GUIDE FOR PRECONFERENCE TOUR PERTH - GERALDTON 28 AUGUST 1988 @ ECOLOGICAL SOCIETY OF AUSTRALIA 1 AUSTRALIAN ECOSYSTEMS: 200 YEARS OF UTILISATION, DEGRADATION AND RECONSTRUCTION BIENNIAL SYMPOSIUM - GERALDTON, WESTERN AUSTRALIA 28 AUGUST - 2 SEPTEMBER 1988 PRE-CONFERENCE FIELD TRIP Angas Hopkins, Ted Griffin, David Bell & John Dell TABLE OF CONTENTS PAGE INTRODUCTION • ....•.........•••.•••••••.•.•••••••••...•.•.•..••..... 2 CL IMA TE . ••••.•.•...•.•••..••••••••••••••••••••••••.••••..••.•••••.• 2 GEOLOGY • •••••.•••••••••..•••••••••••••••••••.••••••••••••..•••••••. 2 BIOGEOGRAPHY AND VEGETATION ..•.•.•...•••••..••...•.•....•......••.. 5 BOTANICAL HISTORY . ...........••••••••••••••.•...•...•••.••..•..•... 7 HUMA.N OCCUPATION .••....•.....•••••••••••••••••..•..••.•••••.•.•••.. 8 TUART WOODLANDS - YANCHEP NATIONAL PARK •••••..•....••.•••..•••.•.. 10 BANKSIA WOODLANDS - MOORE RIVER NATIONAL PARK •..••.•••••••.••.•••. 11 GINGIN SHIRE- CEt1ETERY . ..•.•..•••••••••••••••.•.•••••••••.......•.. 12 BANKSIA WOODLAND FAUNA •••••••••••••••••••••••••••••••••••••••••••• 12 STREAMSIDE WOODLAND - REGAN'S FORD •••••••••.••••••••••.•.•••...•.. 13 BADGINGARRA NATIONAL PARK ••..••••••••.•••••••...••.••••••••..•.•.• 14 WOODLAND AND SHRUBLANDS - COOMALOO CREEK •••••••••••••••••••••.•••. 14 WOODLAND FAUNA . ••.•.•••.•.•••••••••••••••••••••••.••••••.•••••.•• • 16 ENEABBA KWONGAN - SAND MINING OPERATIONS ••••••••••••••••.•••.•••.. 16 GREENOUGH HISTORICAL VILLAGE •••••••••••..•••.•••••••••••.•••••••.. 18 REFERENCES • •••••..•.••••.••.•.•••••.•••..•••.••..••••••....••••••. 19 2 INTRODUCTION This Pre-Conference tour has been designed to highlight the transition from the woodlands of the Perth region to the shrub­ · dominated vegetaton further north and to look at some of the land management issues along the way (Fig. 1). The traverse from Perth to Geraldton covers a general south-to-north climatic gradient with a decline in precifpitation and an increase in temperature. Three sites to be visited illustrate the response of the vegetation to this gradient as well as to variations in substrate. CLIMATE The Western Australian region of wet winter and dry summer climate has been subdivided by some workers (eg. K8ppen 1983, Trewartha 1968) into mesothermal CSa and CSb sections based on whether the average temperature of the warmest month is over or under 22 degrees C. The present tour is restricted to the CSa region. The remainder of the Australia mediterranean climate areas, those along the southern coast of Western Australia and those in South Australia are categorized as CSb climates due to their lower summer temperatures. The western coastal region of southwestern Western Australia shows a considerable equatorial extension compared with the latitudinal ranges of the mediterranean climate regions of the rest of the world. This is undoubtedly due to the lack of an off~shore cold ocean current. In addition to the south to north gradient reflecting a decrease in rainfall and increases in temperature referred to earlier, as one proceeds inland there is also a gradient of decreasing rainfall and increase in temperature from the coast to the interior. These trends are illustrated in Table 1 which provids climatic data for Perth, Eneabba and Carnamah to the east of Eneabba. GEOLOGY Western Australian geology is dominated by an Archaean Shield which is among the oldest and most stable land masses in the world. The shield is bordered by sedimentary basins which are also very old. This tour will be over the northern portion of the Perth Sedimentary Basin, which is a narrow strip on the Western margin of the Shield (Fig. 2). The most prominent geological feature of the southwestern corner of Western Australia is the Darling fault. This north-south trending fault which is over 1,000 km long separates the Perth basin from the Archaean granitic rocks of the shield. Near Perth, the Darling fault is evidenced by the prominent Darling scarp but its presence becomes obscured towards its northern limit as we approach Gingin. 3 MULL EWA ~ , GERALDTON ', \ r~t- }:;;.·f 0~ ~ Nature Reserves GREENOUGH National Parks MING!=NtW 0 50 krn ' \ NEW ORCIA INDIAN OCEAN Fig. 1. Western Australian region of the Pre-Conference Field Trip. Stops have been indicated. 4 Table 1. Climatic data for representative stations for regions of the northern sand plain. ------------ Rainfall Perth Eneabba Carnamah Mean annual(mm) 883 590 398 Mean no. rain days/yr 119 99 78 Wettest month (mm) June(187) June(l68) June(83) Driest month (mm) Jan.(8) Dec.(5) Dec.(9) Temperature 0 Annual mean max( C) 23.5 26.6 26.7 0 Annual mean min( C) 13.5 11.6 12.1 0 Hottest month ( C) Jan.(30.3) Feb.(35.7) Feb.(35.3) 0 Coldest month ( C) Aug.(9.1) Aug.(6.8) July(7.0) Relative Humidity Mean annual(% 3 pm) 50 39 36 The rocks of the Perth basin are mainly Mesozoic sandstones with minor amounts of siltstones and shales. Zones of faulting are evident in the Perth basin but relative stability has existed for over 60 million years. Geological modifications in that time have been minor, with subsequent deposits being shallow and poorly consolidated. Quaternary sands are thickest in the coastal zone. With its great age and geological stability, Western Australia's landscape shows little relief. Very ancient soils including laterites have developed on deeply weathered rocks. A low plateau reaching heights of 200 to 300 m above sea level occupies the eastern portion of the Perth basin. A coastal belt of 10 to 20 km wide and reaching 100 m above sea level flanks the plateau. A marine escarpment, which formed during a period when the relative sea level were higher, separates the coastal zone from the plateau. 5 I ! \ I I \ < ~ ,, ("\ I • ' \ \ ' \ ' I I \ \ I 50 I I %"'"~ ', .... ~ ,,.. ...4 \~ 0 S: <a- ' ' ' ENEABBA \ PLAIN \ \ ...,I 0 0 -MOOIC' Rwc•r DARLING I I I \ \ l:IO , I I I I I I ,,. ' 0 50 100 I.SO km ' ' ' 1100 Fig. 2. Physiographic regions, Perth Basin and adjoining areas. (From Playford et al. 1976). 6 Rivers which drained the Archaean shield during periods when rainfall was much greater than at present have strongly dissected the western portion of the plateau. This erosion provides the most striking landscape features to be seen in this area - small mesas and steep-sided valleys. Erosion by the present-day streams is minor and flow in most streams is low and occurs only after heavy, winter rainfall. Few streams flow directly into the Indian Ocean because of the limestone deposits on the coastal belt. Alluvial deposits developed east of the limestone where these streams were blocked. Many shallow, ephemeral lakes occur in these areas. Drainage from the Archaean shield is low and ineffective at present. This has produced shallow unconsolidated deposits on the eastern portion of the Perth basin. These deposits are mainly quartz sand. Saline lakes are a feature of the shield. The Perth Basin contains deposits of economic importance. Natural gas, coal and water occur in the Mesozoic sediments. Heavy mineral sands and diatomaceous earth deposits occur in the shallow Quaternary sands. Mineral sands are mined at Eneabba along the margin between the ancient laterite uplands and the coastal basin deposits. BIOGEOGRAPHY AND VEGETATION The southwest of Western Australia has one of the richest angiosperm floras in the world. About 3,600 named species were known from the region by the mid 1960s, with 68 per cent of these being endemics. Recent taxonomic research indicates that many endemic taxa (from 10 to 30 per cent of the total) remain undescribed, so that the actual number of species present in the south-west is probably in the region of 4,500. There are in the order of ~,000 species in the area seen on this tour. J.D. Hooker, in 1860, was the first biogeographer to note the apparent enigma in the southwest of a rich flora in terrain of relatively low relief and subdued topography. The region certainly has no mountains comparable to those which harbour the rich flora of say South Africa. However, it is now apparent that areas of the southwest that are particularly rich in species occur where Tertiary plateau surfaces have been greatly dissected to form complex soil mosaics. Ample evidence of this dissection will be seen on the present tour, especially between Badgingarra and Eneabba. The traverse begins at Perth in the Darling Botanical District of the South-West Botanical Provence. This District take in the major forest types of the South-West including the karri (Eucalyptus diversicolor), jarrah (~ marginata) and tuart (~ gomphocephala), all of which are best developed in the higher rainfall areas south of Perth. Both tuart and jarrah, together with marri (~ calophylla) 7 occur relatively sparcely from Perth northwards. The major vegetation type, however, is Banksia woodland. This woodland is dominated by Banksia attenuata and B. menziesii and has a rich understorey of shrubs, which is closelyrelated floristically to the shrublands further north. Eneabba is within the Irwin Botanical District, more commonly known as the Northern Sandplain. The major vegetation of the region is known as kwongan, the indigenous name given to the extensive sclerophyllous shrublands, equivalent to the fynbos of South Africa or the chaparral of California. The boundary between the Darling and Irwiri Districts is about at Coomalloo Creek, the site of the second stop for this tour. However, it is not an obvious boundary, particularly along the tour route; rather the climatic gradient is manifested in gradual decline in the height and density