form.—This uniform vegetation type is dominated by narrow-leaved ironbark and bloodwood. Shrubs of many species are abundant, while the ground cover is sparse but floristically rich. (ii) Mixed Shrub Woodland.—This complex, variable vegetation type never occupies more than 45% of any land system. The type is distinguished by the abundant E. populnea, ironbarks, and open brigalow and by the absence of gums and bloodwoods. Subtypes can be distinguished on the basis of the dominant trees. Shrubs are abundant throughout, the most common being Eremophila mitchellii and Carissa under box, and Acacia spp. under narrow-leaved ironbark (Plate 3, Fig. 2). Aristida, Bothriochloa, and Heteropogon are the dominant grasses and make up the eastern mid-height grass community. (iii) Savannah Woodland.—This open woodland has few shrubs and a ground cover dominated by the same grasses as in the mixed shrub woodlands (Plate 4, Fig. 1). Subtypes can be recognized according to whether box, ironbarks, bloodwoods, gums, or coolibah form the dominant trees. (iv) Downs.—The vegetation of the downs is dominated by the grasses, chiefly Heteropogon in the north-east and Bothriochloa and Dichanthium elsewhere; Aristida is also common (Plate 4, Fig. 2). Sparsely distributed eucabypts, including ironbarks, bloodwoods, and mountain coolibah, occur, particularly on rises where the soils are shallower. 20 R. W. GALLOWAY

(v) Scrubs.—Most of the areas mapped as scrubs are dominated by brigalow (Plate 5, Fig. 1), occurring as pure stands or in association with eucalypts, Geijera, Carissa-Eremophila-Terminalia, or softwood scrubs. Brigalow with emergent E. cambageana forms a very extensive community along the central axis of the area. Pure softwood scrubs are restricted to limited patches in the north-east and south of the area; bottle tree is characteristic. Lancewood scrubs occur on breakaways on weathered rocks and are often associated with yapunyah (E. thozetiana) and sometimes with ironbarks. Bendee and lancewood scrubs are of minor importance.

III. TYPES OF COUNTRY Ten broad types of country can be recognized; they provide the basis for grouping the land systems on the land system map. (a) Mountains The mountainous land systems occupy 1900 sq miles and have a local relief ranging from 500 to 2500 ft with shallow rocky soils and savannah woodland dominated by narrow-leaved ironbark. Carborough is rugged quartz sandstone country with many heath-like shrubs in the woodland (Plate 5, Fig. 2); Black Alley is a high tableland on basalt, with some gum and box; Percy consists of steep mountains on dissected basalt flows and volcanic plugs (Plate 6, Fig. 1); Britton is steep dissected mountains on Lower Bowen Volcanics with some softwood scrub in places. (b) Hills with Woodlands Stony hills and sandy plateaux make up Planet and Skeleton land systems which occur in this group and extend over 700 sq miles. Shallow rocky soils or uniform coarse-textured soils predominate with savannah woodland of ironbark and some bloodwood. Waterford land system (about 350 sq miles) consists of tabular hills of unweathered basalt and limited intervening lowlands. Shallow rocky soils occur on the steeper parts and shallow to moderately deep cracking clay soils elsewhere. An open woodland dominated by silver-leaved ironbark prevails. (c) Hills with Softwood Scrub Only the small Bedourie land system (125 sq miles) occurs in this class. Low hills on Triassic shales and stony benches on basalt predominate, with shallow rocky soils, dark brown and grey-brown soils, and some cracking clays. (d) Hills with Lancewood Scrub Durrandella land system of just over 1000 sq miles comprises stony hills with lancewood or savannah woodland of narrow-leaved ironbark. Shallow rocky soils or shallow red and yellow earths are the dominant soils. (e) Tablelands and Lowlands with Red and Yellow Earths Junee land system covers some 700 sq miles and comprises undulating tablelands and plains which are little-modified remnants of the Tertiary land surface. Deep loamy soils of low fertility and savannah woodland of narrow-leaved ironbark are characteristic. SUMMARY DESCRIPTION 21

(/) Lowlands with Woodlands This extensive type of country (3000 sq miles) is level to undulating, with local relief generally less than 50 ft. Texture-contrast soils predominate and range from deep in lower sites to shallow on the rises. Savannah woodland is. the dominant vegetation. Cotherstone land system consists of narrow-leaved ironbark woodland on Permian sandstone (Plate 3, Fig. 2). Hillalong land system is on Permian shales and soft sandstone and has a fairly well-marked groved pattern of box and ironbark. Moorooloo land system comprises gravelly clay over weathered basalt supporting silver-leaved ironbark woodland. Monteagle land system is on lightly stripped survivals of the Tertiary land surface and has well-marked texture-contrast soils under box (Plate 4, Fig. 1). Nebo land system is on Permian volcanics and gravel derived therefrom; both texture-contrast and cracking clay soils are represented and bloodwood, ironbark, and box are the dominant trees. Rewan land system consists of lowlands on shales with a widespread cover of billy gravel; texture-contrast soils and savannah woodland of ironbark and box are the rule. (g) Lowlands with Brigalow Scrub Plains with brigalow and scrub grass occupy 4750 sq miles, rather more than one-quarter of the Isaac-Comet area (Plate 5, Fig. 1). Soils are mostly cracking clays, often deeply gilgaied, but texture-contrast and dark brown and grey-brown soils occur in places. Somerby land system is formed on weathered Tertiary clay with deep gilgais; Blackwater is on similar material without gilgais. Humboldt land system is also on deeply weathered clay but has texture-contrast soils and blackbutt (E. cambageana) is dispersed throughout the brigalow. Arcadia land system occurs on shales with extensive gravel patches; a strong admixture of wilga is usual in the brigalow. Daunia land system is likewise on shales but has little wilga. Barwon land system is on folded Permian sediments and has well-marked groves, aligned along the strike, of brigalow and eucalypts. (h) Lowlands with Softwood Scrub This minor type of country covers only 165 sq miles. Softwood scrub is the characteristic feature of Racecourse land system on weathered basalt near Rolleston. Cracking clay soils and dark brown and grey-brown soils predominate. The relief ranges from gently undulating lowlands to plains. (i) Grassland Fully 1500 sq miles of the area are grassland. Rolling downs with cracking clay soils and few trees occurring on unweathered basalt form Oxford land system (Plate 4, Fig. 2). Girrah land system on gently folded Permian shales has broad belts of downs aligned along the strike alternating with open brigalow scrub; shallow to moderately deep cracking clay soils are the rule. (j) Alluvium Alluvium has been mapped as separate land systems with a total area of 2250 sq miles where it exceeds half a mile in width. Higher alluvial plains, terraces, and sandy levees above flood level form Connors land system characterized by a 22 R. W. GALLOWAY

savannah woodland of box over texture-contrast soils (Plate 6, Fig. 2); channels are deep and narrow with sandy beds dry for much of the year (Plate 7, Fig. 1). Funnel and Comet land systems consist of lower alluvial plains with deep cracking clay soils subject to flooding. The dominant trees are coolibah and brigalow respectively.

IV. LAND USE The dominant land use is beef cattle raising and, because of restrictions imposed by climate, soil, topography, and location, is likely to remain so. Heretofore this industry has been carried out mainly on natural pastures but there is considerable scope for pasture improvement and some scope for cultivation and irrigation. (a) Natural Pastures The natural pastures grow rapidly in early and middle summer when adequate moisture is available and the temperatures are optimal but later they quickly degenerate into poor-quality dry feed. The "hungry gap" in the drier part of the year is the funda- mental obstacle to more intense use of the natural pastures, which are under-grazed for much of the year (Plate 7, Fig. 2; Plate 8, Fig. 1). The mean annual period of pasture growth ranges from 24 weeks in the north-east round Nebo to 20 weeks in the west and 18 weeks round Comet. When the four main pasture types outlined in Part IX are considered in relation to relief, 11 pasture lands can be recognized and mapped. The downs community and the Bothriochloa-Heteropogon-Aristida community (eastern mid-height grass) on lowlands have the best carrying capacity, while that of the sparse grasses of the shrub woodland (sandstone form) and of the various scrubs is low to moderate. About 10% of the area is too steep and rocky to have much value for grazing. (b) Improved Pastures Extensive areas of scrub have recently been cleared by highly mechanized methods and put down to improved pastures, mainly Rhodes grass (Plate 8, Fig. 2). These improved pastures have a much higher carrying capacity than the natural pastures and rather better nutritive value during the dry season. The soils are generally fertile with good water-retaining capacity. Problems include higher clearing costs where E. cambageana is associated with the brigalow (Humboldt land system), regrowth of the scrub, soil erosion on steeper slopes, and large gilgais impeding cultivation. There is also scope for pasture improvement on the downs but here attention is being directed more towards cropping. (c) Cultivation Cultivation for forage and grain crops is becoming increasingly important on the cracking clays which are the most suitable soils on account of their favourable water-retaining properties, generally good fertility, and gently sloping relief. The most critical factor is soil moisture and the most favoured area appears to be in the north-east round Nebo, whereas in the west and centre drought is likely to be a greater hazard. Currently some 50,000 acres are under cultivation for winter crops of sorghum, safflower, oats, and wheat, and there is undoubtedly scope for extension of this area. SUMMARY DESCRIPTION 23

(d) Irrigation At present no significant irrigation is carried out in the area but a proposed scheme near Emerald could supply water to 57,000 acres. There may be some irrigation possibilities along other streams in the area though the costs of water supply and flood control may well be prohibitive. The possibility of cultivating alluvial fiats irrigated by natural flooding may be worth investigating. PART III. LAND SYSTEMS OF THE ISAAC-COMET AREA

By R. STORY,* R. W. GALLOWAY,* and R. H. GUNN*

The area has been mapped and described in terms of 28 land systems (Christian and Stewart 1953f) which are set out in alphabetical order in the pages which follow. The characters of each land system are tabulated, and illustrated with a block diagram. The section above the block diagram lists the main features of the land system; the section below the block diagram deals with the features of each land unit, the land units being arranged in descending order of relief. In the last column of each table the estimated land capability class and symbols denoting the kind and degree of limitations are given for each land unit. The classes and symbols are defined in Appendix I. The areas of the land systems were determined from the land system map with a dot grid (25 dots per sq in), and rounded to the nearest 5 sq miles. The relative areas of land units in each land system were estimated from field experience and air-photo pattern. More detailed information on the geology, land forms, soils, vegetation, and land use of the land systems can be obtained from Parts V-X.

* Division of Land Research, CSIRO, Canberra. t CHRISTIAN, C. S., and STEWART, G. A. (1953).—General report on survey of Katherine- Darwin region, 1946. CSIRO Aust. Land Res. Ser. No. 1. LAND SYSTEMS OF THE ISAAC-COMET AREA 25

ARCADIA LAND SYSTEM* (675 SQ MILES) Lowlands with brigalow and wilga mainly on little-weathered shale and grave] in the south; dark brown and grey-brown and cracking clay soils.

Land Area and Land Forms Soils Vegetation Land Uni Distribution Class

1 15% Sandy or gravelly fans Texture-contrast soils, Mixed shrub woodland {Alstonia, Cadellia, IVpM, Mainly in below sandstone ranges; mainly with thin loamy Brachychiton, brigalow, Erythroxylum, Cro- the south undulating; local relief surface horizons and ton phebalioides, Geijera, Maba humilis, 10-50 fi; up to 2 miles strongly alkaline subsoils, Acalypha eremorum, Heterodendrum olei- across Retro (Dbl.13, Dr2.13), folium, Eremophila, E. populnea, Carissa, minor Taurus (Db 1.13) Hypoestes floribunda); sparse ground cover of Paspalidium,, Aristida, Chloris, Enneapo- gon, Cheilanthes sp., and mosses

2 45% Plains and lowlands Mainly dark brown and Mainly brigalow with Geijera andi:. populnea, ir-irie^ Widespread mainly on shales; up to grey-brown soils with sea ttered woody associates and ground 8 miles across; slopes coarse-textured surface cover as in unit 1 generally 1-3% soils grading to reddish, alkaline clayey subsoils, Cheshire (Gn4.13, 3.13); minor texture-contrast soils, Retro and Spring- wood (Ddl.33, Dr2.32)

3 35% As unit 2, but much billy Cracking clay soils, III-IV Widespread gravel on surface strongly alkaline at or Sa-4, T3_4, near the surface and acid beneath, commonly with «4 surface gravel, gilgaied in places, Rolleslon and Pegunny (Ug5.16, 5.24)

4 <5% As unit 2 Cracking clay soils, Rol- Brigalow in dense circular clumps 20 yd His,, k2_3 Mainly in leston (Ug5.38) diam., with sparse Paspalidium below; the east intervening areas more open, with denser ground cover of Chloris, Thellungia adverta, and Aristida

5 <5% Alluvial flats; mainly clay; Mainly tex lure-contrast Savannah woodland of E. populnea over Sporadic small braided channels up soils with thin sandy sur- Bothriochloa, with patches of mixed shrub to 5 ft deep face horizons and neutral woodland; levees savannah woodland of E. subsoils, Springwood populnea, E. tereticornis, E. tessellaris, and (Dbl.12, Ddl.32); minor E. melanophloia over Bothriochloa and Luxor and Retro (Dr2.22, Arundinella Dd 1.13) and cracking clay soils, Vermont (Ug5.15) ! Similar to Wharton land system in the Nogoa-Belyando area. 26 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

BARWON LAND SYSTEM* (140 SQ MILES)

Bands of brigalow and open savannah woodland on unweathered Permian sediments in the centre of the area; cracking clay and texture-contrast soils.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

1 10% Sand and gravel patches Texture-contrast soils Mixed shrub woodland (E. populnea, E. IVPa-4 Sporadic on rises; generally less with thin sandy surface cambageana, brigalow, Terminalia, Carissa, than i mile across; level horizons and strongly Eremophila, Bauhinia, and Casuarina cristata, to gently undulating alkaline subsoils, Taurus with sparse to fair ground cover of Aristida, (Db3.23, Dr4.23); gravel- Paspalidium, Chloris, Bothriochloa, and ly surface strew in places Heteropogori)

2 55% Lowlands; undulating; Mainlycracking claysoils, Bands upwards of 20 yd wide of brigalow or III-IV Widespread local relief 20-50 ft; slopes moderately shallow, mixed shrub woodland, species as in unit 1 eE-3, d,, up to 5%; some outcrop Teviot (Ug5.12, 5.33); P3-4 on rises minor texture-contrast soils, Taurus (Ddl.33) and Retro (Dr3.33)

3 30% Mainly shallow texture- Bands upwards of 20 yd wide of downs or IVd4, ea_n Widespread contrast soils, Southern- open savannah woodland {Bothriochloa, wood and Medway Heteropogon, Themeda, Chrysopogon, and (Dr2.12, 2.13); minor heterogeneous eucalypts) shallow cracking clay soils, Bruce (Ug5.37)

4 5% .. Alluvial flats; usually less No observations; prob- Mixed shrub woodland of brigalow with Sporadic than i mile wide; sand or ably texture-contrast scattered Terminalia, E. microtheca, and E. clay; single channels 5-10 soils mainly cambageana over scanty ground cover of ft deep Paspalidium, Aristida, and Chloris; E. tereticornis and E. papuana near channels, ground cover mainly Bothriochloa and Heteropogon * Has less brigalow and shallower soils than Barwon land system in the Dawson-Fitzroy area. LAND SYSTEMS OF THE ISAAC-COMET AREA 27

BEDOURIE LAND SYSTEM* (125 SQ MILES) Softwood scrub on uplands and low hills on weathered basalt and shales; dark brown and grey-brown and texture-contrast soils.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

1 20% Tops of low hills and Shallow rocky soils, Open savannah woodland of E. orgadophila VIIt7, r5 Widespread mesas; rocky; up to £ mile Rugby (Uml); much out- and E. dichromophloia, with dense ground except for across crop and gravel in places cover of Dichanthium,Bothriochloa,Themeda, Bedourie Heteropogon, Iseilema, Cymbopogon sp., area Aristida latifolia, and Enneapogon

2 35% Benched slopes of low Shallow rocky soils, Softwood scrub {Terminalia, Canthium vac- VIIt7, r6 Widespread basalt hills in unit 1; local Rugby (Uml), and shal- ciniifolium, Erythroxylum australe. Macro- except for relief 20-100 ft; often low cracking clay soils, pteranthes, Denhamia obscura, Carissa, Bedourie stony Bruce (Ug5.12) Citriobatus); sparse ground cover of area Paspalidium, Aristida, Chloris, Enneapogon, Cheilanthes sp,,, and mosses

3 45% Hills and uplands on Dark brown and grey- Softwood scrub (Macropteranthes dominant, IV-VIte, In Bedourie shales; local relief 30-100 brown soils, Ingelara Excoecaria dallachyana, Casuarina cristatd), area in the ft; slopes up to 15%; (Um5.2), and texture- dense tangled undergrowth. (Acalypha Pa-i south-east minor outcrop on upper contrast soils, Luxor eremorum dominant over Hypoestes flori- slopes and colluvial (Dy3.32) bunda and Ancistrackne); smaller areas of aprons on lower parts savannah woodland {E. populnea, E. melanophloia, narrow-leaved ironbark) with fair ground cover of Bothriochloa, Chrysopogon, and Eragrostis * Similar to Kareela land system in the Nogoa-Belyando area and Womblebank land system in the Dawson-Fitzroy area. R. STORY, R. W. GALLOWAY, AND R. H. GUNN

BLACK ALLEY LAND SYSTEM (55 SQ MILES) High tablelands on unweathered basalt in the south-west of the area; shallow rocky soils; savannah woodland of narrow-leaved ironbark, gum, and box.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

1 85% Tablelands; undulating to One observation; shallow Savannah woodland, height 50 ft, visibility VITi7 Throughout hilly; 3000-3500 ft above rocky soils, Rugby (Uml) 200-300 yd, narrow-leaved ironbarks, E. sea level; slopes up to punctata, E. meHiodora, Angophora sp., 10%; stony in places Casuarina torulosa, Callitris sp.; Macro- zamia common below; dense ground cover of Themeda

2 15% Cliffs and scarps bound- Shallow rocky soils, Savannah woodland, height 40 ft, visibility V1I-VTIT Throughout ing unit 1; local relief Rugby (Uml) 200-300 yd, narrow-leaved ironbark, E. 200-1000 ft; very rocky dichromophloia, E. microcarpa\ Macrozamia common below; dense ground cover of Themeda LAND SYSTEMS OF THE ISAAC-COMET AREA 29

BLACKWATER LAND SYSTEM* (825 SQ MILES) Brigalow plains and cracking clay soils on weathered Tertiary clay and older rocks along the central axis of the area.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

1 5% Rises; local relief 10-25 Texture-contrast soil, Mixed shrub woodland, E. populnea with IVp3-4,e3 Occasional ft; up to i mile across; Wyseby (Dr2.12) Carissa and Eremophila; poor ground cover slopes up to 5%; iron- of Eragrostis, Enneapogon, and Cymbopogon stone gravel and sandy patches common

2 10% Rises and foot slopes of Texture-contrast soil, Mixed shrub woodland of E. cambageana IVp3-i, Widespread hills on margin of unit 1; thin sandy surface and and brigalow, commonly with Carissa and e - up to i mile across; local strongly alkaline subsoil, Eremophila, other woody associates varied 3 4 relief 10-25 ft; slopes up Taurus (Dbl.23) but uncommon; ground cover of Bothrio- to 10%; some outcrop chloa, Aristida, Eragrostis, and Enneapogon and stony areas; sheet erosion and gullying

3 15% Lowlands and plains; Cracking clay soils, Rol- Mixed shrub woodland, mainly of brigalow, IIIs3l ka_3 Sporadic level to undulating; local leston(Ug5.16, 5.38) Carissa, Eremophila, and Terminalia, other relief 10-25 ft; up to 4 woody associates varied and fairly common miles across; slopes up to (Citriobatus, Erythroxylum australe, Brachy- 2% but usually less than chiton, Owenia, Acalypha eremorum, Albizia, 1%; weathered clay with Geijera, Atalaya); scanty ground cover of much surface gravel in Paspalidium, Aristida, Chloris, Enneapogon, places; occasional gilgai Cheilanthes sp., and mosses

4 55% As unit 3, but gravel less Cracking clay soils, main- Brigalow, with Carissa, Eremophila, and Ills3, k2_3 Widespread common ly Rolleston (Ug5.16, Terminalia; ground cover as in unit 3 5.38), minor Teviot (Ug5.32)

5 10% As unit 3, but in slightly Gilgaied cracking clay As unit 3 with Panicum buncei, Leptochloa IVg4j s3_4 Widespread lower sites soils, Pegunny (Ug5.24, debilis, Muehlenbeckia, and Cyperaceae 5.34) common in depressions 6 5% Alluvial flats; up to i One observation; texture- Mixed shrub woodland very variable (briga- IVps-i Sporadic mile wide; clay; shallow contrast soils, Taurus low, Eremophila, Terminalia, E. populnea, braided channels; prob- (Dbl.43) Muehlenbeckia, sparse ground cover of ably subject to flooding Bassia tetracuspis, Bothriochloa, Cyperaceae, Panicum buncei, Leptochloa debilis, Thel- lungia advend) f Similar to parts of Wandoan land system in the Dawson-Fitzroy area. 30 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

BRITTON LAND SYSTEM (50 SQ MILES) Rugged mountains and shallow rocky soils with narrow-leaved ironbark and softwood scrub on unweathered volcanics in the extreme north-east of the area.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class 1 60% Rugged mountains with No observations; prob- Savannah woodland of narrow-leaved iron- VII-VIII Throughout steep cliffs and much ably shallow rocky soils bark and some E. melanophloia over Bothrio- outcrop; local relief up to chloa or Heteropogon u 2000 ft 2 40% Mainly deep, sheltered No observations; prob- Softwood scrub Throughout valleys in unit 1 ably shallow rocky soils LAND SYSTEMS OF THE ISAAC-COMET AREA 31

CARBOROUGH LAND SYSTEM (1510 SQ MILES) Mountains and hills with shallow rocky soils and narrow-leaved ironbark, bloodwood, and lancewood on little-weathered quartz sandstone in the north-west and the south.

Land Area and Land Unit Distribu don Land Forms Soils Vegetation Class 1 30% Mountains and hills; very Shallow rocky soils, Lancewood over sparse Aristida, Calypto- VII-VHI Widespread broken and dissected; Shotover (Ucl.2) chloa gracillima, and Ancistrachne; or shrub t , r local relief 10O-1500 ft; woodland, sandstone form, mostly narrow- 7 5 structural benches and leaved ironbark, bloodwood, and E. cliffs common; rocky with cloeziana over sclerophyll shrubs and sparse much outcrop; some deep ground cover (Triodia, Caustis, Patersonia, weathering in shalier Hardenbergia violacea, Pomax umbellatd); zones; narrow, inacces- on slopes of Carborough and Cherwell sible valleys Ranges some savannah woodland of narrow- leaved ironbark over Heteropogon and Aristida 2 60% As unit 1, but no deep Mainly shallow rocky As unit 1 but without lancewood patches VII-VIII Widespread weathering and often soils, Shotover (Ucl .2); t , r slightly lower minor areas of uniform 7 5 coarse-textured soils, Petrona and Highmount (Ucl.23)

3 10% Lower slopes and hills; Texture-contrast soils Savannah woodland of narrow-leaved iron- IVp3-4 Widespread local relief 30-200 ft; with thick sandy surface bark and E. populnea over Heteropogon, slopes up to 25%; assoc- horizons and acid to Aristida, and Chrysopogon, with patches of iated sandy aprons and neutral subsoils, Luxor Acacia cunninghamii, Petalostigma, and fans (Dy3.21) Alphitonia; occasional brigalow with E. cambageana and E. thozetiana

4 <5% Alluvial flats in major No observations; prob- Savannah woodland, sandy alluvium with Sporadic valleys; up to \ mile ably as unit 3 narrow-leaved ironbark and E. populnea over across; usually sandy but Heteropogon, fine-textured alluvium with E. may be argillaceous where dichromophloia, E. orgadophila, and E. derived from basalt or populnea over Bothriochloa and Heteropogon shale; not flooded; single channel 10-30 ft deep 32 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

COMET LAND SYSTEM* (805 SQ MILES) Alluvial plains with brigalow and cracking clay soils, often flooded, along major streams.

Land Land Area and Land Forms Soils Vegetation Unit Distribu tion Class

1 10% Levees of present chan- Texture-contrast soils Savannah woodland of E. microtheca or E. IVp3-4 Widespread nels; back slopes up to 2% with thin loamy surface populnea, sometimes with Acacia, Cassia, but usually less; sandy or horizons and neutral sub- and Bauhinia to form a mixed shrub wood- silty; rarely flooded soils, Wyseby (Ddl.12) land; sparse to fair ground cover (Cyper- aceae, Chloris, Aristida)

2 15% Levees of abandoned Alluvial soils, Clematis Savannah woodland of E. tessel/aris, E. II-IIIk3_3 Sporadic channels; 1-10 ft high; (Uf6.33) and Moolayem- melanophloia, or E. tereticornis\ dense back slopes range from ber (Um5.5 on sand and ground cover of Heteropogon, Bothriochloa, almost flat to over 2%; clay) and Chloris sandy; not flooded; minor patches of wind-blown sand

3 50% Alluvial clay plains; Cracking clay soils, main- Brigalow, woody associates scattered II-Vwa_s, Widespread usually back-swamp sites ly Vermont (Ug5.16), throughout {E, microtheca, Terminalia, k _ or abandoned channels; minor Pegunny (Ug5.34) Eremophila, E. cambageana, Bauhinia)-, 2 3 minor occurrences of ground cover usually sparse (Paspalidium, weathered clay with gil- Sporobolus mitchellii, Bassia tetracuspis, gai; flooded in parts Bothriochloa, with Panicum buncei, Lepto- chloa debilis, Muehlenbeckia, and Cyper- aceae common in depressions) 4 10% As unit 2, but slightly Uniform fine-textured Savannah woodland of E. microtheca with III-1V South of lower alluvial soils, Clematis fair ground cover of Bothriochloa, Cyper- W3_4 Comet (Uf6.33) aceae, and Thellungia advena, Muehlen- beckia, and Leptochloa debilis common near channels and depressions

5 10% Cracking clay soils, Ver- Brigalow or savannah woodland of E. li-vW8_B, South of mont (Ug5.16) microtheca, with associates as in units 3 and k - Comet 4 respectively 3 3 6 5% Active channels; in minor No observations Banks as unit 1 Widespread valleys 3-15 ft deep with braided pattern; in larger valleys 10-40 ft deep with simple meanders or braided subchannels within single main channels

* Similar to parts of Coreen land system in the Dawson-Fitzroy area. LAND SYSTEMS OF THE ISAAC-COMET AREA 33

CONNORS LAND SYSTEM* (970 SQ MILES) Alluvial plains with box on texture-contrast soils throughout the area.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

1 10% Alluvial terraces; level; Uniform, medium- to Savannah woodland of E. populnea, some- II-IlIk2_a Along silty texture mainly; up fine-textured alluvial soils, times forming mixed shrub woodland Mackenzie to 40 ft above river; not Clematis (Um5.5, Uf6.31) (Carissa, Eremophila, Citriobatus); ground River flooded cover of Bothriochloa and Aristida 15% Sandy levees and small Mainly texture-contrast Savannah woodland of E. tessellaris, E. IVp^, Sporadic sand sheets; up to 30 ft soils with thick sandy sur- melanophloia, and E. tereticornis, dense m above river; not flooded face horizons and neutral ground cover of Heteropogon, Bothriochloa, 3 subsoils, Luxor (Dr.4.22, and Chloris Dy5.22); minor uniform coarse-textured alluvial soils, Davy (Uc5.11)

3 50% Alluvial plains, terraces, Texture-contrast soils Savannah woodland of E. populnea; fair IVp3_4 Widespread and levees; up to 2 miles with sandy surface hori- ground cover of Bothriochloa, Heteropogon, wide; occasionally zons and neutral to and Chloris flooded in lowest parts strongly alkaline sub- only soils, mainly Springwood (Dbl.22, Dr2-22) and Broadmeadow (Dbl.23); minor Luxor (Dy3.42)

4 <5% Texture-contrast soils Mixed shrub woodland (E- populnea, Cap- IVp3_4 Sporadic with thin sandy surface paris, EremophUa, Bauhinia, Geijera, Venti- horizons and neutral to lago, and many others); ground cover of alkaline subsoils, Spring- Chloris, Aristida, and Enneapogon wood and Taurus (Dbl.32, 1.43) 5 10% Mainly alluvial soils, Savannah woodland of E. populnea and E. III-IV In south Warrinilla (Gn4.42, 4.31), melanophloia, either species predominating; only Consuelo (Uf6.33), and ground cover mainly Bothriochloa Moolayember (Um5.5); minor texture-contrast soils, Wyseby (Ddl.22)

6 10% Back swamps and minor Cracking clay soils, main- Brigalow with scattered E. microtheca, Ter- Vwd_0, g, Along occurrences of gilgaied ly Vermont (Ug5.15, minalia, Eremophila, E- cambugeana, and margins deeply weathered clay; 5.16); minor gilgaied clay Bauhinia; sparse Paspalidium, Sporobolus mostly flooded soils, Pegunny (Ug5.16) mitchellii,Bassia tetracuspis,a.nd Bothriochloa 7 <5% Channels; usually single As unit 2 with Casuarina cunninghamiana Widespread and 15-35 ft deep; in and Melaleuca common on stream banks flood-out areas braided and 5-15 ft deep; bed- load sand; some permanent water-holes * Similar to Alpha land system in the Nogoa-Belyando yrea and Dingo land system in the Dawson-Fitzroy area. 34 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

COTHERSTONE LAND SYSTEM* (580 SQ MILES) Stony hills and lowlands on weathered Permian sandstone and shale, mainly in the west of the area; texture- contrast soils; savannah woodland (ironbark) or mixed shrub woodland (box).

Land Land Area and Land Forms Soils Vegetation Unit Dis tribution Class

1 30% Hills and strike ridges; Mainly shallow rocky Savannah woodland of narrow-leaved iron- VIta, d,_B In extreme local relief 30-100 ft; soils, Shotover (Ucl.2); bark and lancewood over Heteropogon, north and slopes up to 15%; often small pockets of uniform Aristida, and Chrysopogon; patches of Acacia Cherwell stony with outcrops coarse-textured soils, cunninghamii, Alphitonia, and Petalostigma Range Petrona (Ucl .23) and Highmount(Uc5.11); and texture-contrast soils, Luxor (Dy3.21)

2 5% Shallow sandy red earths, Lancewood with E. thozetiana, and (where VItB, d, Sporadic Gregory (Gnl.12); minor stony) shrubs, over Aristida, Calyptochloa areas of shallow texture- gracillima, Paspalidium, and Ancistrachne; contrast soils, Southern- patches of bloodwood, Acacia cunninghamii, wood (Dr3.ll); much Alphitonia, and Petalostigma, ground cover gravel as in unit 1

3 30% Undulating terrain and Texture-contrast soils, Savannah woodland of narrow-leaved iron- IVp3_4 East of low indefinite strike mainly with thick sandy bark, E. melanophloia, or E. populnea over Springs ure ridges; local relief 10-50 surface and acid to neutral Heteropogon, Aristida, Cyperaceae, and and round ft; slopes up to 10%; subsoils, Luxor (Dy5.21, Eragrostis; patches of bloodwood, etc. as in Cherwell sandy or stony as a rule 3.21), minor Springwood unit 2 Range with some outcrops (Dy3.22, Dbl.32) 4 30% Undulating terrain and Texture-contrast soils, Mixed shrub woodland of E. populnea with Widespread gentle colluvial foo t slopes mainly with thin sandy Eremophila, Capparis, Erythroxylum australe, below units 1, 2, and 3; surface horizons and acid and many others; sparse Heteropogon, local relief up to 20 ft; to neutral subsoils, Bothriochloa decipiens, Aristida, and Chloris slopes up to 5%; sandy Springwood (Dy3.21, surface common; gully- 2.42), some Taurus ing active (Dy3.23, Dr2.13)

5 Sandy alluvial flats with Texture-contrast soils, Mixed shrub woodland, commonly E. lVp3_4)m3 Widespread single meandering chan- Luxor (Dy3.42), and uni- populnea with very varied shrubs; some nels; up to i mile across; form coarse-textured al- savannah woodland of E. melanophloia; not flooded luvial soils, Davy ground cover of Aristida, Eragrostis, and (Uc5.11) Heteropogon

6 <5% Sharply dissected sand- Dark brown and grey- Savannah woodland, E. maculata and some VIt8, e. South of stone and conglomerate brown soils, Ingelara narrow-leaved ironbark with patches of Reid's hills ( U m4.2); and tex ture- Acacia cunninghamii; good cover of Dome contrast soils, Spring- Themeda, Eremochloa, Cymbopogon, and wood (Dy2.12) Heteropogon

* Similar to Hope land system in the Nogoa-Belyando area. LAND SYSTEMS OF THE ISAAC-COMET AREA 35

DAUNIA LAND SYSTEM (480 SQ MILES) Lowlands with brigalow and cracking clay soils on weathered and fresh Permian shales and lithic sandstone in the north and centre.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class 1 15% Rises and low hills; local ~No observations; prob- Savannah woodland of narrow-leaved iron- IV-VIl,, Widespread relief 10-100 ft; slopes up ably red and yellow earths bark and E. populnea, patches of Acacia to 15%; outcrop com- cunninghamii, Alphitonia, and Petalostigma; mon; also some sandy fair ground cover of Heteropogon, Bothrio- aprons with slopes 2-5% chloa, and Aristida

2 10% Lowlands and very low Texture-contrast soils Mixed shrub woodland, commonly E. IVp3_4 Sporadic strike ridges; local relief with thin sandy surface populnea with a great variety of woody 10-30 ft; slopes up to and neutral subsoils, associates (Bauhinia, Brachychiton, briga- 3%; probably some out- Springwood (Dr2.12, low, Canthium vacciniifolium, Capparis, crop; gravelly in places Dbl.32) Carissa, Croton phebalioides, Eremophila); ground cover rather sparse (Bothriochloa, Aristida, Chrysopogon, Enneapogon)

3 5% Texture-contrast soils Mainly brigalow and scattered E. cambage- IVp3-4 Sporadic with thin sandy surface ana, with Carissa, Eremophila, and Ter- and strongly alkaline minalia over scanty ground cover of subsoils, Taurus (Dy3.43, Paspalidium, Aristida, Chloris, and Ennea- Ddl .13), minor Spring- pogon wood (Dy3.42) 4 15% As unit 2 but slightly Cracking clay soils, Mixed shrub woodland, very varied, com- ll-UIea-j, Sporadic lower Teviot(Ug5.12)andRol- monly brigalow, Carissa, Eremophila, Ter- leston (Ug5.34) minalia (abundant between Fairhill and Emerald), E. populnea, Erythroxylum australe, Bursaria spinescens, Brachychiton, Geijera, Owenia, Canthium vacciniifolium, E. cambageana:, ground cover as in unit 1 5 50% Cracking clay soils, Brigalow, usually with Carissa, Eremophila, III-IV Widespread Teviot (Ug5.12, 5.32); and Terminalia; ground cover as in unit 2 e2-s, dH_a, minor texture-contrast P -4 soils, Taurus (Dy2.13) 3

6 5% Plains and depressions; Gilgaied cracking clay As unit 5, with Panicum buncei, Leptochloa IVgi, s3^ Sporadic up to £ mile across; soils, Pegunny (Ug5.38) debilis, Muehleribeckia, and Cyperaceae weathered clay with billy common in depressions and sandstone gravels 36 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

DURRANDELLA LAND SYSTEM (1010 SQ MILES) Hills with lancewood and narrow-leaved ironbark on weathered Tertiary and Permian rocks in the north-west, centre, and south-east; shallow rocky soils.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

1 20% Mesa tops; undulating; Loamy red and yellow Savannah woodland of narrow-leaved iron- IVn3_,,m3 Widespread up to 1 mile across; earths, Dunrobin and bark, bloodwood, Acacia cunninghamii, and slopes generally less than Struan (Um5.2, Gn2.21); Alphitonia; fair ground cover of Heteropogon, 3%; sandy surface; sheet some uniform coarse- Bothriochloa, Themeda, Aristida, and occas- erosion active in steeper textured soils, Petrona ional Triodia; some lancewood and bendee margins (Ucl.21) over Aristida

2 25% Tabular hills; benched Mainly shallow rocky Lancewood or bendee with E. exserta, VIItT, ra Cher well slopes with rocky bluffs; soils, Shotover (Ucl); sparse ground cover {Aristida, Ancistrachne, Range narrow rocky valleys; minor shallow red earths, Calyptochloagracillima, Triodia, Lomandra); local relief 50-200 ft; Gregory (Gn 1.12), and or savannah woodland of narrow-leaved slopes 5-50% shallow texture-contrast ironbark and bloodwood, sometimes with soils, Southernwood Acacia cunninghamii, Erythroxylum australe, (Dy3.51) Alphitonia, and Petalostigma; ground cover of Heteropogon, Themeda, Aristida, Chloris, Chrysopogon, and Eragrostis

3 35% Breakaways and low Shallow rocky soils, Rug- Lancewood or bendee wiih E, exserta and E. V1I-VIII Widespread stony hills below unit 1; by and Shotover; some thozetiana; sparse ground cover {Aristida, local relief 10-200 ft; dark brown and grey- Ancistrachne, Calyptochloa gracillima, Trio- slopes up to 100%; much brown soils, Bullaroo dia, Lomandra) outcrop; rapid sheet ero- (Gn4.31) sion and gullying

4 15% Foot slopes below uniLs 1 Texture-contrast soils, Variable, mainly mixed scrub woodland of !Vp3_, Widespread and 3; undulating; up to Luxor (Dr3.61, Dy3.12) E. populnea, Eremophila, and Carissa or 1 mile long but usually and Wyseby (Dr2.ll) savannah woodland of E. populnea or E. less than 4 mile; upper melanophloia; ground cover of Aristida, parts stony with slopes up Chloris, Chrysopogon, Themeda, Eragrostis, to 10%; lower parts Enneapogon, and Cymbopogon; occasional sandy or locally clayey "scalds" with slopes up to 3%

5 <5% Lower foot slopes; gently Texture-contrast soils, Brigalow, E. thozetiana, and E. cambageana !Vp3_4 Sporadic undulating to level; up to Broadmeadow (Dy3.23) with scanty ground cover of Aristida, I mile long; slopes up to and Taurus (Dy3.43) Chloris, and Paspalidium 2%; weathered shale and clay 6 <5% Alluvial flats, usually No observations; prob- Savannah woodland of narrow-leaved iron- Widespread sandy with single mean- ably texture-contrast soils bark and E. citriodora, or E. populnea, or E. dering channels up Lo mainly melanophloia, ground cover fair, of Themeda, 10 ft deep Heteropogon, and Chrysopogon; channels of E. tereticornis and E. tessellaris over Ihe same grasses; some brigalow and E. cambageana over Aristida LAND SYSTEMS OF THE ISAAC-COMET AREA 37

FUNNEL LAND SYSTEM* (465 SQ MILES) Flood-plains with coolibah along major streams and in basalt areas; cracking clay soils.

Land Land Area and Land Forms Soils Vegetation Unit Distribution Class

1 15% Levees; mainly silly; not Texture-contrast soils, Savannah woodland of E. populnea, E. IVP»_4 Widespread flooded Luxor (Dy3.42) and tessellaris, E. tereticornis, and E. microtheca, Taurus (Dr2.13) sometimes with Acacia, Cassia brewsten, and Bauhinia to form a mixed shrub woodland; dense ground cover (Heteropogon, Bothriochloa, and Chloris)

2 15% Higher alluvial plains; Cracking, self-mulching Downs (dense ground cover of Dichan- II-IIIk2_3 Mainly in practically level; 20-40 ft clay soils, Vermont thium, Bothriochloa, Thellungia advena, and north-west above channels; up to 1 (Ug5.16) Cyperaceae); scattered E. m'tcrotheca mile across; silt and clay mainly; not flooded

3 10% Lower alluvial plains; Cracking clay soils, Ver- Brigalow, woody associates scattered VWt-5, Sporadic generally level but occas- mont (Ug5.15, 5.25) throughout (E. microtheca, Terminal ia, ionally with faint channels Eremophila, E. cambageana, Bauhinia); and levees; mainly clay; ground cover usually sparse (Paspaliclium, flooded Sporobolus mitchellii, Bassia tetracuspis, Bothriochloa, with Panicum buncei, Lepto- chloa debilis, Muehlenbeckia, and Cyperaceae common in depressions)

4 55% Cracking clay soils, Ver- Savannah woodland of E. microtheca with Widespread, mont (Ug5.16, 5.4); minor dense ground cover of Dichanthium, Bothrio- especially uniform fine-textured al- chloa, Aristida latifolia, Panicum queens- on Funnel luvial soils, Clematis landicum, Cyperaceae, and Thellungia Creek (Uf6.33) advena; Muehlenbeckia and Leptochloa debilis common in depressions

5 5% Channels; usually braided No observations, prob- Banks as in unit 1 Widespread and 3-10 ft deep; occas- ably recent alluvial soils ionally single and 10-40 ft deep; bed-loads sand and silt

* Similar to Coolibah land system in the Dawson-Fitzroy area. 38 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

GIRRAH LAND SYSTEM (525 SQ MILES) Lowlands with downs and brigalow and cracking clay soils on unweathered Permian shale and lithic sandstone in the north and centre.

Land Area and Land Forms Soils Vegetation Land Unit Distribution Class 1 30% Lowlands and low rises; Mainly shallow cracking Open savannah woodland of E. orgadophila, IVd^e^ Widespread local relief 10-100 ft; clay soils, Bruce (Ug5.12); E. populnea, E. dichromophloia, E. papuana, slopes 2-5%; mainly clay minor shallow texture- narrow-leaved ironbark, or E. melanophloia on shales but some stony contrast soils, Southern- over dense ground cover of Dichanthium, patches on sandstone wood (Dr2.12) Bothriochloa, Themeda, Heteropogon, Isei- lema, Cymbopogon, Aristida latifolia, and Enneapogon

2 45% Lowlands and plains on Cracking clay soils, Tevio t Downs, dense grass flora as in unit 1 II-IIIe2_3, Widespread shales and detrital clay; (Ug5.15), commonly with d - slopes 0-5% linear gilgai; minor dark 2 3 brown and grey-brown soils, Cheshire (Gn3.93)

3 5°/ Texture-contrast soils Open savannah woodland mainly of E. IVpa-4, Mainly near mainly with thin sandy populnea, some E. melanophloia and E. e2_3 Girrah surface horizons and orgadophila; ground cover as in unit 1 s Lrongly alkaline subsoils, Taurus (Dr2.13, Ddl.23), minor Wyseby (Dr2.22)

4 20% Texture-contrast soils, Brigalow, with varied associates (Carissa, III-JV Widespread Taurus (Dbl.33), and Eremophila, Terminalia, Denhamia obscura, cracking clay soils, Rol- Acalypha eremorum, Brachychiton, Can- leston (Ug5.24) thium vaccinii'folium, Croton phebalioides, Erythroxylum australe); fair to scanty cover of Paspalidium, Aristida, Chloris, Ennea- pogon, Cheilanthes hirsuta, and mosses

5 <5% Alluvial flats; up to i No observations; prob- Savannah woodland of E. tessellaris and E. Widespread mile wide; mainly clay; ably texture-contrast soils tereticornis or of E. populnea, ground cover probably flooded in parts; mainly of Heteropogon both single and braided channels LAND SYSTEMS OF THE ISAAC-COMET AREA 39

HILLALONG LAND SYSTEM (120 SQ MILES) Lowlands with box and ironbark and texture-contrast soils on little-weathered Permian shale and sandstone in the north and near Consuelo in the south-west.

Land Area and Land Forms Soils Vegetation Land Unit Distribution Class

1 90% Undulating lowlands and Mainly shallow texture- Savannah woodland, tops of rises narrow- IVd,,e2_3 Throughout very low strike rises; local contrast soils, Medway leaved ironbark and bloodwood, slopes E. relief 10-50 ft; slopes up (Dr2.23, Dbl.23) and populnea, fairly dense ground cover Hetero- to 6% but usually less; Southernwood (Dr2.12); pogon, Bothrlochioa decipiens, Themeda, minor outcrops on some minor deep texture-con- Chrysopogon, Aristlda, Enneapogon^ Cyper- crests; limited sandy fans trast soils, Springwood aceae, Eragrostis, Panicum, Chloris; trees up to 1 mile long below (Dbl.22) and Taurus often denser along strike lines and rock out- sandstone ranges (Dr2.13) crops, sometimes with non-eucalypts to form a mixed shrub woodland

2 Plains and shallow strike One observation; cracking Open savannah woodland of E. populnea or HId2_3, Widespread vales, up to i mile wide clay soils, Teviot (Ug5.14) downs, grasses as in unit 1

3 <5% As for unit 2 but billy One observation; very Brigalow, sometimes in bands along strike nis3,k2_3 In Consuelo gravel common deep cracking clay soils, lines, with Carissa, Eremophila, and Ter- area strongly alkaline near the minalia; south of the Springsure—Duaringa surface and moderately highway with abundant Geijera and rare acid beneath, Rolleston Termination, sparse ground cover of Paspa- (Ug5.15); surface strew lidium, Aristida, Chloris, Enneapogon, Cheil- of billy gravel anthes sp., and mosses 4 <5% Alluvial flats less than £ No observations; prob- Savannah woodland of E. populnea or E. Sporadic mile wide; single channels ably texture-contrast soils melanophloia, in the north of the area with 2-5 ft deep mainly some E. orgadophila, in the south with some Angophora floribunda, E. tereticornis common along creek banks; ground cover fairly dense, of Heteropogon and Bothriochloa 40 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

HUMBOLDT LAND SYSTEM* (2245 SQ MILES) Blackbutt and brigalow on weathered clay plains occurring in most parts of the area; texture-contrast and cracking clay soils.

Land Area and Land Forms Soils Vegetation Land Unit Distribution Class

1 Crests of rises and low Mainly loamy red and yel- No consistency; bendee or lancewood over IVn3_3,m3 Sporadic hills; sandy; local relief low earths, Dunrobin Aristida, or savannah woodland of blood- 10-50 ft (Um5.5) and Siruan wood and ironbark over Heteropogon, or (Gn2.22); minor sandy mixed shrub woodland grading into sofL- red earths, Annandale wood scrub (Gn2.12)

2 10% Slight rises; local relief Texlure-contrast soils, Mixed shrub woodland of E. populnea, E. IVpS_fl, Sporadic 5-30 ft; sandy or loamy Luxor (Dr2.22), Taurus cambageana, and brigalow with Eremophila e - surface; some gullying and (Dy2.43), and Broad- and Terminalia over scanty ground cover of 3 4 sheet erosion; includes meadow (Dbl.13) Bothriochloa, Aristida, and Heteropogon some sandy colluvjal aprons below unit 1

3 45% Plains and lowlands; Texture-contrast soils with Brigalow and E. cambageana, often open, IVp - Widespread slopes less than 2%; up to thin sandy or loamy with Carissa, Eremophila, and Terminalia; a 4 10 miles across; deeply surface soils and strongly scanty ground cover of'Paspalidium, Aristida, weathered Tertiary clay alkaline subsoils, Taurus Chloris, and Enneapogon and older rocks; quartz (Ddl.l3,Dbl.23,Dy2.43) and billy gravel common and Retro (Ddl. 13) in places 4 25% Cracking clay soils, Rol- Brigalow and mixed shrub woodland with HIs3,k2_8 Widespread leston (Ug5.16) occasional E. cambageana and (in Morpeth area) abundant Terminalia, other shrubs and ground cover as in unit 3

5 10% Plains and shallow depres- Gilgaied cracking clay Brigalow and mixed shrub woodland with IVg4,s,_4, Widespread sions ; slopes less than 1 %; soils, Pegunny (Ug5.16, occasional E. cambageana, other shrubs and up to 4 miles across; 5.24) ground cover as in unit 3; Leptochloa debiHs, weathered clay with deep Muehlenbeckia, and Cyperaceae common in gilgai; narrow alluvial depressions flats with braided channels

6 10% As unit 5 but gilgai only Mosaic of cracking clay Small separate communities of brigalow and IVs3_4, Sporadic sporadic soils, Rolleston and Pe- mixed shrub woodland with E. cambageana; P3-4 gunny, and texture-con- shrubs and ground cover as in unit 3 trast soils, Taurus and Retro * Similar to Thomby land system in the Dawson-Fitzroy area. LAND SYSTEMS OF THE ISAAC-COMET AREA 41

JUNEE LAND SYSTEM* (685 SQ MILES) Tablelands and plains with narrow-leaved ironbark and red and yellow earths on intact Tertiary land surface throughout the area except in the north-east and extreme south.

Land Area and Land Forms Land Unit Distribution Soils Vegetation Class 1 20% Tablelands; level to gently Mainly loamy red earths, Savannah woodland of narrow-leaved iron- IVn^, Junee undulating; up to 4 miles Dunrobin (Gn2.12, Urn bark, bloodwood, Acacia cunninghamii, m3 Tableland across; slopes generally 5.2), minor loamy yellow Alphitonia, Petalostigmat and E. tenuipes less than 2%; sandy sur- earths, Struan (Gn2-22); over fair cover of Heteropogon, Bothriochloa, face; shallow, oval clay extensive sandy red earths Themeda, Arisiida, and occasional Triodia; depressions up to 1 mile in areas of quartz sand- some lancewood and bendee over Aristida; across stones, Annandale (Gn in depressions, savannah woodland of 2.12, 2.11); shallow silts E. tereticornis over water-weeds and fine sands with blocks of massive lateri te in depressions

2 5% Scarps and hills; l(M00 Shallow rocky soils, Shot- Lancewood or bendee with E. exserta, and VItB, r5 Mainly ft high; stony with much over (Ucl.2), and shallow sparse ground cover {Aristida, Ancistrachne, round Junee outcrop red earths, Gregory (Gn Calyptochloa gracillima, Triodia, Lomandra Tableland 1.12) sp.)

3 50% Plains and undulating Loamy red and yellow Savannah woodland of narrow-leaved iron- IVn3_4, Bombandy earths, Dunrobin (Gn2.12) bark and bloodwood over Heteropogon and country; up to 5 miles Pa-., ea area across; slopes less than and Struan (Gn2.22, Bothriochloa, with patches of Acacia cunning- 2%; sandy or loamy Um5.2); minor sandy red hamii, Alphitonia, and Petalostigma over the surface earths, Annandale (Gn same but sparser grasses 1.12), on upper slopes, grading to texture-contrast soils, mainly Luxor (Dy5.21, Dr4.22), some Broadmeadow (Dy3.43), and Springwood (Dbl.22) on lower slopes

4 20% Lowlands and gentle foot Texture-contrast soils, Savannah woodland of E. populnea and IVp3_, Widespread slopes below units 1 and Luxor (Dy3.21), Broad- some narrow-leaved ironbark over Both- 3; up to 3 miles across; meadow (Dy3.43), Spring- riochloa and Heteropogon; some mixed slopes less than 3% wood (Dbl.22), and Taur- shrub woodland in the east {Macropter- us (Dy3.23) anthes, Erythroxylum australe, Brachychiton, Geijera, Acacia cunninghamii, sparse Chryso- pogon, Heteropogon, Cymbopogon, Aristida, Enneapogon)

5 5°/ Depressions and lowest Texture-contrast soils with Softwood scrub or brigalow with Carissa, IVp3_4 South of parts of units 3 and 4; thin sandy or loamy sur- Eremophila, and Terminalia, ground cover Comet weathered clay often with face soils, Wyseby (Dd Paspalidium, Aristida, Chloris, Enneapogon, Downs billy or ironstone gravel 1.32) and Retro (Dbl.43); Cheilanthes sp., and mosses, some savannah minor cracking clay soils, woodland of E. alba over Bothriochloa and Rolleston(Ug5.16) Heteropogon between Rookwood and Ver- mont Park * Similar to Kaiuroo land system in the Dawson-Fitzroy area. In the north-west this land system is the same as the Lennox land system in the Nogoa-Belyando area. 42 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

MONTEAGLE LAND SYSTEM (1655 SQ MILES) Lowlands vvith box and texture-contrast soils on undissected Tertiary land surface throughout the area except in the extreme south and north-east.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

<5% Rises and inlerfluves; un- Sandy red earths, Annan- Savannah woodland of E. tessellaris, E. IVn3_4l Widespread dulating; up to 2 miles dale (Gn2.12, 1.12) polycarpa, narrow-leaved ironbark, and E. m3 across; local relief 10-50 papuana, some E. melanophloia; patches of ft; slopes up to 3 %; gener- Acacia cunninghamii, Alphitonia, and Petalo- ally sandy or loamy sur- stigma; fair ground cover of Heteropogon, face Chrysopogon, and Aristida

2 15% Gentle slopes just below Texture-contrast soils Savannah woodland of narrow-leaved iron- IVp3_. Sporadic unit 1 with thick sandy surface bark over fair ground cover of Bothriochloa and acid to neutral sub- and Aristida soils, Luxor (Dy3.21) 3 70% Plains, lowlands, colluvial Texture-contrast soils Savannah woodland, mainly E. populnea; a IVpa-i, Widespread foot slopes below unit 1; with thick sandy surface little E. alba with some narrow-leaved iron- up to 4 miles across; level and neutral to strongly bark, E, tessellaris, and E. papuana; shrubs to gently undulating with alkaline subsoils, mainly uncommon (Grewia retusifolia, Melaleuca slopes less than 3%; local Broadmeadow (Dy3.23), nervosa, Capparis, Eremophila); rather poor relief 5-20 ft; occasional- extensive Luxor (Dy3.42) grass cover (Heteropogon, Bothriochloa, ly gravelly; some gullying Chrysopogon, Aristida, Chloris)

4 5% As unit 3 but rather more Texture-contrast soils, Mixed shrub woodland of E. populnea, IVp3-4, Sporadic gravel mainly Taurus (Dy2.23, Eremophila, and Carissa, less commonly with 3.23) with thin sandy sur- other trees and shrubs; ground cover rather face and strongly alkaline sparse, of Chrysopogon, Chloris, Aristida, subsoils, commonly with and Ancistrachne columnar structure, minor Springwood (Dy3.22, Dr2.32) and Broad- meadow(Dy3.23,Dr2.13) 5 5% Depressions, shallow val- Cracking clay soils, com- Brigalow with Carissa, Eremophila, and ITI-IV

Widespread leys; level to gently undu- monly gilgaied, Pegunny Terminalia over Paspalidium, Aristida, S3-4,g4, lating; less than \- mile (Ug5.24) and Rolleston Chloris, Enneapogon, Cheilanihes sp., and k _ across; local relief 0-10 (Ug5.16, 5.34) mosses a 3 ft; weathered Tertiary clay; occasionally with gilgai and gravel

6 <5% Alluvial flats up to \ mile Texture-contrast soils, Mixed shrub woodland or brigalow, as in IVP3-4 Widespread wide; usually sandy; not Broadmeadow (Dy3.23) units 4 and 5; E. tereticornis common along flooded as a rule; usually creek banks a single channel 5-20 ft deep LAND SYSTEMS OF THE ISAAC-COMET AREA 43

MOOROOLOO LAND SYSTEM (135 SQ MILES)

Gravelly Interfluves with silver-leaved ironbark and texture-contrast soils overlying basalt east of Springsure.

Land Area and Land Forms Soils Vegetation Land Unit Distribution Class

1 85% Broad interfluves; gently Texture-contrast soils Open savannah woodland (£•. melanophloia IVP3-4 Widespread undulating; slopes up to with thin sandy or loamy with some£. dichromophloia, E. orgadophila, 2%; up to 3 miles across; surface soils and neulral and E. papuana) over dense ground cover of gravelly clay on weathered to alkaline subsoils, Dichanthium, Bothriochloa, Themeda, Hetero- basalt Wyseby (Dr2.12, DbU2) pogon, Iseilema, Cymbopogon, Aristida and Taurus (Dr2.13, latifolia, and Enneapogon Dbl.13); minor areas of reddish brown cracking clay soils, Glenora (Ug- 5.37); some quartz gravel mainly in surface horizons 2 Lowlands on fresh basalt; Moderately shallow Downs, dense ground cover of Dichanthium, II-III Sporadic undulating slopes up to cracking clay soils, Arc- Bothriochloa, Themeda, Heteropogon, Isei- e - , d 5%; up to 1 mile across turus (Ug5.12) lema, Cymbopogon, Aristida latifolia, and 2 B 3 Enneapogon

3 As unit 1 No detailed observations; Brigalow with various associates (Carissa, Sporadic mainly cracking clay soils Eremophila, Terminalia, Casuarina cristata, (Ug5.1); minor texture- Geijera, sparse ground cover of Paspalidium, contrast soils, Taurus Aristida, Chloris, Enneapogon, Cheilanthes (Dr2.13) sp., and mosses) 4 Alluvial flats; up to i No observations; prob- Savannah woodland; where sandy, E. tereti- Sporadic mile wide; generally clay; ably cracking clay soils, cornis and E. tessellaris; where clayey, E. single channels 5-15 ft Vermont microtheca, Terminalia, and Melaleuca deep bracteata; ground cover of dense Hetero- pogon and Bothriochloa 44 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

NEBO LAND SYSTEM (180 SQ MILES) Lowlands with bloodwood, box, and ironbark on Lower Bowen Volcanics and gravel derived therefrom in the north-east of the area; cracking clay and texture-contrast soils.

Land Area and Land Forms Land Unit Distribution Soils Vegetation Class 1 60% Lowlands and plains; Cracking clay soils, May Savannah woodland, varied trees (E. III-IV Throughout level to gently undulating; Downs (Ug5.14), andtex- papuana, E. tessellaris, E. alba, narrow- Pj-i. r up to 4 miles across; ture-contras t soils with leaved ironbark, E. melanophloia, E. orgado- s gravelly surface as a rule thin sandy or loamy sur- phila, E. populnea), fairly dense ground face horizons and neutral cover of Bothriochloa, Heteropogon, Dichan- to alkaline subsoils, thium, and Themeda Taurus (Db 1.13) and Wyseby (Dr2.12)

2 35% Lowlands on volcanic Mainly shallow reddish Open savannah woodland of narrow-leaved IVd,, ea Along rocks; undulating with brown cracking clay soils, ironbark, E. polycarpa, and E. dichromo- Bruce occasional low rocky Bruce (Ug5.37); minor phloia, grasses as in unit 1, but cover denser Highway rises; up to 4 miles across; shallow texture-contrast slopes up to 5% soils, Southernwood (Dr- 2.12)

3 5% Alluvial flats; sandy and Mainly texture-contrast Savannah woodland, mainly of E. populnea IVp3_4 Sporadic flooded in vicinity of soils, Taurus (Dbl.43); over Bothriochloa; E. lessellaris and E. major channels; else- minor cracking clay soils, tereticornis on levees; Casuarina cunning- where forms silty terraces Vermont (Ug5.16) hamiana along channels above flood level LAND SYSTEMS OF THE ISAAC-COMET AREA 45

OXFORD LAND SYSTEM (1000 SQ MILES) Downs and cracking clay soils on slightly weathered or unweathered basalt widespread throughout the area.

Land Area and Land Forms Soils Vegetation Land Unit Distribution Class 1 20% Low rises, ridge crests, Shallow to moderately Open savannah woodland of E. melano- III-IV Sporadic and valley sides; slopes shallow cracking clay phloia, E. dichromophloia, E. orgadophila, da-i, e2_3 up to 5 %; minor outcrops soils, Bruce (Ug5.12) and and E. papuana over dense ground cover of common Arcturus (Ug5,12); minor Dichanthium, Bothriochloa, Heteropogon, reddish brown cracking Iseilema, and Aristida latifolia; Panicum clay soils, Glenora decomposition and Aristida leptopoda com- (Ug5.37, 5.32); minor mon near and to the south of Emerald shallow rocky soils, Rug- by, near outcrops 2 20% Broad, gently undulating Moderately shallow Downs, ground cover as in unit 1, with II-III Widespread to level interfluves and cracking clay soils, Arc- minor differences d3_3,k2)e2 plains; slopes less than turus (Ug5.12); minor 3 %; minor pa tches of shallow cracking clay gravelly clay; some ex- soils, Bruce (Ug5.12); tremely stony areas near stony phases in some Burton Downs and Planet areas Downs

3 55% Gentle middle and lower Mainly deep cracking clay IIe3, k2 Widespread slopes, largely colluvial; soils, May Downs slopes up to 3%; occas- (Ug5.12,5.16), stones and ional gullies linear gilgai in places; minor moderately shallow, cracking clay soils, Arcturus (Ug5.12)

4 Narrow alluvial clay flats; Deep, cracking clay soils Savannah woodland of E. microtheca, IIIw3, k3 Sporadic single or braided channels on basaltic alluvium, Ver- Tenninalia, and Melaleuca bracteata; ground 3-10 ft deep mont (Ug5.15) cover as in unit 1, with minor differences 46 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

PERCY LAND SYSTEM (300 SQ MILES) Mountains, shallow rocky soils with narrow-leaved ironbark and mountain coolibah on volcanic rocks in the south-west, west, and north.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class 1 80% Basalt mountains; steep, Shallow rocky soils, Savannah woodland; near Consuelo table- VII-VIII In south- benched and cliff ed Rugby (Uml) land of narrow-leaved ironbark, E. dichro- west slopes; local relief 500- mophloia, and E. microcarpa with Macro- 1500 ft; slopes up to ver- zamia common below and dense ground tical but generally around cover of Themeda; further north, E. 60%; much outcrop; also orgadophila, and E. dichromophloia, with undulating rocky summits dense ground cover of Themeda, Hetero- and deep fairly narrow pogon, and Bothriochloa valleys with limited alluvial flats and bouldery terraces

2 10% Volcanic plugs; very Shallow rocky soils, Rug- Mixed shrub woodland, trees commonest in VIIIt7,rs In north and sleep isolated mountains by (Uml); minor areas of sheltered places, grasses sparse (E. exserta, west up to 1000 ft high; much reddish brown cracking narrow-leaved ironbark, E. citriodora, E. bare rock clay soils, Glenora (Ug- polycarpa, Acacia curvinervia, A. cunning- 5.37) hamii, Macrozamia, Xanthorrhoea, Triodia, Cymbopogon, Aristida) 3 10% S teep to rugged very Mainly shallow rocky Savannah woodland (narrow-leaved iron- VII-VIII In north rocky hills up to 500 ft soils, Shotover (Ucl); bark over Heteropogon) t7,r5 (Mt. Flora high on granite and meta- minor areas of shallower and Mt. morphic aureoles texture-contrast soils, Gotthardt) Southernwood (Dy3.22) LAND SYSTEMS OF THE ISAAC-COMET AREA 47

PLANET LAND SYSTEM* (400 SQ MILES) Sandy lowlands, plateaux, and low hills, shallow uniform coarse-textured soils with narrow-leaved ironbark and bloodwood on quartz sandstone in the south-east, west, and north.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

1 35% Quartz sands tone hills; Mainly uniform coarse- Shrub woodland, sandstone form, mostly VIIt7,rs Widespread local relief 50-150 ft; textured soils, Petrona narrow-leaved ironbark, bloodwood, and slopes up to 15%; rocky andHighmount(Ucl.21); E. cloeziana over scattered tall shrubs with much outcrop minor shallow red earths, (Lysicarpus angustifolius, Acacia, Astro- Gregory (Gn2.11); tricha pterocarpa, Xanthorrhoea, Petalo- strongly to extremely acid stigma, Erythroxylum australe, Hakea) and denser low shrubs (Dodonaea, Notelaea 2 10% Stony colluvial foot slopes Uniform coarse-textured ovata, a dwarf Petalostigma, Hovea, VIt6>r3 Widespread below unit 1; local relief soils, Highmount (Uc- Boronia); ground cover sparse (Triodia, 10-50 ft; gravelly surface 4.11); minor texture-con- Caustis, Patersonia, Hardenbergia violacea, with some outcrop; gul- trast soils, Southernwood Pomax umbellatd); occasional lancewood lying (Dy3.42) patches 3 50% Plateaux, lowlands, and No observations. Prob- Presumably as in unit 1 (air observations Upper plains presumably on ably shallow rocky soils, only) valley of weathered sandstone Sholover Planet Creek

4 5% Narrow alluvial fla ts; One observation. Tex- Shrub woodland as unit 1; but with fewer IVp3_4 Sporadic sandy with single chan- ture-contrast soils with shrubs, no Triodia, and an admixture of E. nels 5-20 ft deep thick sandy surface and citriodora, Angophora costata, A. floribunda, acid subsoil, Luxor (Dy- and Imperata cylindrica 3.41) * Similar to part of the Nathan land system in the Dawson-Fitzroy area. 48 R. STO'RY, R. W. GALLOWAY, AND R. H. GUNN

RACECOURSE LAND SYSTEM* (165 SQ MILES) Softwood scrub and brigalow lowlands with cracking clay soils on weathered basalt, mainly in the south.

Land Area and Land Unit Distribution Land Forms Soils Vegetalion Class

1 35% Lowlands; gently undu- Dark brown and grey- Softwood scrub (Terminalia, Canthium IVd4, e3 Widespread lating; up to 5 miles brown soils, mainly Gin- vaccinii/olium, Erythroxylum australe, Mac- across; slopes generally die (Uf6.33 on secondary ropteranth.es, Denhamia obscura, Carissa, less than 5%; gravelly in carbonate), minor Ches- Citriobatus); sparse ground cover of Pas- places; occasional low hire (Uf6.33) and Bul- palidium, Aristida, Chloris, Enneapogon, rises with outcrop laroo (Gn4.32) Cheilanthes sp., and mosses 2 45% Mainly dark reddish Brigalow, often with an admixture of soft- II-III Widespread brown to dark brown, wood scrub as in unit I e2—3, k2 alkaline, cracking clay soils, Glenora (Ug5.37, 5.15), minor Rolles ton (Ug5.I4)

3 20% As unit 1, but rather One observation; dark Downs, dense ground cover of Dichan- IVd4 Widespread more rises and outcrop reddish brown shallow thium, Bothriochloa, Themeda, Heteropogon, cracking clay soils on Iseilema, Cymbopogon, Aristida latifolia, and weathered basalt, Bruce Enneapogon (Ug5.32) * Similar to Eurombah land system in the Dawson—Filzroy area. LAND SYSTEMS OF THE ISAAC-COMET AREA 49

REWAN LAND SYSTEM* (310 SQ MILES) Gravelly lowlands with ironbark and box on shales in the south; texture-contrast soils.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

1 15% Low hills; local relief 30- Texture-contrast soils Savannah woodland of narrow-leaved iron- IVp3_, At Morella 150 ft; slopes up to 25%; with thin sandy surface bark and Acacia cunninghamii over sparse extensive sheet erosion on and neutral subsoils, Bothriochloa and Eremochloa some steeper slopes; oc- Springwood (Dy2.22) casionally rocky near crests

2 75% Lowland and lower slopes Texture-contras t soils Savannah woodland of ironbark over sparse IVpa-4 AtBedourie below unit 1; local relief mainly with thin sandy or Bothriochloa, Heteropogon, Aristida, some- and 10-50 ft; slopes up to loamy surface horizons limes with E. populnea or E. microcarpa and Rougemonl 10%; outcrops rare; ex- and acid to neutral sub- Eremophila to form a mixed shrub wood- tremely gravelly in places soils, Wyseby (Dr2.31, land Dbl.ll) and Springwood (Dr2.32, Db2.22), minor Luxor (Dy3.42, 3.22); commonly with gravel or stone in surface soils 3 5% Lowlands on shales and Cracking clay soils, Rol- Brigalow with Geijera, Carissa, and E. ir-iu Sporadic colluvial fans leston (Ug5.34) cambageana, or with Casuarina cristota, k., s, • some softwood scrub (Macropteranthes, Exocarya dallachyana, Casuarina cristata, Acalypha eremorum) 4 5% Alluvial flats; usually Recent alluvial soils, Davy Savannah woodland (E. popuinea, E. mellio- IJI-IV Sporadic sandy with single mean- (Uc5.11) and Moolayem- dora) with some shrubs (Eremophila); fairly W3—i dering channels ber (Ucl .23 on clayey dense ground cover (Bothriochloa decipiens, substrata) Chrysopogon, Arundinella)

* Similar in part to Davy land system in the Dawson-Fitzroy area. 50 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

SKELETON LAND SYSTEM (285 SQ MILES) Dissected slopes with ironbark and shallow rocky soils around the high ranges in the south-west of the area.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class 1 10% S teep upper slopes on Shallow rocky soils, Rug- Savannah woodland of narrow-leaved iron- VIT-VIIT Sporadic basalt; dissected; stony; by (UmlJ bark, E. dichromophloia, and Macrozamia t7,r5 slopes up to 100% over dense Themeda 2 55% Middle slopes and hills; Mainly shallow rocky Savannah woodland of E. melanophloia, E. VII-VIII Widespread local relief 50-300 ft; soils, Rugby (Uml); dichromophloia, and narrow-leaved iron- t7,r5,e4 slopes up to 60%; rocky minor shallow cracking bark over Heteropogon and Bothriochloa; deep gullies common clay soils, Bruce (Ug5.37) gullies with an admixture of E. orgadophila

3 30% Lower slopes; local relief One observation; crack- VIIt7, r5 Widespread 10-100 ft; slopes up to ing clay soils derived from 25%; coarse boulder fans basalt, May Downs (Ug- and terraces common; 5.15) locally derived from basalt 4 5% Alluvial flats; usually One observation; crack- Savannah woodland, mainly E. melanophloia, III-IV Widespread with sandy surface above ing clay soils, Vermont with some Angophora floribunda, fairly wa_4j ka-;, flood level; single chan- (Ug5.15) dense cover of Bothriochloa, Aristida, Era- nels 20-30 ft deep grostis, and some Arundinella; E. tessellaris* E. tereticornis, and Casuarina cunninghamiana along creek banks LAND SYSTEMS OF THE ISAAC-COMET AREA 51

SOMERBY LAND SYSTEM* (365 SQ MILES) Gilgaied plains with brigalow and cracking clay soils on weathered Tertiary clay along the central axis of the area.

Land Area and Land Unit Distribution Land Forms Soils Vegetation Class

1 5% Low rises; local relief up Texture-contrast soils Mixed shrub woodland of E. populnea with IVp3_4 Sporadic to 15 ft; mainly on with thin sandy surface scattered brigalow, associates Carissa, Ere- weathered Tertiary rocks; and alkaline subsoils, mophila, Geijera, Bauhinia, and Cassia some gravelly patches Taurus (Dy2.23, 3.23) brewsteri; scanty ground cover of Aristida, Chloris, and Ermeapogon

2 15% Plains and very gently un- Texture-contrast soils Mixed shrub woodland of E. cambageana IVp3_. Widespread dulating areas; weathered with thin sandy or loamy with scattered brigalow, associates and clay with some billy and surface horizons and ground cover as in unit 1 ironstone gravel; occas- strongly alkaline sub- ional outcrops of pre- soils, mainly Retro (Dy- Tertiary rocks 2.13, Dr2.13), minor Taurus (Db2.43) and Wyseby (Dbl.22) 3 20% As unit 2, but slightly Texture-contrast soils, Brigalow, associates Carissa, Eremophila, III-IV Widespread lower in the landscape Taurus (Dy2.23), grading Terminalia, Geijera, and Bauhinia; scanty Pa-4, Sa_3, to cracking clay soils, ground cover of Paspalidium, Aristida, ka-a Rolleston (Ug5.24) Chloris, Enneapogon, Cheilanthes sp,, and mosses

4 10% As unit 2 Mosaic of texture-con- Mixed shrub woodland of brigalow, E. IVPs-i, g4 Widespread trast and gilgaied crack- cambageana, and E. populnea in small ing clay soils, Taurus separate communities, associates and ground (Ddl.23, Dy2.13) and cover as in unit 1 Pegunny (Ug5.24)

5 50% As unit 2, but in slightly Gilgaied, very deep crack- Brigalow, associates as in unit 3, with IVg4,s,-4 Widespread lower sites; gilgai up to ing clay soils, usually Panicum buncei, Leptochloa debilis, Muehlen- 6 ft deep strongly alkaline at or beckia, and Cyperaceae in depressions near the surface and moderately to strongly acid beneath, Pegunny (Ug5.24, 5.34, 5.38) 6 <5% Alluvial flats mainly clay; Cracking clay soils, Ver- Mixed shrub woodland very variable III-IV Sporadic flooded; up to i mile mont (Ug5.16, 5.34) (brigalow, Erernophila, Terminalia, E. popul- w3_4, k2_3 wide; small braided chan- nea, Muehlenbeckia; sparse ground cover of nels, limited silty levees Bassia tetracuspis, Bothriochloa, Cyper- above flood level aceae, Panicum buncei, Leptochloa debilis, Thellungia advend) s Similar to Highworth land system in the Dawson-Fitzroy area 52 R. STORY, R. W. GALLOWAY, AND R. H. GUNN

WATERFORD LAND SYSTEM (355 SQ MILES) Undulating country and low hills, shallow cracking clay soils with silver-leaved ironbark on little-weathered basalt in the west.

Land Area and Land Forms Land Unit Distribution Soils Vegetation Class

1 55% Mesas and hills; benched Shallow cracking clay Open savannah woodland of E. orgadophila, IVd4,e3_, Widespread rocky slopes; local relief soils, Bruce (Ug5.12, E. dichromophloia, and E. melanophloia with 50-150 ft; slopes up to 5.37); shallow rocky soils dense ground cover of Dichanthium, Both- 60% locally, but usually near outcrops, Rugby riochloa, Themeda, Heteropogon, Iseilema, up to 10% (Ural) Cymbopogon, Aristida latifolia, and Ennea- pogon 2 40% Colluvial aprons; slopes Moderately shallow crack- Downs, dense ground cover as in unit 1 ITi-IV Widespread up to 10% on upper parts ing clay soils, Arcturus ea-4,d3 decreasing to 1 % on lower (Ug5.32) parts; mainly clay with some gravel in upper part; severe gullying in places; also gently undulating lowlands with shallow, widely spaced valleys and occasional outcrops on rises

3 5% Alluvial flats; clay; up to No observations; probably Downs, dense ground cover as in unit 1, IVw3_4 Widespread ^ mile wide; some flood- alluvial cracking clay scattered Acacia farnesiana, Melaleuca ing; braided channels 3- soils, Vermont, and uni- bracteata along gullies, and occasional E. 10 ft deep form fine-textured alluvial microtheca soils, Clematis PART IV. CLIMATE OF THE ISAAC-COMET AREA By E. A. FITZPATRICK*

I. INTRODUCTION (a) Principal Climatic Features The climate of the area has general characteristics intermediate between those of "tropical" and "temperate" climatic types that occur to the north and south respectively. Also, in its prevailing moisture conditions, the climate is transitional between the higher-rainfall zone along the Queensland coast and the semi-arid zone further inland. It is thus difficult to characterize the climate in any concise qualitative descriptive way, but according to Thornthwaite's (1931) classification, the climate may be regarded generally as subhumid. A well-defined summer maximum rainfall is characteristic of the area. The winter season, although dry, normally has rainfalls higher than those typical within the tropical monsoon climates of northern Australia. Day temperatures are high throughout the year, but minimum temperatures during the winter months fall low enough to create a significant frost risk. The seasonal pattern of humidity, cloudiness, radiation, and evaporation is closely related to the characteristic wet summer-dry winter rainfall regime. (b) Principal Climatic Controls The broad character of the climate reflects the sun-controlled latitudinal shifting of the prevailing pressure and wind systems. In Figure 4 the seasonal changes in frequency of winds from eight compass intervals are shown graphically for Emerald. The wind roses are based only upon observations at 9 a.m., and slightly different and more variable wind conditions occur later in the day. Also it must be realized that both the strength and direction of winds are much affected by local terrain conditions. Nonetheless, some seasonal trends are evident in Figure 4, and these may be taken as generally representative for the area. The most persistent general winds are the south-easterlies, commonly known as trade winds. From Figure 4 it is seen that a large proportion of winds throughout the year are from compass points between east and south. The dominance of south- easterly winds is most marked between April and August, that is, during that part of the year when the paths of the eastward-moving anticyclones have a northerly position approximately midway between the northern and southern margins of the continent, and when the intertropical convergence zone has retreated well beyond the northern coasts of Australia. Also at this time the easterly-moving low-pressure * Division of Land Research, CSIRO, Canberra. 54 E. A. FITZPATRICK

systems of higher latitudes exert their greatest control upon weather within the southern parts of the continent. The centres of these systems are, however, usually south of the continent, and their passage is normally realized in the vicinity of the area by no more than either a northward-extending weak trough or a col which sepa-

Fig. 4.—Wind direction and speed at Emerald. Areas enclosed within the eight sectors of the wind roses are proportional to the percentage frequency of winds from directions within those compass intervals, and the area of the central circle is proportional to the percentage frequency of calms. Histograms show percentage frequency of winds with velocities within specified intervals. rates two successive anticyclones. Fine, sunny weather with mild days and cool nights is characteristic at this time, and those falls of rain which do occur are normally light and short-lived. Between September and December there is a weakening of the dominance of south-easterly winds, and an increasing proportion of winds occurs from other CLIMATE OF THE ISAAC-COMET AREA 55

compass points, particularly from the northerly and north-easterly sectors. With intensifying radiation, the daytime temperature rise is rapid in these months, and the daily maximum not infrequently exceeds 90°F. Active localized convection is a characteristic feature of weather within this period. Thunderstorms commonly occur in association with irregular influxes of moist air over the heated land surface during the late spring and early summer period. The occurrence of thunderstorms is reflected in steadily increasing mean rainfall over these months. As seen from Figure 4, the percentage of calm conditions at 9 a.m. decreases markedly during October and November, and winds are highly variable in direction thoughout the day in these months. Although the frequency of calms decreases, high wind velocities are not common at this time, occurring mainly as brief squalls associated with localized convection. From December to March the centres of the anticyclones are normally well to the south of the area, and the character of weather is strongly influenced by low- pressure systems over northern parts of the continent. During this period, south- easterly extending troughs develop at times across Queensland, causing a stream of moist tropical air to reach the area. This situation commonly brings substantial rainfalls along the Queensland coast, and although normally there is a decline in rainfall towards the interior, the area does receive some very beneficial falls by this means. Also during this interval, tropical cyclones developing in the Coral Sea area are most influential. These commonly approach the north-central Queensland coast from the east or north-east and then recurve toward the south-east moving more or less parallel to the central Queensland coast. The centres of some cyclones do cross the coast, and although the characteristic high winds then normally abate quickly as the storm weakens into an inland rain depression, good rainfall is usually received over large areas of central and southern inland parts of the State. It should be emphasized that although the January-March period is distinctly the most favourable for receiving rain, quite lengthy intervals without rain can intervene between the significant falls even at this time, depending upon existing synoptic controls. In extreme cases the total amount of summer rain (November to April) has been less than half of the long-term average for this period. One general effect which the prevalence of tropical cyclones and thunderstorms has upon the character of rainfall is to add to its variability, in terms of both temporal incidence and the amounts received.

II. GENERAL CLIMATIC CHARACTERISTICS (a) Rainfall Mean annual rainfall within the area ranges generally between 22 and 30 in. The isohyetal map in Figure 5 is based upon mean annual rainfalls for all stations having records over the 35-year period 1926-60. This shows two areas of relatively high mean annual rainfall, one in the north in the vicinity of Nebo and another in the south around Warrinilla. The central portion of the area is notably drier with averages generally less than 24 in. The strong concentration of rainfall during the summer months over the whole of the area is seen from the data given in Table 2. Approximately three-quarters of 56 E. A. FITZPATRICK

Fig. 5.—Mean annual rainfall. TABLE 2 MEAN MONTHLY, ANNUAL, AND SEASONAL RAINFALL FOR 13 STATIONS*

Annual May-Oct. Nov.-Apr. Station Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. with S.D.f with S.D.t with S.D.f

Arcturus Downs 402 4-67 2-86 1-45 119 1-40 1-19 0-60 0-95 1-78 2-54 3-63 26-28 711 19-17 ±10-47 ± 403 ± 8-91 Blackwater 350 4-53 2-51 118 1-30 1-21 1-06 0-46 0-80 1-92 2-54 3-21 24-22 6-75 17-47 n ± 7-59 ± 3-50 ± 6-33 C Bombandy 4-73 5-56 2-68 1-48 0-96 1-42 1-12 0-38 0-57 1-49 2-37 3-15 25-91 5-94 19-97 ± 7-24 ± 3-52 ± 6-41 > Comet 3-60 4-27 2-35 115 1-17 1-12 108 0-46 0-58 1-58 2-24 3 04 22-64 5-99 16-65 M ± 7-24 ± 3-25 ± 5-80 O Emerald 3-64 4-49 2-78 1-33 I 08 1-28 1-23 0-54 0-69 1-64 2-79 3-20 24-68 6-46 18-23 ± 9-05 ± 404 ± 6-95 m 105 Gordon Downs 3-58 4-18 2-75 114 1-26 119 0-49 0-65 1-46 2-36 3-02 23 08 619 16-94 t/i ± 9-70 ± 5-82 ± 7-99 > Logan Downs 3-69 4-82 2-56 1-30 104 1-25 107 0-43 0-61 1-37 2-00 3-51 23-71 5-77 17-95 > ± 8-77 ± 4-94 ± 7-66 Nebo 4-90 6-43 4-50 2-00 110 1-61 1-29 0-62 0-53 1-29 1-91 3-55 29-73 6-44 23-29 I ±10-47 ± 3-36 ±8-67 Rolleston 3-39 410 2-49 1-72 1-24 1-43 1-20 0-62 0-93 1 99 2-71 3-43 25-25 7-41 17-84 s ± 8-98 ± 4-20 ± 6-48 > Somerby 3-64 416 2-71 1-51 1-15 1-38 0-90 0-64 0-82 1-81 2-68 3-51 24-92 6-71 18-21 m ± 9-11 ± 413 ± 6-70 > Springsure 421 4-46 2-80 1-67 116 1-61 1 -33 0-69 0-98 200 3-21 3-66 27-76 7-77 21 01 ±11-48 ± 4-55 ±7-33 Warrinilla 3-55 5-31 2-82 1-88 1-44 1-46 1-50 0-72 0-98 2-42 2-78 3-94 28-80 8-52 20-28 ±11-71 ± 5-14 ± 8-66 Westgrove 3-24 3-64 2-67 1-52 1-28 111 1-22 0-70 0-83 202 2-66 3-67 24-56 7-16 17-40 ± 9-48 ± 3-68 ± 6-59 * Source of data: Bureau of Meteorology records, 1926-60. t Standard deviation. 58 E. A. FITZPATRICK

the mean annual rainfall occurs between November and April. An examination of the areal pattern of the percentages of the annual rainfall occurring within the November-April and May-October periods indicates a very small general decline of summer rainfall southward and of winter rainfall northward, a feature not unexpected in view of the prevailing rain-producing mechanisms. Mean monthly falls are highest in February (4-0 to 6-0 in.) and lowest in August and September ( 0-01 in.) throughout the year follow generally the annual regime of the mean rainfall. Data for four stations are included in Table 4. It is notable that although February has considerably higher mean rainfall than January (Table 2), the mean number of rain days for February is only slightly higher, thus indicating a greater likelihood for the daily falls to be heavier during that month. This characteristic can be related to February being a favoured month for well-developed troughs extending across the area from low-pressure centres over the northern part of the continent, as well as to a high incidence of tropical cyclones at that time. The mean number of rain days increases rather abruptly in October from the previous low levels of the winter months, and thereafter it rises steadily until December. Except for Nebo, the values for December do not differ greatly from those for January. This rise is associated with the increasing incidence of thunderstorms during late spring and early summer. The observed areal differences in the mean number of rain days are in general agreement with areal differences in mean rainfall as shown in Figure 5. The highest number of rain days occurs at Nebo, and this is the case throughout the winter season TABLE 3 MONTHLY AND ANNUAL RAINFALLS EXCEEDED IN 10, 50, AND 90 % OF ALL YEARS, COMPARED WITH MEAN RAINFALLS FOR THREE STATIONS*

n Criterion Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year r Bombandy (50 yr of records) > 10% 900 10 00 7 00 3-30 1-80 3-40 2-80 1-80 2-50 3-30 600 7-70 37-50 50% 4-40 3-80 1-90 0-80 0-50 1-20 010 0-30 0-40 0-90 1-90 2-70 25-80 o Mean 4-73 5-56 2-68 1-48 0-96 1-42 112 0-38 0-57 1-49 2-37 3-15 25-91 90% 1-40 100 0-40 010 Nil Nil Nil Nil Nil 0-20 0-30 0-60 15-40 w tn Emerald (75 yr of records) 10% 8-70 8-80 6-30 3-70 3-30 3-90 3-20 210 2-80 3-60 4-60 6-70 3900 $ 50% 3-20 2-90 2-40 0-80 0-60 100 0-60 0-50 0-40 1-20 1-60 2-70 24-40 Mean 3-64 4.49 2-78 1-33 108 1-28 1-23 0-54 0-69 1-64 2-79 3-20 24-69 8 90% 0-60 0-40 0-30 Nil Nil 010 Nil Nil Nil 0-10 0-20 0-40 10-60 o tn Springsure (89 yr of records) H > 10% 8-10 10-00 700 4-20 3-40 410 3-30 2-50 3-00 400 5-40 6-60 39-05 a 50% 3-40 3 00 2-20 0-80 0-90 100 0-70 100 0-80 1-60 1-80 2-80 24-90 > Mean 4-21 4-46 2-80 1-67 116 1 -61 1-33 0-69 0-98 2-00 3-21 3-66 27-78 90% 0-80 0-50 0-20 010 0-10 Nil Nil Nil 010 0-20 0-40 0-50 15-30 ' Data supplied by Department of National Development from records of the Bureau of Meteorology. 60 E. A. FITZPATRICK

in spite of the station's northerly location. This is apparently related to the com- parative nearness of Nebo to the coast.

TABLE 4 PERCENTAGE OF RAIN DAYS WITH FALLS WITHIN SPECIFIED RANGES

Range (in.) Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

Nebo 001-0-24 55 56 57 70 76 68 68 75 75 57 60 53 0-25-0-99 33 29 29 21 18 22 22 7 18 35 31 33 1-00-1-99 9 9 8 4 5 7 9 6 5 6 8 12 2-00-3-99 4 4 4 2 1 3 1 1 1 2 1 3 400-5-99 — 1 1 1 — — — — — — — — >600 — 1 — 2 — — — — — — — — Mean no. of 115 12-2 9-8 5-4 4-3 5 •3 4-1 2-4 2-4 3-9 5-1 7-9 rain days

Bombandy 0-01-0-24 31 23 36 35 43 37 29 41 55 46 45 34 0-25-0-99 39 45 47 46 35 49 50 45 36 41 32 45 1-00-1-99 20 26 13 8 18 8 16 14 4 8 17 15 200-3-99 9 5 4 10 3 6 5 — 4 5 6 5 400-5-99 — 1 — 1 — — — — — — — 1 >600 — 1 — — — — — — — — — — Mean no. of 6-3 6-7 4-8 2-4 1-8 2 7 1-9 10 1-4 30 3-3 5-1 rain days

Comet 001-0-24 25 25 24 24 23 29 25 44 54 37 31 29 0-25-0-99 52 48 49 58 47 46 48 51 34 53 53 50 1 00-1-99 16 17 17 14 21 23 23 5 6 11 15 17 200-3-99 6 8 7 2 9 2 4 — 6 — 2 5 4-00-5-99 1 2 1 2 — — — — — — — — ^6-00 1 1 — — — — — — — — — Mean no. of 4-5 4-7 3-1 1-9 1-5 2 0 1-7 1-3 1-0 3-4 3-6 3-9 rain days

Rolleston 0-01-0-24 45 41 39 44 51 48 56 62 51 54 44 40 0-25-0-99 44 39 43 40 34 36 34 34 36 36 42 42 1-00-1-99 7 13 14 9 9 14 8 3 10 9 10 16 2-00-3-99 3 6 3 6 6 2 2 1 2 1 4 2 400-5-99 1 1 1 2 — — — — — 1 — — 5*6-00 Mean no. of 6-4 6-6 4-5 2-9 2-6 3 0 2-9 20 2-4 4-7 5-4 6-4 rain days

Some appreciation of seasonal differences in the character of daily rainfalls can be drawn from the percentage frequencies of falls within specified ranges. It is of interest that even over the wettest part of the year at least 75% of the daily falls are less than 1 in. There are no apparent large seasonal variations in the percentage of falls within this range, and Table 4 shows clearly the greater likelihood of high daily CLIMATE OF THE ISAAC-COMET AREA 61

totals (over 2-00 in.) during the late summer season. A feature of some interest is the abruptness of the drop in the percentage frequency of daily falls above 1 in. at Nebo and Rolleston, in contrast to Bombandy and Comet where the percentages of falls in the intermediate range (1 00 to 1-99 in.) are higher except in the dry months, August to October. Although Comet has lower monthly mean rainfalls (Table 2) and fewer rain days than either Nebo or Rolleston, the proportion of daily falls exceeding 1 in. is higher, particularly during the months May to July. This implies that the higher total rainfalls in the Nebo and Rolleston areas are largely the result of a larger number of days having light to moderate falls, and that the heavier falls are generally widespread over the whole of the area. Long runs of days with rain are not common. Even during the summer months rainfall normally occurs within periods not exceeding 5 days; over the dry winter months, and continuing until December, the falls generally occur in groups of 2 or 3 days or as isolated occurrences. The intervals between rains are very variable in length. The passage of a month without some rain is unusual during the summer months, but on occasion even longer rainless spells have occurred. During the driest part of the year it is not uncommon for one or two months to pass without any rainfall, and often the falls separating these dry periods are negligible in their effect.

{b) Temperature The only temperature data available are for Emerald and Springsure, and these should be considered in the light of the inland location of both stations. Monthly average maximum, minimum, and mean temperatures, and the mean number of days with temperatures above and below selected thresholds are given in Table 5. Mean maximum temperature ranges from somewhat above 70°F during the coolest months, June and July, to about the mid nineties in the warmest months, December and January. Although insufficient data preclude any quantitative assessment of areal differences in maximum temperatures, it can be expected that there will be a general decrease in temperature with decreased distance from the coast. Some increase in temperature from south to north may also be expected, particularly during the winter months. Even so, differences of more than a few degrees from the levels given in Table 5 are unlikely within the area. As seen from the table, the monthly mean maximum temperatures at Emerald are approximately 2°F higher than at Springsure over the whole of the year. This difference apparently reflects the higher elevation of Springsure (1057 ft) than of Emerald (588 ft). Except on the high country of the Consuelo Tableland, the altitudinal range within the area is limited and no significant vertical zonation of temperature occurs. On the average, temperatures above 90°F occur on more than 20 days per month between November and January inclusive, and not infrequently these exceed 100°F. A marked decrease in the mean maximum temperature and in the frequency of temperatures above 90°F and 100°F occurs in February, reflecting the increased cloudiness of that month. Temperatures above 90°F do not often occur after mid May and before mid August. Mean minimum temperatures range from about 43°F in July to about 70°F in January. Although day temperatures are high throughout the winter, under prevailing TABLE 5

AVERAGE MEAN MAXIMUM, MEAN, /

Element Ian. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year

Emerald Maximum (°F) 95 1 93 1 90-5 85-8 79-2 73-5 72-9 77-1 83-2 89-8 93-5 95-3 85-8 Mean (°F) 82-9 81-8 78-7 72-6 65-6 60-5 58-5 61 -3 68-2 75-1 79-8 82-2 72-3 m Minimum (°F) 70-7 70-1 66-8 59-3 519 47'5 44-3 45-5 53-3 605 66 0 690 58-7 No. of days with max. Ss 90°F 23 -4 17-4 161 4-7 0-2 — — 0-3 3-2 12-5 21-5 26-1 125-4 No. of days with max. >100°F 6-4 2-4 10 0-1 — — — — — 1-4 2-5 5-3 191 No. of days with min. < 36°F — — — — 0-3 3-9 5-9 3-4 01 — — — 13-6 No. of days with min. < 32°F — — — — — 0-5 15 0-6 — — — — 2'6 3 JO Springsure O Maximum (°F) 93-3 91-7 89-2 84-3 77-6 71-5 70-7 74-9 81-2 87-6 91-4 93 1 83-9 Mean (°F) 81 -4 801 11-2 71-3 64-2 58-6 56-9 59-9 66-8 73-4 780 80-5 70-7 Minimum (°F) 69-4 68-6 65-3 58'3 50-8 45-6 43 1 450 52-3 59-2 64-5 67-9 57-5 No. of days with max. > 90°F 21-2 17-4 14-6 4-2 01 — — 0-2 2-2 110 18-7 22-5 112-1 No. of days with max. 3=100°F 4-9 3'1 0-9 — — — — — — 09 2-6 4-7 17-1 No. of days with min. < 36°F — — — — 1-3 5'1 8-5 4-7 0-6 0-1 — — 20-3 No. of days with min. < 32°F — — — 01 1-8 3-5 1-6 — — — 70 * Source: Published data of the Bureau of Meteorology (1962). TABLE 6 MEAN MONTHLY DATA FOR ELEMENTS OTHER THAN RAINFALL AND TEMPERATURE AT EMERALD AND SPR1NGSURE

Element Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Annual

Emerald n 9 a.m. vapour pressure (inHg)* 0-662 0-669 0-623 0-500 0-389 0-343 0-309 0-319 0-383 0-467 0-551 0-621 0-486 r Average index of mean relative humidityt 62 65 66 62 61 68 65 58 58 53 55 58 61 1 tn 3 p.m. relative humidity (%)* 39 42 44 40 41 47 43 36 34 31 35 36 39 9 a.m. saturation deficit (inHg)* 0-405 0-360 0-321 0-307 0-248 0-162 0 166 0-231 0-326 0-414 0-451 0-449 0-320 o 9 a.m. cloudiness (tenths)* 4-6 4-9 3-9 2-8 2-5 3-3 2-5 21 2-4 30 3-7 4-2 3-3 H 3 p.m. cloudiness (tenths)* 5-4 5-7 4-7 3-9 3-6 3-7 30 2-6 2-7 3-3 4-1 4-7 40 tn Total (global) radiation (cal/cm2/day)+ 519 518 433 391 330 299 327 390 465 516 581 556 5325 Evaporation (in./month)§ 8-49 7-17 6-03 5-17 4-18 3-39 3-74 4-71 5-75 7-80 8-85 9-21 74-48 > > n Springsure n 9 a.m. vapour pressure (inHg)* 0-603 0-605 0-552 0-446 0-360 0-318 0-285 0-290 0-334 0-418 0-493 0-571 0-440 o Average index of mean relative humidityt 59 62 61 56 56 61 58 52 49 50 52 57 56 9 a.m. saturation deficit (inHg)* 0-419 0-371 0-353 0-350 0-282 0-204 0-206 0-268 0-347 0-417 0-455 0-431 0-342 9 a.m. cloudiness (tenths)* 4-1 4-3 3-5 2-6 2-5 3-3 2-2 20 2-2 2-5 3-3 3-7 30 > Evaporation (in./month) § 8-51 6-72 6-22 5-19 411 3-27 3-55 4-51 5-88 7-51 8-68 8-88 71-10 tn > * Extracted or derived from data published by Bureau of Meteorology (1962). t Calculated from the ratio of 9 a.m. vapour pressure to the saturation vapour pressure at the mean air temperature. X Estimated by method of Black, Bonython, and Prescott (1954) from duration of sunshine as determined empirically from cloudiness data and shown on maps published by Bureau of Meteorology (1954). § Estimated by method of Fitzpatrick (1963) from mean maximum temperature, vapour pressure, and day length. 64 E. A. FITZPATRICK clear skies and stable anticyclonic conditions of that season, radiational cooling at night is intense, and frosts can be expected throughout the area. The data in Table 5 show that screen temperatures as low as 36°F have occurred as early as May at both Emerald and Springsure and as late as September and October respectively. As surface temperatures are likely to be several degrees lower than the screen values, the extreme frost risk period at these stations is about 5 months. Such low temperatures before June and after August are, however, rare. The period between the average dates of the first and last occurrences with temperatures below 36°F is 8 weeks at Emerald (June 21 to August 11) and 11 weeks at Springsure (June 4 to August 22). Between June and August frosts can be expected on an average of from 3 to 6 days in June and August and from 6 to 9 days in July. July is distinctly the coldest month. Screen temperatures below 32°F can be interpreted generally as an indication of widespread severe frosts. These occur mainly in July, but on occasion can be expected in June and August as well. The risk of frost can be expected to decrease generally from south to north within the- area, and frosts are naturally most frequent and severe where the surrounding topography favours the accumulation of cold air within surface depressions. In spite of the latitudinal position of the area and its nearness to the coast, the daily range of temperature is normally quite large owing to frequent occurrence of calm cloudless days and nights. At Emerald and Springsure the largest mean daily temperature range occurs in August (approx. 32°F and 30°F respectively) and the smallest in February (approx. 23 °F at both stations).

(c) Humidity In Table 6 data are given which depict the mean monthly humidity conditions at Emerald and Springsure. These are the only data available, and it should be borne in mind that slightly more humid conditions can be expected at lesser distances from the sea. The annual regime of the mean 9.00 a.m. vapour pressure is of interest as an indication of actual changes in average atmospheric water vapour content. A close agreement between the seasonal trends in this element and those in rainfall is at once apparent. Between November and April mean 9.00 a.m. vapour pressure exceeds 0 • 5 inHg at both Emerald and Springsure, and for each of these it falls to about 0 • 3 inHg during July and August. Between January and July there is very little change in the levels of the average index of mean relative humidity. This condition results from the general decrease in temperature which occurs concurrently with the decline in vapour pressure. The average index values, which may be regarded as approximations of the mean daily relative humidities, range between 60 and 70% at Emerald and between 56 and 62% at Springsure during this interval. Between August and November they are distinctly lower, this being a period with low to moderate vapour pressure and increasing temperature. The 9 a.m. saturation deficits may be taken as a general indication of the drying power of the air. Very high saturation deficits (^ 0 • 4 inHg) occur between October and January. A considerable fall occurs in February, and thereafter the CLIMATE OF THE ISAAC-COMET AREA 65 mean saturation deficit continues to decrease until June. A sharp rise occurs between August and November, reflecting the marked increase in temperature at this time.

(d) Cloudiness, Sunshine, and Radiation Cloudiness decreases from east to west over the area and the mean values for Emerald and Springsure given in Table 6 should be interpreted accordingly. During the December-March period, the mean cloudiness is about four-tenths, February being the cloudiest month. Except for some increase in cloudiness during June, there is a steady decline until the lowest amount of cloudiness (approx. two- tenths) occurs in August. Thereafter cloudiness increases steadily until February. As shown by the data for Emerald (Table 6), afternoon cloudiness is appreciably higher than that at 9 a.m. throughout the entire year. No data are available for duration of sunshine, but empirical estimates of average duration of sunshine per day based upon mean cloudiness range from nearly 10 hr in November to about 7•5 hr in June. The estimated mean duration of sunshine per day in February, the cloudiest month, is about 8 hr. Day length changes by about 3 hr during the year, ranging from about 10-5 hr in June to about 13-5 hr in December. From an empirical relationship of Black, Bonython, and Prescott (1954) the estimated mean total radiation ranges from about 580 cal cm~2 day"1 in November to about 300 cal cm~2 day-1 in June. No instrumental data are available in the vicinity of the area to assess the accuracy of these estimates, but with the possible underestimation of radiation during the rainiest part of the year, the levels are in generally good agreement with observations made at Townsville (Bureau of Meteorology 1963a). (e) Evaporation There are no observations of evaporation within the area, but estimates of the monthly tank evaporation based upon mean maximum temperature, vapour pressure, and day length have been made for Emerald and Springsure (Fitzpatrick 1963), and these are included in Table 6. The values are in good agreement with the levels shown on monthly evaporation maps of Australia as determined from the most reliable data from the standard Australian tank evaporimeter (Bureau of Meteorology 19636). In view of the inland situation of these stations, it may be assumed that the monthly evaporations in Table 6 represent approximately the highest rates which occur within the area. For both stations the highest estimated evaporation occurs in December, when the rate is about 9 • 0 in. per month, and the lowest in June, when it is between 3 • 0 and 3 • 5 in. per month. The estimated mean evaporation falls sharply in February; this is to be expected in view of lower radiation and lower temperature combined with an increase in vapour pressure at that time. The estimated evaporation rises very rapidly from about 4-5 in. in August to over 8-5 in. in November. In Figure 6 a graphical comparison between several rainfall statistics and potential evapotranspiration equal to 0-8 times the estimated tank evaporation is given for Springsure. This coefficient is based upon a relationship between potential 66 E. A. FITZPATRICK

evapotranspiration from short grass and evaporation of free water under summer radiation conditions at higher latitudes (Penman 1948, 1956). A somewhat higher coefficient might be justified in this area considering the higher radiation levels which occur, but since the tank evaporation estimates are likely to be higher than that appropriate to an extended free water surface, the value of 0- 8 has been retained here,

Fig. 6.—Comparison of several rainfall statistics with the estimated potential water use at Springsure. The frequencies referred to relate to rainfall received in any one month and not to the frequency of the complete curve.

In the absence of supporting data, this estimated potential evapotranspiration can be regarded only as an approximation of water use where soil moisture is kept at a high level and where a crop or pasture is actively transpiring. It can be seen from Figure 6 that throughout the year the monthly mean and median rainfalls fail to satisfy the estimated potential water use; however, in February the difference between the mean and the estimate is small. The relative dryness of the period August to November is apparent. Somewhat smaller differences can be CLIMATE OF THE ISAAC-COMET AREA 67

expected over parts of the area (e.g. in the vicinity of Nebo where evaporation is probably lower and where rainfall is higher), and it should be noted also that at Springsure monthly rainfalls exceeding the estimated potential water use occur during the summer months (January to March) with a mean frequency of 2 years in 10. Because potential evapotranspiration is not satisfied under average conditions, it should not be inferred that the area lies beyond the limits of safe agriculture, for useful crop production can be achieved over a range of soil moisture conditions well below those needed to maintain the potential rate of water use. Nonetheless, the relationships shown in Figure 6 do show clearly the need for water conservation and dry farming techniques within the area in order to obtain the maximum soil moisture storage and the most efficient crop water usage.

III. AGROCLIMATOLOGY An assessment of climate in relation to agricultural and pastoral land use within the area is not presented here, as it has been reported elsewhere (Fitzpatrick 1965). IV. REFERENCES

BLACK, J. N., BONYTHON, C. W., and PRESCOTT, J. A. (1954).—Solar radiation and the duration of sunshine. Q. Jl R. met. Soc. 80, 231-5. BUREAU OF METEOROLOGY (1954).—Maps of average monthly and annual hours of sunshine. (Govt. Printer: Melbourne.) BUREAU OF METEOROLOGY (1962).—Climate of Central Highlands, Region 11—Queensland. (Govt. Printer: Melbourne.) BUREAU OF METEOROLOGY (1963a).—Australian radiation records 1958-61 and monthly means 1953-61. (Govt. Printer: Melbourne.) BUREAU OF METEOROLOGY (19636).—Maps of average monthly and annual evaporation (Australian Standard Tank). (Govt. Printer: Melbourne.) FITZPATRICK, E. A. (1963).—Estimates of pan evaporation from mean maximum temperature and vapor pressure. /. appl. Met. 2, 780-92. FITZPATRICK, E. A. (1965).—Climate in relation to pasture and crop growth. In "Fitzroy Region, Queensland, Resources Series, Climate". (Dep. Natl. Development: Canberra.) PENMAN, H. L. (1948).—Natural evaporation from open water, bare soil and grass. Proc. R. Soc. A193, 120-46. PENMAN, H. L. (1956).—Evaporation: an introductory survey. Neth. J. agric. Sci. 4, 9-29. THORNTHWAITE, C. W. (1931).—The climates of North America according to a new classification. Geogrl Rev. 21, 633-55. PART V. GEOLOGY OF THE ISAAC-COMET AREA

By R. W. GALLOWAY*

I. INTRODUCTION The Isaac-Comet survey area occupies the central part of the great Bowen Basin which is one of the major structural units of Queensland. Geological work in the area up to 1959 is conveniently summarized in a publication of the Geological Society of Australia (Hill and Denmead 1960). Since the publication of this volume a considerable amount of further work has been carried out by officers of the Common- wealth Bureau of Mineral Resources and the Geological Survey of Queensland, and extensive use has been made in this survey of the maps and reports produced by these workers (Dickens, Malone, and Jensen 1964; Malone, Corbett, and Jensen 1964; Mollan, Exon, and Kirkegaard, unpublished data, 1964; Veevers et al. 1964a, 19645). A regional bulletin on the Bowen Basin which is being prepared by officers of the Commonwealth Bureau of Mineral Resources will give a full account of the geology of the area. This bulletin may introduce some changes in the established nomenclature followed here. The present Part is mostly concerned with those aspects of the geology which are of particular significance in understanding the nature of the land systems.

II. GENERAL GEOLOGY

(a) Permian The Permian rocks in this part of Queensland comprise three major units generally referred to as the Lower Bowen Volcanics, the Middle Bowen beds, and the Upper Bowen Coal Measures (Fig. 7). (i) Lower Bowen Volcanics.—Andesitic flows and pyroclastics, together with more acid volcanics and interbedded sediments, crop out in the extreme north-east. They are the oldest rocks in the area. (ii) Middle Bowen Beds.—The Middle Bowen beds occur widely in the north and centre although in many places they are obscured by younger basalt and terrestrial sediments. In the north-east between the Bruce Highway and Connors River and in the north round Homevale they comprise folded marine sediments, mainly quartz-lithic sandstone, siltstone, and limestones. In the Cherwell Range in the north- west these rocks are only gently folded, consist of quartz sandstone intercalated with * Division of Land Research, CSIRO, Canberra. GEOLOGY OF THE ISAAC-COMET AREA 69

Fig. 7.—Generalized geology, based partly on 1 : 250,000 maps published by Bureau of Mineral Resources, Geology and Geophysics. 70 R. W. GALLOWAY

siltstone and shale, and may include freshwater as well as marine sediments. A small area of steeply dipping quartz sandstone and siltstone is exposed near the Mt. Flora granitic intrusion. In the centre of the area, Middle Bowen beds are exposed east of Comet where they comprise lithic and quartz sandstone, siltstone, and shale. In the south-west, Middle Bowen beds crop out in a long, narrow anticlinal belt south of Springsure where they consist of alternating calcareous shale, mudstone, and quartz sandstone, moderately to steeply folded. (iii) Upper Bowen Coal Measures.—These rocks are widely distributed along the central axis of the survey area. They consist of terrestrial sediments, dominantly calcareous lithic sandstone, siltstone, and calcareous shale; coal seams and quartz sandstone also occur. These rocks are mainly unresistant and so form lowlands, and the high proportion of basic weatherable minerals may furnish potentially fertile soils where weathering has not proceeded too far.

(b) Triassic The Triassic sediments in the north consist of synclinally disposed terrestrial quartz sandstone, often current bedded, overlying shale and with subsidiary siltstone and conglomerate. These highly resistant rocks form the rugged Carborough-Kerlong and Burton Ranges. Between the Carborough and Kerlong Ranges softer micaceous sandstone and siltstone occur in the axis of a syncline and give rise to lower hills. The Triassic sequence in the southern half of the area consists of three major elements. At the base and extending down into the Permian is the Rewan Formation, comprising red and buff mudstone, siltstone, and lithic sandstone which crop out extensively in the east and south of the Comet catchment. Some of the sediments in the Rewan Formation have the property of swelling on wetting which possibly helps to account for the occurrence of deep gilgai on soils derived from these rocks. Over- lying the Rewan Formation is the highly resistant quartz Clematis Sandstone which gives rise to rugged country such as the Fantail and Shotover Ranges. This sandstone is in turn overlain by the tuffaceous shale and lithic sandstone of the Moolayember Formation which forms undulating country or low hills in the Bedourie area, and Rougemont in the extreme south.

(c) Jurassic and Cretaceous Resistant quartz sandstone of Lower Jurassic age forms striking cliffs capping the ranges which frame the extreme south of the Comet basin. Three eroded granitic stocks of Mesozoic age are exposed in the north of the area, two of which have resistant metamorphic aureoles and associated mineralization (Mt. Gotthard and Mt. Flora mineral fields). The presence of other stocks at depth in this area is indicated by up warping of overlying Permian sediments.

(d) Tertiary The Tertiary rocks include basalt, acid igneous intrusions, and terrestrial sediments. The main basalt spreads are along the western watershed of the area GEOLOGY OF THE ISAAC-COMET AREA 71 from Grosvenor Downs south to the Carnarvon National Park, but more limited occurrences are found in the south around Rolleston and in the north near May Downs and Nebo. A wide variety of basalts is represented, including dense, fine- grained olivine basalt, porphyritic, vesicular, and ashy basalts, and tuffs. Some have trachytic affinities and locally, near Springsure and in the Peak Range, trachyte flows cap the basalts. The original extent of the basalt was probably much greater than the present area of about 2000 sq miles. At many points the basalt flows overlie a silicified horizon (grey billy) capping the underlying sediments. Rhyolite and trachyte plugs form steep, rocky hills in the Peak Range and near Springsure in the west and in the north-east. During the Tertiary there was widespread accumulation of clays, sand, and gravels formed by weathering and erosion of adjacent pre-Tertiary rocks. These terrestrial sediments have now been extensively lithified to form claystone, current- bedded quartz sandstone, and conglomerate. They are sometimes interbedded with basalt, particularly in the lower part of the sequence. The conglomeratic facies is usually found near the present major rivers, implying that the latter already existed at the time when the Tertiary sediments formed and were capable of transporting coarser material than they can now. Sandstone and conglomerate horizons are also characteristic of the upper parts of the Tertiary sediments and more argillaceous material of the lower parts. At one time the Tertiary sediments extended over practically the entire area and they still cover more than 6000 sq miles. Extensive erosion in late Tertiary times after the major Tertiary deposition was followed by renewed deposition when widespread fluviatile deposits were formed, usually consisting of gravel in a matrix of silt and clay. These gravelly deposits occur as dissected terraces along the major rivers and as fans around some of the higher hills, notably in the south and west. As a rule they are extremely coarse in the upper valleys, but downstream the stones become smaller and the proportion of quartz and quartzite increases at the expense of more readily weatherable rocks such as basalt. These gravelly sediments are often not readily distinguishable from the main body of Tertiary sediments. Deep weathering occurred extensively during the Tertiary and thick weathered profiles developed over most of the landscape. Deep weathering was usually associated with the development of a laterite profile with ferruginous, mottled, and pallid zones.

(e) Post-Tertiary During at least the latter part of the Quaternary, deposition of alluvial sediments took place in the valley floors, accompanied by intermittent dissection and leading to the formation of terraces and flood-plains. As a rule, these deposits range in texture from sand to clay, although gravels are found in and around rugged country.

III. STRUCTURE

The Bowen Basin which underlies the entire area is a great synclinorium. The Palaeozoic volcanic rocks which form the basal horizons of the basin do not crop out in the survey area except in the extreme north-east and for the most part the area is 72 R. W. GALLOWAY

occupied by sedimentary rocks ranging in age from Permian to Recent, together with extensive Tertiary basalt flows and small Mesozoic and Tertiary intrusions. Folding and faulting, generally more or less parallel to the north-north-west to south-south-east axis of the Bowen Basin as a whole, affected the area during the Mesozoic, but since then only gentle warping and local disturbance round intrusions have taken place. In the north-east and centre the rocks are moderately to steeply folded and locally domed by granitic intrusions. Major features include the Carborough syncline along the axis of the Carborough-Kerlong Range, a fault along the eastern side of the Burton Range, a belt of folding west of the Bruce Highway and another running from Batheaston to Barwon Park, and a series of subparallel broad anticlines and synclines around Comet. In the north-west, there has been less folding and the rocks generally have dips of less than 10° in the Cherwell Range. In the south-east, dips in the Permian rocks are moderate and decrease upwards through the section while the overlying Triassic rocks are almost horizontal. In the south-west the meridional Springsure-Serocold anticline extends for nearly 100 miles and forms one of the major structural features of the area. The anticline has a number of separate culminations, the biggest of which, known as Reid's Dome, is towards the southern end. To the east of the main anticlinal axis there are a number of more or less parallel shallow folds, decreasing in intensity away from the main structure. West of the Springsure-Serocold anticline the structure is largely concealed under Tertiary basalt but it is known that dips become gentler.

IV. GEOLOGY AND THE LAND SYSTEMS

Since it is lithology rather than stratigraphy which determines the relationship of the land systems to geology, the stratigraphic information presented in the previous section must be reclassified. A classification based on lithology must also take into account both deep weathering, which can drastically alter the original nature of the rocks, and structure, which often determines how lithologic variations are expressed in land forms and the pattern of soils and vegetation. The classification adopted here is summarized in Table 7. Seven major lithologic classes have been recognized (Table 7), some of which are divided according to weathering status and subdivided according to structure.

(a) Non-quartzose Pre-Tertiary Sedimentary Rocks This lithologic class consists of shale, mudstone, sandstone, and tuff, which occupy some 17% of the entire area. Although they may contain quartz fragments they also have a moderate to high proportion of other minerals, usually favouring the formation of clay and often forming potentially fertile soils. The extent to which these rocks have been affected by deep weathering is not always clear but on the whole appears to have been fairly minor. Probably a deep weathered zone did formerly exist on these rocks but it has largely been removed by subsequent erosion. GEOLOGY OF THE ISAAC-COMET AREA 73

The effects of folding are important where the rocks consist of alternating sandstone and shale beds: if the rocks dip steeply, narrow, sharply defined groves and glades of contrasted vegetation following the strike are characteristic, whereas if dips are moderate, broader, less clearly defined groves are usual. Girrah land system consists of undulating country on little-weathered, moderately folded Permian shales and lithic sandstones with broad, ill-defined vegetation bands following the strike.

TABLE 7 GEOLOGY AND THE LAND SYSTEMS

Lithology and Formations Weathering Status Structure Land Systems

Non-quartzose, pre-Tertiary sedi- Fresh Unfolded Arcadia, Rewan (part), mentary rocks: Middle Bowen Bedourie (part) beds, Upper Bowen Coal Meas- Moderately Girrah, Hillalong, ures, Rewan Formation, Moolay- folded Skeleton ember Formation Highly folded Barwon Weathered Folded Daunia (part), Racecourse (part)

Quartzose sedimentary rocks: Fresh or moderately Unfolded and Cotherstone Middle Bowen beds weathered folded Weathered Unfolded and Durrandella (part) folded

Quartz sandstone: Clematis Sand- Mainly fresh, locally Unfolded and Carborough, Planet stone, Precipice Sandstone, Mid- weathered folded dle Bowen beds

Basalt (no formation name) Fresh or moderately Unfolded Percy, Waterford, Volcanics: Lower Bowen Volcanics, weathered Oxford Tertiary intrusions Folded Britton, Nebo (part) Deeply weathered Unfolded Bedourie (part), Racecourse (part)

Tertiary sandstone (no formation Weathered Unfolded Junee, Durrandella name) (part), Monteagle, Moorooloo, Nebo (part), Rewan (part)

Tertiary clay (no formation name) Weathered Unfolded Humboldt, Black- water, Somerby

Post-Tertiary alluvium Fresh Unfolded Connors, Funnel, Comet

Barwon land system likewise consists of undulating country on little-weathered Permian shales and lithic sandstones, but in this case the dips are much steeper, resulting in narrow, clearly defined vegetation bands. Hillalong land system is similar to Girrah land system but sandstones are predominant and banding of the vegetation is much less pronounced. 74 R. W. GALLOWAY

Arcadia land system is on slightly folded, unresistant shale of the Rewan Formation which gives rise to plains and lowlands with dense brigalow-wilga scrubs. Rewan land system is on the lithic sandstone and shale of the Triassic Moolayember Formation, covered over much of its extent by coarse billy gravel. The weak, practically unfolded rocks give rise to gently undulating topography. Skeleton land system is on rocks similar to those underlying Rewan land system though with rather steeper dips. It has, however, a much steeper relief since the soft sediments are capped by resistant Tertiary basalt. Deep weathering of the non-quartzose sedimentary rocks results in increased occurrence of brigalow, some blackbutt, and deep gilgai in lower sites. Much of Daunia land system consists of plains and lowlands on deeply weathered Permian shale. (b) Quartzose Sedimentary Rocks This lithologic class is relatively small, cropping out over some 6% of the area. It consists of quartz-rich sandstones and interbedded lithic sandstone, siltstone, and shale. The resistant nature of these rocks tends to produce hills with structurally controlled features such as scarps and benches, or lowlands with shallow soils. Where these rocks are practically horizontal (mainly round the Cherwell Range), tabular relief is the rule. Where the rocks have considerable dips, on the other hand, linear strike ridges and vales occur where the available relief is considerable as at the southern end of Reid's Dome. Where considerable dips are present, but there is little local relief, as at the northern end of the Springsure-Serocold anticline, the trees form groves aligned along the strike. Cotherstone land system consists of lowlands on fresh or moderately weathered sediments on the flanks of the Cherwell Range and at the northern end of the Springsure-Serocold anticline. Some of the higher parts of Durrandella land system consist of stony hills on deeply weathered Permian sandstone carrying dense lancewood scrubs on their steep, rocky slopes. (c) Quartz Sandstone Rocks in this lithologic class may have been subjected to deep weathering but show little effect on account of the high resistance of the quartz sandstone to chemical attack. The Clematis Sandstone, Precipice Sandstone, and particularly quartzose elements of the Middle Bowen beds comprise this lithologic unit which occupies 12% of the area. Tertiary quartz sandstones and conglomerates are not included. Rugged relief and much outcrop are usually associated with this lithology except in the upper parts of Planet Creek where the stream has not incised. Where dips are low, deeply dissected plateaux are the rule, such as the Fantail Range in the south of the area. Where dips are high, linear scarps and steep strike ridges are found, such as those flanking Reid's Dome, south of Springsure. Carborough land system consists of mountains, dissected plateaux, and scarps. Planet land system consists of lower hills with some lancewood and also the undulating upland occupied by the upper part of Planet Creek. GEOLOGY OF THE ISAAC-COMET AREA 75

(d) Basalt and Volcanics The greater part of this lithologic unit, which covers 12% of the area, consists of Tertiary olivine basalt. Small areas of Lower Bowen Volcanics in the north-east, granitic intrusions and metamorphic aureoles in the north, and Tertiary volcanic plugs in the north-east and west, have been included. While many of the rocks show such signs of deep weathering as reddish soils and secondary carbonate, areas on basalt have preserved a distinctive character which weathering has modified but not destroyed. Since the basalt flows are not folded, tabular relief is the rule, with steep conical peaks on the intrusive plugs. Percy land system comprises mountains on deeply dissected, unweathered basalt flows and volcanic and granitic intrusions. Black Alley land system is found on the little-dissected summit surface of the basalt. Britton land system likewise consists of mountains, but mainly on folded Lower Bowen Volcanics. Part of Nebo land system is on undulating country on unweathered Lower Bowen Volcanics. Waterford land system on fresh or little-weathered basalt comprises low rocky hills and undulating colluvial foot slopes. Oxford land system consists of undulating lowlands and plains on little-weathered or fresh basalt. Bedourie and Racecourse land systems are largely on deeply weathered basalt, but their distinguishing feature of softwood scrub vegetation does extend onto other rocks. (e) Tertiary Sandstone This is the second most extensive lithologic class, covering 20% of the area. The lithologies included here in one unit range from sandy claystone through sandstone and conglomerate to gravelly clay, but rather soft quartz sandstone with a kaolinitic matrix is most common. All are deeply weathered. Tabular relief, in keeping with the unfolded nature of the rocks, is the rule, and the surface is sandy or loamy. Steep breakaways round Tertiary sandstone mesas are included in the land systems on this lithologic group. Junee land system occupies the undulating sandy summits of mesas of Tertiary sandstone. Monteagle land system is likewise on Tertiary sandstone but has a more loamy surface and forms lowlands rather than high mesas. Similar country forms part of Broadlee land system. Part of Durrandella land system comprises small, dissected Tertiary mesas with steep bounding breakaways and adjacent foot slopes. All of Moorooloo and part of Nebo and Rewan land systems are on gravelly Tertiary deposits. Moorooloo land system has a cover of quartzose pebbles from the Springsure-Serocold anticline to the west, mixed with a reddish clay presumably derived from the underlying basalt. Nebo land system is partly on gravelly fans derived from Lower Bowen Volcanics to the east. Much of Rewan land system is covered by coarse billy gravel. (/) Tertiary Clay This most extensive lithologic class covers 21% of the area. It consists of weathered Tertiary clay and claystone, with various admixtures of quartz, billy, and 76 R. W. GALLOWAY

ironstone gravel, together with fairly small areas of deeply weathered, shaly, older rocks. Plains and lowlands are naturally associated with the unresistant nature of the rocks, while Tertiary deep weathering has clearly been highly effective. Alkaline A horizons over deep acid B horizons are usual, and gilgai is common in the lowest sites. Humboldt land system consists of clay plains and lowlands with brigalow- blackbutt vegetation. Blackwater land system is similar but without the blackbutt, while Somerby land system is likewise similar but with deep gilgai.

(g) Post-Tertiary Alluvium Alluvial flats margin streams throughout the district but only those more than half a mile wide could be mapped and they occupy about 12% of the area. The usual variations in texture exist, from coarse on levees to fine in back swamps, and in addition variations in texture and relation to the nature of the sediment supplied by the headwaters can be detected. Rather coarser alluvium is associated with sandstone and with steep relief, while fine-textured material is related to lowlands and shales or basalt. Connors land system comprises sandy or loamy alluvium, probably not flooded, mainly found near the mountains of the south-west. Funnel land system consists of clays and loams derived from basalt and volcanic rocks, and is subject to flooding. Comet land system is developed on fine-textured alluvium derived from shales and basalt, and is also subject to flooding.

V. REFERENCES

DICKENS, J. M, MALONE, E. J., and JENSEN, A. R. (1964).—Subdivision and correlation of the Permian Middle Bowen Beds, Queensland. Rep. Bur. Miner. Resour. Geol. Geophys. Aust. No. 70. HILL, DOROTHY, and DENMEAD, A. K., Eds. (1960).—The geology of Queensland. /. geol. Soc. Aust. 7. MALONE, E. J., CORBETT, D. W. P., and JENSEN, A. R. (1964).—Geology of the Mt. Coolon 1 : 250,000 sheet area. Rep. Bur. Miner. Resour. Geol. Geophys. Aust. No. 64. VEEVERS, J. J., MOLLAN, R. G., OLGERS, F., and KIRKEGAARD, A. G. (1964a).—The geology of the Emerald 1 :250,000 sheet area, Queensland. Rep. Bur. Miner. Resour. Geol. Geophys. Aust. No. 68. VEEVERS, J. J., RANDALL, M. A., MOLLAN, R. G., and PATEN, R. J. (19646).—Geology of the Clermont 1 : 250,000 sheet area, Queensland. Rep. Bur. Miner. Resour. Geol. Geophys. Aust. No. 66. PART VI. GEOMORPHOLOGY OF THE ISAAC-COMET AREA

By R. W. GALLOWAY*

1. GENERAL DESCRIPTION

The area may be likened to a figure 8 with a length in the north-south direction of just over 300 miles and a maximum width of 100 miles (frontispiece). The northern loop of the figure 8 comprises the catchment of the Isaac River and the western part of the catchment of its principal tributary, the Connors River. The southern loop is the catchment of the Comet River. The intervening waist is drained by the Nogoa- Mackenzie, which in the course of making its way to the sea traverses this part of the area from south-west to north-east, and to which the Isaac-Connors and Comet Rivers are tributary. (a) Isaac-Connors Catchment This catchment is clearly bounded on the east, north, and south-west by mountains or hills, but on the west and north-west the border is lower and less distinct. The mountainous country forming the eastern part of the Connors River catchment falls outside the survey area except for a small portion at the northern end, and in general the eastern boundary of the survey area follows the break of slope at the foot of the ranges. At the northern end of the area the boundary follows the crest of part of the Denham Range, which here consists of hills rising a few hundred feet above the surrounding country. The north-western and western boundary of the Isaac catchment is likewise termed "Denham Range" but here it does not follow high ground and is located on or at the edge of undulating plains and low tablelands on weathered basalt and Tertiary sediments; at many points its exact position is difficult to identify. The south-western border of the Isaac basin follows the Peak Range, a belt of steep hills developed on Tertiary intrusions and basalt flows, rising 500 to 1500 ft above the surrounding rolling country, and with summits up to 2700 ft above sea level. Within these borders the Isaac-Connors catchment consists of plains and undulating lowlands from which rise a number of ranges and isolated hills. The plains and lowlands are between 400 and 1000 ft above sea level, and are developed mainly on Permian sediments with some Tertiary basalt. They are mantled over wide areas by a variable thickness of detrital gravel, sand, and clay, the oldest of which is consolidated into rock and frequently deeply weathered and extensively redissected, while the youngest consists of wide alluvial spreads along the major rivers subject to flooding in places and still accumulating. The most extensive hill area within the Isaac-Connors catchment is a north- north-west to south-south-east belt some 50 miles long west of the Isaac, comprising * Division of Land Research, CSIRO, Canberra. 78 R. W. GALLOWAY the Cherwell and Harrow Ranges and consisting of low dissected plateaux, occasionally deeply weathered, of flat-lying or gently folded Permian sandstone with some shale. In the north are three dissected plateaux of gently folded Triassic sandstone. The largest, called the Carborough Range on its eastern side and the Kerlong Range on its western side, is some 30 miles long from north to south and 4 to 6 miles wide and rises 300-600 ft above the surrounding country; to the west lies the smaller Burton Range some 10 miles long and 2 to 3 miles wide while to the south is the still smaller massif of Iffley Mountain. Low tablelands on Tertiary sandstone capped by a deeply weathered zone occur in the north-west near Annandale. A number of steep, isolated hills, such as Mounts Flora, Fort Cooper, and Yatton, developed on resistant igneous intrusions or metamorphic aureoles, rise 100-600 ft above the surrounding lowlands in many parts of the Isaac-Connors basin.

(b) Comet Catchment This catchment is nearly enclosed by rugged ranges. The eastern side is bounded for fully 100 miles by the abrupt escarpments, 200-1500 ft high, of the Shotover and Expedition Ranges which form the margin of extensive Triassic sandstone plateaux. Parts of these plateaux drained by the upper Planet and Clematis Creeks are included in the survey area. In the extreme south the boundary lies on a narrow belt of lowland which passes south between the Carnarvon and Expedition Ranges into the Dawson catchment. In the south-west the boundary follows the summit of the Carnarvon Range which forms the highest part of the area, rising to over 3500 ft, coinciding in part with the Great Divide, and consisting of thick basalt flows over sandstone. Valleys in the Carnarvon Range are up to 2000 ft deep, very narrow in resistant sandstone and somewhat wider in softer rocks. Basalt flows also form the rather lower dissected tablelands and mesas that mark the western edge of the Comet catchment. Most of the Comet basin enclosed by these bounding ranges is a gently undulating lowland from 500 to 1000 ft above sea level developed on Permian sediments and Tertiary basalt and sandstone. As in the Isaac-Connors catchment, surficial materials including sand, gravel, and clay in various degrees of consolidation are widespread. Extensive young alluvial sand, silt, and clay, and older, dissected, gravel terraces occur along the major creeks. Hill areas within the Comet catchment include a number of dissected plateaux of Triassic sandstone in the south, bounded by steep scarps 200-500 ft high: examples are the Fantail and Rougemont Ranges. In the western part of the catchment a meridional belt of high country extends for 100 miles along the breached Springsure- Serocold anticline in Permian sediments. In the south, this belt forms the mountainous area of Reid's Dome but gradually sinks northward to merge with the lowlands north-east of Springsure. In the north moderately resistant, gently folded Permian sediments (capped by weathered detrital deposits) have been dissected into low stony hills north and east of Comet.

(c) Central Area Draining to the Nogoa-Mackenzie This central area forms the narrow waist of the survey area, has less clearly denned borders than the catchments of the Comet and the Isaac-Connors, and in GEOMORPHOLOGY OF THE ISAAC-COMET AREA 79

many places is bounded by arbitrarily chosen limits rather than by watersheds. Most of the country consists of undulating lowlands and plains with extensive alluvial deposits, including well-developed terraces along the Mackenzie. Deeply weathered rock and surficial deposits of gravel, sand, and clay are widespread. Tablelands on Tertiary sediments occur extensively. The largest is the Junee Tableland which covers nearly 150 sq miles and rises abruptly 100-400 ft above the surrounding lowlands. In the north-west (around the head of German Creek) the land rises more gradually to form hills which are a southern extension of the Cherwell Range in the Isaac catchment and are likewise a dissected plateau of gently folded, partially weathered, Permian sediments.

II. EVOLUTION OF THE LAND FORMS The geomorphic history of the area can be conveniently taken as beginning when the major deposition of sedimentary rocks and the major earth movements and

Fig. 8.—Cross profile of the lower Comet valley showing land form evolution, (a) Up to formation of Tertiary land surface; (b) since formation of Tertiary land surface.

igneous intrusions ceased in the Mesozoic. The history may be divided into eight stages, which are here treated as successive for clarity but which may have partly overlapped or alternated in any given part of the survey area. Figure 8 illustrates aspects of this history. (a) Late Mesozoic Erosion During the latter part of the Mesozoic era immense quantities of rock were removed by erosion and some of the present major land forms first became apparent. Because much of this landscape was subsequently buried under Tertiary basalt and sediments some of its features were preserved and can now be reconstructed. 80 R. W. GALLOWAY

Undulating lowlands formed on relatively weak Permian sedimentary rocks in the east and centre while low hills with strike ridges, escarpments, and transverse valleys developed in the west on the more resistant quartzose sediments of what is now the Cherwell Range and the northern end of the Springsure-Serocold anticline. Areas of highly resistant Triassic quartz sandstone already formed upstanding hill masses which in modified form survive today as the Carborough, Kerlong, Burton, and Expedition Ranges. In the north-west (e.g. near Highland Plains) the late Mesozoic land surface was close to that of today, while in the extreme south of the area, on the other hand, this surface has been deeply dissected and survives only high up in the interfluves under a cover of Tertiary basalt. The occurrence of Tertiary basalt flows on low ground near the foot of the western escarpments of the Cherwell and Expedition Ranges shows that these escarpments existed before the basalt flows and that there has been no more than a mile or two of scarp retreat here since the close of this stage in the geomorphic history. The drainage pattern was significantly different from that of today. In the western Isaac catchment it was apparently directed to the south-west while around Springsure it flowed north-eastwards as it does today. The southern third of the present Comet basin probably drained southwards towards the upper Dawson. A major valley cut through the resistant sandstone of the Expedition Range south- east of Rolleston, but it is not known in which direction it flowed. The deep valleys in which the upper Isaac River and Anna Creek now cross the Carborough Range must already have existed at this time and testify to a still more ancient land surface from which their present south-westward course was superimposed on the resistant sandstone. (b) Lower Tertiary Basalt Early in the Tertiary extensive basalt flows spread across the landscape and may have covered almost the entire area to an average depth of scores, or even hundreds, of feet. In the south at least, and perhaps everywhere, the basalt flows were laid down during at least two separate phases with a notable intervening period of erosion and deposition. The Tertiary intrusive rocks may have formed about the same time as this second basalt phase. (c) Post-basalt Erosion After formation of the basalt there was a period of erosion which was probably severe and prolonged. Only occasional residuals, such as Anvil Peak protected by a resistant cap of trachytic lava, now give an indication of the original much greater thickness of the basalt. As a rule, if the basalt were not entirely removed it was reduced to an average thickness of a few tens of feet. Thus erosion in this stage cut down to about the old pre-basalt level. The main lines of the present landscape were already apparent by the end of this phase with the resistant quartz sandstone forming dissected plateaux overlooking lowlands and plains on softer rocks.

{d) Tertiary Deposition Erosion continued during this stage but the resulting products were not removed from the area and accumulated to form the complex Tertiary sediments. These GEOMORPHOLOGY OF THE ISAAC-COMET AREA 81 sediments range from conglomerate and quartz sandstone through sandy claystone to clay. Variations in lithology reflect variations in source rock and position in the landscape, and changes in weathering and erosion. Sandstone sources such as the Carborough Sandstone tended to supply sandy sediments while basalts and shales furnished more argillaceous material such as that which forms an extensive sheet near Leichhardt Downs. Gravelly sediments formed in the vicinity of the major rivers which already occupied approximately their present position, while poorly sorted rubbles accumulated around scarps and ranges. Variations in the nature of weathering and erosion in the supply areas, presumably caused by climatic changes, are reflected in a commonly occurring sequence upwards through the Tertiary sediments from argillaceous to sandy material. The Tertiary sediments reach a maximum thickness of about 400 ft in the Junee Tableland but as a rule thicknesses of 20 to 50 ft are the rule. Frequently, at May Downs for instance, the Tertiary sediments were laid down over remnants of the basalt flows, thus protecting them from further weathering and erosion. Although the Tertiary sediments have now been extensively dissected, they still survive in many places such as around Annandale and Red Hill in the north-west, in the May Downs-Junee area, near Bombandy, south-east of Comet, and in the Humboldt-Planet Creek area.

(e) Tertiary Deep Weathering Deep weathering was associated with the formation of the Tertiary sediments which usually display a lateritic profile with mottled and pallid zones capped by laterite. The resultant deep weathering profile is herein termed the Tertiary weathered zone. The weathering has often penetrated through the Tertiary deposits into the underlying older rocks. While much of the weathering seems to have taken place after deposition of the Tertiary rocks, there are indications that intense weathering also preceded and accompanied their formation. The argillaceous Tertiary rocks imply prior deep weathering of the source areas while the laterite itself is often a detrital deposit forming part of the Tertiary rocks rather than a weathering modi- fication of them. The depth of the weathering profile varies widely: the maximum observed was about 80 ft at Red Hill in the north-west, the minimum about 10 ft on quartz sandstone at the southern end of the Cherwell Range. Weathering resulted in the leaching of bases from the rocks, which naturally reduced the fertility of the soils that subsequently formed on them. Where weathering affected basalt, the leached material was often redeposited at depth and the resulting enriched layers have now been exposed at the surface by stripping of much of the weathered profile; in such situations carbonate or gypsum is common in the soil and the underlying rock. Around Annandale, Saltbush Park, and Roper Creek weathering has been associated with the development of a quartzose billy horizon in the deep weathered profile, but in the area as a whole billy tends rather to be associated with the base of the basalt flows. The conjunction of Tertiary erosion on higher areas, deposition on lowlands, and deep weathering resulted in the formation of a very gently undulating landscape 82 R. W. GALLOWAY

here termed the Tertiary land surface. Major valleys existed in the same places as those of today, but the drainage pattern was much more open. This land surface was erosional in its higher parts and depositional in its lower, and was diversified by low ranges on the especially resistant Triassic and Permian quartz sandstones. The Carborough-Kerlong massif formed one such range at its southern end, but merged with the general level of the Tertiary weathered land surface at its northern end. Likewise, the Expedition Range formed a distinct scarp at its northern end but became progressively less prominent southwards and eventually merged with the general undulating surface in the southern part of the Comet valley.

(/) Late Tertiary Erosion Subsequent to the formation of the Tertiary land surface and deep weathered zone, they were reduced by erosion. In some places the surface has survived almost intact, elsewhere only the middle or lower parts of the weathered zones survive, and often erosion has cut right through to the older unweathered rocks beneath. Where the surface is almost intact, it is level to gently undulating, with red sandy or loamy soils. Shallow depressions with clay floors often littered with blocks of laterite form a common and unexplained feature of these remnants of the old land surface. Present geomorphic action is confined to sheet erosion on more steeply sloping sites and localized deposition of sandy wash in hollows. The relics of the old surface usually now form the tops of mesas which rise 20 to 400 ft above the adjacent valley floors. Examples include the Junee Tableland and fiat-topped hills west of Annandale. Where only the middle or lower parts of the weathered profile survive as a result of continued surface stripping, a very different landscape of plains and lowlands on heavy, acid clay with dense brigalow and brigalow-blackbutt scrub results. The plains are usually developed on the more argillaceous lower layers of the Tertiary sediments but have also developed on older rocks where weathering had penetrated through the Tertiary cover. This type of country is widespread in the Morpeth- Bombandy area, in the Blackwater Creek and lower Comet valleys, and around Humboldt. Where the weathered rock now exposed is basalt the clays tend to be alkaline rather than acid, and carbonate and gypsum are common. Over wide areas the Tertiary rocks and the deep weathering profile were removed entirely and the underlying little-weathered Permian rocks or basalt have been exposed. Where this has happened, lithologic variations exercise a decisive influence on the present soils and vegetation, unless a later generation of detrital material has been laid down. These fresh rock areas often occur below the higher mesas on which the Tertiary land surface is preserved and on the flanks of which the deep weathering profile is exposed. As a rule the erosion has not penetrated deeply into the rocks below the Tertiary sediments and the present surface closely corresponds to that developed in late Mesozoic times on which the Tertiary basalt was deposited. This shows that there has been little overall movement of the area relative to base level of erosion since that time. Removal of the Tertiary sediments has increased the range of relief and has rejuvenated some of the sandstone scarps which previously rose slightly above the GEOMORPHOLOGY OF THE ISAAC-COMET AREA 83

Tertiary land surface. In particular, the Kerlong Range and the northern end of the Shot over Range were practically doubled in height as a result of this process. It is noteworthy that dissection of the Tertiary sediments and land surface often commenced in valleys running close to, and parallel with, the foot of the scarps, e.g. Blackwater and Annandale Creeks. These valleys now form lowlands bounded by a laterite breakaway on one side and a steep, rejuvenated sandstone scarp on the other (Fig. 9). The dissection of the deeply weathered land surface was also associated with considerable readjustment of the drainage. In the north there was an overall shift of drainage eastwards: headwaters of Connors River encroached on the Isaac drainage and captured what was upper Anna Creek (now upper Bee Creek) and Carborough Creek, while the Isaac captured Grosvenor Creek and upper Hill and Skull Creeks which formerly flowed west to the Suttor drainage. The capture of upper Anna Creek was indirectly responsible for the formation of the semi-permanent Lake Elphinstone situated at the entrance of Anna Creek gorge through the Carborough Range. When Anna Creek lost most of its headwaters to the Connors River the

Fig. 9.—Relationship of Blackwater Creek valley to the Tertiary land surface and the Triassic sandstone scarp, south of Blackwater. truncated survivor still retained the flat, long profile developed when it was a larger stream, and consequently it no longer had sufficient erosive power to remove all material reaching its bed from the sides of the gorge. As a result detrital material from the steep adjacent slopes dammed the valley and formed the lake. Blackwater Creek, working along the strike at the foot of the Shotover Range, has captured drainage which previously flowed west from the scarp to the Comet River. In the south of the area, a number of streams which formerly flowed southwards to the Dawson catchment, notably Carnarvon Creek, have been captured by headwaters of the Comet and the Dawson itself may eventually be captured in the same way.

(g) Late Tertiary Deposition Renewed deposition occurred in the latter part of the Tertiary though it is often not easy to distinguish its effects from those of the main phase of Tertiary deposition. The deposits form fans and colluvial aprons around uplands, and gravelly dissected terraces along the major streams. The nature of the material in these deposits is generally related to that of the source areas. Numerous gravel fans between the Bruce Highway and Funnel Creek are often highly calcareous as a result of the 84 R. W. GALLOWAY

base-rich nature of the volcanic rocks from which they have been derived. Rivers issuing from sandstone ranges laid down extensive sandy fans such as that on Cherwell Creek west of its junction with the Isaac River, or those fringing the Kerlong Range in the Burton Downs area. Streams such as Carnarvon Creek that issue from the high, dissected Blackdown Tableland in the extreme south-west laid down extensive gravelly fans and coarse bouldery terraces at this time. Over wide areas deposits of this stage contain reworked quartz and billy gravel derived from dissection of the main Tertiary sediments. The late Tertiary deposits were, in their turn, subjected to weathering and dissection though these processes were less intense or prolonged than those which operated earlier in the Tertiary.

(h) Quaternary Alluviation During the Quaternary extensive alluviation occurred along the major streams and a complex landscape of levees, flood-plains, channels, and back swamps developed. The higher parts of the alluvial flats are now stable with well-developed soil profiles and are above flood level. The lower parts are still subject to scouring, deposition, and flooding. Two definite terraces are developed along the Mackenzie River, where the higher level is as much as 50 ft above the present river bed, and along the upper Isaac River. In the Comet drainage, on the other hand, terraces are poorly developed and the present flood-plain extends across the entire valley floors as a rule. Usually the higher parts are coarser-textured than the lower contemporary flood-plains, but along Funnel Creek there are places where a high clay terrace exists; it is possible that this clay is part of the Tertiary deeply weathered deposits rather than alluvium. Channels in the flood-plains are either single with a meandering pattern, or complex with a braided pattern. The single channels tend to be deeper and are usually associated with higher alluvial plains, rarely, if ever, flooded. The braided channels tend to be associated with younger, finer-textured alluvial areas subject to frequent flooding. Rapid accumulation of younger alluvial deposits along Moolayember Creek has dammed its tributary Arcadia Creek and so formed the shallow, intermittent Lake Nuga Nuga.

III. GEOMORPHOLOGY AND THE LAND SYSTEMS The land systems have been classified into five major groups according to their relationship to the Tertiary land surface and weathered zone: those on intact or slightly denuded Tertiary land surface, those formed on erosional areas within the Tertiary weathered zone, those on depositional areas within the weathered zone, those on erosional areas cut on older rocks beneath the Tertiary weathered zone, and those on post-Tertiary alluvium. These major groups have been divided into subgroups according to relief: mountains, tablelands, hills, lowlands, and plains. Mountains have local relief from 300 to 2000 ft; hills have local relief from 50 to 400 ft; lowlands have local relief from 10 to 100 ft and slopes up to 4° or 5° but usually less; plains have local relief up to 20 ft and few slopes exceeding 1%. Within these relief-determined subgroups the individual land systems are arranged according to lithology with GEOMORPHOLOGY OF THE ISAAC-COMET AREA 85

dominantly quartzose rocks first and the more basic rocks last. This tripartite classification is adopted in the following description and summarized in Table 8. Some land systems extend over more than one geomorphic category and this is discussed in the text and indicated in the table.

TABLE 8 GEOMORPHOLOGY AND THE LAND SYSTEMS

Relationship to Tertiary Land Relief Category Land Systems in Order of Lithology— Surface and Weathered Zone Quartzose to Basic

Intact or slightly denuded Tablelands Junee, Durrandella (part) Tertiary land surface Lowlands and plains Monteagle, Moorooloo, Nebo (part)

Erosional areas within the Hills Durrandella (part), Bedourie (part) Tertiary weathered zone Lowlands and plains Humboldt (part), Daunia (part), Race- course

Depositional areas within the Plains and lowlands Daunia (part), Blackwater, Humboldt Tertiary weathered zone (part), Somerby

Erosional areas below the Mountains Carborough, Britton, Percy Tertiary weathered zone Tablelands Black Alley Hills Planet (part), Bedourie (part), Skeleton, Waterford Lowlands and plains Planet (part), Cotherstone, Rewan, Ar- cadia, Barwon, Girrah, Hillalong, Nebo (part), Oxford

Post-Tertiary alluvium Higher alluvial plains Connors Lower alluvial plains Funnel, Comet

(a) Land Systems on Intact or Slightly Denuded Tertiary Land Surface Extensive remnants of the old Tertiary land surface, with gently undulating relief, sandy or loamy surface, and a deep weathered zone have survived in the centre and north of the area and near Planet Downs. In the south, subsequent erosion has completely removed it. Where deep late and post-Tertiary erosion by the major streams has occurred, the remnants of the old landscape are perched on top of mesas which may range from a fraction of a mile to several miles across and are usually bounded by steep, broken slopes with lancewood. Where incision of major streams subsequent to the formation of the Tertiary land surface has been slight, these land systems form undulating areas without clear-cut steeper bounding slopes and may possibly have been subject to more severe surface stripping than the higher mesa tops. (i) Tablelands.—Junee land system consists of tablelands on Tertiary sandstone with gently undulating sandy summits 50-400 ft above the surrounding lowlands. Smaller tablelands, up to 1 mile across, form the higher units of Durrandella land system. (ii) Lowlands and Plains.—Monteagle land system consists of gently undulating lowlands with rather heavier-textured soils. Moorooloo land system, found east of 86 R. W. GALLOWAY

Springsure, consists of detrital spreads of quartz gravel in a matrix of red clay, overlying weathered basalt. Part of Nebo land system is similar but the gravels are derived from volcanic rocks.

(b) Land Systems on Erosional Areas within the Tertiary Weathered Zone Land systems within this group tend to have heavy soils for the most part, formed within the lower part of the weathered zone and coinciding with the argillaceous lower layers of the Tertiary deposits. Limited higher areas with loamy or sandy surfaces rise from the clays and correspond to survivals of the upper part of the Tertiary weathered zone, capped in places by relics of the Tertiary land surface. (i) Hills.—The lower part of Durrandella land system is formed on dissected sandstone hills, often capped by scarps of Tertiary sandstone and overlooking stony colluvial foot slopes. Low hills on weathered basalt and Permian sediments form part of the Bedourie land system. (ii) Lowlands and Plains.—Gently undulating country on deeply weathered Permian sediments forms part of Humboldt and Daunia land systems; stony patches derived from sandstone beds are common. Racecourse land system is formed on deeply weathered basalt with frequent occurrences of secondary carbonate and gypsum, and patches of quartz gravel.

(c) Land Systems on Depositional Areas within the Tertiary Weathered Zone This group of land systems occurs on detrital material derived by reworking of Tertiary sedimentary rocks, from which they are not always readily distinguishable. (i) Plains and Lowlands.—Part of Daunia land system consists of sandy colluvial aprons derived from dissection of Tertiary sandstone mesas. Blackwater, Somerby, and much of Humboldt land systems are all very similar and consist of plains on weathered Tertiary clay usually showing some indication of reworking and redeposition. Deep gilgai is characteristic of Somerby land system.

(d) Land Systems on Erosional Areas cut below the Tertiary Weathered Zone This group of land systems is found where erosion has completely stripped off the Tertiary land surface and weathered zone and cut down to the fresh rocks beneath. As a result, lithologic variations in the pre-Tertiary rocks are highly significant for vegetation, soil, and detailed land forms. In those land systems formed within the Tertiary weathered zone, on the other hand, deep weathering has gone far towards masking such variations. Included in this group of land systems are those on quartz sandstone which were, in fact, subject to deep weathering but were nevertheless little affected. (i) Mountains.—Carborough land system comprises exceptionally rugged country on quartz sandstone. Extensive structural control of relief, much bare rock, and rapid run-off are features of this type of country. Britton land system occupies a small area of mountains in the extreme north-east on Lower Bowen Volcanics. Percy land system consists mainly of a deeply dissected basalt-capped plateau in the south-west of the area, but in addition includes very steep conical hills on Tertiary intrusive plugs and steep ridges on metamorphic aureoles and granitic intrusions. GEOMORPHOLOGY OF THE ISAAC-COMET AREA 87

(ii) Tablelands.—The small Black Alley land system occupies the undissected relics of a former extensive basalt cover in the extreme south-west of the area. The land system is sufficiently high above sea level (3000-3500 ft) for the altitude to influence appreciably the climate and, through it, the vegetation. (iii) Hills.—Planet land system, in part, consists of rocky sandstone hills with pockets of loose sand on the more gently sloping sites. Part of Bedourie land system consists of lower hills and lowlands on sandy and shaly rocks. Skeleton land system, with local relief up to 500 ft, is surprisingly steep in view of the weak sandstones and shales on which it is developed. However, these weaker rocks have been partially protected by a resistant basalt cap (part of Percy land system) and in the lower parts extensive fans of coarse billy gravel have further contributed to the protection of the bed-rock; middle slopes are deeply scored by narrow valleys. Waterford land system is found on hilly basalt areas and consists of a mixture of small mesas and colluvial clay foot slopes. This land system in many places shows traces of a former deep weathered zone which has not been entirely removed, and the soils are correspondingly reddish rather than black and secondary silica, carbonate, and gypsum are common. (iv) Lowlands and Plains.—These land systems often have distinctive vegetation patterns, such as groves and glades aligned along the strike, which reflect variations in the underlying lithology. It is also common to find remnants of a former cover of Tertiary rocks and weathered zone on the higher parts. Planet land system has been included in this group on account of the gently undulating area in the upper part of the Planet Creek watershed. However, this area was not visited during the course of the survey and might be better allocated to the group of land systems on erosional surfaces within the Tertiary weathered zone. Cotherstone land system consists of lowlands and low hills mainly round the Cherwell Range and north-east of Springsure; shallow, stony soils and rather weakly developed groving of the vegetation are usual. Girrah and Hillalong land systems form gently undulating terrain on non-quartzose sediments with moderately well-developed grove patterns. Barwon is similar but with well-developed groves. Rewan land system consists of lowlands on shales but extensive areas are covered by a thin but persistent layer of coarse billy gravel with stones up to a foot or more across. Arcadia land system in the extreme south of the area likewise consists of plains on shales, in some places with abundant billy gravel, but has a vegetation of dense brigalow-wilga scrub. Part of Nebo land system is undulating terrain formed on Lower Bowen Volcanics with heavy clay lowlands alternating with rather stony ridges. Oxford land system represents typical downs country of black soils and grassland developed on basalt. As a rule soils are deep but thin out on the low rises where outcrops occur.

(e) Land Systems on Post-Tertiary Alluvium Only plains are found in this group of land systems but there are profound differences between the higher parts not subject to flooding, with mature soils and usually coarse-textured material, and the lower parts subject to flooding, scouring, and alluviation, with immature soils and finer-textured material as a rule. It is 88 R. W. GALLOWAY

suspected that some areas of acid clay within these lower deposits are outcrops of underlying Tertiary weathered clay. (i) Higher Alluvial Plains.—Connors land system consists of levees and higher alluvial deposits mainly supporting box and bloodwood. (ii) Lower Alluvial Plains.—Funnel land system consists of flood-plains on silt and clay with poorly developed levees and supporting mainly coolibah. Comet land system consists of alluvial clay with brigalow found mainly along the major rivers in flood-out and back-swamp situations, and supporting dense brigalow scrub. PART VII. SOILS OF THE ISAAC-COMET AREA

By R. H. GUNN*

I. INTRODUCTION

Parent material lithology and the past history of weathering, erosion, and deposition are the most important factors which determine the nature and distribution of soils in the area. As described in Part VI the greater part of the area was at one time covered by claystone, sandstone, and conglomerate of Tertiary age. These rocks were subjected to deep weathering resulting in the development of laterite profiles with ferruginous, mottled, and pallid zones. Subsequent denudation of the weathered landscape led to the formation of a range of soils occurring in catenary sequence from ridge crest to valley bottom. On the more or less intact Tertiary surface red and yellow earths predominate. Where erosion has exposed the underlying weathered zones, soils with abrupt textural contrasts occur in mid sequence and cracking clay soils commonly with gilgai microrelief occur in bottom lands. Over wide areas the deep weathering profiles have been removed completely by erosion exposing the underlying relatively fresh rocks. In these parts lithology of parent rocks, relief, and recent climatic conditions are the dominant soil-forming factors. Cracking clay soils have developed on shales, lithic sandstones, and basalt, and texture-contrast soils have tended to form on coarse- to medium-textured parent materials. There are extensive areas of shallow or skeletal soils on resistant quartz sandstones. The widespread occurrence of solodized solonetz, solodic, and saline cracking clay soils indicates that soil formation has been influenced markedly by the presence of soluble salts. These salt-affected soils occur mainly on the lower parts of the Tertiary weathered zone described in Part VI. Most of the soils that occur in the area have been previously studied and described in Queensland, notably by Hubble (1961) and Isbell (1957, 1962).

II. SOIL GROUPS AND FAMILIES

The soils of the area have been arranged in seven major groups and 33 families as shown in Table 9. The major groups generally are broader than great soil groups; the cracking clay soils, for example, include the Australian black earths and grey and brown soils of heavy texture. The texture-contrast soils include solodized solonetz and solodic soils as well as polygenetic soils with similar characteristics. The families have been defined according to differences in properties considered to be of importance * Division of Land Research, CSIRO, Canberra. TABLE 9 SOIL GROUPS AND FAMILIES o Major Appropriate or Approximate Principal Profile Form Group Family Brief Description Equivalent Names (Northcote 1965) Alluvial Davy Uniform coarse textures Ucl.22, 1.23 soils Clematis Uniform medium to fine textures Uml.21,Uf6.33 Consuelo Stratified medium and fine textures Uml.2, 5.5,Uf6.33 Moolayember Coarse- to medium-textured soils on fine-textured • Alluvial soils (Stephens 1962) Um5.5 substrata Warrinilla Uniform medium- to fine-textured soils on coarse- Um5.5, Gn4.31 textured substrata Cracking Tertiary weathered zone parent materials clay soils Pegunny Gilgaied deep clay soils — mainly dark grey-brown Grey and brown soils of heavy texture Ug5.16, 5.24 strongly alkaline surface over mottled acid subsoils (Stephens 1962) Rolleston Deep clay soils — not gilgaied Grey and brown soils of heavy texture Ug5.J6, 5.38 (Stephens 1962) Sedentary on bas lit and other volcanic rocks O Arcturus Dark grey-brown to black self-mulching clay soils, Black earth (Stephens 1962) Ug5.12, 5.32 moderately shallow (24-36 in.) c 2 May Downs Dark grey-brown to black self-mulching clay soils, Black earth Ug5.12, 5.16 2 deep (> 36 in.) Glenora Dark brown or reddish brown clay soils, deep Brown soil of heavy texture Ug5.37, 5.15 Sedentary on var ous sedimentary rocks Teviot Dark brown to very dark grey clay soils, moderately Black earth Ug5.12, 5.15 deep to deep On alluvial parent materials Vermont Deep, brown to dark grey alkaline clay soils Grey and brown soils of heavy texture Ug5.16, 5.25,5.4 Shallow clay soil > on various materials Bruce Shallow clay soils (24 in. or less) Grey and brown soils of heavy texture Ug5.12, 5.37 Texture- Shallow soils (<.U in.) contrast Southernwood Sandy or loamy surface soils, acid to mildly alkaline Solod (Stephens 1962) Dr2.12 soils subsoils Medway Sandy or loamy surface soils, strongly alkaline Solodized solonetz and solodic Dr2.13, Dbl.23 subsoils (Stephens 1962) Deep soils (>36 in.) Thick sandy surface soils (> 15 in.) Luxor Acid to mildly alkaline subsoils Sandy solodic soils (Downes and Dy3.21, 3.42, 5.21 Sleeman 1955), sandy solod (Isbell 1957) Broadmeadow Strongly alkaline subsoils, generally mottled Solodized solonetz and solodic (Isbell Dr2.13, Dbl.23, Dy3.23 1957) Thin sandy surface soils (< 15 in.) Springwood Acid to mildly alkaline subsoils Solod Dr2.32, Dbl.32, Dy2.22 Taurus Strongly alkaline subsoils Solodized solonetz and solodic Dbl.23, Dy2.43,Ddl.23 Loamy surface soils (generally < 15 in.) Wyseby Acid to mildly alkaline subsoils Solod Dr2.31, Dbl.12 Retro Strongly alkaline subsoils Solodized solonetz and solodic Dr2.13, Dbl.13, Dy2.13 en O Red and Dunrobin Loamy red earths — sandy loam to sandy clay loam Lateritic red earths (Stephens 1962) Gn2.12 (/> yellow surface soils grading to light clay subsoils o earths Struan Loamy yellow earths — sandy loam to sandy clay Yellow earths (Stewart 1959; Stephens Gn2.22 H loam surface soils grading to light clay subsoils 1962) Annandale Sandy red earths — sand to loamy sand surface soils Gnl.12 m grading to sandy loam or sandy clay loam subsoils > Gregory Shallow red and yellow earths (< 24 in.) Gn2.11

Dark Cheshire Dark brown medium-textured surface soils grading to Gn4.13, 4.15, 3.93 o brown fine-textured alkaline subsoils and Bullaroo Dark grey-brown coarse-textured surface soils grading Gn4.31 I grey- to brown, acid, medium- to fine-textured subsoils > brown Gindie Shallow, uniform medium- to fine-textured soils on Uf6.33 JO soils highly calcareous materials m Ingelara Shallow, uniform medium-textured, neutral to strongly Um5.2,4.2 > acid soils

Uniform Petrona Moderately shallow, uniform coarse-textured soils Ucl.21 coarse- (<36in.) textured Highmount Moderately deep to deep, uniform coarse-textured Ucl.23,4.11 soils soils (>36 in.)

Shallow Rugby Shallow, uniform medium- to fine-textured soils Uml V Skeletal soils (Stephens 1962) rocky soils Shotover Shallow, uniform coarse-textured soils Ucl.2 92 R. H. GUNN

to land use and the differentiae vary from group to group. In the cracking clay soils parent material, microrelief, depth, reaction, and colour are the main properties. The texture-contrast soils are differentiated on the basis of effective depth, thickness and texture of surface soils, and subsoil reaction. Soils that are common to the three survey areas in the Fitzroy region have been given the same group and family names. Correlations between the soil families and great soil groups and the dominant principal profile forms (Northcote 1965) are shown in Table 9. It will be noted that a particular family may be equated with more than one principal profile form and vice versa for the reason that different criteria are used in grouping the soils.

III. DESCRIPTIONS OF THE SOIL GROUPS AND FAMILIES

The following descriptions of the soils are based on the examination of approximately 500 profiles. Examination was carried out by means of auger borings but numerous small pits were dug in order to examine the upper soil horizons in situ. The standard terminology suggested by the United States Department of Agriculture (1951) has been used to describe the soils. Some of the more important soil properties affecting land use are discussed in Part X. (a) Alluvial Soils The soils of this group occur on recent alluvial deposits and show little or no profile development apart from slight accumulation of organic matter at the surface or lime in the deeper layers. The soils are deep, commonly stratified, and have textures that range from sands to clays. Structure is usually massive. These soils are widespread throughout the area and occur on alluvial flats adjacent to major streams. They are derived from predominantly fine-textured alluvium but coarser textures occur where source materials originate in areas of quartzose recks. These soils are imperfectly to moderately well drained but in some areas they are subject to flooding of varying depth and duration in the wet season. The group includes five families which have been distinguished on the basis of their textural characteristics. (i) Davy.—These soils have uniform sand or loamy sand textures, single-grain structure, and dominantly brown colours. They occur generally on levees and support savannah woodland of Moreton Bay ash. Soil reaction is slightly acid throughout. (ii) Clematis.—These soils have layers of medium to fine textures ranging from fine sandy loams to medium clays, predominantly silty clay loams, and silty clays. They occur on broad levees and lower-lying parts of alluvial flats which are subject to flooding. Colours are very dark brown to very dark grey-brown and there is a gradual change to dark brown or grey-brown with increasing depth. Structure is generally massive and vesicular. Soil reaction is slightly acid at the surface and mildly to moderately alkaline at depth. The vegetation is savannah woodland dominated by Moreton Bay ash, silver-leaved ironbark, or blue gum. SOILS OF THE ISAAC-COMET AREA 93

(iii) Consuelo.—This family comprises stratified soils with textures ranging from clay loam to heavy clay and colours that vary from black at the surface to dark brown or brown at depth. A little soft carbonate was noted occasionally in the deeper layers. Soil reaction varies from slightly acid to neutral at the surface to moderately alkaline below 2 ft. The vegetation is savannah woodland dominated by silver-leaved ironbark or Moreton Bay ash. (iv) Moolayember.—These soils have sand to clay loam surface layers up to 2 ft thick underlain by light to medium clays. Dark grey-brown colours predominate in the surface layers and dark brown or brown in the underlying clays. Soil reaction is about neutral throughout. Savannah woodland dominated by silver-leaved ironbark or Moreton Bay ash is the characteristic vegetation. (v) Warrinilla.—These soils are dark grey or brown clay loams to medium clays, 1 to 3 ft thick, overlying sand or loamy sand substrata. The upper layers are usually massive and vesicular but some clays have weak, blocky structure. The underlying sands are structureless. Soil reaction at the surface is slightly acid to neutral and is mildly to moderately alkaline above the sandy layers. The soils have moderate internal drainage but they are subject to periodic flooding by overflow. The vegetation is savannah woodland dominated by silver-leaved ironbark, Moreton Bay ash, poplar box, or blue gum.

(b) Cracking Clay Soils The main characteristics of these soils are their uniform medium to high clay contents and pronounced swelling and shrinking properties. Gilgai microrelief is an important feature in some soils of this group. They are widespread throughout the area and have formed on parent materials derived from basalt and other volcanic rocks, various sedimentary rocks, alluvium, and unconsolidated clays of the Tertiary weathered zone. Most of the soils may be classified broadly as grumusols (Oakes and Thorp 1950) and as grey and brown soils of heavy texture or black earths (Stephens 1962). Certain of these soils were classified and mapped by Isbell (1962) in his study of the brigalow lands of eastern Australia. They have been arranged in five subgroups, according to parent material differences, and eight families, generally according to differences in depth, reaction, and colour. (i) Tertiary Weathered Zone Parent Materials Pegunny.—These soils have been previously described by Hubble and Isbell (1958), Isbell (1962), and Reeve, Isbell, and Hubble (1963). They are very deep medium to heavy clays (50-70% clay) and have strongly developed gilgai microrelief with vertical intervals between mounds and depressions ranging between 1 and 4 ft. They occur generally in low-lying areas with very gently undulating to nearly level relief and are believed to have developed on the lower zones of truncated deep weathering profiles (Fig. 10). Gravelly and stony phases are included. Surface soil colours are predominantly dark grey-brown, but dark grey, brown, or reddish brown colours also occur. The colours generally become gradually lighter with depth and prominent, coarse, red, yellow, or brown mottles are common below 94 R. H. GUNN

4 ft. Occasionally colours are uniform throughout. Dark brown or black manganiferous staining frequently occurs at a depth of about 3 ft. The surface soils on the mounds generally have a thin, massive crust underlain by medium to coarse blocky structure. When they are dry, large cracks form in the depressions and there is a thin granular self-mulching layer at the surface and blocky structure beneath. The majority of these soils are moderately to strongly alkaline at or near the surface and become slightly to extremely acid at depths generally below 3 ft. In a few profiles reaction was neutral to mildly alkaline at the surface grading to strongly alkaline at depth or reaction at the surface was neutral to slightly acid and gradually became moderately to strongly acid at depths of 5 to 6 ft.

Bottom land Lower slope Intermediate 1 Crest and upper slope of low rise slope

Brigalow scrub Blackbutt- Poplar Narrow- Narrow-leaved ironbark woodland brigalow box leaved woodland ironbark scrub woodland

Gilgaied Cracking Texture- Texcure- Yellow Red earth— Dunrobjn family cracking clay earth- clay soil— soil— soil- soil — Struan Broad- Pegunny Kolleston Taurus family family meadow family family family

Fig. 10.—Soil catena on deeply weathered Tertiary sediments near Morpeth.

The alkaline-over-acid soils commonly contain low to moderate amounts of soft carbonate in the upper 3 ft and gypsum was noted in a few profiles at the same depth or slightly deeper. Surface drainage and internal drainage are poor and water may be retained in the gilgai depressions for considerable periods. These soils support a brigalow scrub vegetation sometimes in association with belah, blackbutt, or yapunyah. Analytical data on samples from three mound profiles are similar to those reported by Isbell (1962) and Reeve, Isbell, and Hubble (1963). Soluble salt contents determined by conductivity measurements on saturation extracts are low in the upper 2 ft (range 0-02-0-18%) but moderately high (0-35-0-60%) at lower levels. The exchangeable sodium percentage is less than 10 in the upper 1 to 2 ft but exceeds 15 at greater depths and in two profiles ranged from 25 to 53. The cation exchange capacities gradually increase with increasing depth and range from 25 to 48 m-equiv./lOO g soil. The soils are 60-80% saturated with metal cations even in the strongly acid SOILS OF THE ISAAC-COMET AREA 95

subsoils. Calcium is the dominant metal ion at or near the surface but it gradually decreases with increasing depth and magnesium becomes dominant. Organic carbon and total nitrogen in two profiles ranged from 0-7 to 2-3% and 0-06 to 0-22% respectively. Available phosphorus ranged from 48 to 120 p.p.m. Clay mineral determinations indicate that montmorillonite and kaolinite are co-dominant. Rolleston.—These soils are very similar to those of Pegunny family but gilgais are absent or weakly developed. They form a transitional belt between texture- contrast soils at higher levels and the gilgaied clays in lower situations. They have formed on unconsolidated clays in the lower parts of deep weathering profiles developed in a variety of parent rocks. Depths usually exceed 5 ft but indurated mottled- or pallid-zone materials sometimes occur below 4 ft. These soils correspond generally with the Miscellaneous Deep Clay Soils described by Isbell (1962). Textures are uniform medium to heavy clays throughout and a surface strew of coarse billy gravel is a common feature. Colours are predominantly dark brown or grey-brown and manganiferous staining and prominent grey and red mottling frequently occur in the lower profiles. At the surface there is either a thin, granular, self-mulching layer or a platy crust below which the structure is medium to coarse blocky. Reaction at the surface is usually slightly acid and there is a rapid change to moderate or strong alkalinity at depths of 2-3 ft. Below this depth, reaction becomes moderately to strongly acid. Small amounts of soft carbonate are generally present and gypsum sometimes occurs in the upper 3 ft. No analytical data are available in respect of these soils but chemical properties are probably similar to those of Pegunny family. The characteristic vegetation is brigalow scrub, usually with an understorey of false sandalwood and currant bush. (ii) Sedentary Soils on Basalt The soils of Arcturus, May Downs, and Glenora families have formed in situ, mainly on fresh basaltic or other basic volcanic materials. In some areas they appear to have been affected directly by deep weathering, in other areas indirectly by the leaching of weathering profiles that at one time lay above them, leading to the accumulation of masses of secondary carbonate. Stony phases occur in the three families. Arcturus.—The soils of this family occur mainly on the upper slopes of low rises in gently undulating areas on Tertiary basalt, often in association with shallow clay soils on the crests. Shallow linear gilgais sometimes occur. They are medium to heavy clays 25 to 36 in. deep, and are generally dark brown or grey-brown, occasionally black, in colour. The surface soils have a thin, friable, granular, self- mulching layer when dry, and are underlain by medium to coarse subangular blocky peds with firm to hard consistence. Surface drainage and internal drainage are judged to be moderate, and mottling is absent. Soil reaction is neutral to mildly alkaline at the surface, becoming strongly alkaline in the subsoils. Occasionally the profiles are strongly alkaline throughout. Small to moderate amounts of carbonate concretions are generally present. The characteristic vegetation is grassland or grassy woodland of mountain coolibah or bloodwood. 96 R. H. GUNN

No samples were taken during the survey but analytical data in respect of two profiles in the adjoining Nogoa-Belyando area indicate very high cation exchange capacities (65-85 m-equiv./lOO g soil). Calcium is the dominant metal cation and magnesium is second in importance. Exchangeable potassium is moderately high (0-8-1-1 m-equiv./lOO g soil) in the surface soil and exchangeable sodium is low throughout. Total nitrogen in the surface soil was 0 07% and the analyses indicated high contents of available phosphorus (800 and 3820 p.p.m.). May Downs.—These soils are similar to those of Arcturus family but they are more than 3 ft deep. They occur on gentle lower slopes and are somewhat less well drained. Soil reaction is slightly to moderately alkaline at the surface and gradually becomes strongly alkaline in the subsoils. A few small carbonate nodules are generally present in the upper profile and increase with depth to about 15% in some profiles. A thin, crusty, self-mulching layer forms at the surface on drying and the underlying structure is medium to coarse blocky. Cobbles and stones occur infrequently on the surface and in places are sufficient to interfere to varying degree with the use of machinery. Grassland is the characteristic vegetation. Glenora.—The soils of this family generally occur on crests or upper slopes of low rises in gently undulating areas. They have formed on materials derived from basalt or other basic volcanic rocks which have probably been subjected to more intense weathering than those of May Downs family. Depth to bed-rock is usually more than 4 ft. Colours are dark brown to reddish brown at the surface and dark reddish brown in the subsoils. There is a fine, granular, self-mulching layer 1 to 2 in. thick at the surface, with medium to coarse subangular blocky structure beneath. Reaction is neutral to mildly alkaline at the surface, becoming strongly alkaline at depth, or the soils are strongly alkaline and calcareous throughout. Small amounts of carbonate concretions are usually present in the lower profiles. The soils are moderately well drained but may be saturated for a few days after heavy rainfall. The vegetation is silver-leaved ironbark woodland or brigalow with softwood scrub species. (iii) Sedentary Clay Soils on Sedimentary Rocks Teviot.—This family comprises dark brown to very dark grey, moderately shallow to deep, cracking clay soils derived from Permian shales, siltstones, and lithic sandstones. They occur in gently undulating lowlands, commonly with linear gilgais, and have somewhat poor internal drainage. Depth to rock is generally more than 3 ft but is shallower in some areas where they occur in narrow, strike-controlled belts alternating with texture-contrast soils. Soil reaction is usually slightly acid at the surface, becoming strongly alkaline in the subsoils. A few profiles were strongly alkaline throughout. Small amounts of carbonate concretions are present below 2 ft and the subsoils are generally calcareous. When dry the soils crack and a thin, weak granular, self-mulching layer forms at the surface. The vegetation is grassland with scattered bloodwood or poplar box or brigalow with shrubs. (iv) Clay Soils on Alluvial Parent Materials Vermont.—The soils of this family are widespread and occupy fairly extensive areas in alluvial flats near major streams. The relief is very gently sloping to nearly SOILS OF THE ISAAC-COMET AREA 97 level but dissection by numerous braided stream channels occurs in some areas. Melon-hole gilgais occur in places, possibly where a relatively thin cover of clayey alluvium is underlain by the lower parts of denuded deep weathering profiles. These soils are very deep, dark brown to very dark grey, medium to heavy clays, generally with slightly acid to neutral reaction at the surface becoming moderately to strongly alkaline below about 2 ft. In some areas they are strongly alkaline throughout. Small to moderate amounts of carbonate are usually present and gypsum occurs infrequently. There is a weak, platy structure in the surface 1-2 in. when dry, and the underlying soil has a medium to coarse subangular blocky structure. The soils are very sticky and plastic when wet. Internal drainage is slow to very slow and these soils are liable to periodic or seasonal inundation to considerable depths. The characteristic vegetation is an open woodland of coolibah or brigalow scrub.

(v) Shallow Clay Soils on Various Rocks Bruce.—These are shallow cracking clay soils 24 in. or less in depth. They occur in areas of gently undulating to hilly relief and have formed on a variety of parent rocks, mainly basalt and shales. Colours range from reddish brown to very dark grey and reaction is generally neutral at the surface and moderately to strongly alkaline beneath. (c) Texture-contrast Soils The soils of this group have profiles with sandy or loamy surface horizons and abrupt changes to clayey subsoils. They are widespread throughout the area and have been described elsewhere in Queensland by Hubble (1961), Isbell (1957), Beckmann and Thompson (1960), and others. The soils have formed on a wide variety of parent materials derived from igneous and sedimentary rocks, alluvium, and the lower zones of denuded deep weathering profiles. Some of the members of this group are solodized solonetz or solodic soils formed by clay illuviation under the influence of sodium salts, resulting in the development of coarse, columnar-structured B horizons. Other soils are almost certainly polygenetic in origin and have formed by the deposition of medium- to coarse-textured materials on older clayey soils. They frequently have stone lines consisting of rounded or subangular quartz, billy, or ferruginous gravels above the subsoils. Gravelly or stony phases occur in all the soils of this group. They generally occur in areas of very gently undulating relief with slopes of less than 5%, but they also occur in areas of hilly relief on steeper slopes. They have been arranged in two main subgroups according to depth of sola. These are further subdivided into eight families according to differences in texture and thickness of surface soils and subsoil reaction (Table 9).

(i) Shallow Texture-contrast Soils Southernwood.—This family has sandy or loamy surface soils generally less than 15 in. thick, occasionally thicker, which are underlain by acid to mildly alkaline, sandy clay to heavy clay subsoils. Bed-rock of varying lithologies occurs at depths of 24 in. or less. 98 R. H. GUNN

Surface soil texture is predominantly sandy loam but ranges between sand and clay loam; moderate to large quantities of gravel frequently occur in the subsurface horizons. The surface soils are chiefly dark brown to reddish brown in colour. These soils have massive structure and set hard when dry. Subsurface soils are frequently lighter in colour and a sporadic or conspicuous bleach may occur. Subsoil texture is usually light to medium clay but ranges from sandy to heavy clay. Colours are mainly dark red or reddish brown, but brown, grey-brown, or very dark grey-brown also occur. Structure is medium, subangular or angular blocky, and consistence firm to hard when dry. Reaction is generally slightly acid or neutral but ranges from strongly acid to mildly alkaline. The vegetation is chiefly eucalypt woodland dominated by silver-leaved or narrow-leaved ironbarks or blackbutt- brigalow scrub. Medway.—These soils are similar to those of Southernwood family but have strongly alkaline subsoils, occasionally with columnar structure. Eucalypt woodland dominated by silver-leaved ironbark or blackbutt-brigalow scrub is characteristic.

(ii) Deep Texture-contrast Soils Luxor.—The soils of this family have dark grey-brown to reddish brown sand to sandy loam surface soils 15 in. or more in thickness, overlying grey-brown, yellowish brown, or reddish brown, moderately acid to mildly alkaline, clayey subsoils. Promin- ent, coarse, red, yellowish red, or brown mottles are common in the subsoils. They occur in areas of gently undulating relief and slopes rarely exceed 5%. They are poorly drained. The typical vegetation is poplar box woodland with a few shrubs and sparse grasses. The surface soils are usually massive and have firm to hard dry consistence, but some coarse sands do not set hard on drying. They are generally about 2 ft thick and there is a gradual change to lighter colours or a conspicuous bleach in the subsurface horizon. Reaction is slightly to moderately acid. Subsoil texture is generally sandy clay but ranges from sandy clay loam to medium clay. In the upper subsoil, structure is commonly massive but grades to coarse blocky beneath. Coarse columnar structure occurs occasionally. Dry consistence is firm to very hard and root penetration is poor. Reaction ranges from neutral to strongly acid. Broadmeadow.—These soils are similar to those of Luxor family but small to moderate amounts of carbonate are present in the subsoils, columnar structure is more common, and the subsoil reaction is strongly alkaline. Analytical data on four profiles indicate that cation exchange capacities are very low in the surface soils (less than 6 m-equiv./lOO g soil) and are less than 20 m-equiv./lOO g in the subsoils. Calcium is the dominant metal cation in the surface horizons and magnesium is dominant in the subsoils. Total soluble salts are low throughout but the exchangeable sodium is high in the subsoils and ranges from 20 to 45% of the exchange capacity. The preponderance of sodium and magnesium accounts for the poor physical properties of these soils. Total nitrogen and available phosphorus determinations in the surface soils indicate marked deficiencies of these SOILS OF THE ISAAC-COMET AREA 99

nutrients. Clay mineral analyses indicate that kaolinite and illite are co-dominant, with gibbsite accessory. Springwood.—These soils have thin, dark grey-brown or brown sand to sandy loam surface soils underlain by dark brown or yellowish brown clay subsoils. They occur on slopes of up to about 5% and support a savannah woodland or mixed shrub woodland of poplar box or narrow-leaved ironbark. The surface soils are about 8 in. thick, have massive structure, and are hard when dry. The subsurface soil is generally light grey or pale brown and is bleached sporadically at certain sites. Soil reaction is slightly acid to neutral. The subsoils are usually medium clays but sandy clay and light clay textures also occur. Structure is medium to coarse blocky, occasionally columnar, and consistence in the dry condition ranges from slightly to extremely hard. Mottling is uncommon. The soil reaction varies from neutral to moderately acid. The total thickness of the solum above bed-rock is generally more than 36 in. Taurus.—These soils have thin (less than 15 in.) sand to sandy loam surface soils, dark brown to grey-brown in colour over brown, yellowish brown, or reddish brown light to medium clay subsoils. The subsurface soils commonly are lighter in colour and sometimes sporadically or conspicuously bleached. The surface soils are generally slightly acid and there is a gradual increase to strongly alkaline reaction in the subsoils. Structure at the surface is massive and angular blocky, occasionally columnar, in the subsoils where small to moderate amounts of carbonate are generally present. The surface soils set hard when dry and subsoil consistence is commonly hard to very hard. These soils occur mainly on very gentle, intermediate or lower slopes and poplar box woodland or blackbutt-brigalow scrub are characteristic. No analytical data are available in respect of these soils but their chemical properties are probably similar to those of Broadmeadow family. Wyseby.—The soils of this family have brown or dark brown, sandy clay loam to clay loam surface soils, generally less than 12 in. thick, over yellowish brown, brown, or reddish brown, medium to heavy clay subsoils. A sporadically bleached subsurface horizon commonly occurs. Reaction is slightly acid in the surface soils and moderately acid to mildly alkaline in the subsoils. The surface soils have massive or very weak, fine blocky structure and the subsoils have medium angular or subangular blocky, occasionally columnar, structure and generally hard to very hard consistence when dry. These soils occur on very gentle lower slopes under poplar box woodland or blackbutt-brigalow scrub. Coarse billy gravel is commonly present in the surface soils in some areas. Retro.—These soils are extensive and widespread throughout the area. They occur mainly on very gentle slopes on the lower parts of the Tertiary weathered zone, formed on a variety of parent rocks. They have thin, brown to dark grey-brown, sandy clay loam to clay loam surface soils, generally 2-8 in. thick, occasionally thicker, over brown, dark brown, or red, medium to heavy clay subsoils. A very thin, sporadically bleached subsurface horizon commonly occurs. They are more than 3 ft deep. Reaction is slightly acid to mildly alkaline in the surface horizons and strongly or very strongly alkaline in the subsoils where small to moderate amounts of 100 R. H. GUNN

soft carbonate accumulations are generally present. Massive surface soils and blocky, occasionally columnar, structure and hard consistence in the subsoils are characteristic. The vegetation is typically brigalow scrub, sometimes with yapunyah, or blackbutt- brigalow communities. Poplar box or silver-leaved ironbark woodlands are less common. Analytical data on samples from four profiles in the adjoining Nogoa-Belyando area indicate cation exchange capacities of 12-15 m-equiv./lOO g soil in the surface horizons and 14-21 m-equiv./lOO g soil in the subsoils. Base saturation ranges from about 50% in the surface soils to more than 90% in the lower horizons. Calcium is the dominant exchangeable cation in the upper profiles but magnesium commonly increases at depth and may become dominant. Exchangeable potassium values range from 0-1 to 1-0 with the higher values in the surface soils. Exchangeable sodium is low at and near the surface but increases with depth and comprises 14-25% of the exchange capacities in two of the four profiles. Total nitrogen contents in the surface soils of two profiles were 0-08 and 0-09% and organic carbon was 1-1% in both cases. The available P2O5 contents were 45 and 74 p.p.m. Clay mineral determinations on subsoil samples from two profiles indicate that montmorillonite is dominant or subdominant and kaolin, illite, and quartz either subdominant or accessory. (d) Red and Yellow Earths These soils occur on tablelands, plains, and undulating land on residuals of the more or less intact Tertiary land surface. They are underlain by the deeply weathered zones of laterite profiles developed mainly in Tertiary sediments but also in other rocks of varying lithologies and ages. The more important characteristics of these soils are their red to yellowish brown colours, gradational or occasionally uniform texture profiles, and moderately acid to neutral reaction throughout. The loamy soils are massive with earthy, porous fabric and the sandy soils have single-grain, sandy fabric. They frequently contain varying amounts of ironstone concretions and are well drained. Four families are recognized according to differences in colour, texture, and depth. (i) Dunrobin.—The soils of this family have dark reddish brown or dark brown, sandy loam to sandy clay loam surface soils that grade to red or yellowish red, sandy clay loam or light clay at depths of less than 2 ft. They are generally more than 3 ft deep but may be underlain by massive laterite or indurated mottled zone between 2 and 3 ft. Pisolitic ironstone occurs infrequently in the lower profiles. Soil reaction is usually slightly acid to neutral throughout but occasionally is moderately acid. In undulating areas these soils occur on ridges and low rises and grade to yellow earths on intermediate slopes. The typical vegetation is narrow-leaved ironbark woodland. Analytical data on one profile indicate low exchange capacities of less than 8 m-equiv./lOO g soil; calcium and magnesium are the predominant metal cations. Total nitrogen and organic carbon were 0-05 and 0-7% respectively and available phosphorus was 16 p.p.m. SOILS OF THE ISAAC-COMET AREA 101

(ii) Struan,—These soils are similar to those of Dunrobin family but they are yellowish brown or brownish yellow in colour, sometimes with mottled subsoils, and they generally contain ironstone concretions in the lower profiles. They are more than 2 ft deep and are somewhat less well drained. Woodlands of narrow-leaved or silver- leaved ironbarks are characteristic. (iii) Annandale.—Sand to sandy loam textures to depths of 2 ft or more, and a gradual increase in clay content to sandy clay loam or light clay at depth, are characteristic of the soils of this family. Depths generally exceed 4 ft and in most cases are greater than 6 ft. Colours are brown to reddish brown at the surface, gradually becoming red or yellowish red at depth. Soil reaction is moderately acid to neutral throughout. Typical vegetation is an open woodland dominated by bloodwood, ghost gum, or narrow-leaved ironbark. (iv) Gregory.—These are shallow red earths 24 in. or less in depth and they occur on low rises or near scarp edges where the surface cover has been stripped off. Soil reaction ranges from neutral to very strongly acid. Lancewood or bendee scrubs are characteristic.

(e) Dark Brown and Grey-brown Soils The soils of this group have either uniform medium to fine textures or gradational texture profiles in which the clay content gradually increases with depth. They occur mainly on colluvial slopes on parent materials of varying origin and they form a somewhat heterogeneous group. Soil reaction ranges from strongly alkaline to very strongly acid. Four families are distinguished, mainly according to differences in depth, textural characteristics, and soil reaction. (i) Cheshire.—These soils have mainly gradational, occasionally uniform, fine texture profiles and dark brown or dark reddish brown colours. They are more than 3 ft deep and have formed on gentle slopes on outwash materials derived from sandstones and shales below ranges and hills chiefly in the extreme south of the area. Textures at the surface are sandy clay loams to clay loams and there is a gradual increase with depth to light or medium clay at 3 or 4 ft. Colours are very dark brown to reddish brown at the surface and there are gradual changes to brown, red, or yellowish red in the subsoils. Structure is weak, fine to medium subangular blocky, generally with rough-faced but occasionally with smooth-faced peds. Soil reaction at the surface is slightly acid and becomes moderately or strongly alkaline at depth. Small amounts of soft carbonate or hard concretions occur in some profiles. The characteristic vegetation is brigalow with an understorey of softwood scrub species. (ii) Bullaroo.—These soils are similar to those of Cheshire family but subsoil reaction is slightly to very strongly acid. Textures grade from sandy loam or sandy clay loam at the surface to light or medium clays below 2 ft, often with fine gravel. They have formed on colluvial slopes below hills and ranges in the south, probably on materials that have been strongly weathered. Colours range from very dark brown or dark reddish brown at the surface to brown or reddish brown in the subsoils. They have weak blocky structure with rough-faced peds and are more than 3 ft deep. 102 R. H. GUNN

Soil reaction at the surface is slightly acid to neutral and gradually becomes moderately to very strongly acid in the subsoils. The typical vegetation is woodland of narrow- leaved ironbark or lemon-scented gum. (iii) Gindie.—Uniform light to medium clays generally less than 2 ft thick underlain by secondary carbonate are the main characteristics of these soils. They occur in areas of undulating relief formed on weathered basalt and support a dense softwood scrub vegetation. The organic matter content is moderately high and the surface soils are loose and friable. Soil reaction is strongly alkaline throughout. (iv) Ingelara.—These are shallow soils, less than 2 ft deep with uniform sandy or silty clay loam textures and neutral to very strongly acid reactions. They occur in areas of hilly relief on parent materials derived from shales. Softwood scrub or spotted-gum woodland is characteristic. They are not extensive.

(/) Uniform Coarse-textured Soils The soils of this group are uniform sands to sandy loams formed on materials derived from quartz sandstones. There is little profile development apart from slight humic staining at the surface. Two families are distinguished according to differences in depth. (i) Petrona.—These soils are uniform sands or loamy sands less than 3 ft in depth and occur generally in areas of hilly relief on slopes of up to 10%. Colours at the surface are brown to dark brown and change gradually to brown, pale brown, or yellowish brown in the lower profiles. They are structureless and are slightly to strongly acid throughout. The characteristic vegetation is silver-leaved or narrow-leaved ironbark woodland with admixtures of cypress pine and black wattle. Rock outcrops are numerous in some areas. (ii) Highmount.—These soils occur on gentle, lower slopes below sandstone ranges and hills. They have brown, humic-stained surface soils about 12 in. thick underlain by brown, yellowish brown, or yellowish red subsoils. Textures are uniform sands to loamy sands throughout and they are more than 3 ft deep and commonly much deeper. Soil reaction is slightly to moderately acid. Woodlands of silver- leaved ironbark or ghost gum with admixtures of cypress pine, black wattle, or bloodwood are characteristic.

(g) Shallow Rocky Soils This group comprises very shallow, rocky soils with little or no profile development apart from slight humic staining at the surface. They are widespread and occur extensively throughout the area, mainly on steep hills and mountains. The criteria that distinguish the two families included in this group are texture and the nature of the parent rock. (i) Rugby.—These soils are very shallow (less than 12 in. deep) and have uniform, medium to fine textures. They have formed on basalt or shaly rocks and contain many freshly or partially weathered rock fragments. Hard rock outcrops are numerous. Soil reaction is slightly acid to neutral. Savannah woodland dominated by ironbarks is characteristic. SOILS OF THE ISAAC-COMET AREA 103

(ii) Shotover.—These soils occur extensively on the sandstone ranges and hills in the area. They have uniform coarse textures and are generally very shallow. Soil reaction ranges from slightly to strongly acid. The typical vegetation is shrub woodland usually dominated by narrow-leaved ironbark.

IV. ORIGIN AND OCCURRENCE OF THE SOILS

The occurrence of the soils in relation to the land systems and to some of the more important factors that have influenced their development are discussed briefly in this section. (a) Occurrence of the Soils The distribution of the various soils in the 28 land systems is shown in Table 10, and in respect of the area as a whole the soil distribution is shown in the small-scale soil map. Table 10 shows the estimated occurrence of individual soil families in each land system and their relationships to groups of land systems arranged according to geomorphology. (b) Past Climate and Geomorphic Influences The nature and distribution of the soils in the nine land systems which occur wholly on residuals of the Tertiary land surface or on erosional and/or depositional landscapes within the weathered zone have clearly been influenced more by past climate and geomorphic history than by any other factors. In particular, the effects of deep weathering on parent rocks tend to mask lithologic differences in all except quartz sandstones, and there are gradual changes from highly weathered to less weathered materials with increasing depth in the laterite profile. The land systems together cover about 7500 sq miles in the area and the dominant soils fall into three main groups which occur generally in catenary sequence, as shown in Figure 10. Red and yellow earths are dominant in Junee land system and are of minor importance in other land systems. They cover an estimated area of 1000 sq miles mainly in the northern half of the area on lunee tableland and in the vicinity of Bombandy, Iffley, and Annandale. In the southern half they are most extensive near Comet Downs. These highly leached soils rich in sesquioxides and kaolinitic clay are believed to have formed under more humid climatic conditions than those of the present day. Texture-contrast soils are dominant in Monteagle, Humboldt, and Moorooloo land systems on truncated, deeply weathered profiles. They also occur extensively in Junee, Durrandella, Daunia, Blackwater, and Somerby land systems. They cover about 3000 sq miles in these eight land systems. In some areas these soils have evidently formed by clay illuviation under the influence of sodium and/or magnesium salts and in others by the deposition of coarse- to medium-textured materials over older clayey soils. In Durrandella land system with hilly relief on weathered sediments shallow rocky soils are also extensive. Cracking clay soils, mainly Pegunny, Rolleston, and Glenora families, are dominant in Blackwater, Somerby, Daunia, and Racecourse land systems and are o

TABLE 10 ESTIMATED OCCURRENCE OF SOILS IN LAND SYSTEMS Percentage area of land system with each soil

Tntact or Erosional and/or Erosional Land Systems largely below the Tertiary Weathered Zone Alluvia Slightly Denuded Depositional Land Systems Land Areas on within Tertiary Mountains, Tablelands, ant Lowlands and Systems Major Group Tertiary Surface Weathered Zone Hills Plains and Family I Skeleto n Girra h Oxfor d Connor s Funne l Come t June e Monteagl e Mooroolo o Blackwate r Somerb y Racecours e Perc y Plane t Arcadi a Barwo n Hillalon g Neb o Humbold t Carboroug h Britto n Blac k Alle y Bedouri e Waterfor d Cotherston e Daum' a Durrandell a Oi 1 Alluvial soils O Davy <5 <5 5 Clematis 10 10 15 z Consuelo 5 •z Moolayember <5 5 5 Warrinilla 5

Cracking clay soils Pegunny <5 5 15 10 55 10 <5 10 Rolleston <5 <5 5 25 60 10 10 30 10 < 5 5 Arcturus 10 40 30 May Downs 30 30 45 Glenora 10 35 5 5 Teviot 40 10 45 35 5 Vermont 5 <5 5 5 <5 5 10 70 60 Bruce 20 10 10 45 5 20 25 15 Texture-contrast soils Southernwood 5 5 5 15 <5 10 25 10 Medway 10 25 Luxor 10 35 5 <5 10 5 30 35 10 20 10 Broadmeadow 5 50 5 <5 20 Springwood 5 <5 10 5 25 20 50 20 Taurus 5 5 35 5 25 30 15 20 5 20 10 15 20 20 5 Wyseby <5 40 5 5 5 <5 15 30 <5 10 Retro <5 20 10 15 2 Red and yellow earths o Dunrobin 35 5 10 5 Struan 25 5 5 <5 Annandale 10 <5 <5 I—I Gregory <5 10 5 <5 CO > Dark brown and grey -brown soils Cheshire 5 35 10 h Bullaroo 5 5 O Gindie 25 S Ingelara 30 <5 > JO Uniform coarse-textur ed soils w Petrona 5 10 25 <5 > Highmount 10 20 <5

Shallow rocky soils Rugby 15 100 85 100 30 55 10 <5 Shotover <5 30 70 5 40 20 106 R. H. GUNN

important in Humboldt land system. They are estimated to cover in these land systems 2200 sq miles, of which 640 sq miles have strongly developed gilgai microrelief. The most extensive areas are in the vicinity of Blackwater, Leichhardt Downs, and Morpeth, and along the Bruce Highway. Racecourse land system on weathered basalt also has extensive areas of dark brown and grey-brown soils.

(c) Lithology and Relief In the erosional land systems largely below the Tertiary weathered zone, soil distribution is governed mainly by lithology of parent rocks and relief. In five land systems (Carborough, Britton, Percy, Black Alley, and Skeleton) with mountainous to hilly relief covering 1900 sq miles, shallow, rocky soils predominate on quartz sandstones and basalt. They also occur extensively in Planet and Bedourie land systems in association with uniform coarse-textured and texture-contrast soils. The hilly Waterford land system on basalt has mainly shallow cracking clay soils. Shallow and deep texture-contrast soils are dominant in three land systems (Cotherstone, Hillalong, and Rewan) with gently undulating relief on sandstones and shales. Cotherstone land system, with a high proportion of deep texture-contrast soils with thick sandy surface horizons, occurs below sandstone ranges and hills mainly in the north-west. Shallow texture-contrast soils predominate in Hillalong land system in the extreme north. Deep texture-contrast soils, chiefly with thin sandy or loamy surface soils and acid subsoils, are dominant in Rewan land system in the extreme south. Barwon land system has about equal proportions of shallow texture-contrast and cracking clay soils which occur in narrow, strike-controlled belts on steeply dipping Permian sediments. Basalt, shales, and materials derived from volcanic rocks in Oxford, Girrah, and Nebo land systems give rise to predominantly cracking clay soils low in quartz. These land systems occur in gently undulating lowlands and plains and together cover 1700 sq miles. Cracking clay and dark brown and grey-brown soils derived mainly from shales are co-dominant in Arcadia land system in the extreme south. Land form, mode of deposition, and the nature of source materials largely determine the nature and distribution of soils in the three alluvial land systems. Cracking clay soils are dominant in Comet and Funnel land systems, covering 1270 sq miles of lower alluvial plains that are subject to seasonal flooding. They are most extensive along the Comet, Mackenzie, and lower Isaac Rivers and Funnel Creek. These streams rise chiefly in areas of shales and basalt and their deposits are consequently fine-textured. Connors land system occurs on moderately well-drained higher plains and terraces of streams with source areas of mainly quartzose rocks, and texture-contrast soils predominate.

(d) Halomorphic Influences The extensive occurrence of texture-contrast soils with solodized solonetz or solod morphology and cracking clay soils with appreciable contents of soluble salts indicate that halomorphic influences have been widespread. These soils occur chiefly in the erosional and/or depositional land systems on denuded Tertiary weathering SOILS OF THE ISAAC-COMET AREA 107

profiles. The possible source of salts which influenced soil formation at these sites is indicated by analytical data on several samples of mottled- and pallid-zone materials exposed on scarps in the area and in the adjoining Nogoa-Belyando area to the west (Fig. 1). The soluble salt contents ranged from 0-14 to 7-0%. In three samples collected near Morpeth, Rookwood, and Foxleigh, sodium and magnesium were the dominant exchangeable metal ions. The source of the salts and the processes whereby they accumulated in these materials are not clear, but it is considered most likely that the salts originated from the parent rocks and accumulated as a result of deep weathering. If appreciable quantities of sodium or magnesium salts are generally present in these materials, their distribution in subsurface seepage and run-off may account for the widespread occurrence of solonized soils in the catenary sequence on weathered Tertiary landscapes.

V. REFERENCES

BECKMANN, G. G., and THOMPSON, C. H. (1960).—Soils and land use in the Kurrawa area, Darling Downs, Queensland. CSIRO Aust. Div. Soils, Soils and Land Use Ser. No. 37. DOWNES, R. G., and SLEEMAN, J. R. (1955).—The soils of the Macquarie region, New South Wales. CSIRO Aust. Soil Publ. No. 4. HUBBLE, G. D. (1961).—Soils. In "Introducing Queensland", pp. 27-37. (Govt. Printer: Brisbane.) HUBBLE, G. D., and ISBELL, R. F. (1958).—The occurrence of strongly acid clays beneath alkaline soils in Queensland. Aust. J. Sci. 20, 186. ISBELL, R. F. (1957).—The soils of the Inglewood-Talwood-Tara-Glenmorgan region, Queensland. Qd Bur. Invest, tech. Bull. No. 5. ISBELL, R. F. (1962).—Soils and vegetation of the brigalow lands, eastern Australia. CSIRO Aust. Div. Soils, Soils and Land Use Ser. No. 43. NORTHCOTE, K. H. (1965).—A factual key for the recognition of Australian soils. 2nd Ed. CSIRO Aust. Div. Soils divl Rep. No. 2/65. OAKES, H., and THORP, J. (1950).—Dark clay soils of warm regions variously called rendzina, black cotton soils, regur, and tirs. Proc. Soil Sci. Soc. Am. 15, 347-54. REEVE, R., ISBELL, R. F., and HUBBLE, G. D. (1963).—Soil and climatic data for the brigalow lands, eastern Australia. CSIRO Aust. Div. Soils divl Rep. No. 7/61. STEPHENS, C. G. (1962).—"A Manual of Australian Soils." 3rd Ed. (CSIRO Aust.: Melbourne.) STEWART, G. A. (1959).—Some aspects of soil ecology. In "Biogeography and Ecology in Australia". Monographiae biol., Vol. 8, pp. 303-14. UNITED STATES DEPARTMENT OF AGRICULTURE (1951).—Soil survey manual. Agric. Handb. No. 18. PART VIII. VEGETATION OF THE ISAAC-COMET AREA

By R. STORY*

I. INTRODUCTION

The following points should be noted: (1) Where only the generic name is given it refers to the genus in general, or to one particular species if only one is listed in Appendix II. (2) The available common names of the plants mentioned are listed in Appendix II. (3) E. is used throughout for Eucalyptus. (4) Trees, shrubs, and grasses are listed alphabetically if they are equally common, otherwise the commonest come first.

TABLE 11 DOMINANCE OF EUCALYPTS, GRASSES, AND ACACIAS IN AREAS WITH DIFFERENT RAINFALL

Highest Eucalypt- Grass or Average Grass Acacia-Grass Rainfall Dominant Dominant (in.) (%) (%)

Hunter valley (humid) 60 90 6

Isaac-Comet area (intermediate) 29 65 35

Central Australia (arid) 14 Negligible 98

The overall character of the vegetation in the Isaac-Comet catchment is between that of the humid parts of Australia, dominated by grasses and eucalypts, and that of the arid parts, dominated by grasses and acacias. Table 11 shows the relationship in the areas in question, and indicates that here, as in most parts of the world, the prevailing vegetation is determined by the climate. The figures are from this survey and two others carried out by CSIRO (Perry et al. 1962; Story et al. 1963). Overriding though the climatic influence is, it varies only slightly over the area and the structure of the vegetation is rather uniform in consequence. The only botanical features which suggest some connection with a local climatic change are the breaks in the distribution of several species, as shown in Figure 11. * Division of Land Research, CSIRO, Canberra. VEGETATION OF THE ISAAC-COMET AREA 109

Fig. 11.—Some limits of distribution of vegetation observed within the area. 110 R. STORY

Other than this, the details of vegetation distribution are determined mainly by the topography, soils, geology, and reciprocal influences of different species. Examples will be pointed out in the following review of the vegetation types, which are: (a) Shrub woodland, sandstone form—narrow-leaved ironbark, bloodwood, E. cloeziana, many shrubs, scanty grasses; (b) Mixed shrub woodland—ironbark, box, many shrubs, fairly dense grasses; (c) Savannah woodland—ironbark, box, few shrubs, dense grasses; (d) Downs—grassland with scattered eucalypts; (e) Brigalow scrub (Acacia harpophylla); (/) Softwood scrub—mainly non-sclerophyll trees and shrubs; (g) Lancewood scrub (Acacia shirleyi); (h) Bendee scrub (Acacia catenulata); (/) Blackwood scrub (Acacia sp.).

Fig. 12.—Usual interrelations of vegetation types. Broken line, merging; solid line, contact; double line, disunity. The distribution of these types through the land systems is given in Table 12. Their merging or disunity, diagrammatically represented in Figure 12, shows that the only two types which can be looked upon as homogeneous and sharply defined are the lancewood scrub and the shrub woodland, sandstone form. The rest are relatively ill defined and the classification is thus a matter of convenience rather than unvarying accuracy. The relationships with geology and soils are shown in Figure 13.

II. DESCRIPTION OF THE VEGETATION TYPES (a) Shrub Woodland, Sandstone Form (i) General.—Its most consistently characteristic features are the dominance of an association of narrow-leaved ironbark and bloodwood, and the absence of box, TABLE 12 DISTRIBUTION OF MAIN VEGETATION TYPES IN THE LAND SYSTEMS, SHOWING PERCENTAGE OF LAND SYSTEM OCCUPIED BY EACH TYPE AND UNITS IN WHICH THE TYPES OCCUR Shrub Woodland, Mixed Shrub Savannah Softwood Lancewood Land System Sandstone Form Woodland Woodland Downs Brigalow Scrub and Bendee

0/ 0/ 0/ /o Units /o Units % Units Units Units °/ Units °/ Units /o /o /o Planet 100 1,2,3,4 Carborough 85 2, part of 1 10 3 5 Part of 1 Black Alley 100 1,2 Hillalong 100 1,2,4 <5 3 Nebo 100 1,2,3 i Skeleton 100 1,2,3,4 Monteagle 5 4 90 1,2,3 5 5 Moorooloo 90 1,4 5 2 5 3 O Percy 10 2 90 1,3 Connors 5 4,7 85 1,2,3,5 10 6 Z Rewan 10 Part of 2 85 1,4, 5 3 o part of 2 Junee 5 Part of 4 80 3, 5 5 10 2, part of 1 wX part of 1,4 Funnel 75 1,4,5 15 2 10 3 55 Britton 60 1 40 2 > Cotherstone 35 4,5 60 1,3 5 2 Waterford 55 1 45 2,3 Oxford 25 1,4 75 2,3 o Girrah 35 1,3 45 2 20 4 Arcadia 15 1 85 2,3,4 1 Humboldt 30 2, part of 70 3, part of 4,5,6 4,5,6 Somerby 30 1,2,4 70 3,5 Daunia 25 2,4 15 1 60 3,5,6 Blackwater 45 1,2,3,5,6 55 4 Comet 45 1,2,4,6, 55 3, part of 5 part of 5 Racecourse 20 3 45 2 35 1 Barwon 30 1,4, 25 Part of 3 5 Part of 3 40 Part of 2 part of 2 Bedourie 25 1, part of 3 75 2, part of 3 Durrandella 10 Part of 4 30 Part of 1,2,4 5 5 55 3, part of 1, 2

°/a of survey area 10 12 39 8 26 1 4 112 R. STORY

Bothriochloa, and Dichanthium. It is a uniform type of vegetation with little differentiation into communities and few deviations from the description that follows. The trees in the upper storey are 30-40 ft high, with a uniformly discontinuous canopy which gives more sunlight than shadow below. Mature trees have a diameter at breast height averaging about 8-9 in. with a maximum of about 12 in., and are so spaced that visibility at eye level, except where tall shrubs intervene, is 150-200 yd. No tree acacias occur, with the exception of Acacia cunninghamii, which grows in tree or shrub form. Their absence is strange in view of their prominence in the area as a whole and the prominence of the shrubby acacias in this vegetation type.

Fig. 13.—Main vegetation types in relation to geology and soils. A, Triassic sandstone and skeletal soils; B, Triassic shale and sandstone and skeletal soils; C, texture-contrast soils; D, cracking clay, commonly with melon-hole gilgais; E, cracking clay, basaltic and self-mulching, commonly with linear gilgais on slopes; F, basalt and skeletal soils; G, lateritic mesa and red and yellow earths; H, Tertiary sediments and skeletal soils. 1, Shrub woodland, sandstone form; 2, savannah woodland or mixed shrub woodland, bloodwood and narrow-leaved ironbark dominant; 3, savannah woodland or mixed shrub woodland, E. populnea dominant; 4, brigalow scrub; 5, downs; 6, savannah woodland, E. orgadophila, E. melanophloia, bloodwood, and/or narrow-leaved ironbark dominant; 7, lancewood scrub.

The upper-storey trees recorded are given in Table 13. Small trees are uncommon. Petalostigma, Xanthorrhoea, and Alphitonia were those most frequently recorded. Shrubs are abundant, 2-10 ft high, with ericoid forms fairly frequent, and of many species. Those given in Table 14 are representative. Except for some of the acacias, most of those recorded are restricted to this vegetation type. They are almost without exception evergreen and are usually mixed, pure stands seldom extending over more than a few acres or so. No lianes were recorded. The ground cover is scanty but floristicallyrich, and mostly of evergreen perennial dicotyledons, which are erect or trailing, often with soft leaves and very mixed. The most colourful and varied patches are in sandy pockets among the rocks {Helichrysum, Stylidium, Actinotus, and Isotoma). Monocotyledons are prominent although in the minority, and tend to be rather harsh, especially the grasses. Grasses are not a feature of this vegetation type, but those given in Table 15 are characteristic, and Triodia, Arundinella, and Themeda form pure communities up to an acre or so in size in some places. Pure communities are otherwise as unusual among the herbs as among the shrubs. (ii) Distribution.—With minor variations this type is found on the fresh quartzose sandstone throughout the area, that is, on Planet and Carborough land systems. VEGETATION OF THE ISAAC-COMET AREA 113

(b) Mixed Shrub Woodland (i) General.—Its characteristic features are the scarcity of gums and bloodwoods, and the abundance of E. populnea, open brigalow scrub, and ironbarks, with shrubs TABLE 13 UPPER-STOREY TREES RECORDED IN SHRUB WOODLAND, SANDSTONE FORM

Name Remarks

E. citriodora Mainly in upland valleys, not north oflat. 22°45'S. E. cloeziana Locally abundant on Reid's Dome and the Expedition Range E. peltata Expedition Range E. watsoniana Not south of lat. 25° S. Narrow-leaved ironbark Widespread, common Tristania suaveolens Rocky or damp places towards the south, uncommon

TABLE 14 SOME CHARACTERISTIC SHRUBS OF SHRUB WOODLAND, SANDSTONE FORM

Name Remarks

Acacia Boronia Dodonaea Grevillea Hovea Jacksonia scoparia Kunzea Labichea Leptospermum Lysicarpus angustifolius Notelaea ovata Seen only on the Expedition Range (see Petalostigma pubescens) Petalostigma pubescens In shrub form—seen only on the Expedition Range. Sometimes co-dominant with Notelaea ovata over several acres at a time Phebalium Prostanthera Pultenaea Ricinocarpus and grass below. It contains few large areas of homogeneous vegetation except for those dominated by E. populnea. Usually it is a complex, and from place to place it becomes added to or floristically poorer, or changes occur in the proportions of the plants within it. 114 R. STORY

As in the sandstone form of the shrub woodland, the trees in the upper storey are 30-40 ft high, with a diameter at breast height averaging about 8-9 in. and reaching about 12 in. The canopy, on the other hand, is irregularly discontinuous, and visibility at eye level is very variable. The trees of the lower storey are thinly scattered except near the transition between this mixed shrub woodland and the softwood or brigalow scrubs. Most of the shrubs are evergreen, but deciduous and semi-deciduous species are common enough to give a distinct character to the vegetation. All the shrubs vary widely in density and in height (2-12 ft). They tend to group more than in the sandstone form of shrub woodland, and the species are different.

TABLE 15 SOME CHARACTERISTIC GROUND COVER PLANTS OF SHRUB WOODLAND, SANDSTONE FORM

Name Remarks

Aristida Scattered in more open places Arundinella nepalensis Occasional, patchy Astrotricha pterocarpa Widespread, uncommon, diagnostic Caustis Widespread, common on Expedition and Carnarvon Ranges Chloris Scattered in more open places Cleistochloa subjuncea Cherwell Range Dactyloctenium radulans Scattered in more open places Dianetta Occasional Dinwrphochloa rigida Expedition and Carnarvon Ranges Eragrostis Scattered in more open places Hardenbergia Widespread, fairly common Helichrysum Widespread and common Heteropogon Scattered in more open places Hibbertia Widespread and common Lomandra Widespread and common Patersonia Occasional Pomax Fairly common Perotis Scattered in more open places Themeda Scattered, occasional patches in deeper soil Triodia Widespread, fairly common, patchy Tripogon loliiformis Scattered in more open places Schizachyrium obliqueberbe Scattered in more open places Setaria Scattered in more open places Lianes (five species) are occasional. The grasses, which make up nearly all the ground cover, belong to the eastern mid-height grass community of Perry and Lazarides (1964) and Pedley (1967). Most have a bunch habit with leaves up to 1 ft high and flowering culms up to 3 ft; mat-forming grasses are rare. Cyperaceae are frequent. Non-graminoid herbs are uncommon but their proportion rises where the shrubs are dense. The boundary between the mixed shrub woodland and the savannah woodland (where shrubs are uncommon or absent) can often be correlated with habitat differ- VEGETATION OF THE ISAAC-COMET AREA 115

ences, but sometimes the disappearance of the shrubs coincides with roads or fences where artificial influences have obviously been at work. Some difficulty arose in distinguishing between these intrinsic and induced differences, and for this reason the subdivision of the two vegetation types may not always be a natural one. (ii) Communities.—The communities are classified according to the dominant trees, which are a feature less easily influenced by burning and grazing than the shrubs and grass, and which are easily identified. Five communities are recognized: the complex; E. populnea and shrubs; narrow-leaved ironbark and shrubs; softwood scrub stragglers; E. melanophloia and shrubs. (1) The Complex.—This comprises more than half of the mixed shrub woodland, and is characterized by the general absence of dominant species among the trees. (2) E. populnea and Shrubs.—E. populnea is the commonest tree in this vegetation type, sometimes virtually the only one over many square miles. It is also locally co-dominant with other trees, and widespread as a subordinate constituent. It grows mostly on plains, low tablelands, or undulating country, and with even slight breaks of slope it normally gives way to other species, notably the ironbarks. It was not recorded on soils derived from basalt or granite, nor on steep slopes or quartzose sandstone, and with certain exceptions is uncommon on heavy clay or sandy red and yellow earths. It tends to occupy the soils between those two extremes, for example in Junee land system between brigalow on cracking clay at slightly lower levels and narrow-leaved ironbark on sandy red and yellow earth rises. It is particularly common on texture-contrast soils. E. populnea is also common as a mixture with brigalow, a mixture not of alternating trees of these two species, but of alternating clumps, in all shapes and sizes. The biggest area of this mixture, which is a feature of Arcadia land system, is in the Arcadia Creek basin. Areas almost as large, and many smaller areas, are widespread, and towards the north E. cambageana is also represented in the clumps of E. populnea. Soil differences were observed between the clumps of brigalow and E. populnea, and the shrubs and grasses in each are distinct. They are described later respectively under this subheading and under the subheading of brigalow scrub. Where E. populnea grows together with E. melanophloia (silver-leaved ironbark), the mixture is intimate and homogeneous, but ironbarks as a whole tend to have fewer shrubs below them, and to be more prominent as constituents of the savannah woodland. The shrubs with E. populnea include probably every one not confined to the Triassic sandstone. Eremophila mitchellii is the commonest of them all, particularly on texture-contrast soils, and tends to form pure communities. Two other species of Eremophila are locally dominant—E. latrobei (recorded in steep rocky places) and E. maculata. Carissa is common, and patchy although it occurs on a variety of soils. It is often in pure communities and is dense enough to suppress the grass and render considerable areas unfit for grazing. Grewia retusifolia is scattered everywhere, commoner in the north, and in open parts of the shrub woodland rather than in the deeper shade. It is also on a variety of soils. 116 R. STORY

Capparis is fairly frequent, especially C. lasiantha, which may be in the form of a shrub or a scrambler. The species are widespread but not gregarious. Bauhinia, which is more or less gregarious and occasionally dominant, is usually on hard-setting or clayey soils, often with Terminalia. It may have a stunting effect on the grasses within a few yards' radius of the stem. Two species occur in the area, but they could not be distinguished in the field. Eremocitrus is rare but widespread, and undiscriminating as to soils and associated shrubs. Grasses almost constantly present are Aristida, Bothriochloa, and Heteropogon, Aristida being dominant where the shrubs are thickest. The commonest species of Aristida are different from those of the downs and appear as a group to be ecologically distinct. Bothriochloa and Heteropogon are as often in pure communities as they are co-dominant, and in areas varying from acres to square miles. Locally each community is often confined to its own habitat (e.g. Heteropogon on flats, Bothriochloa on slopes), but no correlation was found to hold good over the whole area, and indeed a correlation may not only break down but become reversed (e.g. Bothriochloa on flats, Heteropogon on slopes). About seven species of Chloris were recorded, all common (C. acicularis probably more so than the others) but seldom in pure communities. Although individual species seemed to have their own special requirements, the genus as a whole seemed to grow as well in sunlight as in shade, and in all types of soil. Chrysopogon is widespread but patchy, and usually on red and yellow earths, but it was recorded also on heavy clay. The basal leaves form an open irregular mat up to a yard or so in diameter. Five species of Eragrostis were recorded, widespread and fairly common, but seldom in association with Heteropogon or Bothriochloa, and never in pure communities. Three species of Enneapogon are widespread but thinly scattered, and commoner on hard-setting soils. (3) Narrow-leaved Ironbark and Shrubs.—On sandy rocky slopes this is a fairly common community, other common trees being Petalostigma, Acacia cunninghamii, and Alphitonia, which often grow together, characteristically in patches of a few acres or so. The shrubs comprise Acacia curvinervia, A. bancroftii, and several other acacias, in thickets or otherwise. Grewia retusifolia, Erythroxylum australe, and Citriobatus are next in importance, the last two occasionally in thickets but more often singly. The grasses are as described in the E. populnea areas except that Hetero- pogon is slightly more common than Bothriochloa. (4) Softwood Scrub Stragglers.—The softwood scrub stragglers form a mixed shrub woodland on their own, especially towards the eastern side of the area, but the point at which they cease to form mixed shrub woodland and become softwood scrub is indefinite. A convenient but arbitrary indication of this is the disappearance of all eucalypts except E. cambageana. (5) E. melanophloia and Shrubs.—E. melanophloia (silver-leaved ironbark) is a fairly common dominant in mixed shrub woodland except in the Isaac catchment VEGETATION OF THE ISAAC-COMET AREA 117

TABLE 16 MINOR CONSTITUENTS OF THE MIXED SHRUB WOODLAND

Name Remarks

Acacia rhodoxylon Uncommon, recorded singly and in communities on low hills and rarely on level country between the Springsure-Duaringa and Clermont-Coast highways Albizia Patchy and uncommon Alternanthera Widespread and fairly frequent Ancistrachne Rare, in deep shade, more with softwood scrub than with eucalypts Apophyllum anomalum Widespread, occasional Atalaya Uncommon, widespread, in fair quantity north-west of Mt. Sirloin Brachychiton rupestre, Occasionally patchy, more often widely scattered, more with soft- B. australe wood scrub species than with eucalypts Bursaria incana Rather rare, patchy Callitris In fair quantity in parts of Durrandella and Monteagle land systems north of Planet Downs but otherwise rather rare, in sandy or rocky places, often with narrow-leaved ironbark and its associates. Sometimes widely scattered but more often in small patches of a few square yards up to several acres. The larger patches are structurally a form on their own, but are too unimportant over the area as a whole to warrant separate consideration Croton phebalioides Uncommon, more with softwood scrub species than with eucalypts Cymbopogon Widespread and frequent but never dominant Dodonaea Widely scattered E. exserta Occasional in rocky lateritized escarpments E. microcarpa Recorded in 3 patches of a few square miles in all (Bedourie, Car- narvon Highway near Christmas Creek, western foot of Shotover Range) E. tenuipes Rare, scattered or patchy in sandy or rocky places. Fairly plentiful 12 miles or so south of May Downs, and in that vicinity E. thozetiana Common on rocky slopes below lateritic mesas E. watsoniana Rare, at bases of sandstone hills with Petalostigma and Alphitonia Heterodendrum diversifolium, Widespread, occasional H. oleifolium Hibiscus Fairly frequent in rocky or sheltered sandy places Hovea Fairly frequent in rocky or sheltered sandy places Owenia Rare but widespread Paspalidium Rare, in deep shade, more with softwood scrub species than with eucalypts Santalum lanceolatum Etare but widespread Triodia Fairly frequent on sandy lateritized mesas Ventilago Uncommon, scattered, in level or undulating country, widely tolerant of soils and their parent materials 118 R. STORY

above Leichhardt Downs. It grows on a variety of soils and with almost every other plant in this vegetation type. Although it is thus presumably a tolerant species, it is rarely found in company with the narrow-leaved ironbarks. (6) Minor Constituents.—These are listed in Table 16. (iii) Distribution.—The mixed shrub woodland is commonest in broken country and on slopes, and on medium-textured or gravelly soils and rocky soils other than the poor quartzitic soils which support the sandstone form of shrub woodland. It is the most heterogeneous of the vegetation types, with a correspondingly complex pattern on the aerial photographs, not only because of its diversity but also because it is so often irregularly broken by savannah woodland and brigalow and softwood scrub patches. In Barwon land system the mixed shrub woodland is arranged in bands alternating with more open country, but although there is this regularity in the vegetation, there is no corresponding regularity in the floristics, and the composition of the bands varies widely. They correspond to the strike pattern of the Permian rocks, and the reason for dense trees on some and scattered trees on others is at present obscure. The grasses are similar throughout, but densest where the trees are scattered. (c) Savannah Woodland (i) General.—The savannah woodland differs from the mixed shrub woodland in having an open grassy floor with few shrubs, and a tree flora without the stragglers from the brigalow and softwood scrubs. The floristics and vegetation are accordingly much simpler. It grades without any definite boundary into mixed shrub woodland at one extreme and into downs at the other, according to whether the shrubs increase in number or the trees decrease. The visibility extends to 800 yd and averages about 400 yd. For all practical purposes the dimensions of the upper-storey trees may be taken as the same as the dimensions of those in the two types of shrub woodland (30-40 ft high, diameter at breast height averaging 8-9 in. with a maximum of about 12 in.). If shrubs are present at all, they are of the species found in mixed shrub woodland, and widely scattered. As mentioned under mixed shrub woodland, their presence or absence may in some places be an artificial characteristic. No lianes were recorded. The ground cover is eastern mid-height grass as described for mixed shrub woodland, that is with bunch grasses dominant, Cyperaceae frequent, and non- graminoid herbs uncommon. Evidence was found during the survey that two eucalypts of the savannah woodland may be increasing, namely E. papuana and E. microtheca. E. papuana seedlings about 2 ft high are common in most places where E. papuana is growing even sparsely, and E. microtheca seedlings about 5 ft high form thickets in much of the low-lying ground in the central part of the area, about 40 miles north and 20 miles south of the railway. The rainfall was abnormally high in 1954-56 (A. McGhie, personal communication; Bisset 1960, p. 403) and the abundance of E. microtheca VEGETATION OF THE ISAAC-COMET AREA 119

seedlings up to a certain contour level indicates that they are correlated with the flooding that took place in those years. Increases in E. populnea, E. melanophloia, and E. tessellaris have also been reported. (ii) Communities.—As in mixed shrub woodland, the communities are classified according to the dominant trees. The ten recognized are: the complex; E. populnea; narrow-leaved ironbark; E. polycarpa-E. tessellaris; E. melanophloia; E. tereticornis- E. tessellaris-E. polycarpa; E. microtheca; E. alba; E. maculata; vegetation of Black Alley land system. (1) The Complex.—As in mixed shrub woodland, this community is characterized by the absence of dominant species among the trees. It makes up about one-third of the total area of savannah woodland, and is represented in many land systems. (2) E. populnea.—E. populnea is not associated with shrubs or brigalow in savannah woodland, but its other associates and its behaviour are much the same as in mixed shrub woodland. This community covers about three-quarters of Monteagle land system, and smaller parts of many others, on plains, low tablelands, or undulating country. (3) Narrow-leaved Ironbark.—Only one of the four species known to occur in the area could be distinguished in the field. This was E. decorticans, a "gum-topped" species. It has a wide distribution on the Expedition and Carnarvon Ranges but its frequency is unknown. It was recorded with certainty on the sandstone, where it forms a savannah woodland (sometimes with E. maculata) within the sandstone form of shrub woodland which covers these ranges. The associated grasses include Aristida, Chrysopogon, Chloris, Cymbopogon, and Heteropogon, usually a rather poor cover. It could not be established whether the other narrow-leaved ironbarks were specific to any soil or geological formation. They are sometimes in a rather attractive pure stand over a dense cover of grasses in which Heteropogon, Bothriochloa, and Themeda are prominent. This community is dominant on the granitic intrusives of Percy land system and on the metamorphosed rocks associated with them. It is also found scattered through the lowlands on slight rises of sandy red and yellow earths, where it merges upslope with the following (£. polycarpa-E. tessellaris) community (e.g. on Junee land system); and occasionally and sporadically on clayey soils; and on the slopes of the sandstone ranges of Carborough land system. On these sandstone ranges, however, Bothriochloa is absent, except where interbedded shale occurs. In mixtures with all the other eucalypts of the savannah woodlands, narrow- leaved ironbark is common or dominant over large areas of country, but in such varying proportions that it would not be feasible at this scale of working to sort and classify the profusion of communities that occur. (4) E. polycarpa-E. tessellaris.—These two dominants are often mixed with E. watsoniana, and north of the latitude of Springsure with E. papuana, and are found mostly on sandy red or yellow earths on the tops of hills and low rises, covering large areas in Junee and Durrandella land systems, with minor occurrences in many others. Heteropogon is strongly dominant among the grasses, the commonest thereafter being Chrysopogon, Aristida, Themeda, Eriachne, and Eragrostis. 120 R. STORY

(5) E. melanophloia.—E. melanophloia is characteristic of low rocky rises in the basalt plains of Oxford and Moorooloo land systems, usually mixed with a little bloodwood and E. orgadophila, and with a fairly dense ground cover of Heteropogon and lesser amounts of Bothriochloa ewartiana and Aristida. It is also characteristic of the foothills of the basalt ranges of Skeleton land system, with Themeda dominant or common in the ground cover. It does not extend to the steeper slopes of the hills themselves. Elsewhere than in the basalt country it behaves as it does in the mixed shrub woodland, apart from the differences that result from the absence of shrubs. It often grows in pure stands with a sharp and inexplicable boundary between it and other trees, a characteristic also shown in the mixed shrub woodland but not as clearly, because of the complications and obscurities caused by the shrubs. The grasses are the common ones of the savannah woodland, namely Bothriochloa, Heteropogon, Aristida, and Chrysopogon. They extend beyond the E. melanophloia community without any corresponding break at its boundary. (6) E. tereticornis-E. tessellaris-E. polycarpa.—This community lines the larger creeks where the banks are sandy, being less common along ephemeral streams or where the soils are clayey, e.g. in the basalt country. The trees listed are often accompanied by Casuarina cunninghamiana, and sometimes by Melaleuca and Callistemon. The grasses are usually dense, with Heteropogon and Bothriochloa predominating. E. tereticornis without other trees is characteristic of the occasional swampy hollows that occur in various parts of the level country generally, fringing those permanently wet and covering those which are not. The ground cover is of Cyperaceae, Marsilea, Cynodon, and Eragrostis speciosa, singly or in varying combinations. (7) E. microtheca.—Communities dominated by E. microtheca, often with E. tessellaris, are widespread and common on the dark basaltic clays along the larger streams, or where the land is intermittently flooded. They are commoner than the communities of E. tereticornis over the area as a whole. The ground layer is of Bothriochloa, Aristida latifolia, Panicum queenslandicum, Cyperaceae, Thellungia advena, and Sporobolus mitchellii, forming a dense but coarse and unpalatable cover. (8) E. alba.—E. alba was not seen south of latitude 22° 30'. It is most abundant in the undulating sandy country between Oxford Downs and Annandale in Monteagle land system, mixed with E. polycarpa, E. papuana, and narrow-leaved ironbark, or locally in pure and scenically attractive communities up to a mile or more across. The ground cover is most commonly of Heteropogon with lesser amounts of Chrysopogon, Aristida, Eragrostis, and Themeda. It is also found in broad and shallow valleys in Junee land system, where it is mixed with E. populnea and has Bothriochloa and Heteropogon below. (9) E. maculata.—E. maculata is dominant over several square miles of the south-eastern foothills of the Black Alley Range in Cotherstone land system, associated with Acacia cunninghamii, narrow-leaved ironbark, Themeda, Cymbopogon, Eremochloa, Heteropogon, and Panicum fulgidum. Other than this, only scattered individuals were recorded, most at the foot of the Carnarvon and Expedition Ranges VEGETATION OF THE ISAAC-COMET AREA 121

in company with E. citriodora and Angophora floribunda, occasionally with A. costata. It was not seen north of the headwaters of Planet Creek or on the quartzitic sandstones. (10) Vegetation of Black Alley Land System.—The savannah woodland of this high basalt country in the Carnarvon National Park has floristically little in common with the savannah woodland vegetation so far dealt with. The slopes are of narrow- leaved ironbark and E. dichromophloia, with a thin scatter of Casuarina torulosa, E. microcarpa, E. punctata, E. melliodora, and Angophora floribunda. The only small tree is Macrozamia, sparsely but evenly distributed. The ground cover is a dense and

TABLE 17 MINOR CONSTITUENTS OF SAVANNAH WOODLAND

Name Remarks

Acacia salicina Widely scattered, usually on low-lying country and on the sandier soils Alphitonia Widespread and common in communities of up to a few acres on sandy soils Cassia brewsteri In sandy soil or clay, locally fairly frequent. Not recorded south of lat. 24°S. Casuarina luehmannii Patchy, often locally dominant in poor-looking country with sparse and wiry grasses Cymbopogon Widespread and common but rarely dominant Cyperaceae Common and widespread on a wide variety of soils Eucalyptus orgadophila Common on hilly basalt country Eremochloa Appears to be more frequent in the southern half of the area, forming mats of irregular size and shape Eriachne Widespread and common on sandy soils, in circular mats a yard or so across Grevillea parallela Widespread but scattered and rare, on sandy soils on level or undulating country Hakea lorea Widespread but scattered and rare, on sandy soils on level or undulating country Macrozamia moorei Mainly along the mountains on the western and south-western border of the area, locally common in open communities in spite of widespread destruction on account of its poisonous properties Panicum fulgidum Widespread but uncommon, on level sandy soils Petalostigma Widespread and common in communities of up to a few acres on sandy soils Perotis Widespread and common on sandy soils uniform sward of Themeda, a leafy strain about 12 in. high. Visibility is about 400 yd. On the plateau the trees are somewhat taller and denser than on the slopes—up to about 50 ft high and with a visibility of about 300 yd. Except for E. dichromophloia, all the trees of the slopes were recorded on the plateau as well, together with several add tional eucalypts that could not be determined. In both habitats the ground cover and the distribution of Macrozamia were similar. (11) Minor Constituents.—These are listed in Table 17. 122 R. STORY

(iii) Distribution.—The savannah woodland is mostly on level or gently undulating country with sandy red and yellow earths or texture-contrast soils, or on slopes on volcanic rocks. (d) Downs (i) General.—The downs are grassland, with visibility measurable in miles and with trees very widely scattered or in small patches. Bloodwoods, ironbarks, and boxes are present, gums and non-eucalypts are absent. The ground cover is of even and dense 2-3 ft perennial bunch grasses with few other herbs and with practically no shrubs. The topography is level to slightly undulating, the soil a heavy clay. The grasses, being dominant, are dealt with first and in more detail than the subordinate trees and shrubs. The commonest are Dichanthium, Bothriochloa erianthoides, and Heteropogon, sometimes in separate communities and sometimes growing together, the communities in either case being from a few yards to several miles across. The ecological interrelations between Dichanthium and Bothriochloa on the one hand and Heteropogon on the other could not be fully elucidated during the survey, nor could any reason be found for the strong bias in the distribution of Heteropogon. It is the dominant grass in the downs towards the north-east of the area, where in places it constitutes up to 90% of the cover, but is much less common in the rest of the downs. Dichanthium on the downs includes D. humilius, D. sericeum, D. tenue, and an unidentified species. Bothriochloa is represented by B. erianthoides, B. intermedia, B. decipiens, and B. ewartiana. In the woodlands only the last three species of Bothriochloa were recorded, and little Dichanthium. Subdominants over much of the downs are Panicum decompositum and Aristida leptopoda, harsh grasses which increase with faulty grazing management (Bisset 1960). They are common near and to the south of Emerald, but become scarcer towards the north, and beyond the Mackenzie catchment they were not recorded although they do occur further north outside the area. Neither was recorded from the woodlands. Aristida latifolia is a common constituent of the downs throughout the area; A. ramosa is also widespread but less common. Both have been recorded in the woodlands as well as in the downs. Iseilema vaginiflorum is an annual or a short-lived perennial, widespread and frequent, often more so in disturbed places. It is not a grass of the woodlands. Astrebla lappacea is locally common in the downs and confined to them. A. elymoides and A. squarrosa were also recorded. Minor constituents are listed in Table 18. Much of the downs country is gilgaied, invariably in the linear form except in some parts of Oxford land system south-west of Nebo where peculiar crescent-shaped hollows were observed. The correlation between the downs vegetation and gilgai is not consistent. Usually Heteropogon occupies the ridges and Dichanthium and Bothriochloa the hollows between them, but Cyperaceae and Eriochloa are sometimes dominant in the hollows, and near Grosvenor Downs Heteropogon was observed in the hollows and Thellungia advena on the ridges. VEGETATION OF THE ISAAC-COMET AREA 123

The trees are E. melanophloia, E. dichromophloia, E. tessellaris, narrow-leaved ironbark, E. papuana, E. orgadophila, and E. populnea, all tending to be a little commoner on slight rises than on plains or hollows. E. orgadophila is characteristic of the undulating parts bordering the basalt hills, E. populnea was recorded from soils derived from shales but not from the basalt. E. papuana was not seen south of the latitude of Springsure. The rest were ubiquitous.

TABLE 18 MINOR CONSTITUENTS OF THE DOWNS AND THEIR OCCURRENCE IN WOODLANDS

Name Downs Woodlands

Astrebla Fairly frequent, widespread Not recorded Chrysopogon Occasional Frequent Coelorachis rottboellioides Sometimes evenly scattered, and may make up Not recorded 10% of the cover. More often confined to damp places, where it may be dominant Cymbopogon Uncommon, scattered Uncommon, scattered Echinochloa colonum Sometimes locally dominant. Annual Not recorded Enneapogon Uncommon, scattered Uncommon, scattered Eragrostis Rare, scattered Common Eriochloa Several species, patchy and uncommon Not recorded Glycine tabacina Frequent and widespread Recorded, frequency unknown G. lomentosa Frequent and widespread Not recorded Neptunia Frequent and widespread Not recorded Ocimum sanctum Scattered, ubiquitous Not recorded Paspalidium globoideum Annual, and varying in frequency according to Not recorded conditions. At present rare Pimelea haematostachya Scattered, ubiquitous Not recorded Rhynchosia minima Frequent and widespread Occasional, widespread Thellungia advena Commonest in damp places Commonest in damp places Themeda Uncommon, scattered Uncommon, scattered

The shrubs recorded were mostly Grewia retusifolia, Acacia farnesiana, and Melaleuca bracteata. Grewia retusifolia is in the drier parts, the other two in well- watered parts like alluvium which is periodically flooded or receives run-off from the surrounding country. In such places Acacia farnesiana is usually scattered and Melaleuca bracteata concentrated along the channel banks. (ii) Distribution.—Although there are exceptions, a general rule is that the downs vegetation is on clays throughout the area except where they are occupied by brigalow scrub. (e) Brigalow Scrub (Acacia harpophylla) (i) General.—Comprehensive studies are being and have been carried out in Queensland on this economically important species. Papers by Everist (1962), Isbell 124 R. STORY

(1962), and Johnson (1962a, 1962ft) cover the soils and ecology on an extensive scale, but some results of intensive work have not yet been published. The papers cited have been freely used in drawing up this section of the report. Brigalow dominates a quarter of the area, and is widespread also as a less common constituent of the vegetation. Mature trees are erect, slender, and up to 60 ft high, with diameter at breast height up to 28 in. They have a clean bole for more than half their height, a fibrous, fissured, dark bark, and a rounded crown of rather dense branches set with silvery or dull green leaves. However, mature trees are uncommon, for fires have thinned and set back the brigalow over an enormous area. The regrowth is most vigorous from the roots, less so from coppice shoots, and in the early stages is in a shrub form known as "sucker" or "whipstick" brigalow. (ii) Brigalow Communities.—All the communities mentioned by Isbell (1962) and Johnson (1962a) occur in the area, but for the purposes of this report only about half are distinct and extensive enough to warrant separate consideration. The rest are considered together as a complex, and the brigalow will accordingly be dealt with under the following headings: brigalow complex; pure brigalow; brigalow with Carissa, Eremophila, and Terminalia; brigalow with eucalypts; brigalow with Geijera; and brigalow with softwood scrub. It is noteworthy that the ground cover is relatively uniform throughout, except in gilgai and seasonally flooded country. This point will be dealt with later. (1) Brigalow Complex.—This covers by far the greater part of the brigalow- dominant country. It is not readily divisible into formalized communities but is associated with a great variety of other trees, and its only consistent character is the dominance of brigalow. (2) Pure Brigalow.—Relatively undisturbed and dense communities have an unbroken canopy and are deeply shaded below, in the darkest parts with a layer of trash on the ground and patches of moss and fern, mostly Cheilanthes sp. The mosses and ferns are not present in the more open parts but scattered scrub grasses appear (Paspalidium caespitosum, P. gracile, P. constrictum), becoming thicker in the open spaces and floristically richer with an addition of Aristida, Sporobolus caroli, Brachyachne, Chloris unispicea, C. acicularis, Calyptochloa gracillima, and Leptochloa debilis. Dicotyledons in the ground cover are as a rule poorly represented. Hypoestes floribunda and Spartothamnella juncea are occasional in deeply shaded places, and Achyranthes, Rhagodia, Malvastrum spicatum, and Abutilon where the light is stronger. Where they abut upon the open country of the downs, dense brigalow communities end abruptly or through a fringe of Terminalia up to 20 yd in width, and with both species there is often a tapering in height. Where brigalow communities have a common boundary with savannah woodland or mixed shrub woodland the transition belt is usually from 50 to 100 yd wide and mostly of Eremophila mitchellii or Casuarina cristata. (3) Brigalow with Carissa, Eremophila, and Terminalia.—This is the largest and most widespread of the distinct brigalow communities, usually on level or low-lying ground and with Carissa and Eremophila mitchellii more frequent than Terminalia except in flooded or badly drained places, where Terminalia is the most abundant. VEGETATION OF THE ISAAC-COMET AREA 125

South of a point about 4 miles south of Rolleston Terminalia does not occur, though the other members of the community continue south to the edge of the mountainous country. The indications are that Carissa will not grow where it is liable to prolonged flooding, for it is usually absent from the flood-plains of the bigger rivers except on hummocks or along the levees. Eremophila mitchellii is scarcer on the flood-plains, and is joined by another member of the genus, E. bignoniiflora. Bauhinia is patchily distributed and fairly frequent in this community. (4) Brigalow with Eucalypts.—The small clumps of E. populnea associated with brigalow have already been mentioned under mixed shrub woodland. E. cambageana is a second associated eucalypt, normally growing a little more intimately with the brigalow, not only in small clumps but also singly, and with scrub grasses under it instead of the Heteropogon and Bothriochloa which are usually found with E. populnea. It is an indicator of texture-contrast soils. (5) Brigalow with Geijera.—Geijera occurs singly with brigalow throughout the area, but towards the south it is more often in communities, especially as an understorey in shrub form in the country south-east of Rolleston. The communities are in places mixed with softwood scrub. (6) Brigalow with Softwood Scrub.—The softwood scrub species are present in almost any proportion in this community. It gives way to pure brigalow or pure softwood scrub gradually or abruptly, often without perceptible habitat differences. The main constituents are: Citriobatus, Erythroxylum australe, Heterodendrum, Denhamia obscura, Geijera (in tree form), Macropteranthes, Br achy chiton, Capparis, Ventilago, Notelaea, Elaeodendron australe, Myoporum, Apophyllum anomalum, Canthium, Albizia, Eremocitrus, and Santalum lanceolatum. (iii) Distribution.—Brigalow scrub is dominant over Arcadia, Blackwater, Comet, Daunia, Humboldt, and Somerby land systems, and common on many others, but on the survey aerial photographs, which were mostly at a scale of 1 : 80,000, it was with few exceptions not possible to distinguish it from lancewood, softwood, bendee, or Casuarina cristata scrubs, and estimates are based on field traverses accordingly. It is mainly on dark cracking clay soils, being uncommon on steep slopes, texture- contrast soils, and deeply weathered basalt, and absent from rugged country, red and yellow earths, and fresh or slightly weathered basalt. It is common in bands on Barwon, Daunia, and Girrah land systems, and (often in association with softwood scrub species) occurs locally in bands on Humboldt land system as well. The same species grow in the bands as between them, the difference being merely a matter of density. Some unusual communities of pure brigalow were observed on soils developed on Permian sediments. They are circular and up to about 30 yd in diameter, sometimes separate and sometimes merging at the edges to form a massed community in which the basic pattern of circles can be seen only from the aerial photographs, and dimly at that. They were not studied in detail. The communities dealt with, and the complex, may all be associated with melon-hole gilgais, but the trees grow only on the ridges. The hollows are treeless, and bare at the bottom or covered by Marsilea. On the sides they have pure or mixed 126 R. STORY

herbaceous communities which include Panicum buncei, Leptochloa debilis, Thellungia advena, Cyperaceae, Muehlenbeckia, and Sporobolus mitchellii. Seasonally flooded country has a similar ground cover, but Panicum buncei is absent except in gilgai hollows. About half the brigalow-dominant country is gilgaied, one-quarter flooded, and small areas both flooded and gilgaied.

(/) Softwood Scrub (i) General.—Structurally this is a uniform type of dense, mostly evergreen, non-eucalypt trees branching low down and spreading upwards to form a deep interlacing canopy with its upper surface 20 ft above the ground. It is uniform on top except for scattered emergent trees, but indefinite below, for the shrubs and trees are not sharply distinct. Usually the shrubs are dense, sometimes impenetrable, with visibility reduced to a few yards. The average visibility is about 30 yd. Floristically the scrub is rich and heterogeneous, and the only locally abundant trees recorded among many mixed communities were Macropteranthes and Excoecaria dallachyana. Macropteranthes or bonewood, commonly associated with Carissa and Paspalidium, is distributed widely and sporadically in the scrub south of Emerald, apparently independently of soil, topography, or geology. It is a spindly tree which casts less shade than most scrub species. Excoecaria dallachyana is common in some of the scrub on Bedourie land system. It has a thick canopy which in the areas examined was sheltering a dense tangled undergrowth of Acalypha eremorum, Hypoestes, Ancistrachne, and many other less common plants. Of the emergent trees only Brachychiton ranges through the area from south to north. Cadellia pentastylis is fairly common in the south-east part of the country between the Carnarvon and the Springsure-Duaringa highways, but was seen nowhere else except for what is probably an island occurrence on the property Ardurad, between Blackwater and Rolleston. Araucaria was recorded only from Mt. Fort Cooper. Lianes are fairly frequent, but the survey notes are inadequate for a representative species list. Patches of mosses and ferns are scattered on the floor as they are in dense brigalow, and a layer of trash is present. Herbaceous plants, grasses or otherwise, are sparse or dense but only a few species occur. They are those of the denser brigalow, and include Paspalidium, Aristida, Ancistrachne, Hypoestes floribunda, Spartothamnella juncea, Achyranthes, Mahastrum spicatum, and Abutilon. Some of the commonest woody plants are listed in the brigalow-softwood scrub community (see under brigalow). (ii) Distribution.—Softwood scrub covers an insignificant area by comparison with brigalow and the patches are smaller. It is richest in species, least interrupted, and most extensive south-east of Rolleston, mainly on Bedourie land system, with minor patches on several others. It is common also along the Bruce highway, and extends to Britton land system in the extreme north. It is less common towards the west, and more open. Patches in the west occur on Racecourse land system and on volcanic rubble in Percy land system. The boundary is abrupt or changes at the edges very gradually into brigalow or mixed shrub woodland. In common with the VEGETATION OF THE ISAAC-COMET AREA 127

brigalow, it shows a close correlation with the strike of the Permian rocks where the soil is shallow enough. Even a cursory examination shows that softwood scrub includes distinct types of vegetation, and cannot be considered as an ecological entity. Patches may be found in cool wet areas, and floristically different patches on hot exposed north-western slopes. Those in cool wet areas are dense, and eucalypts probably cannot become established in the deep shade they cast (Cremer 1960). Those on hot north-western slopes are open, but presumably grow under conditions too severe for eucalypts, which are found on the same geological strata and on slopes as steep on the southern aspect.

(g) Lancewood Scrub (Acacia shirleyi) (i) General.—Lancewood does not grow as tall as the tallest brigalow but is on the average higher, for widespread burning like that which has stunted the brigalow has either not taken place in the lancewood or has had less effect upon it. The average height is about 35 ft, the bole is usually about 5 ft high and the crown correspondingly deep, and more open, erect, and rigid than that of the brigalow. It has a fibrous, fissured bark and yellowish green leaves. The communities are usually a little more open than the brigalow and not as mixed. Visibility averages about 70 yd but may be reduced by undergrowth when, as it often does, the lancewood grows on rocky hill sides. Associated trees are E. thozetiana, or more rarely E. decorticans, sometimes with scattered E. exserta around plateau margins. The hillside undergrowth mentioned includes any of the shrubs of the mixed shrub woodland. The ground cover is invariably sparse, often of Ancistrachne in rocky places, and on level ground a mixture of Aristida (particularly A. caput-medusae), Paspalidium, Calyptochloa gracillima, Eragrostis, Brachyachne, and Cymbopogon. Bare eroded areas (scalds) often occur downslope of the lancewood communities in Durrandella land system between Junee and May Downs. (ii) Distribution.—Lancewood appears to occur mainly on shallow, gravelly, strongly to extremely acid, texture-contrast soils, and dark brown and grey-brown earths, developed on parent materials that have been subjected to intense weathering and leaching. It is characteristic of the upper parts of lateritic breakaways in hilly country and of lateritic remnants in Durrandella, Junee, Cotherstone, and Carborough land systems, where these features most frequently occur.

(h) Bendee Scrub (Acacia catenulata) Bendee is too uncommon to warrant detailed treatment within the scope of this survey. It is found in the general area where lancewood grows, and in similar situations, usually in pure and somewhat denser communities. Patches occur also on red earths on the level mesa tops of Junee land system.

(i) Blackwood Scrub (Acacia sp.) Blackwood is an unnamed species of Acacia which was recorded in only two places—a few miles north of May Downs and 12 miles west of May Downs. It is in 128 R. STORY pure communities in close association with brigalow but sharply divided from it, in appearance rather like lancewood but more massive, and taller. Differences between blackwood and brigalow as shown on the aerial photographs are too slight to rely on, but the field records indicate that it is rare in the area. In its behaviour and requirements it appears to be much like brigalow.

III. REFERENCES

BISSET, W. J. (1960).—Overcoming white spear and yabila grass problems. Qd agric. J. 86, 401-6. CREMER, K. W. (I960).—Eucalypts in rain forest. Aust. For. 24, 120-6. EVERIST, S. L. (1962).—Making decisions. Qd agric. J. 88, 716-9. ISBELL, R. F. (1962).—Soils and vegetation of the brigalow lands, eastern Australia. CSIRO Aust. Div. Soils, Soils and Land Use Ser. No. 43. JOHNSON, R. W. (1962a).—Knowing the country. Qd agric. J. 88, 720-6. JOHNSON, R. W. (19626).—Clearing the scrub. Qd agric. J. 88, 737-50. PEDLEY, L. (1967).—Vegetation of the Nogoa-Belyando area. CSIRO Aust. Land Res. Ser. No. 18, 138-69. PERRY, R. A., MABBUTT, J. A., LITCHFIELD, W. H., QUINLAN, T., LAZARIDES, M., JONES, N. O., SLATYER, R. O., STEWART, G. A., BATEMAN, W., and RYAN, G. R. (1962).—Lands of the Alice Springs area, Northern Territory, 1956-57. CSIRO Aust. Land Res. Ser. No. 6. PERRY, R. A., and LAZARIDES, M. (1964).—Vegetation of the Leichhardt-Gilbert area. CSIRO Aust. Land Res. Ser. No. 11, 152-91. STORY, R., GALLOWAY, R. W., VAN DE GRAAFF, R. H. M., and TWEEDIE, A. D. (1963).—General report on the lands of the Hunter valley. CSIRO Aust. Land Res. Ser. No. 8. PART IX. GRASSES OF THE ISAAC-COMET AREA AND THEIR UTILIZATION

By R. STORY*

I. THE MAIN GRASS COMMUNITIES

In the following short account the grasses are dealt with independently of the woody growth which usually accompanies them. They have been divided into four main communities on a generalized basis and with special reference to the commoner grasses. Communities (a) and (d) are too sparse to contribute much towards the grazing, regardless of the time of year or of climatic conditions, and it is communities.(b) and (c) that produce most of the bulk per unit area. In all of them, growth ceases during the winter. Their seasonal palatability and nutritive value are discussed later, and their distribution through the land systems is given in Table 19.

(a) Sparse Mixed Grasses of Shrub Woodland, Sandstone Form A description of this community has been given in Part VIII in the account of the vegetation type concerned. It is found in rugged sandstone country, with skeletal soils. (b) Eastern Mid-height Grass Community This community is found on hilly or undulating country and on a wide variety of soils, most commonly on texture-contrast soils, clay soils, shallow rocky soils, red earths, and alluvial soils. It is a rather heterogeneous assortment which varies also in its cover and general vigour, and is characteristic of mixed shrub woodland and savannah woodland. The commonest grasses, particularly in savannah woodland, are Bothriochloa decipiens, B. intermedia, and Heteropogon, and in places these species make up nearly all of the pasture. They are found mixed or in pure stands. In the more open parts of mixed shrub woodland the dominant grass is Aristida, usually not in pure communities but mixed with a number of less common species of annuals and perennials which are individually insignificant but together important in terms of cover and grazing value. They commonly include Chloris, Chrysopogon, Eragrostis, Enneapogon, and Cymbopogon, with Themeda widely scattered. Some of the Aristida-dommdint country has a very sparse cover of stunted grasses and an obviously low carrying capacity. Other parts, with approximately the same species * Division of Land Research, CSIRO, Canberra. TABLE 19 CHARACTERISTICS OF PASTURE LANDS Proportions of Grass Pasture Land Relative Constituent Area Communities ("/,)* and Area Topography Grazing Value Land Systems (sq miles) (a) (b) (c) (d) 1 (1905 sq miles) Mountains and hills, some plains Poor Carborough 1490 85 10 5 Planet 415 95 5 2 (640 sq miles) Mountains, some hills Good, but access difficult Black Alleyf 55 100 Percy 300 10 90 Skeleton 285 100 3 (2675 sq miles) Lowlands, some hills Good Cotherstone 580 95 5 Hillalong 120 100 Monteagle 1655 95 5 Rewan 320 95 5 4 (1490 sq miles) Lowlands, some low hills Good to excellent Moorooloo 135 5 90 5 Oxford 1000 100 Waterford 355 100 5 (2920 sq miles) Lowlands Poor Arcadia 675 100 O Humboldt 2245 10 90 6 (180 sq miles) Lowlands Good Nebo 180 65 35 7 (1435 sq miles) Lowlands Good Connors 970 90 10 Funnel 465 75 15 10 8 (1060 sq miles) Mountains and hills Poor Britton 50 60 40 Durrandella 1010 40 60 9 (685 sq miles) Lowlands and tablelands Fair to good Junee 685 85 15 10 (2475 sq miles) Lowlands Poor Black water 825 15 85 Comet 805 45 55 Daunia 480 40 60 Somerby 365 30 70 11 (955 sq miles) Lowlands and low hills Fair to good Barwon 140 30 70 Bedourie 125 5 15 80 Girrah 525 80 20 Racecourse 165 20 80 * Community (a), sparse grasses of the shrub woodland, sandstone form; (6), eastern mid-height grass; (c), downs; (d), scrub grasses, t Themeda dominant. GRASSES OF THE ISAAC-COMET AREA 131

in the same proportions, have a denser and taller growth. No correlation could be found between these differences and the habitat or grazing intensity. Where the shrubs are dense, an admixture of scrub grasses occurs {Paspalidium, Ancistrachne, Aristida, and Chloris).

(c) Downs Community The composition and distribution of this community have been dealt with in Part VIII under the relevant vegetation type. It is found only on level or undulating clay plains. (d) Scrub Grasses This community usually forms a scanty ground cover in the brigalow, softwood, lancewood, bendee, and blackwood scrubs, mostly on level or undulating clay plains, less commonly on rocky hill sides. It is characterized by Paspalidium, Brachyachne, Ancistrachne, Chloris, Aristida, and Eragrostis, and by the predominance of the annuals. Paspalidium and Ancistrachne grow only in the shade but the others also grow in the open, where, however, the competition from Bothriochloa and Heteropogon keeps them subordinate.

II. THE PASTURE LANDS

The land systems may be arranged in groups which have similar grass communities on similar topography, as shown in Table 19. These groups (pasture lands) are described in this section, with reference to common landscape features and to their use for grazing, and with a brief diagnostic note on the constituent land systems. (a) Pasture Land 1 To call this a pasture land at all is to stretch the term a little, for the country is broken and rocky and the ground cover poor. Most of it is of sparse mixed grasses on rugged sandstone mountains with shallow rocky soils, in association with shrub woodland, sandstone form. The best grazing is to be found on lower hill slopes with their associated sandy aprons and fans and alluvial flats, where Heteropogon, Aristida, and Chrysopogon are common constituents and provide a fair cover, but these areas make up less than 10% of the whole. The grasses provide little grazing, not only because of their scarcity but also because of the presence of hard, woody, unpalatable species among them. Triodia is a common and characteristic example; Dimorphochloa rigida and Cleistochloa subjuncea are less common but also characteristic. A little indifferent grazing is provided by Arundinella, and better-quality but very scanty grazing by sporadic Themeda, Heteropogon, Aristida, Chloris, Eragrostis, and a number of annuals (Perotis, Schizachyrium obliqueberbe, Dactyloctenium radulans, Setaria, and Tripogon loliiformis). Where lancewood occurs, the grazing is even poorer, for it consists of little else than sparse Aristida, Calyptochloa gracillima, and Ancistrachne, and thus lacks even the saving grace of variety. 132 R. STORY

Some savannah woodland of narrow-leaved ironbark over Bothriochloa, Heteropogon, and Aristida is found on the Carborough and Cherwell Ranges on shaly benched slopes. The grazing is fairly good but is offset by the steepness of the terrain generally, and as a whole, pasture land 1 is poor stock country. It comprises Carborough and Planet land systems, on rugged and hilly country respectively.

(b) Pasture Land 2 As in pasture land 1, the country here is mountainous, but the grasses are dense and of high quality, mainly Bothriochloa, Heteropogon, Themeda, and Aristida in association with a rather open savannah woodland. In the present state of our knowledge of conservation, however, the country is too steep and rocky for full exploitation. Other disadvantages are the scarcity of perennial water and the frequency of Macrozamia moorei, a poisonous plant that can cause heavy stock losses. The three land systems included are Black Alley, Percy, and Skeleton. Black Alley differs from the other two in being undulating, but is included with them because of its inaccessibility, being bounded by sheer cliffs with high steep slopes below them. It differs also in having more Themeda among the grasses, and more varied and denser trees. Part of it lies within the Carnarvon National Park. A few volcanic necks are under the sparse and woody grasses of the shrub woodland, sandstone form. They are negligible both in area and in grazing value.

(c) Pasture Land 3 The country of pasture land 3 is level or undulating. Grasses are broadly similar to those of pasture land 2, but as they are sparser and contain much more Aristida than Themeda, they are poorer. This, however, is compensated for by the gentle topography and deeper soils. Now and potentially, pasture land 3 is better grazing country than pasture land 2. The most valuable parts are alluvial, for apart from small areas that are densely wooded, they are thickly grassed and well watered. Hills are uncommon, and their associated patches of lancewood and scanty short grasses are negligible. The soils are mainly texture-contrast, and under E. populnea and narrow-leaved ironbark. The four land systems which make up this pasture land differ mainly in their geology. They are Cotherstone, Hillalong, Monteagle, and Rewan.

(d) Pasture Land 4 This pasture land comprises the level grasslands of the downs community (c). Although most of it is arable and considerable areas near Emerald are now under cultivation, it is as a whole still used as grazing land. The climax grasses provide good grazing for all classes of stock during summer, but are innutritious in winter and liable to give way under poor management to two unpalatable grasses, Aristida leptopoda and Panicum queenslandicum (Bisset 1960), of which Aristida leptopoda is strongly awned and consequently a great obstacle to sheep farming. It is perhaps significant that the available records of the downs east of Springsure (Anon. 1959; Bisset 1960) indicate that mainly sheep were run from the early days of settlement until the early 1940s. They are greatly outnumbered by beef cattle today. GRASSES OF THE ISAAOCOMET AREA 133

The country is thinly wooded in parts, mostly on low gravelly rises, and includes patches of brigalow. The brigalow is an asset rather than a disadvantage. It contributes practically nothing to the feed, but affords shelter in this generally exposed pasture land. The three component land systems are Moorooloo, Oxford, and Waterford. Moorooloo has gravelly texture-contrast soils, and Waterford and Oxford have shallow and deep cracking clays respectively. (e) Pasture Land 5 Pasture land 5 is under scrub grasses, mainly on undulating lowlands with dark cracking clay soils, gilgaied in places. The grasses are palatable and nutritious and drop relatively little in value during the dry season, but they are too sparse to be of economic importance, and the carrying capacity is consequently very low, about 100 acres to a beast. The country is densely wooded with a mixture in which brigalow is dominant, but is now being extensively cleared for the establishment of high-yielding introduced pastures. Arcadia and Humboldt are the two land systems in this pasture land. They differ in the associated trees of their brigalow communities, Arcadia having E. populnea and Geijera, and Humboldt mainly E. cambageana.

if) Pasture Land 6 Generally speaking, lowlands and plains with downs grasses are characteristic of this pasture land; strictly speaking, the downs make up only about 35%, but a strong "downs" character is shown also in the remaining eastern mid-height grass community by a noticeable admixture of downs grasses and by the density of the sward. The grazing is good and the country level. The only land system is Nebo, with texture-contrast and cracking clay soils on Lower Bowen Volcanics. The commonest trees are E. populnea, bloodwood, and ironbark. (g) Pasture Land 7 Pasture land 7 comprises two land systems on alluvium, and is partly flooded during the rainy season. The grasses are eastern mid-height grasses {Bothriochloa, Heteropogon, and Aristida), but are denser than normal, with areas of typical downs and other areas that have an admixture of downs grasses in the pasture (Dichanthium, Thellungia advena, Iseilema). Small areas of flooded and sometimes gilgaied brigalow are widespread, with the usual scanty cover of scrub grasses. For the most part, the grasses provide good summer grazing. There are two land systems—Connors, which is mainly under E. populnea on texture-contrast soils, and Funnel, under E. microtheca on cracking clays.

(h) Pasture Land 8 The greater part of this is under scrub grasses, of less value than usual because of the rugged, hilly, or broken country on which they grow. In the extreme north of the area they are associated mostly with softwood scrub, elsewhere with brigalow and lancewood scrubs, and with widespread and extensive sheet and gully erosion. 134 R. STORY

The smaller part of this pasture land is on tablelands with eastern mid-height grass and scattered Triodia, and the grazing is fairly good; the foot slopes lack the Triodia but otherwise have the same grass species. Considered as a whole, this is poor stock country. The two component land systems are on rugged mountains with narrow-leaved ironbark and softwood scrub on unweathered volcanics (Britton), and on hills of weathered Triassic and Permian rocks with lancewood and narrow-leaved ironbark (Durrandella). Both have shallow rocky soils.

(0 Pasture Land 9 This is mainly under eastern mid-height grasses on tablelands and undulating lowlands, with an admixture of scattered Triodia on the tablelands. Scrub grasses occur on lateritic scarps, and sporadically throughout. The communities are identical with those of pasture land 8 but the proportions are different—this and the relatively unbroken terrain make it a fairly good pasture land. The only land system is Junee. It is largely under narrow-leaved ironbark on red and yellow earths. (;) Pasture Land 10 Most of this pasture land is under scrub grasses on level or undulating country, and of this about 30% is on alluvium, with a somewhat denser and floristically richer grass cover which includes Thellungia advena, Leptochloa debilis, Panicum buncei, and some edible Cyperaceae in the flooded areas. About half of this brigalow and scrub country is gilgaied, and because water is held in the hollows after rain it allows the cattle an unlimited range. The lesser part of the pasture land is made up of eastern mid-height grasses on slight rises and levees. As a rule Heteropogon is uncommon and the cover rather sparse. The communities are identical with those of pasture land 8, and roughly in the same proportions, but are on very different terrain. The pasture land provides nutritious but scanty grazing. It is densely wooded, but is being extensively cleared for the introduction of improved pastures. Of the four constituent land systems, all have cracking clay soils. Comet is on alluvium, Somerby is gilgaied, Daunia is on Permian rocks, and Blackwater on weathered Tertiary clay and older rocks.

(k) Pasture Land 11 This pasture land comprises hills and lowlands with two main grass communities —downs and scrub grasses, sometimes in narrow, alternating, strike-aligned bands and sometimes in unbroken patches several miles across. Minor patches of eastern mid-height grasses occur on alluvial fiats or with mixed shrub woodland on gravelly rises. Grazing is good or poor according to the proportions of downs and scrub grasses, and according to what has already been written on these communities. Four land systems make up this pasture land. Bedourie and Racecourse, on hills and lowlands respectively, are characterized by softwood scrub; Girrah and GRASSES OF THE ISAAC-COMET AREA 135

Barwon both have a mixture of brigalow and downs, but Girrah has a broader and more indefinite pattern of bands and some mountain coolibah.

III. THE BROAD ASPECTS OF UTILIZATION (a) General Apart from localized agriculture and a little sheep-raising, the only primary industry is beef production, mainly from Herefords on native pastures. The health of cattle is discussed by Brooks (1962) with particular reference to the brigalow country, but most of his observations would apply to the Isaac-Comet area in general. The hazards appear fairly numerous but light by comparison with some other great beef-producing countries, for it is inaccessibility and poor grazing rather than pests and disease that restrict stock numbers in some places. Dingoes are the only predators, and do not create a problem except where calves are concerned. Losses have been reported through pleuropneumonia and also through poisoning by Trema, but the plant is uncommon and is poisonous only seasonally. More serious plant poisoning is caused by Terminalia and, in the mountainous country of the south-west, by Macrozamia. Inoculation against redwater is done on some properties, and tick control is carried out on most, eight or nine times during the year for breeding cattle. (It is worthy of note that in the Cape Province of South Africa dipping must be done every week in summer, and about fortnightly in winter.) Beattie (1956) states that endoparasites are fairly serious. The beef nodule worm is apparently universal, and there is strong evidence of Trichostrongylus and barber's pole worms on the Mackenzie and Comet Rivers. Pica, probably caused by phosphate deficiency, occurs sporadically and can lead to death from botulism. A taste for the larvae of the sawfly may be connected with the same deficiency. This insect, which is one of the pests of E. melanophloia and to a small extent of E. populnea and E. tessellaris, is the cause of losses in the southern part of the area. Their seriousness is emphasized in government files and by graziers personally, and it is on record* that 25% of a total of 1000 cattle on one property alone died from this cause in one season. The larvae when fully grown collect at the base of the trees in their own slimy exudate, and are eaten fresh or decomposed, the results in either case being fatal within a few days. Tryon (1921) quotes reports that "cattle fight for a place in their efforts to satisfy their craving for the larva", and ascribes the plague proportions of the larvae to the virtual eradication of opossums, which used to be "very numerous indeed" and which compete with the larvae for food by specially favouring the young foliage of E. melanophloia when feeding. The only potentially serious introduced weed in the native pastures is a small trailing cactus (Harrisia sp.) which is widespread but was not observed in any heavy infestations. Encroachment by indigenous trees and shrubs is taking place today on cleared areas as well as those naturally open and is likely to become an increasing problem in the future (Everist and Blake 1961).

* CSIRO Division of Entomology, Canberra, File 12/49, letter from G.V.O. Rockhampton dated 24 September, 1937. 136 R. STORY

(b) Herbage and Browse The grasses make up the bulk of the feed with only small contributions from the non-grass herbage, which is scanty, and from the browse plants, which are uncommon in the predominantly eucalypt vegetation. The highest proportion of non-grass herbage is probably to be found in the downs, where sedges and indigenous legumes, commonly Glycine tomentosa, G. tabacina, Rhynchosia minima, and Neptunia gracilis, produce scraps of green feed until killed by frost; elsewhere some of these and other non-grasses, including Portulaca oleracea and a few chenopods in the brigalow and Hypoestes floribunda in the softwood scrub, make a bigger variety but are more widely scattered. As for browse plants, Bauhinia, Eremophila maculata, and Grewia in the mixed shrub woodland are among those eaten extensively, but many others are sampled, for cattle will take a few leaves of almost anything, including eucalypts and brigalow. (c) Pasture Quality The dry season lasts from May to October inclusive (Table 2), and for this period and more the grasses are dormant and generally of very poor quality (see Part X), although the communities do not all deteriorate to the same extent. Those of the shrub woodland, sandstone form, cannot deteriorate, for they are poor at the best of times; the scrub grasses include a large proportion of annuals, which keep enough of their good qualities to make a standing hay that provides a maintenance or even a fattening ration; the eastern mid-height grasses drop severely, and the downs almost as much. During this time the cattle, as they are known to do in other parts of the world, probably seek out the non-grasses, and their importance may therefore be out of proportion to their frequency, but in the absence of detailed information on the feeding habits of cattle in the Isaac-Comet area this remains uncertain. The work of Shaw and Bisset (1955) in the spear grass country shows the significance of seasonal grazing preferences of cattle and the bearing that such studies could have on controlled grazing.

(d) Stocking Rate and Grazing Management Over most of the area the stocking rate is roughly 30 or 40 acres to a beast, ranging from 11 acres on the downs to more than 100 in dense scrub (Bureau of Agricultural Economics 1963). Under present conditions in the area, that is, without supplementary feed, little of the available fodder is utilized, for the native pastures have to carry the animals through the year, and the stocking rate must accordingly be adapted to the lean period. This is usually done by keeping the stocking rate low. Surplus grass then accumulates during the growing season, and the animals can maintain condition through the ensuing winter by picking out the best in a poor but abundant pasture. If the surplus is not large enough, the "best" referred to is depleted and a period of stress and stock losses may be expected in the early summer months October-December, when hot dry weather with little pasture growth occurs (J. Round, personal communication). In any case, the surplus grass of the downs and woodlands is usually burnt at the end of winter. Two disadvantages are inherent in this system. One is that most of the herbage is wasted, for if enough cattle were carried to utilize the herbage fully in the growing GRASSES OF THE ISAAC-COMET AREA 137

season when it is at its best, they would starve on what remained later in the year. The other is that the cattle can graze selectively both when the grasses are green and good and when they are neither. One may assume that they will select the best, and that continued exploitation will weaken and finally kill the most valuable of the native grasses. Naturally, the whole mixed pasture cannot be pampered for the sake of minor good-quality elements, but selection does not stop with them.

(e) Research and its Application These problems are recognized by the Queensland Government, as may be seen from the unpublished proceedings of the North Queensland Agrostology Con- ference held at South Johnstone in June 1962, in which all of them are specifically mentioned. A programme of pasture investigations in Queensland is listed also in the CSIRO Division of Tropical Pastures annual report (1965). Research has been and is being done on ways of carrying the animal through the time of scarcity and on ways of improving the feed, through crop fattening, introduction of other species into the native pasture, haymaking and silage, treatment of roughage with urea, growing of lucerne, feeding of concentrates, and replacement of the native pastures with introduced legumes and pastures of higher quality—this last often in conjunction with the clearing of brigalow scrub, a matter which has been the subject of papers by Everist (1962), Johnson (1962a, 1962&), and others. Legumes are a vital need in the brigalow lands for supplying nitrogen both to the introduced grasses and to the grazing animals. Except for the results of the brigalow research, the experimental work is being applied in the Isaac-Comet area to a small extent only, and the area is still under extensive management. Winter production of lucerne and oats is restricted by lack of rain, but small patches are nevertheless grown on downs country and under irrigation on alluvial flats, and provide a valuable winter feed high in protein. A little Stylosanthes has been introduced into the native pastures here and there but at present contributes practically nothing to the feed, and the small amount of hay that is made from the native pastures is likewise insignificant over the area as a whole. The brigalow research, however, has been applied to a programme of widespread clearing which was begun after the field work for this survey had ended. It was done for the establishment of improved pastures, which give a higher yield of better fodder than most of the native grasses (Bureau of Agricultural Economics 1963). The initial programme is fairly straightforward. Brigalow is readily uprooted by heavy machinery, the trash burns well and gives a good seed-bed, and the native grasses which come up after burning are sparse and offer little competition. The disadvantages are that the clearing of brigalow, although cheap in relation to the clearing of most other communities, is still expensive, that there may be a delay of up to two years before returns can be expected, and that drought, which is a normal feature of the erratic climate, can result in the failure of the sown pasture. If this happens, the recommended firing of the new pasture cannot be carried out, and a dense sapling regrowth results, too pliant for mechanical uprooting. This is a common form of brigalow today, for most brigalow clearing in the past, having been done unmethodically and without enough knowledge of the implications, has been a failure. Even now, newly cleared brigalow 138 R. STORY

land is sometimes infested with weeds and suckers and threatens to become an economic burden for the future. The improved pastures on cleared brigalow land are grown without irrigation and are mostly of Rhodes grass, and although climatic conditions are marginal for it, some was excellent in vigour and density after a good season in 1962. Hardier strains of Rhodes are under investigation. A little of the more drought-resistant panic and buffel is also grown, and Sorghum almum as a cultivated crop. Like the native grasses, these introduced grasses die back in winter and drop in palatability and nutritive value, and unless they are cut in the early stages for hay they contribute much more to summer than to winter grazing. Nevertheless, they offer better winter grazing than most of the native grasses, and their establishment for this purpose would allow a greater use of the remaining natural pastures during their summer growing season, and increased stocking rates. The clearing of eucalypts is usually done to induce a more vigorous growth of the natural grasses, and is thus an understandable policy on any property. However, it may also lead to a change in the grass flora; for example, a paddock was observed near Wilpeena Park which contained an unfenced but regular block of ringbarked E. populnea over Heteropogon, sharply divided from live E. populnea over Chrysopogon. The changes are not necessarily disadvantageous, but the possibility should be borne in mind before clearing is undertaken. It is still uncertain how long the high-yielding and good-quality introduced pastures will persist in the Isaac-Comet area. In view of this, and in view of the proportion of hilly or stony country where their establishment would be difficult, it would appear wise to continue research work as well on all aspects of the utilization of the native pastures, and to reserve for study adequate areas of the native vegetation, even vegetation like the brigalow which is at present considered valueless.

IV. REFERENCES

ANON. (1959).—A short history of Springsure and district. Springsure centenary 1859-1959 booklet. (City Printing Works: Rockhampton.) BEATTIE, W. A. (1956).—A survey of the beef-cattle industry of Australia. CSIRO Aust. Bull. No. 278. BISSET, W. J. (1960).—Overcoming white spear and yabila grass problems. Qd agric. J. 86, 401-6. BROOKS, O. H. (1962).—Keeping cattle healthy. Qd agric. J. 88, 773-6. BUREAU OF AGRICULTURAL ECONOMICS (1963).—The economics of brigalow land development in the Fitzroy basin, Queensland. (Commonw. Govt. Printer: Canberra.) CSIRO DIVISION OF TROPICAL PASTURES (1965).—Annual report 1964-65. EVERIST, S. L. (1962).—Making decisions. Qd agric. J. 88, 716-9. EVERIST, S. L., and BLAKE, S. T. (1961).—"Features of the Queensland Flora." (Govt. Printer: Brisbane.) JOHNSON, R. W. (1962a).—Knowing the country. Qd agric. J. 88, 720-6. JOHNSON, R. W. (19626).—Clearing the scrub. Qd agric. J. 88, 737-50. SHAW, N. H., and BISSET, W. J. (1955).—Characteristics of a bunch spear grass (Heteropogon contortus (L.) Beauv.) pasture grazed by cattle in subtropical Queensland. Aust. J. agric. Res. 6, 208-21. TRYON, H. (1921).—Special cattle fatality in the Maranoa district and its relation to the larvae of Pterygophorus analis Costa. Qd agric. J. 16, 208-321. PART X. LAND USE IN THE ISAAC-COMET AREA

By R. H. GUNN*

I. INTRODUCTION

Present land use over the greater part of the area is the grazing of natural pastures for the production of beef cattle. A small proportion of land is used for grazing wooled sheep near Emerald and Rolleston. Extensive clearing of brigalow and softwood scrubs for the establishment of improved pastures and for cultivation is being carried out (Plate 8, Fig. 2), and the stocking rates of these pasture lands are being increased about sixfold (Sutherland 1962). The production of sorghum, wheat, and other crops such as safflower, linseed, and oats is carried out mainly on the basaltic clay soils near Rolleston, Springsure, Gindie, and Nebo and to lesser extent on alluvial clay soils near Emerald and Comet. The total area of cultivated land is probably of the order of 50,000 acres. The beef cattle industry is by far the most important in the area and because of natural limitations is likely to remain so. The Fitzroy Basin Land Development Scheme and the subdivision of large properties into smaller units will, however, result in more intensive land use, particularly in those parts with suitable soil and climatic conditions. According to Mawson (1962) the trend in the future demand for beef is for animals aged about 18 to 30 months without excess fat, giving a dressed weight of about 550 lb. To achieve this objective, Mawson suggests that some crop-fattening would appear to be necessary. In this Part an attempt is made to interpret some of the data given earlier in this report in terms of potential land use. Areas of similar soils and relief judged to be dominantly of one capability class are shown in Figure 14 and potential land use in relation to land systems is indicated broadly in Table 20. Land capability classes in respect of land units are given in the tabulated descriptions of the 28 land systems in Part III. The capability classes are those defined by the United States Department of Agriculture (1958) and they indicate the degree of limitations to specific forms of land use. Tentative subclasses indicating the kind of limitation are also shown. The classes and subclasses are defined in Appendix I. These interpretations are intended to be no more than guides to potential land use in the area and they will almost certainly be modified when more practical experience has been gained.

* Division of Land Research, CSIRO, Canberra. 140 R. H. GUNN

Fig. 14.—Estimated potential land use. LAND USE IN THE ISAAC-COMET AREA 141

II. CLIMATE AND LAND USE In comparison with the eastern part of the Fitzroy region, the area has lower, more variable rainfall, and extremes of temperature, both below and above the optimum for plant growth, occur more frequently. These, together with high rates of evaporation, are the most important climatic factors influencing land use in the area. In the following brief discussion on the growth of pastures and crops in relation to these factors, the climatic data are taken mainly from Part IV and from an assessment of climate and plant growth in the Fitzroy region by Fitzpatrick (1965).

TABLE 20 ESTIMATED POTENTIAL LAND USE IN LAND SYSTEMS

Land Estimated Potential Land System Limitations Class Use

II Cultivation with slight Oxford and part of Nebo Erosion, unreliable rainfall limitations III Cultivation with moderate Arcadia, Blackwater, and parts Erosion, salinity and/or limitations of Daunia, Girrah, and Race- alkalinity, microrelief, course unreliable rainfall IV Limited cultivation and/ Barwon, Connors, Monteagle, Erosion, shallow soils, or pasture improvement Humboldt, Junee, Mooroo- salinity and/or alka- loo, Somerby, and parts of linity, microrelief, un- Bedourie, Cotherstone, Dau- reliable rainfall nia, Girrah, Hillalong, Nebo, Racecourse, Rewan, and Waterford V Intensive grazing Comet, Funnel Very frequent overflow VI Moderate grazing Parts of Bedourie, Cotherstone, Shallow soils, erosion Hillalong, Rewan, and Water- ford VII-VIII Limited grazing Black Alley, Britton, Carbo- Topography, shallow rough, Percy, Planet, Skeleton, rocky soils Durrandella

(a) Pasture Growth The growth pattern of both natural and improved pastures is controlled by suboptimal temperatures during the winter months and the marked seasonal distribution of rainfall. With the onset of rains and increased temperatures in early summer, grass growth is rapid and there is generally a surplus of stock feed at this time. Following the flowering stage there is a rapid decline in the rate of growth and pasture quality deteriorates. During winter, growth rates remain at low levels irres- pective of moisture conditions (Miles 1949) and the effects of frost or rain on dry pastures during this period cause further deterioration in quality. The estimated mean annual duration of useful growth (i.e. adequate to provide some green feed for stock) during the period from mid September to mid May ranges from 24 weeks in the extreme north-east to 19 or 20 weeks in the west. In a small area in the centre around Comet the estimated mean number of weeks of useful pasture growth is 17 142 R. H. GUNN to 18. Furthermore, not only does the useful growth period decrease westwards, but the year-to-year variability increases westwards.

(b) Dryland Crops

In order to assess the suitability of climatic conditions for summer and winter cropping, Fitzpatrick (1965) has analysed the lengths of individual sequences or "runs" of weeks during which there is available soil moisture without interruption. These are referred to as "growth sequences". In these analyses no account is taken of special practices to conserve soil moisture such as fallowing. At Nebo in the extreme north-east the median length of growth sequences during the period mid January to early April varies from 26 to 30 weeks and the percentage of weeks without available soil moisture does not exceed 7. At Emerald for the same period the median length of growth sequences is 8 to 9 weeks and the percentage chance of there being a week without available soil moisture is about 30. With regard to winter cropping, the median length of growth sequences at Nebo during the period May to July varies from 11 to 18 weeks and the percentage of weeks without available soil moisture is about 20. At Emerald for the same period the median length of growth sequences does not exceed 7 weeks and there is about a 50% chance of there being a week without available soil moisture. The occurrence of extreme temperatures and their effects on crops in the Central Highlands Region is discussed by Skerman (1953). There is an appreciable risk of frosts in the west and south of the area from May to August, particularly in low- lying sites, and damage to wheat at time of flowering or to late-planted summer crops is possible. The incidence of heat waves when temperatures exceeding 100°F occur on several consecutive days is a further hazard to crops, especially during the period November to January. These observations indicate the risks of there being inadequate soil moisture for both summer and winter cropping in the area, particularly in the west, where rainfall is lower and more variable than in the north, and possibly in the extreme south. The risks can be reduced to some extent by careful selection of soils with adequate depth and high water-holding capacity and by measures to conserve soil moisture such as summer fallowing, contour cultivation, and thorough weed control. The selection of drought-hardy, short-season crops would also appear to be desirable. The best means of reducing the effects of poor-quality pastures on grazing animals during winter appear to be the growing of crops such as sorghum, oats, and safflower for grazing in areas of suitable soils. A study by the Bureau of Agricultural Economics (1964) indicates that liveweight gains of 2 to 3 lb/day are possible by cattle grazing on sorghum and oats during the period May to November in the Central Highlands. There is less likelihood of there being complete failures through lack of adequate soil moisture with the production of grazing crops than with those grown for grain only, although the volume of stock feed may be much reduced. A further advantage of this system of cropping is that it provides a very satisfactory method of controlling regeneration in areas newly cleared of brigalow, especially if the land is ploughed in summer (Johnson 1964). LAND USE IN THE ISAAC-COMET AREA 143

III. SOILS AND LAND USE

(a) Soil-Water Relationships Under the climatic conditions in the area the more important soil properties affecting soil-water-plant relationships are the available water-holding capacity, effective depth, the rate at which water enters and moves through the soil, and the physiographic position in relation to run-off and overflow. Data reported by Stirk (Reeve, Isbell, and Hubble 1963) indicate that the cracking clay soils are likely to have available moisture storage capacities ranging between 2 and 2-5 in. per foot depth. On the other hand, the sandy red earths, uniform coarse-textured soils, and shallow rocky soils, in view of their low porosities, probably have available storage capacities of the order of 0-7 in. per foot depth. The loamy red and yellow earths have medium- to fine-textured subsoils and their storage capacities are likely to be somewhat higher but still generally low. Moisture storage capacities in the texture-contrast soils are variable. The sandy surface soils of Luxor and Broadmeadow families have low storage capacities and they tend to dry out rapidly. Although moderately high storage capacities are possible in the clayey subsoils, permeability and root penetration are often severely restricted by their compaction and massive structure. For this reason the deep texture-contrast soils have been classified according to differences in the texture and thickness of the surface horizons. A thickness of 15 in. has been taken as the dividing line between those with thick and thin surface soils. The effective depth of soil in relation to the rooting habits of plants is important because it controls the volume of the moisture reservoir. Root penetration in the cracking clay soils is confined mainly to the upper 2 or 3 ft, but a small proportion of roots may penetrate to 4 ft or more. In the deep sandy soils, with lower water storage capacities, there is a tendency for roots to range more widely and draw on stored moisture from a greater volume of soil. In times of moisture stress, the cracking clay soils with depths of 3 ft or more provide larger reservoirs of stored moisture and plants are generally less likely to be affected by drought than in shallow or sandy soils that tend to dry out more rapidly. The rates at which water enters and moves through soils are controlled largely by their texture, structure, porosity, and moisture content. The cracking clay soils when moist have low rates of infiltration and permeability, but the cracks that form on drying facilitate penetration and absorption when rain subsequently occurs (Plate 2, Fig. 1). Moisture movement in the texture-contrast soils depends mainly on the texture and thickness of the surface soils. Those with deep sandy, friable surface soils tend to absorb water readily but the slowly permeable subsoils retard deeper penetration and lead to periodic saturation or lateral subsurface seepage. Most of the surface soils are massive and become hard and compacted when dry, causing low infiltration and high run-off rates (Plate 2, Fig. 2). The sandy red earths and uniform coarse-textured soils are likely to have high rates of infiltration and permeability. The loamy red and yellow earths are permeable but tend to set hard at the surface so that infiltration is reduced. 144 R. H. GUNN

Seasonal inundation through overflow by rivers and creeks is an important factor influencing the use of some soils, particularly the alluvial and gilgaied deep clay soils where these occur near major streams, mainly in Comet and Funnel land systems. Many of these soils are flooded seasonally to depths of 5 ft or more. The depth and duration of flooding clearly depend on the magnitude of flood flow and on the elevation of the land, the most serious flooding occurring mainly along the larger streams which are subject to high floods. The depressions in the gilgaied clay soils are also subject to flooding or waterlogging by rainfall and run-off, especially where they are commanded by long slopes with texture-contrast soils. The possibility of exploiting soil moisture reserves for limited cropping during the winter months in areas that are subject to flooding might be explored in sites where flood velocities are low. (b) Erosion Although high-intensity rain storms occur regularly, the incidence of accelerated erosion in the area is generally slight. However, all soils that occur in areas of sloping relief are liable to erode where the natural vegetation is seriously disturbed. The texture-contrast soils appear to be the most susceptible (Plate 2, Fig. 2), particularly shallow soils on base-rich sediments in areas of undulating relief (Barwon and Hill- along land systems). Most of these soils have hard-setting, massive, slowly permeable surface horizons, and a sparse grass cover. These properties, together with moderately steep slopes, tend to cause rapid run-off and often severe sheet and gully erosion, especially where overgrazing has occurred. Despite moderate to strong aggregation in the cracking clay soils and dark brown and grey-brown soils (Cheshire family), they are liable to erode severely in areas of sloping relief where the natural vegetation is disturbed. The occurrence of linear gilgais in some areas of clay soils (May Downs and Teviot families) tends to aggravate the position. Except in the vicinity of scarps where natural erosion is occurring, the red and yellow earths appear to be relatively stable. Sheet and gully erosion was observed in some overgrazed areas and where run-off was concentrated by roads and cattle tracks. (c) Fertility Red and yellow earths have formed on materials that have been subjected to intense weathering and leaching and they consist largely of residual sesquioxides, kaolinitic clay, and quartz. They are very low in exchangeable bases and are deficient in nitrogen and phosphorus. In the south and north-west of the area there are extensive occurrences of hilly or mountainous land formed mainly on quartz sandstones where poor sandy or shallow soils are widespread. Furthermore, climatic conditions in the area do not favour the accumulation of organic matter and the soils generally have low contents of nitrogen. For these reasons low levels of fertility may be expected in many of the soils. On the other hand, the soils formed on relatively fresh rocks and fine-textured alluvium, particularly those derived from Tertiary basalt and some basic sediments (Arcturus, May Downs, Glenora, Teviot, and Vermont families), have moderate to high fertility. They are extensive and widespread in the west and north-central parts LAND USE IN THE ISAAC-COMET AREA 145 of the area in Oxford and Girrah land systems and throughout the area in Comet and Funnel land systems. The basaltic soils are similar to those of the Darling Downs but are generally shallower (Hubble 1961). The fertility status of the clay soils formed within the Tertiary weathered zone (Pegunny and Rolleston families) has been assessed by Isbell (1962). They have moderate fertility but will require careful management to maintain an adequate supply of the major plant nutrients, particularly nitrogen and phosphorus. (d) Salinity Slight to moderate salinity hazards are probable in certain cracking clay and texture-contrast soils in the event of their use for crop production or improved pastures with plants that do not tolerate such conditions. In fact most of the crops and improved pasture species which are grown at present in the area have moderate to high tolerance to saline and/or alkaline conditions. Available analytical data in respect of the soils of Pegunny family indicate that they are slightly to moderately affected by soluble salts, generally below depths of about 2 ft. Exchangeable sodium percentages are commonly 15 or more below the surface 12 in. The texture-contrast soils, particularly those with strongly alkaline subsoils (Medway, Broadmeadow, Taurus, and Retro families), are likely to have exchangeable sodium percentages in excess of 15. They are slightly affected by soluble salts and commonly have the typical morphology of solodized solonetz or solodic soils.

(e) Other Aspects The moderate to strong development of melon-hole gilgais in the soils of Pegunny family presents difficult problems in their use for cropping or improved pastures and brigalow regrowth tends to be most vigorous in such areas (Isbell 1962; Johnson 1964). The gilgais with very abrupt slopes and closely spaced mounds and depressions present the most serious obstacles to machinery. The soils of Pegunny and Rolleston families, however, provide more suitable media for pasture establishment than those soils which form strong granular, self-mulching surface layers. Because of their high clay contents and narrow moisture range for working, the extensive use of suitable cracking clay soils for cultivation would generally require sufficient machinery to plant and cultivate when conditions were optimum. Apart from the shallow rocky soils of Rugby and Shotover families, varying degrees of stoniness would limit, either entirely or in part, the use of certain other soils for pasture establishment or cultivation. In places, the basaltic clay soils (Arc- turus and May Downs families) are so stony as to prohibit or seriously hinder the use of implements. Similarly, the presence of masses of large boulders of secondary quartzite (billy) in some areas of soils formed within the Tertiary weathered zone (Rolleston, Taurus, and Retro families) makes it impracticable to use them for purposes other than extensive grazing.

IV. IRRIGATION Apart from a few small irrigated areas there are no irrigation schemes in the area, but proposals in respect of an area near Emerald are presently being examined. 146 R. H. GUNN

The storage of about 1 • 2 million acre-feet would be made possible by the construction of a dam about 12 miles upstream from the town. The supply of water would be by gravity and pumping to canals on either bank. A gross area of 57,000 acres is considered suitable for the irrigation of cotton, sorghum, lucerne, and wheat on the right bank within the area (Bureau of Agricultural Economics 1965). There are a few streams with small perennial flows, but most of the larger streams have only seasonal flow. Irrigation on a moderate scale would, therefore, involve the construction of storage reservoirs. In terms of irrigable land the soils and relief in parts of Connors and Funnel land systems are well suited, particularly in the south-west along the lower Carnarvon, Consuelo, Peawaddy, and Meteor Creeks. In the centre and north-east similar land occurs along the Mackenzie River and Denison and Funnel Creeks. The principal soils are fine-textured alluvial soils (Clematis and Warrinilla families) and alluvial cracking clays (Vermont family). Water supply and flood control are likely to be major problems. There is also scope for irrigation on a small scale in many parts of the area for the production of fodder crops such as lucerne, if adequate water can be supplied from storage reservoirs or bore-holes. The quality of both surface water and ground water should be examined in order to prevent salinity problems, particularly in the more impermeable cracking clay soils.

V. REFERENCES

BUREAU OF AGRICULTURAL ECONOMICS (1965).—"Emerald Irrigation Project, Queensland." (Bur. Agric. Econ.: Canberra.) BUREAU OF AGRICULTURAL ECONOMICS AND QUEENSLAND DEPARTMENT OF PRIMARY INDUSTRIES (1964).—"The Economics of Crop Fattening of Beef Cattle in Southern and Central Queens- land 1958 to 1962." (Bur. Agric. Econ.: Canberra.) FITZPATRICK, E. A. (1965).—Climate in relation to pasture and crop growth. In "Climate", Fitzroy Region, Queensland, Resources Series. (Dep. Natl. Development: Canberra.) HUBBLE, G. D. (1961).—Soils. In "Introducing Queensland", pp. 27-37. (Govt. Printer: Brisbane.) ISBELL, R. F. (1962).—Soils and vegetation of the brigalow lands, eastern Australia. CSIRO Aust. Div. Soils, Soils and Land Use Ser. No. 43. JOHNSON, R. W. (1964).—Ecology and control of brigalow in Queensland. Qld. Dep. Primary Ind. (Govt. Printer: Brisbane.) MAWSON, W. F. (1962).—Developing the property. Qd agric. J. 88, 710-15. MILES, J. F. (1949).—Plant introduction trials in central coastal Queensland, 1936-46. CSIRO Aust. Div. PI. Ind. divl Rep. No. 6. REEVE, R., ISBELL, R. F., and HUBBLE, G. D. (1963).—Soil and climatic data for the brigalow lands, eastern Australia. CSIRO Aust. Div. Soils divl Rep. No. 7/61. SKERMAN, P. J. (1953).—Some agricultural features of the central highlands region of Queensland. Qd agric. J. 76, 139-49. SUTHERLAND, D. N. (1962).—Using the land. Qd agric. J. 88, 706-9. UNITED STATES DEPARTMENT OF AGRICULTURE (1958).—Land capability classification. Soils Memorandum SCS-22. APPENDIX I

LAND CAPABILITY CLASSES AND SUBCLASSES

I. CLASSES

The capability classes shown in the tabulated land system descriptions indicate broadly the use to which the various kinds of land in the area are best suited. The classes denned below follow the pattern of the United States Department of Agricul- ture* (1958) and have been recommended for use in Queensland by the Soil Con- servation Division, Department of Primary Industries.

(a) Class I Land This is land with few or no limitations. With good management it is suitable for long-continued cropping, without special practices. It is nearly level land, has deep easily worked soil, and erosion hazard is low. The soils are well drained but not droughty and are either well supplied with nutrients or highly responsive to fertilizer applications. The climate is favourable for a wide range of cultivated crops, pastures, or forest. (b) Class II Land This is land with slight limitations. It is arable land, limitations are few, and the practices are easy to apply. It may require moderate conservation practices which will depend on the limitations but will include such practices as strip cropping, stubble mulching, etc., where erosion is the major hazard.

(c) Class III Land This is land with moderate limitations. It is arable land but limitations may restrict the choice of plants grown or require special conservation practices or both. A combination of intensive measures is necessary to use the land permanently. Such measures as adequate mechanical protection will be necessary if erosion is the limiting factor and the land is cultivated.

(d) Class IV Land This is land which is subject to severe limitations and is suitable for occasional but not regular cultivation. It is primarily grazing land. The choice of plants may be very limited or more intensive conservation practices may be necessary.

* UNITED STATES DEPARTMENT OF AGRICULTURE (1958).—Land capability classification. Soils Memorandum SCS-22. 148 APPENDIX I

TABLE 21 CLASSES AND SUBCLASSES—KIND AND DEGREE OF LIMITATION

Limitation Degree of Limitation Class Subclass

Susceptibility to water erosion Slope < 1 %, or up to 2% on short I slopes up to 1000 ft long

Slope 1-3 % II* e2 Slope 3-8 % III* e3 Slope 8-12% IV* e4

Topography Slope 12-20%, or moderate gullying VI te Slope >20%, or extreme gullying VII-VIII ty-8

Microrelief affecting use of Tillage interfered with but not im- III g3 machinery, e.g. gilgais practicable Tillage difficult IV g4 All use of machinery impracticable V g5

Stoniness Tillage interfered with but not im- III T3 practicable Tillage difficult IV T4 All use of machinery impracticable V

Workability affecting use of Slight restriction II k2 machinery, e.g. high clay content, Moderate restriction III k3 compaction Severe restriction IV k4

Physical properties affecting plant Slight restriction II P2 growth, e.g. hard pan, surface Moderate restriction III Pa crusting Severe restriction IV P4

Wetness, frequency of flooding, or 1 in 5 years III W3 waterlogging > 1 in 5 years IV W4 Seasonal V W5

Salinity Slightly affected II S2 Moderately affected III S3 Seriously affected IV-VII S4-7 Salt pan VIII ss Effective depth of soil >48 in. I

36-48 in. II d3 24-36 in. III d3 12-24 in. IV d4 < 12 in. V d5

Available water capacity (in./ft 2 in. or more—high I depth of soil) 1-2 in.—moderate II ttl2 < 1 in.—low III ni3

Soil nutrient status Low III n3 Very low IV ru * The class may be downgraded according to the susceptibility of a particular soil to erosion, e.g. texture-contrast soil. APPENDIX I 149

(e) Class VLand This is nearly level land which has little or no erosion hazard even if cultivated, but has other limitations which it is not practical to remove and which prevent the normal production of cultivated crops. It may be used for pasture or forestry with few or no limitations. Special crops may be grown on it but only with the use of special practices. (/) Class VI Land This is land which has such severe limitations that it is unsuitable for cultivation but it is suitable for grazing or forestry subject only to moderate limitation in use. Limitations of soils or slopes are such that pasture improvement practices requiring the use of tractors and machinery are practicable.

(g) Class VII Land This is land with very severe limitations that make it unsuitable for cultivation and that restrict its use even for grazing or forestry. Limitations are such that pasture improvement practices requiring the use of tractors and machinery are impractical.

(h) Class VIII Land This is land with such severe limitations that it is not suitable for cultivation, grazing, or commercial forestry. Its main value is for watershed protection and wildlife and recreation reserves.

II. SUBCLASSES

The subclasses, together with the kind and degree of limitations in the various classes, are given in Table 21. APPENDIX II

AVAILABLE COMMON PLANT NAMES

Abutilon auritum Chinese lantern Chloris acicularis Curly windmill grass, Acacia catenulata Bendee spider grass A. cunninghamii Curracabah, Chrysopogon fallax Beard grass black wattle Citriobatus spinescens Wallaby berry A.farnesiana Mimosa bush Cymbopogon refractus Barb-wire grass A. harpophylla Brigalow Cynodon dactylon Couch grass A. rhodoxylon Rosewood Cyperaceae Sedges A. salicina Doolan tree, native willow Danthonia Wallaby grass A. shirleyi Lancewood Dichanthium sericeum Queensland blue grass Achyranthes aspera Chaff-flower Dodonaea Hop bush Actinotus Flannel flower Albizia basaltica Dead-finish Echinochloa colonum Awnless barnyard Alphitonia excelsa Red ash grass Alternanthera Khaki weed Eremochloa bimaculata Poverty grass Ancistrachne uncinulata Hooky grass Eremocitrus glauca Limebush Angophora costata Smooth-barked apple Eremophila mitchellii Budda, false sandal- A.floribunda Rough-barked apple wood, sandalwood Araucaria cunninghamii Hoop pine Eriachne mucronata Aristida caput-medusae Wire grass, three- Wanderrie grass Eucalyptus alba Poplar gum awned spear grass E. cambageana Blackbutt, Dawson A. latifolia Feather-top gum A. leptopoda White spear grass E. citriodora Lemon-scented gum Wire grass, three- A. ramosa E. cloeziana Queensland messmate awned spear grass E. decorticans Gum-topped ironbark Arundinella nepalensis Reed grass E. dichromophloia Red-barked Astrebla lappacea Curly Mitchell grass bloodwood Atalaya hemiglauca Whitewood E. exserta Bendo E. maculata Spotted gum Bothriochloa decipiens Pitted blue grass E. melanophloia Silver-leaved B. ewartiana Desert blue grass ironbark B. intermedia Forest blue grass E. melliodora Yellow box Brachyachne convergens Common native couch E. microcarpa Green-leaved box Brachychiton Bottle tree E. microtheca Coolibah E. orgadophila Mountain coolibah Callistemon Bottlebrush E. papuana Cabbage gum, ghost Callitris columellaris Cypress pine gum, carbeen Carissa ovata Currant bush, E. peltata Yellowjack baroom-bush E. polycarpa Bloodwood Casuarina cristata Belah E. populnea Poplar box C. cunninghamiana River oak E. punctata Grey gum C. luehmannii Bull oak E. tenuipes Narrow-leaved C. torulosa Forest oak mahogany APPENDIX II 151

E. tereticornis Blue gum, forest red Owenia acidula Emu apple, gruie gum E. tessellaris Moreton Bay ash, Panicum buncei Panic carbeen P. fulgidum Panic E. thozetiana Yapunyah P. queenslandicum Yabila grass E. watsoniana Yellowjack Paspalidium caespitosum Brigalow grass P. globoideum Shot grass, sago grass Geijeraparviflora Wilga P. gracile Belah grass Glyclne tabacina Pea glycine Perotis rara Comet grass Petalostigma pubescens Quinine bush Hakea lorea Needlewood Prostanthera Mint bush Heteropogon contortus Black spear grass, bunch spear grass Sporobolus mitchellii Rat's-tail couch Hibbertia Buttercup bush

Iseilema vaginiflorum Flinders grass Terminalia oblongata Yellow-wood Themeda australis Kangaroo grass Leptospermum Tea-tree Trema aspera Poison peach, peach-leaf poison Macropteranthes leichhardtiiBonewood bush Macrozamia moorei Zamia Triodia mitchellii Spinifex Melaleuca bracteata Black tea-tree Muehlenbeckia cunninghamiiLignum Ventilago viminalis Vinetree, supplejack

Neptunia gracilis Native sensitive plant Xanthorrhoea Grass-tree