------,

THE DISTRIBUTION OF EUCALYPTUS VIMINALIS AND

EUCALYPTUS CAMALDULENSIS IN VICTORIA

A Thesis submitted for the Degree of Master of Science

in the University of Melbourne

by

MICHELE MARY BARSON

j • I ~

,i I Melbourne

1978 DECLARAT ION

I hereby declare that this thesis is my own work~ except where specifically stated to the contrary~ and that it is not substantially the same as any other thesis which has already been sUbmitted to any other university.

M 'c-he4e.- B

MICHELE BARSON •

I I

ACKNOWLEDGEMENTS

It is a pleasure to acknowledge the assistance of the fol lowing

people and organizations:

My supervisors, Dr D.H. Ashton and Dr P.Y. Ladiges for guidance and

.. ~ encouragement;

Dr D.M. Calder, School of Botany, University of Melbourne, for

providing facilities;

The National Parks Service for provision of fencing and access to the

study sites at Westerfoldsj

Austral ian Glass Manufacturers Pty. Ltd. who donated acid-washed sand

for use in the sand culture experiments;

Dr R.H.M. van der Graaffe and Mr P. Jefferies of the Soil Conservation

Authori ty;

Mr C. Aeberl i who carefully tended my plants in the glasshouse;

Robert Bartlett, Robert Marshal I and Geoff Hampton for technical

ass i stance;

Phillip Ladd, Chris Anderson, Neville Rosengren, Jane Lennon and

Bruce Moore - thank you.

My mother, Mrs J. Cruise, and Marg Robertson for the typing;

The Department of Geography, University of Melbourne, for a tutorship

which enabled me to carry out this work. iii

CONTENTS

Page

DECLARATION

ACKNOWLEDGEMENTS i i

LIST OF FIGURES v

L I-ST OF TABLES vi i

LIST OF PLATES ix

I NTRO DUCT I ON

CHAPTER 1: THE DISTRIBUTION OF E. VIMINALIS AND 4

E. CAl1ALDULENSIS

Australian Distribution 4

Victorian Distribution 10

CHAPTER 2: THE YARP.A 7ALLEY STUDY SITE 16

eli mate 16

Soi Is 18

Vegetation 19

Westerfolds Study Site 22

CHAPTER 3: SEEDLING GROWTH RATE AND RESPONSE TO NUTRIENTS 26

Introduction 26

Soi I Characteristics 28 1 Comparison of Seedling Growth Rates 33 1 Seedling Growth in the Field 48 t Discussion 52

! Summary 56 IV

CHAPTER 4: SEEDLING TOLEP.ANCE TO DROUGHT 57 Introduction 57

Methods 58 Results 60

Discussion 64

Summary 66

CHAPTER 5: THE P.ELATIVE TOLERANCES OF E. VIMIl'lALIS AND 67

E. CAMALDULEllSIS TO WATERLOGGING

Introduction 67

The Effects of Waterlogging on Soils and Plants 67

The Influence of Waterlogging on Plant Distribution 74

Methods 76

Results 77

Discussion 80

Summary 82

CHAPTER 6: DISCUSSION AND SUMMARY 83

BIBLIOGRAPHY 89 --_.. _. __ .. _... __ ._- ._. --

v

";, - ~ LIST OF FIGURES

Fi g. No. Shortened titles Facing page

The distribution of E. viminaZis and 4 .. E. camaZduZensis in Australia ~

~~, ~ la Location map for Victoria 10 l,. ~ l 2 The distribution of E. viminaZis in Victoria 10 .~ ~ 3 The distribution of E. camaZduZensis in 10 Victoria

4 Average annual rainfall for Victoria 10

5 Location of sites and average annual rainfall 16 in the Yarra Valley

6 Yarra Valley transects 20

7 Westerfolds geology 22

8 Westerfolds landforms 23

9 Westerfolds eucalypt distribution 24

10 pF values for four soils 30

11 Height growth of E. viminalis and E. camaZduZensis 35 in monoculture and mixed culture on two topsoils

12 Shoot dry weights of E. viminalis and 35 E. camaZduZensis in monoculture and mixed culture on two topsoils

13 Replacement diagrams for competition trials 36

14 Height growth of E. viminaZis and E. camaZduZensis 37 on alluvial soils in monoculture and mixed culture

15 Shoot dry weights of E. viminaZis and 37 E. camaZduZensis grown in monoculture and mixed culture on alluvial soils vi

i6 Height growth of E. viminalis 'Westerfolds ' , 40 E. viminalis 'Eltham ' and E. camaldulensis on alluvial soils in monoculture and mixed culture

17 Shoot dry weights of E. viminalis 'Westerfolds ' , 41 E. viminalis 'Eltham ' and E. camaldulensis grown on alluvial soils in monoculture and mixed culture

18 Effect of increasing levels of phosphorus and 44 nitrogen on the height growth of 2. viminalis

and~. camaldulensis

19 The effect of increasing levels of phosphorus 47 and nitrogen on the total dry weights, leaf area and root/shoot ratios of E. viminalis and E. camaldulensis

20 Height growth and percentage death of field 49 trials

21 Variations in percentage soil moisture over one 60 year at the field trial sites

22 Transpiration rates of control and droughted 62 seedlings

23 Height growth of control, half waterlogged and 77 fully waterlogged seedlings

24 Total dry weights of control, half waterlogged and 78 fully waterlogged seedlings I vi i

LIST OF TABLES

No. Shortened titles Page

Description of soil profiles at Westerfolds 24

2 Mean seedling heights for E. viminalis and 27 E. camaldulensis grown in monoculture and compet it i on

3 Soil profiles at four field sites 28

4 Results of particle size analysis of soils at 29 four field sites

5 Percentage disaggregation of soils at four field 31 sites

6 Percentage organic matter of soils at four field 31 sites

7 Chemical analyses of soils at four field sites 32

8 Analysis of variance results for seedling growth 36

9 Analysis of variance results for seedling growth 38 on alluvial soils in monoculture and mixed culture

10 Analysis of var:ance results for the growth of two 41 populations of E. viminalis and E. camaldulensis on alluvial soils

11 Composition of nutrient solutions 43

12 Analysis of variance results of seedling growth at 45 three levels of phosphorus and nitrogen

13 Analysis of variance results for field trials 50

14 Analysis of variance results for transpiration data 61

15 Leaf water potentials for droughted and control 62 seedl i ngs vi i i

16 Leaf area, dry weights and root/shoot ratios of 63 droughted seedlings

17 Analysis of variance results for waterlogging 78 experiment

18 Root dry weights and root/shoot ratios for control, 79 half waterlogged and fully waterlogged seedlings ix

LI ST OF PLATES

No. Shortened Title Faci ng Page

1a The forest form of E. viminalis 11

1b The woodland form of E. viminaZis 11 lc The rough-barked form of E. viminalis 11

2a The forest form of E. camaldulensis 13

2b The plains form of E. camaldulensis 13

3a E. viminalis and E. camaldulensis on the 25 banks of the Yarra at Westerfolds

3b Riverbank understorey at Westerfolds 25

4a Field trials on the E. camalduZensis plot 52

4b Field trials on the E. viminaZis plot 52

5 The growth of E. camaZdulensis roots under 80 fully waterlogged conditions ------

INTRODUCTION

Eucalyptus viminalis and Eucalyptus camaldulensis are closely related and widely distributed species which may at times occupy similar habitats. although they do not usually form mixed stands. Both species show consid­ erable variation throughout their total geographic range (Pryor 1955 •

Karschon 1967. Larsen 1967. Pryor and Byrne 1969), and in Victoria several forms of each species occur. Ladiges and Ashton (1974) have distinguished forest and woodland forms of E. viminalis. the former generally occurring on more fertile soils of higher rainfall areas, the latter on drier sites.

Forest forms of E. camaldulensis are generally found on floodplains, whilst woodland forms commonly occupy rol ling open plains and the drier margins of floodplains. The boundaries of the two species are frequently contiguous. and within the ecotone each species usually occurs in discrete stands which form patterns that are often related to topography.

This study aims to describe the distribution of E. viminalis and

E. camaldulensis in Victoria, and in particular to examine the habitat conditions which may account for their distribution in the riparian envi ronment.

The distribution of eucalypts is often controlled on a broad scale by climatic factors. and locally by edaphic factors (MooreI959a). The concurrence of plant communities and soil types has been shown by Crocker

(1944), Specht and Perry (1948), and Lang (1960). Florence (1965) demon­ strated a consistent relationship between forest composition and variation

in soil parent material and physical characteristics in south-east

Queensland (Qld). 2

Specific chemical properties of soils have also been associated with the distribution of particular communities. Beadle (1954, 1962) has emphasized the role of phosphorus in delimiting plant communities near

Sydney. Coaldrake and Haydock (1958) did not find a similar relationship between topsoil phosphate content and vegetation distribution in south- east Queensland, but Beadle (1962) has suggested that their data supports his contention that phosphorus levels determine the type of vegetation.

Moore (1961) has related the distribution of ~ucaZyptus melliodora and

Eucalyptus rossii on the Southern Tablelands of New South Wales (N.S.W.) to the degree of calcium saturation of the soil. Other properties which have been shown to influence the distribution of certain eucalypt species include sal inity (Parsons 1968a) and 1 ime chlorosis (Parsons and Specht 1967).

The physical properties of soils which influence soil moisture character­ istics may also be important in cantrall ing the distribution of eucalypt species. Specht and Perry (1948), Parsons (1969), Florence (1964), Lamb and Florence (1973) and Ashton, Bond and Morris (1975) have suggested relationships between soil moisture status and species distribution.

Moore (1959b, 1961) and Parsons (1969) have demonstrated the influence of interspecific competition on eucalypt distribution where species tolerances to physiological factors in the environment are shown to overlap. McColl and Humphreys (1967) however found that pot trials of interspecific competition between Eucalyptus ~~fera and Eucalyptus maculata for soil nutrients were inconclusive.

Pryor (1959a)points out that "while some species are widespread in their total geographic extent, the mosaic pattern characteristic of many areas of Eucalyptus is not affected by the occurrence in that area of the widespread species. In almost all cases, such a species, though widespread, is also tied closely to a circumscribed habitat in the particular limited 3 area. This implies that the habitat factors which finally I imit a wide­ spread species evoke a different physiological response in the species, and are perhaps different from those which cause a species to change from site to site in a restricted areal!.

For E. viminalis and E. camalduZensis this may be interpreted to mean

that, although their abil ity to occupy a range of habitats with respect to

climatic, edaphic and topographic factors may be at least partly related to the ecotypic variabil ity observed in each species throughout their range,

it seems likely that local distributions may be related to the subtle changes

in site factors such as drainage and shelter, and to competition between

adjacent species.

In the present study, the distribution of E. viminalis and E. camalduZensis

in Victoria was mapped and correlated with broad environmental factors, and

the behaviour of seedl ings of both species from a riparian habitat at

Templestowe in the Yarra Valley was assessed by field trials and glasshouse

exper i ments.

Nomenclature is according to Willis (1972) unless otherwise stated. Fig. 1 The distribution of N E. camaidulmsis A ~ and & E. viminalis J. L. B 0 in I i Australia

0..., __ '_OOO ___ 2000km \)

B Ir--._._._._._._._._._._._./'_ ...... \ I I I I I I i""~'~ i \..'"'.~. . I. I '", . \J''-'" I ...... _. N j

fI .

o, 100 200 300 400 500, km Sourc:a; CIrtIr 1931. JICbIII _ HtII It'" 1!J70. Sp.cIIt 1m 4

CHAPTER 1

THE DISTRIBUTION OF EUCALYPl'US VIMINALIS AND EUCALYPTUS CAMALDULENSIS

INTRODUCTION

The natural distribution and morphological variation of E. viminalis and E. camaldulensis throughout Australia are examined briefly; the

Victoridn distribution is mapped in some detail and related to broad topo­ graphic. climatic and edaphic patterns to gain insight into factors which may affect the distribution of these two species.

EUCALYPTUS VIMINALIS

Australian Distribution

E. viminalis is widely distributed throughout south-eastern Australia

(Fig. 1); it is found on the Tablelands and western slopes of N.S.W .• in the

Mt. Lofty Ranges and south-eastern South Australia (S.A.), in southern

Victoria (Vic.), and in the north-west and eastern half of Tasmania (Tas.)

(Hall. Johnston and Chippendale 1970). It has also been recorded on Cape

Barren. Clarke, Flinders, Hunter, King and Three Hummock Islands in Bass

Strait.

The species occurs over a wide topographic range, and reaches its optimum development as a tall ribbon-gum form in valleys in moist montane areas. It is also found as a woodland form on plains and undulating terrain, on volcanic scoria cones, granite outcrops, and sometimes on sandy coastal deposits. In southern states, it occurs from just above sealevel to an altitude of 1220 m; in N.S.W. it reaches altitudes of up to 1370 m (Hall,

Johnston and Marryat 1963). 5 cZimate

E. vimina~is occurs predominantly within the marine west coast climatic zone (Cfb of Koppen) (Ladiges 1969), where the mean temperature of the warm­ est month is less than 22 0 C, and where for at least four months of the year t h e temperature excee d s 1O OC. The mean temperature of the coldest month is above -3 0 C (Dick 1975). Frosts occur with greater frequency at higher altitudes and at greater distances from the sea. Hobart, Tas., at 58 m experiences up to seven frosts per year; Alexandra, Vic. (223 m) averages

26. I, and Guyra, N.S.W. (1453 m) may have up to 67 frosts a year (Hall et az' 1963).

E. viminaZis is found over a wide range of rainfall regimes, with annual precipitation ranging from 512 mm to 1500 mm. In the western sector of its range, winter rainfall predominates, but in eastern Vic. and parts of Tas. and N.S.W. rainfall is uniformly distributed. In northern N.S.W. rainfall occurs chiefly in summer (Bureau of Meterology 1975).

SoiZs

The edaphic range of E. viminaZis is also very great; it occurs on soils of widely differing nutrient status and waterholding capacity (Ladiges and Ashton 1974). I-n N.S.W. it has been recorded principally from basalt- derived krasnozems (Brough, McLuckie and Petrie 1924, Pidgeon 1937, Fraser and Vickery 1939), and on transitional alpine humus soils and brown podsols of the Monaro Region (Costin 1954). South Australian occurrences are on grey brown podsols in the Mt Lofty Ranges (Specht and Perry 1948). and sands in the Lower South East (Crocker 1944). In Vic. E. viminaZis is found on krasnozems, brown earths, podzols, yellow podzolic soi 15, rendzinas and terra rossas (Ladiges and Ashton 1974). In Tas. it occurs on soils derived from granite, basalt (J.B. Kirkpatrick pers. comm.) , mudstone, sandstones and dolerite (Jackson 1965, Martin 1940) as well as deeply leached sil iceous sands (Bowden and Kirkpatrick 1974, Kirkpatrick 1975). 6

Systematic Stab~ and Distribution

Throughout its range, E. viminaZis exhibits considerable variation in characters such as habit, tree height, height of rough bark, and number of flower buds per inflorescence. This variation has resulted in a number of taxonomic problems, some of which are yet to be solved (Pryor 1962). The systematic status of E. viminaZis and related populations has been discussed by Ladiges (1971). Their distribution appears to be as follows:

New South Wales

N.S.W. occurrences of E. viminaZis recorded by Byles (1932), Pigeon

(1937), Fraser and Vickery (1939), Brough et al. (1924) and Costin (1954)

indicate that the species is generally true to type here, that is smooth­ barked except at the base, and possessing exclusively three-flowered

inflorescences and orposite, sessi le juvenile leaves. Occasional rough­ barked trees are thought to be hybrids (Pryor 1955).

South Austra 1 i a

There is considerable morphological variation in E. viminaZis and related populations described from S.A. Tall, smooth-barked E. viminalis

is found in the wetter gullies of the Mt Lofty Ranges, and a similar, but more spreading woodland form occurs along lower watercourses (Pryor 1962).

More rough-barked populations which often have more than three flowers per

inflorescence are found in the Mt Lofty Ranges, on Kangaroo Island and in the Lower South East. These trees, known as Eucalyptus huberiana have been

referred to as E. vimina~is ssp. viminalis (Pryor and Johnson 1971). Hall and Brooker (1974) have since revived the name E. huberana for the rough­ barked populations of S.A. and south-west Vic.

Victoria

Ladiges and Ashton (1974) showed that considerable variation also occurs within this species in Victoria. This study confirmed the recognition made by Pryor (1962) of the tall, smooth-barked gully form and the more umbrageous 7 woodland forms of E. viminalis. In higher rainfall areas tall open-forest

populations of mature trees show similar maximum heights, girths and degree of basal bark persistence. In the more diverse habitat of lower rainfall

regions greater variation is observed and some populations could include

E. huherana.

Populations of very rough-barked E. viminalis var. racemosa occur

chiefly on sandy coastal deposits between Melbourne and Metung (Will is 1972).

In the present study, all rough-barked forms have been mapped as this variety, although again some populations could be classified as E. huherana.

Tasmania

The distribution of E. viminalis has been mapped by Jackson (1965).

It occurs in the eastern sector of the island, generally below 820 m, extending along the north coast with some isolated stands on the north­ west coast. Most populations are tall and smooth-barked, although there is

some tendency for trees growing on poor acidic sands to have more rough

bark. However, bark seldom constitutes more than 50% of the bole, and more

usually less than 20% (J.B. Kirkpatrick, pers. corrrn.). A specimen of

E. viminalis near Fingal is 89.92 m tall, making E. viminalis possibly the

third tallest species in the world (Anon. 1976). According to Penfold and

Will is (1961), occurrences of rough-barked E. viminalis var. racemosa are

very restricted in Tas.

EUCALYPTUS CAMALDULENSIS

Aus tl'a lian Dis tl--ibution

Eucalyptus camaldulensis is the most widely distributed eucalypt species

(Fig. 1). It occurs as a network distribution across the whole of the

Australian continent, except on the coastal fringes of most of N.S.W.o

southern Qld •• eastern and western Vic. and southern W.A. (Hall et al. 1970). 8

Throughout most of its range, E. camaldulensis is found along stream­

lines and on adjacent flats. However, it forms extensive woodlands on the

lower slopes of the Ht Lofty and Flinders Ranges in S.A. (Jacobs 1955), and on rolling plains in western Victoria. It is best developed in the Hurray

River basin of south-eastern Austral ia where pure stands form forests with elite individuals up to 49 m tall (Dexter 1970).

Although generally not found above altitudes of 390 m, it has been

recorded at heights of up to 656 m (Hall et al. 1963); seepage of water from higher slopes may allow E. camaldulensis to establish on such sites.

Climate

E. camaIduIensis grows across a wide range of climatic types, but it generally occurs in areas that have warm summers. Surrrner rainfall is characteristic throughout much of its range, but mean annual rainfall

(H.A.R.) varies from less than 100 mm in arid central Austral ia to 1400 mm

in tropical northern Australia. In areas of low rainfall (100-350 mm),

E. camalduZensis is dependent on seasonal flooding or the presence of a high water table for sufficient moisture (Hall et al. 1970). In the cooler, moister climates of south-eastern Australia, it is not generally found in areas which receive more than 1000 mm H.A.R.

With the exception of some northern Austral ian coastal localities,

frosts occur throughout the range of E. camaldulensis. with 5-20 frosts

per annum being common (Hall et al. 1970).

Edaphic Range

Since E. camaIduIenSis is riparian throughout much of its range, it

usually grows on soils derived from alluvial materials. but is also found on sandy plains where permanent subsoil moisture is available (Hall et al.

1963). The red gum woodlands of south-eastern Australia occur on soils

derived from shales, siltstones, basalts, sands and clays, generally 9

showing a preference for soils with some clay content. Specht and Perry

(1948), Boomsma (1950) and Gi bbons and Downes (1964) have reported that

E. camaldulensis occurs on soils of relatively high fertility.

Systematic Status and Geographic Variation

The systematic status of E. camaldulensis Dehnhardt has been discussed

by Pryor and Byrne (1969). Morphological variation has led to the recognition

of two subspecies, E. camaldulensis spp. camaldulensis and E. camaldulensis

spp. obtusa by Pryor and Johnson (1971).

Geographic variation in E. camaldulensis sensu lato has been demon­

strated by Larsen (1967), Karschon (1967) and Pryor and Byrne (1969). On

the basis of population differences in 1 ignotuber frequency and seedl ing

leaf characteristics, Karschon, and later Pryor and Byrne, recognised

northern and southern ecotypes. Karschon also distinguished a Western

Australian subgroup. Ecotypic variation is also indicated by provenance

variation in seedling growth rates and root/shoot ratios (Awe, Shepherd and

Florence 1976), differential frost resistance (Karschon 1971, Awe and

Shepherd 1975), differences in flooding and salinity tolerance (Karschon

and Zohar 1975), by biochemical characteristics (Banks and Hill~s 1969) and

by leaf morphology (Burley, Wood and Hans 1971).

Larsen (1967) distinguished three main groups of E. camaldulensis,

found in the Murray River area, coastal W.A. and inland central Australia.

He found that within these groups introgressive hybridization was taking

place with Eucalyptus rudis (southern W.A.), Eucalyptus alba (northern

Australia) and Eucalyptus tereticornis (eastern Australia).

In Victoria, E. camaldulensis hybridizes with several species,

including E. tereticornis (Willis 1972). On the East Gippsland Plains,

where the ranges of these two groups overla~ it is difficult to make any

morphological distinction between them (Fell 1975). Laurie (1976) has . 0. m e c .~.... . III -oU

III

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~ 1f a. in'... ::!,g- o ... &' ~ ..n ::'I ~ \'! S' n ~ g 3 < 3 ~ g ~, :;:I "0 lED ~ ;8 ....,w ~ ~'" w· ~l ~ I ::::l Cb t ::r a. w """ 0- til r ~: 0 :. w ::r ... I -< I '" Cb ::::l ... ~ f Is til ;.:- i 3 _.~, f ..- &' ~ 3 CD ...... , CD til 10

also shown that there are some genotypic differences between forest and

woodland forms of E. camaldulensis in the Barmah Forest, Vic.

VICTORIAN DISTRIBUTION OF E. VIMINALIS AND E. CAMALDULENSIS

Figures 2 and 3 show the respective distribution of E. viminalis and

E. camaZduZensis in Victoria. These maps were compiled from locality

records made available by the National Herbarium of Victoria, the Herbarium

of the Botany School, University of Melbourne, from published material,

personal communications (D.H. Ashton and P.Y. Ladiges) and fieldwork.

In an attempt to account for some of the natural variation within these

two species each was subdivided into types.

For mapping purposes, three forms of E. viminaZis were differentiated

on the basis of stature and proportion of rough bark on the tree trunk.

These are the tall, smooth-barked tree of gullies and highland areas, the

somewhat shorter woodland form with varying amounts of rough bark, and

populations whose rough bark extends to the secondary branches, that is I E. viminalis var. racemosa E. camaldulensis was categorised by habitat, a distinction made by

Boomsma (1950). In riparian sites, under the influence of accessible water- 11 1 tables and seasonal flooding, trees vary from tall forest to woodland form.

On open plains, where moisture is derived from precipitation, trees are

invariably of woodland form.

E. viminalis

Smooth-Barked Forest Form

This form (Plate la) is common on the northern slopes of the Divide

in the Eastern Highlands where M.A.R. exceeds 1000 mm (Fig. 4). Chiefly

found on brown earths and krasnozems, it occupies moist but well-drained

valley sites and forms tall open-forests (after Specht 1970). a

c

B

PLATE 1

A. Smooth-barked forest form of E. viminaZis at Fernshaw in the Upper Yarra Valley.

B. The woodland form of E. viminaZis on a Si lurian outcrop near Morang, north west of Melbourne.

C. Rough-barked E. viminaZis var. racemosa on podsolized soils near Frankston.

A 11

In the broader valleys below 300 m where average annual rainfall is

less than 1000 mm, E. camaldulensis replaces E. viminalis as the dominant riparian species, with Eucalyptus camphora occupying poorly drained sites.

E. viminalis occurs in tall open-forests with Eucalyptus obliqua and

Eucalyptus radiata between 400 and 1600 m, although it has occasionally been recorded from greater altitudes, such as on the Nunniong Plateau at

1300 m (D.H. Ashton, pers. corrrn.).

On the southern slopes of the Eastern Highlands, smooth-barked

E. viminalis also occupies riparian habitats (but at slightly lower altitudes than on the northern slopes), where M.A.R. generally exceeds 700 rrrn, although

it also occurs in lower rainfall areas in protected gullies. On moist sheltered slopes between 400 m and 1200 m, it forms tall open-forests with

Eucalyptus regnans and Eucalyptus nitens.

In the Western Highlands smooth-barked E. viminalis is chiefly found above 500 m on basalt and granite outcrops where M.A.R. is more than 700 mm.

It forms open-forests and sometimes tall open-forests with E. obliqua and

E. radiata. In slightly drier areas this form of E. viminalis is confined to steep gully sites.

Other major occurrences are in relatively high rainfall (M.A.R. 1000 rrrn) highland areas such as the Otway Ranges and the South Gippsland Highlands.

In the Otways, smooth-barked E. viminalis fringes streams and forms tall open-forests. with Eucalyptus globulus, E. regr.ans and E. obZiqua on fertile brown earths (Parsons, Kirkpatrick and Carr 1977) and is emergent over

Nothofagus closed-forest (Howard and Ashton 1973).

In Western Victoria, isolated occurrences of smooth-barked E. viminalis have been noted in very sheltered valleys at Hall's Gap in the Grampians and on Moleside Creek east of Nelson, where average annual rainfall is 900 mm. 12

Woodland Form

The woodland form of E. viminaZis (Plate 1b) is generally found in the western half of Victoria, where it may occur in areas which receive 600-

300 mm H.A.R., but it is more common where H.A.R. is at least 700 mm. It

is generally found on relatively good loamy or clayey soils. Stands recorded

in areas where H.A.R. exceeds 800 mm are generally growing on deep sandy

soils. At localities near Geelong, E. viminaZis woodlands are known from

sites which receive little more than 500 mm M.A.R.

In the Western Highlands, woodland E. viminaZis tends to be restricted

to basalt cappings and granite outcrops, where M.A.R. is rarely less than

700 mm. Within these areas smooth-barked E. viminaZis also occurs in

sheltered gullies. To the south, on the Western District Volcanic Plains,

E. viminaZis woodlands are found on the wetter margins of the plains, and

are particularly extensive on stony rises along the southern extent of the

basalt. On coastal plains in south-western Victoria it occurs on sandy

soils derived from calcareous materials (Ladiges and Ashton 1977); eastwards

on the coastal plain which flanks the Otway Ranges,woodland E. viminaZis

commonly occurs on the Pliocene Hoorabool Viaduct formation.

In eastern Victoria, woodland E. viminaZis occurs on coastal plains

west of Wilson1s Promontory, and occasionally on the East Gippsland coastal

plains west of Bairnsdale.

Rough-Barked Form (var. racemosa)

Rough-barked populations of E. viminaZis (piate lc) are chiefly found

in coastal areas of eastern Victoria on the deep sandy podzols of Pleistocene

sand sheets and recent dune deposits, where M.A.R. is 630-760 mm. Other

rough-barked populations are found near Torquay, and from Nelson inland to

the Grampians, generally on infertil~ acidic sands. A

PLATE 2

A. The woodland form of E. camaldulensis growing on basalt

, '-'.i#- derived soils near __ fJ.~ ~ Morang. . '~Jo._ B. The forest form of E. camaZdulensis at Barmah on the Murray Ri ver.

B

.~. 13

E. CAMALDULENSIS

E. camaZduZensis occurs throughout Vic. except in the Eastern Highlands

and far East Gippsland. It usually forms woodland or open-woodland (Plate

2a); however, in the Barmah and Gunbower areas along the Murray River, tall

open-forests (Plate 2b) are found on the best quality sites (Laurie 1976).

North of the Dividing Range, on the Northern Plains where M.A.R. is

380-635 mm, E. camalduZensis is restricted to riparian habitats, some of

which may be seasonally waterlogged. Eucalyptus ZargifZorens occupies the

less frequently inundated sites, and both are replaced by EucaZyptus micro­ cappa on the heavy clay soils of the Northern Plains. In north eastern

Vic., E. camaZduZensis is found on the floodplains of the major rivers in areas which receive up to 1000 mm M.A.R.

South of the Divide, E. camaZduZensis is generally regarded as being absent east of Dandenong. although there are sporadic occurrences on the

East Gippsland Plains. West of Dandenong it occurs in both riparian and plains habitats. Riparian E. camalduZensis occurs in areas where M.A.R. is

500-700 mm; where M.A.R. is less than 500 mm it forms a thin, discontinuous fringe along streams. The woodland form is found on heavy clay soils of the

Dundas Tablelands, and on the wetter margins of the Western Volcanic Plains, where- M.A.R. is 600-700 mm. On heavy clay soils south of the Yarra River and near Dandenong. the woodland form of E. camaZduZensis occurs where M.A.R. is 700-1000 !TIn.

ECOTONES OF E. VIMINALIS AND E. CAMALDULENSIS

In Victoria, the ranges of these two widely distributed species over­ lap in both the plains and riparian habitats. However, within these recog­ nizable, broad ecotones, each species tends to occupy a topographically distinct site. 14

Plains Bounda~d

Woodland forms of both species occur on plains in western Vic. south of the Dividing Range. E. camaldulensis commonly occupies the drier sites

(600-700 mm) where soils are predominantly clayey. E. viminalis is generally found in somewhat wetter areas (M.A.R. > 700 mm) on well-drained soils. Where both species occur together, E. camaldulensis commonly occupies the wetter sites, whilst E. viminalis shows a distinct preference for better drained sites.

Riparian Boundary

Riparian communities of E. viminalis and E. camaldulensis overlap at three main regions in Victoria:

(a) On the northern slopes of the Eastern Highlands smooth-barked

E. viminalis is found in upper valley tracts above 300 m, where M.A.R. exceeds 1000 mm. At lower altitudes, E. camaldulensis is the dominant species on the floodplains.

(b) On the south-western flanks of the Eastern Highlands, E. viminalis extends almost down to sealevel along sheltered valleys where M.A.R. is equal to or greater than 700 mm. E. camaldulensis occurs along some water courses on the adjacent coastal plains south-east of Melbourne. and on the basalt plains north of Melbourne. The woodland form of E. viminalis may also be found here on slopes above the river valleys.

(c) In the Western Highlands. smooth-barked E. viminalis occurs on northern and southern slopes, but is largely confined to the headwaters of streams, giving way to E. camaldulensis where stream valleys broaden and M.A.R. decreases.

Both species show preferences for particular sites within the riparian habitat. E. viminalis occupies moist but well-drained river flats and valley slopes. E. camaldulensis grows along river banks often on heavy. poorly structured soils in areas which may be periodically flooded. 15

SUMMARY

Detailed mapping disclosed some of the relationships between the various forms of E. viminalis, E. camaldulensis and environmental factors. The habitat requirements for some forms of these two species are very broadly similar; however, E. viminalis generally shows a preference for the higher rainfall but well-drained localities, whilst E. camaldulensis most commonly occurs in somewhat drier areas on heavy, frequently poorly drained soils.

Where both species occur together, habitat preferences seem to be expressed for particular soil moisture regimes, E. viminalis being found on the better drained sites.

A study site was chosen at Templestowe in the Yarra Valley, where both species occur, to investigate some of the local factors which may influence distribution patterns in the riparian habitat. 8DO- isohyets (mOl.) catchment boundary transects N g A study sites ~ • Westerfolds ".- ... - , ... \ \ ... ,, \ ...... _-----, \, \ \ \ ,, I I - ,...... I' "'~I ... .1 "./ / I I \ ,,-- \ ,---- /' ...... " \ " - ...'..... _,-, ,_/ ...'

Port Phillip Btly

10 Aflef Mlrriott, 1915. L ~ 15, 20 2S.m,

Fig. 5. The Yarra Valley showing the location of Westerfolds, study sites A, B, C and D, transect locations and rainfall isohyets.

16

CHAPTER 2

THE YARRA VALLEY STUDY

I NTRODUCT I ON

Sites within the Yarra Valley were chosen to examine the factors affecting the distribution of E. viminaZis and E. camaZduZensis in the riparian habitat. E. viminaZis fringes the upper tributaries of the Yarra, and is found as far downstream as Templestowe (Fig. 5 ); from this locality

E. camaldulensis occurs along the river and adjacent gentle slopes to the river mouth at Melbourne. Both species are present along the river for

0.7 km between Bonds Road and Homestead Road; Westerfolds State Park was chosen as the primary study site. Both species are present there along the river, and as isolated stands on adjacent slopes. Fenced plots were erected for field trials, and seed and topsoil samples were collected there for use in glasshouse trials.

CLIMATE OF THE YARRA VALLEY

The Yarra Valley experiences considerable variation In rainfall, temperature and other climatic elements due to its location and topography.

Mean annual rainfall increases markedly from west to east across the catchment (Fig. 5), the mountainous upper tract receiving more than 1400 mm, and the western area less than 600 mm per annum. Rainfall is fairly evenly distributed throughout the year, although SUmmer tends to be the driest season. Seven major droughts have been experienced since settlement, although the region is not normally considered drought prone (Commonwealth

Bureau of Meteorology 1968). Frequent floods were common in the Yarra

Valley, and five major floods have been recorded. However, the frequency 17 and severity of floods has been mitigated in recent years by the construction of reservoirs to augment Melbourne's water supply.

Mean maximum temperatures range from about lSoC to 19 0 C east to west across the catchment, and annual mean minimum temperatures from 5°C to 9°C.

Mean maximum temperatures for January range from 25°C to 27°C, for July

10 o C to 13 0 C. Annual average evaporation ranges from 1000 mm over the lower areas of the catchment, decreasing to 750 mm in the upper catchment.

There is considerable local and regional variation in the occurrence of frosts, Melbourne averages nine a year; their frequency increases in the central valley with Healesville experiencing 38 per year. In the mountainous upper reaches as many as 100 may occur annually (Marriott 1975).

PHYSIOGRAPHY AND GEOLOGY

The Yarra Valley catchment extends to the north and east of Melbourne, bounded by the southern slopes of the Great Dividing Range to the north and by the I ine of granite and granodiorite intrusions and acid lavas which form the Dandenong Ranges and the Baw Baw Plateau (Gill 1949) to the south.

To the west it includes part of the Newer Volcanics plains.

The Yarra River has its source in mountainous terrain 48 km upstream from Warburton (Marriott 1975) and flows in a westerly direction to empty

into Port Phillip Bay at Melbourne. In its upper tracts the Yarra Valley

is cut into Silurian mudstones, sandstones and shales. The presence down- stream of acid lavas, a granodiorite intrusion, hornfels and a group of

acid dykes has resulted in the formation of an incised section from

McMahon's Gorge to Warburton Gorge (Gill 1949).

Below the WarrandyteGorge. the Yarra emerges into a broad alluviated

valley with wide flats which are still subject to flooding. At Fairfield 18

the valley narrows again due to partial infilling by Quaternary basalts which flowed down the ancestral valleys of the Darebin and Merri Creeks.

Ponding by basalt here resulted in the development of the broad flats upstream at Heidelberg and Templestowe. Below Fairfield, the Yarra is a

lateral stream cutting a winding valley on the eastern boundary of the

Quaternary basalt against Silurian sediments. The valley widens between

South Yarra and Princes Bridge where a narrow floodplain has developed.

Below Princes Bridge the river winds across its delta to Hobson's Bay

(Ne i I son 1967).

SOILS

Soils of the Yarra catchment upstream from Diamond Creek have been mapped by the Soil Conservation Authority (1976). Major types include yellow brown duplex soils which are most commonly found on Lower Devonian and Silurian siltstones, sandstones, mudstones and shales at altitudes of up to 300 m where M.A.R. is 750-1200 mm. They also occur in the catchment area west of Diamond Creek and south of the Yarra to Gardiner's Creek

(Grant 1972).

At altitudes between 200-1600 mm, where M.A.R. exceeds 1000 mm, red, brown and occasionally reddish brown, yellowish brown and yellowish red gradational soils occur on a wide range of parent materials including granites, granodiorites, rhyodacites and rhyol ites, tertiary basalts and metamorphosed sedimentary rocks.

Soils developed on Recent alluvial sediments along the Yarra and its tributaries include uniform sandy soils on levee banks, loamy soils with mottled subsoils on the occasionally flooded middle Yarra floodplains, and uniform cracking clay soils on the more frequently flooded areas of the middle and lower Yarra Valley. \.Jest of the Plenty River on the

Newer Volcanics, soi Is are generally uniform heavy-textured clays (Grant 1972). 19

VEGETATION OF THE YARRA CATCHMENT

Much of the vegetation of the Yarra catchment has been severely modified by firing, clearing, agricultural practices and the introduction of exotic species since European settlement. The vegetation on public land within the catchment has been mapped by the Land Conservation Council of Victoria (L.C.C.V. Melbourne Study Area 1973).

The mountainous and wetter areas of the catchment (M.A.R. > 1100 mm), which have remained comparatively undisturbed, support tall open-forest of E. regnans and E. deZegatensis, which may extend below 600 m on sheltered sites. E. regnans is usually dominant below 950 m, and is common in the headwaters of the Yarra River. E. nitens frequently occurs at the junction between these two species at 900-1000 m. E. ~dPeZZocarpa~ E. viminalis and

E. obZiqua tall open-forest is common at lower altitudes. In very sheltered gullies, Nothoragus cunninghamii closed-forest is found.

Open-forest of various eucalypt species occurs on drier sites and at lower elevations. On the lower slopes of the Kinglake Plateau,

~. obZiqua~ E. dives and E. radiata form open-forest, sometimes with

EucaZyptus rubida and Eucalyptus polyanthemos. E. dives and E. polyanthemos are found on the driest sites. West of the Donna Buang area, open-forest of E. dives and Eucalyptus goniocalyx occurs on the drier spurs. In the

Upper Yarra Valley, E. obliqua and E. radiata form open-forest on the more exposed sites, and Eucalyptus sieberi occurs variously with E. obZiqua,

E. baxteri and E. radiata on ridges and steep northern slopes.

Much of the catchment downstream from Healesville has been cleared.

Undulating areas of Silurian and Lower Devonian siltstones and mudstones support open-forest or woodland of various species including E. obliqua~

E. baxteri~ E. radiata~ E. dives~ E. macrorhyncha and E. goniocalyx.

At the western end of the catchment, basalt-derived soils supported open d

EcE camaldulmsis E9",£ goniocaLyx E! E. Leucoxylon Emac E macrorhyncha Erne! E melliodom E ob" E. obLiqua Eov E. ovata Ep,E polyanlizemos NNW Fernshaw 1193 mm. SSE E rad . E. radiata Erad Eob E reg £ regnans Ev Eov Ev Ev £ L/imlnalis

pasture

W Healesville 1028 ml1l. E

Erne! Alluvium Emac Ev Ep ~ D... . Newer volcanics [§J~ ;/.-: ... :.' Tertiary sands 0,_- Devonian rhyodacit Silurian sandstone NW Hurstbridge 740 mm. SE - and mudstone Erad Ev Ev Ev Ec Eg Ec

pasture

N Templestowe 788mln. S

Erne! E!

NNW Kew 735 mm. SSE

Ec Erne' Ec

N Richmond (reconstructed from remaining traes) 670 mm. s

Fig. 6. The landform, geology and eucalypt distribution across transects the Yarra Valley. Rainfall (rrm) is for nearest recording station. 20

dry tussock grassland (Willis 1964) which have now largely been replaced by exotic species.

The Distribution of E. viminalis and E. camaldulensis in the River Tract

A series of cross valley transects (Fig. 6) were drawn to examine

the distribution of riparian eucalypt species in the Yarra valley. Along

the valleys of the Upper Yarra and its tributary streams such as the Watts ad River at Fernshaw, where M.A.R. Exceeds 1100 mm, the forest form of

E. viminalis occurs on alluvial flats and riverbanks, sometimes with i E. regnans. At Fernshaw E. regnans is dominant on the well-structured E brown loamy soils of the south facing valley slopes, whilst E. obliqua

occupies the somewhat drier north facing slopes.

Forest-form E. viminalis fringes the Yarra downstream past Healesville,

and was once more widely spread across the broad alluvial flats. Poorly ne ne drained clayey depressions on the flats are occupied by E. ovata, whilst

the Silurian sandstone-derived soils on the valley slopes support

E. obliqua-E. radiata forest. At Hurstbridge on the Diamond Creek, where

rainfall is considerably lower, the forest form of E. viminalis occurs on

silty sands along the creek. E. camaldulenais woodlands occur on the

duplex soils of the lower valley slope beyond the floodplain. On the

shallow rocky soils of the upper slope and slope crest E. camaldulenais

gives way to E. polyanthemos, E. goniocalyx and E. macrorhyncha woodland.

A similar sequence occurs on the Yarra River upstream from Westerfolds.

At Westerfolds both E. viminalia and E. camaldulensis occur on

alluvial soils along the riverbank. Prior to clearing, E. camaldulenais

probably extended across the lower alluvial terraces which are frequently

waterlogged in winter. Now only small stands remain. E. camaldulensis

also grows on the duplex soils of the gentle Silurian slopes. Occasional

stands of E. viminalis also occur here. On the northern aspect where slopes

in 21

are steep and soils shallow and rocky, E. radiata~ E. goniocaZyx and E. rubida occur.

Further downstream at Kew, where M.A.R. is slightly lower,

E. camalduZensis occurs on alluvial terrace deposits and up the lower

slopes of the valley. The upper valley slopes on the east bank support

E. meZliodOra woodland, which grades into E. Zeucoxylon woodland on the

Tertiary sandy capping. E. viminaZis only occurs very sporadically on steep, sheltered banks. At Richmond and further downstream,

E. camaldulensis is the only naturally occuring riparian eucalypt, and

the woodland form of the species occurson undulating topography with

E. melliodOra, and extends across onto the basalt. This latter species was once common in the area now occupied by the City of Melbourne.

The Distribution of E. viminalis and E. camaldulensis ~n the Surrounding Region

The woodland form of both E. viminalis and E. camaldu4ensis occurs on gently undulating terrain around Melbourne. E. camaZdulensis woodlands grow on relatively deep soils on Silurian topography east of Melbourne as

far as Burwood, the easternmost extent corresponding with the 800mm isohyet.

South east of Melbourne, remnants of E. camaZdulensis woodland occur on low­

lying Tertiary sands between St. Kilda and Cheltenham, where M.A.R. is

600-700 mm, on peaty soils south east towards Frankston, and on heavy clay

soils near Dandenong, where M.A.R. is 800 mm. E. camaldulensis also grows on the basalt plains to the north and west of Melbourne where M.A.R. exceeds 500 mm; towards the Maribyrnong River the woodlands become sparser,

further west stunted trees occur in depressions or fringe drainage lines.

Stands of the woodland form of E. viminalis were probably not as extensive as those of E. camaldulensis, and tended to be restricted to .. .., ..• ,,,SJ&:ih a

WESTERFOLDS - GEOLOGY

N

, ,It"

I" "',~' i" I ~.' :~: l' ,~ : i :;; ~ '~.:~ I: ' ..! .. :', "­ , :>.

o o·s 1km

Ii ii ~ ~ 11 Silurian mudstones, siltstones and sandstones E::-a Quaternary alluvial terraces I: ..... :1 Quaternary alluvial flats

;:;..l. ..'1 Source: Melbourne and SuiubI GIatovY. 1959 '~lI!~,.::

~O~ ~.J •• .'9'·· ..,; .. ~~k ~,,~it.r. ~~!.': ~:t· I~.'.' ... ' .~, l' ....,-.

Fig. 7 22 well-drained sites, generally in slightly higher rainfall areas. Remnants

of E. viminaZis woodlands occur on Tertiary sandy cappings in the Wattle

Park-Ashburton area and on older basalt outcrops near Kangaroo Ground where M.A.R. exceeds 800 mm.

WESTERFOLDS - THE STUDY SITE

Westerfolds State Park is located at Templestowe on the Yarra River

(see Fig. 5). The site was chosen for its accessibility and the presence

of ecotone riparian communities of E. viminaZis and E. camaZduZensis.

Impending management of the property by the National Parks Service made

it a convenient place to establish field trials.

Average annual rainfall for the nearest recording station at Doncaster

(altitude 76 m) is 788 mm. Westerfolds which is 40-60 m above sealevel

probably receives slightly less rainfall. The nearest station for which

temperature data are avai lable is Melbourne, which experiences a mean o o maximum of 19.4 c and a mean minimum of 9.S C (Commonwealth Bureau of

Meteorology 1968).

GeoZogy~ Physiography and SoiZs

The bedrock of Silurian siltstones, sandstones and mudstones at

Westerfolds is largely overlain by Quaterna~y alluvial deposits forming

river terraces and flats (Fig. 7). These broad river terraces which are

conspicuous along the Yarra River upstream from Darebin Creek, originated

when lava flows down the Merri and Darebin Creeks dammed the old valley

of the Yarra (Neilson and Jenkin 1967). As the Yarra subsequently deepened

its bed, terraces were cut in the alluvial material. The Yarra River at

Westerfolds consists of a series of meanders, with steep river cliffs up

to 50 m high on the northern bank and a gently sloping spur with terrace · ...... ! c

WESTERFOLDS • LANDFORMS

N t I

, .,', " :~:. (

o 100 200 300 400 !500 met,.. IIIIJ) steep slopes and ridges , ! ! ' , , ~:\+:( • E].... gentle crests !~:':;1~:;;:~ ; " I IIill moderate slopes B E. camaidulensis field trial site .... upper terrace surfaces ,:" D C E. viminalis field trial site ~ upper terrace slopes ',', '" lower terrace '..: "~'I B ... ~" ... " ~,{:~ levee II billabong

Fig. 8 23

deposits on the southern side. Narrow alluvial flats fringe the Yarra.

The meander on the western side of the river was cut off by floods in

the 1930 1 5 (Lennon 1974). 1 The land forms have been mapped by Jeffery and Howe (1976). They have recognised eight major categories, which include steep slopes and

ridges, gentle crests and moderate slopes on Silurian outcrops, upper

terrace surfaces and slopes, lower terraces which border the Yarra and

the main creek, billabongs and levee banks (Fig. 8).

Soils (Table 1) derived from Silurian mudstones, siltstones and

sandstones and some terrace deposits are mottled, yellow and duplex

(Oy 3.41 after Northcote 1965), with sandy loams overlying clays. On some

low terraces soils are deep, brown gradational clay loams (Gn 4). Weakly

differentiated brown uniform profiles are found on levees and in billa­

bongs, with sandy loams on levees (Uc 1.43) and clay loams (Um) in

billabongs (P. Jefferies, pers. comm.).

Vegetation

Figure 9 shCPNS the distribution of the major eucalypt species at

Westerfolds. Most of the 122.2 ha consists of improved pastures, although

some native grass and herbaceous species are still present. The Yarra

banks support a narrow fringe of E. viminalis and E. camaldulensis forest

(Plate 3a); E. camaldulensis is dominant downstream from the main

tributary creek. t~ear Fitzsirrmons Lane E. viminalis is the dominant

riparian species, and between these areas both species are present.

Acacia me~oxylon~ Acacia dealbata~ Acacia mearnsii~ Hymenanthera dentata~

Bursaria spinosa~ Olearia argophylla, Leptospermum lanigerum~ Leptospenmum

phyliaoides, Callistemon paludOsus and Prostanthera lasianthos form a dense

shrubby understorey (Plate 3b) along undisturbed sectors of the bank. The

exotic species Salix babyloniaa and Rubus frutiaosus are common, Salix

is sometimes dominant along the lower river bank. .. '--,-- Po. - ' .,." ...., ., ..' r . ! ... i4~a",,:-. ,-tL.-t,.U"&t ••':'I! ___ Ta b , e ...... c,...... ___ .. __ ·.....F .. V R

Mottled Yellow Duplex (Dy 3.41)* Brown Gradational (Gn 4) Brown Uniform (Uc 1 .~3)

Hor i zon and Description Hor! zon and Description Hor! zon and Description depth (em) depth (cm) depth (cm)

Al 20 sandy loam Al 15 brown 15 Fine sandy loam friable fine sandy loam 10 YR 3/3 10 YR 4/21, pH 5.0 few brown mottles pH 5.9 A2 30 pale brown fine sandy loam 50 fine sandy loam A2 35 sandy loam pH 5.5 10 YR 4/3 very friable pH 5.5 10 YR 6/2 Al 45 brown clay loam pH 6.5 pH 5.5

A2 50 pale brovJn B 100 clay clay loam firm yellow mottles abundant yellow pH 6.0 mottles 10 YR 4/4 BI 80 brown light clay pH 6.9 abundan t ye 110w mottles pH 6.8

B2 100 brown Ii gh t clay abundant yellow mottles pH 7.8

*Northcote (1965). P. Jefferies pers. comm.

"- ._ ._~ .... ~r:"'" .1;- - ~::'->!..~:~ ·1":J~

-. :. ~r-'::;;;: .":,' ;~, ~<~: ¥:-: -.-:; '- - -,~t~;~~~; :t;~,,~;:::~~~~~.;\~,_~~_;Jry ":~ ~~~~~,:;jff- WESTERFOLDS - EUCALYPT DISTRIBUTION

N

,.. ,..

...

~n E. viminalis ~ E. camaldulensis ~ r.?m E. viminalis and E. camaldulensis ~ E. melliodora c:J Improved pasture

o, 100 200 300 400 500 metres

Fi g. 9 24

On the upper terraces and Silurian slopes scattered stands of

E. viminalis~ E. camaldulensis and E. melliodora form woodlands or

open woodlands, but this may be the result of partial clearing (Womersley

1976). Although E. viminalis is generally found on the well-drained deep

brown gradational clay loams of the river banks and lower terraces,

occasional stands occur on duplex soi Is of the Silurian slopes.

E. camaldulensis is also found on both the gradational and duplex soils,

but occurs more commonly than E. viminalis on the duplex soils of the

Silurian slopes. Although neither species is restricted to one soil type,

both E. viminalis and E. camaldulensis show some site preferences on each

soil. Along the river bank E. viminalis tends to occupy the upper bank,

whilst E. camaldulensis is able to grow closer to the river. On the

duplex soils E. camaldulensis generally occurS upslope of E. viminalis,

on the steeper drier slopes .

.. ~

In summary, throughout the Yarra Valley the forest form of E. viminalis

occupies moist but generally well-drained sites where M.A.R. exceeds 700 mm.

Where M.A.R. is less than 700 mm, E. camaldulensis is the dominant

riparian species, it fringes rivers and billabongs and is found on sites

subject to periodic inundation. E. camaldulensis also forms woodlands on

the relatively deep clay subsoils of the surrounding basalt and Silurian

topography, where it may be exposed to drought stress.

Hence, E. camaldulensis appears to be tolerant of greater extremes

in moisture supply, it may be subject to drought stress or flooding and

subsequent waterlogging. Climate, topography, soil texture and soil

structure will all interact to determine these conditions. Small changes

-'~.: in soil nutrient status may act as a more subtle differentiating factor.

Pot trials were therefore established to assess the relative tolerance

of seedlings of both species from the riparian habitat to the effects of

waterlogging and drought. The role of soil nutrients was also examined "4.,

A

B

PLATE 3

A. Riparian occurrences of E. viminaZis (v) and E. camaldulensis (c) at Westerfolds in the Yarra Va lley. B. Typical shrubby riparian understorey at Westerfolds.

< • , . _,i i;ii'A 25 by chemical analysis of soil samples, and the assessment of seedling growth response to varying levels of phosphorus and nitrogen. Inter­ specific competition for nutrients was investigated by growing seedlings in competition on soils from the field. Field trials were conducted to assess survival and growth rates of seedlings in the field.

The possibility of population variation in E. viminalis within the

Yarra Valley was also examined, and seedlings were grown from seed of suspected E. viminaZis x E. camalduZensis hybrids, however the progeny were typical E. viminalis. 26

CHAPTER 3

SEEDLING GROWTH RATE AND RESPONSE TO NUTRIENTS

I NTRODUCT I ON

Field observations on the distribution of eucalypt species along the Yarra River and its tributaries (Chapter 2) suggested that the forest form of E. viminalis occurs predominantly on better drained alluvial soils where M.A.R. exceeds 700 mm. In the drier areas of the Yarra Valley,

E. camaldulensis is the dominant eucalypt on alluvial deposits, but where the ranges of the two species overlap, the latter tends to occupy sites with heavy soi Is which may be subject to waterlogging, or is found on drier gentle slopes, away from the river, which may be prone to drought.

It is suggested that the forest form of E. viminalis may have a faster growth rate than E. camaldulensis on better drained alluvium in the higher

rainfall areas of the Yarra Valley, and that competition between the two

species may in part have determined their present distribution.

A preliminary experiment carried out by D.H. Ashton (unpublished)

suggested that interspecific competition may be an important factor in

the delimitation of these species. When E. viminalis seed collected from

Eltham was germinated and grown for two years in drained two gallon plastic

buckets containing a well structured garden soil seedlings grew much taller

than E. camaldulensis (seed source Heidelberg), both in monoculture and

mixed culture (Table 2).

Previous work with other eucalypt species has shown that the presence

of interspecific competition may influence the distribution of species

which generally occur in discrete stands although their edaphic ranges

overlap, Moore (1961), in an investigation of the factors delimiting

E. melliodora and E. rossii communities on the Southern Tablelands of 27

Table 2. Mean heights (cm) of seven two-year-old E. viminalis and

E. camalduZensis seedlings grown on a friable garden soil mixture in monoculture and mixed culture (D.H. Ashton, pers. comm.).

Species Monoculture Mixed Culture

E. viminalis 188 210 E. camaZduZensis 34 61

N.S.W., found that when the species were grown in competition, increasing levels of exchangeable calcium favoured the growth of E. meZZiodora. He suggested that its success would result in its dominance in a natural community if soil calcium levels were high.

Experimental work by Parsons and Specht (1967) has suggested that the distribution of E. baxteri on siliceous coastal sands in the wetter areas of southern Australia is due to a faster growth rate, which may enable it to replace E. diversifolia and E. incrassata on sites where rainfall is adequate. The distributions of E. incrassata and E. socialis, whose edaphic ranges overlap, have also been related to the competitive advantage of each species under different conditions of soil moisture and fertility

(Parsons 1969).

Chemical and physical analyses were carried out on soils collected from E. viminaZis and E. camalduZensis stands to examine the possible role of edaphic factors in influencing the species distribution. Seedling growth rates were compared in monoculture and mixed culture on the two

topsoils and on riverbank soils and in sand cultures at various levels of

phosphorus and nitrogen in glasshouse trials, and field trials were i:,.. ' ' J S 'If ...... ,~-"' .. --"wc···~'''"'~ ...-·;$\I;)jl'&iL .. ,'<·P!:: .. ,·'-q·\III!itZ~'J!''"'";Il~w'~-''''''~,_ a e • 0 proff edeserlpt 'ons at ~ i .Heldelberg ~B'~ ~ • C::Odmci~cJi.l~"tlltit.~ •• 'U"&". ' T bl ~ r • • • F ~~ -' • , c: E. viminalis plot at Westerfolds, D: Healesvllle (E. viminatis).

D A B c Depth (cm) Description Depth (cm) Description Depth (em) Description Depth (cm) Description

Alluvial Alluvial AI I uv i a 1 te r race Silurian slope chocolate browr 0-15 fine grey-brown 0-55 fine grey-brown 0-35 fine grey-brown 0-20 sandy loam loamy sand loamy sand s 11 ty loamI crumb structurE 55-70 pale yellow-beige fine rock 15-60+ fine 40-50 light grey sandy loamy sand material sandy loam (bleached) loam 20-35 chocolate browr 70-80 pale yellow-beige 50+ grey-brown heavy s II ty loam loamy sand with clay, mottled some yellow clay orange; sma II 35-50 chocolate browr mott I es angular peds silty loam orange yellow 80-90 light brown matt I ing clayey s;:)nd l yellm'l mottles I 50-150 brown s II ty block structure loam wI th Increasing yellow-brown 90-110 clay content l clayey sand wi th orange-yellow orange mot tIes. SI Turian slope mott I I ng block structure 150+ water table brown clayey sandI 0-30 fine grey-brown 110-130 loamy sand orange mott I es coarse sand with 3D-SO fine grey loamy 130+ sand some orange clay. plagioclase and 50+ orange mottled quartz fragments heavy grey clay

.... ~I' "'~',::.ii~~~~,~~ , 28

n .. ~ established to investigate seedling behaviour at Westerfo1ds . ~ ~ -• ~ ~. ~• ~. SOIL CHARACTERISTICS s ~ ~ 0 ~. ~ - ~- Methods ~ ~ 0 0 ~ ~ Soil characteristics were described from the E. camaldulensis (site B) w G. ~ - t and E. viminaLis (site C) field trial plots at Westerfolds. Since these ~ ~ ~ n ~ ~ ~ sites were less than one km apart, it was decided to include data for a ~ ~- ~ 0 ~ -~ downstream site supporting only E. camaLduLensis (site A near the Banksia Co ~ ~ ~ St. bridge, Heidelberg) and a site upstream near Healesvi 11e (site D) ..0 •" > ~ ~ dominated by E. viminaLis. ~ W % G ~ ~ ~ < ~ Five replicate samples were collected from sites Band C each month .... ••~ ~ ~ between June 1976 and July 1977 for the gravimetric determination of soil .... ~ ~ ~ ~ moisture. In January 1977 five topsoil (0-10 cm) and five subsoil (50-60 ~ ~. ~. .~ cm) samples were collected from each of the four sites, bulked and mixed 5 ~ thoroughly. Subsamp1es were used for particle size analysis: the clay and ~. ~ ~ ~ .... ~ s silt fractions were determined using the plummet bulb hydrometer (Hutton ~ ~ ~ 1955), and the sands by decantation of the fine fractions. Percentage

~ .. disaggregation (Downes and Leeper 1940) of the topsoi 1s and subsoils was ..~ measured, and pF (Leeper 1967) estimated. Analysis of the major nutrients,

~ organic nitrogen (Kjeldah1 method), total phosphorus (Chapman and Pratt ~ ~ ~ 1961) J available phosphorus (Colwell 1963) and determination of the s~ ~. ~ exchangeable bases, Ca, K (flame photometry) and Mg (atomic adsorption) J

~ 0 was carried out by Food Laboratories (Aust.) Pty. Ltd. -rt m rt ~ Results •~ ~

•~ Soil profile descriptions are given in Table 3. Two profiles are ~ 0

~ described for site B since soils within the field trial plot were derived -~ from two types of parent material, Silurian bedrock and alluvial terrace

deposits. The particle size analysis (Table 4) indicated that all topsoils 29

Table 4. Particle size analysis of soils at A:Heidelberg (E. camaZduZensis),

B:E. camaZdulensis plot at Westerfolds, C:E. viminaZis plot at Westerfolds,

~ Healesville (E. viminaZis).

Site % Clay % Silt % Fine Sand % Course Sand Texture

A

0-10 em 14.5 20.5 55 10 loam 50-60 em 17 24 57 2 loam

B

0-10 em 8.5 22.5 57 12 loamy sand

50-60 em 25 17.5 46.5 11 clay loam

C

0-10 em 6 15 68 11 loamy sand

50-60 em 28.5 11.5 50.5 9.5 clay loam

D

0-10 em 14.5 27.5 53 5 s i I ty loam

50-60 em 18.5 29.5 49 3 s i I ty loam

*- Values for soil derived from Silurian parent materials. a E. yiminalis • E. camlldullMis (a) 6 A horizon 6 B horizon

5 5

pF 3 3

... 2 ..

o 10 20 30 40 50 60

Soil moisturl (%) (b) 6 A horizon 6 B horizon

5 5

4 4

pf 3 3

2 2

10 20 30 40 50 60 o 10 20 30 50 60

Soil moisturl (")

Fig. 10. pF curves for soils from (a) E. camaldulensis (Site B) and E. viminalis (Site C) field trial plots at Westerfolds, and (b) E. camaldulensis stand at Heidelberg (Site A) and E. viminalis stand at Healesville (Site D). A, horizon 0-10 cm depth; B, 50-60 cm depth. PWP = permanent wilting point, Fe = field capacity (after Leeper 1967). 30

contained a high proportion of fine sand, with varying amounts of clay

and silt. For the levee bank sites at Heidelberg and Healesville there

was no marked texture change with depth, however for Westerfolds sites

on Silurian bedrock, the B horizon, was generally a heavy clay loam.

Table 5 provides some indication of soi 1 structure; topsoi 1 at Heidelberg

(A) had a fine crumb structure, whilst at Westerfolds (sLtes B and C) it

was generally apedal. Percentage disaggregation values for Healesvi lIe

topsoil were similarly high, but in the field the topsoil, which had a

high organic content (Table 6) was quite friable. Subsoils were poorly

structured, the slightly lower values for Westerfolds \'Jere attributed to

the presence of false aggregation (baked clay lumps) in the samples.

-, In order to separate all the fine material from the aggregates it was 60 necessary to continue flushing the soil for up to one hour, three times

the suggested period, and it is thought that the method did not provide

entirely satisfactory results.

Analyses for the major soil nutrients (Table 7) did not indicate any

conclusive differences in the fertility of the four sites. There was some

tendency for the riverbank soils (sites A and D) to have higher levels of

organic nitrogen and total phosphorus. Avai lable phosphorus was highest

at site C which supports E. viminaZis. Calcium levels were highest for

sites A, Band C. The validity of these results as a basis for comparison

--, is somewhat uncertain, since site A has been uti lised for grazing, and 60 sites Band C intensively grazed and probably top dressed. Site 0 is

undisturbed.

A comparison of the pF values (Fig. 10) for topsoils at Westerfolds

suggested that more water would be available at the E. aamaZduZensis

site (8). There was little difference in the amount of moisture available

I. in the subsoils, however exact values were not estimated since these soils i 7) . (and the E. aamaZduZensis topsoil) formed a slurry before field capacity

was reached. Examination of the percentage soil moistures for these two 31

Table 5. Percentage disaggregation of soils at A: Heidelberg, B: E. aamaldulensis plot at Westerfolds, C: E. viminalis plot at

Westerfolds, D: Healesville.

Depth (em) A B C D

0-10 59 73 74 76

50-60 98 86 89 90

Table 6. Percentage organic matter of soils at A: Heidelberg,

B: E. aamaldutensis plot at Westerfolds, C: E. viminatis plot at

Westerfolds, D: Healesville.

Depth (cm) A B C D

0-10 5 2 3 12

60-50 4 3 5 5 32

i': Table 7. Soil analyses for field localities - site A: Heidelberg,

B: E. ~amaZduZenais field trial plot at Westerfolds, C: E. viminaZis field trial plot at Westerfolds, D: Healesvi lIe.

Site pH Ca Mg K p p N (%) mg/l Avail. Total

A

0-8 em 5.5 720 440 50 18 288 0.24 8-15 740 390 18 42 243 0.18

60 6. 1 520 680 14 17 188 0.31

B

0-8 em 5.5 1040 360 40 8 200 0.22

8-15 490 250 20 6 111 0.12

60 5.6 120 340 12 2 100 0.04

C

0-8 em 5. 1 720 800 20 32 129 0.22

8-15 267 220 8 15 72 0.08

60 5.8 180 160 14 5 40 0.04 o

0-8 em 4.8 120 420 32 10 248 0.36

8-15 60 340 22 7 161 0.32 60 5.5 10 250 6 3- 145 0.07

*Oetermined by Food Laboratories (Aust.) Pty. Ltd., Carlton 3053. 33 sites over a 12 month period show that the pF values are not a reliable

indication of the amount of moisture available to plants throughout the year. The E. viminalis site (C) is situated on a slow-draining terrace slope which is effectively waterlogged for part of the year. The

Heidelberg and Healesville sites (A and D) tended to have more avai lable water in their topsoils than the Westerfolds sites, but less in the sub­ soils which contained a smaller clay fraction than the Westerfolds sites.

The results of the soil moisture measurements are further discussed in

Chapter 4.

COMPARISON OF SEEDLING GROWTH RATES

Seedling Growth on Two Topsoils

Methods

Seed was collected from the Westerfolds study site at Templestowe

and germinated in petri dishes under light in a constant temperature

(23 0 C) room. Topsoils (0-10 em) collected from sites adjacent to the

E. viminatis and E. camaZduZensis field trial plots were sieved coarsely

and placed in 12.5 cm pots. Seedl ings were planted. out one week after

germination, two seedlings of the same species per pot for the monoculture

treatment and one of each species for competition. Pots were arranged in

a randomised block, 2 species x 2 soils x 9 replicates each for monoculture

and mixed culture. Plants were grown under glasshouse conditions for 19

weeks (October 1975 - March 1976). Shoot heights were measured and plants

harvested to record oven dry weights.

Statistical analyses

Statistical methods for the analysis of competition experiments where

species are grown in both monoculture and mixed culture trial include

those of Williams (1962). McGilchrist (1965) and Langer (1973). These

methods are based on a comparison of the absolute yields of species 34 grown in monoculture with the yields achieved in mixed culture, and assume that these absolute increases and decreases are approximately the same. The relative yield approach of de Wit and van den Bergh (1965). designed to allow for comparison of the relative reproductive rate of species from a series of harvests when growth may have occurred under different conditions, or when harvests were obtained at irregular inter­ vals, is based on a comparison of the proportional changes in yields of the competing species. Van den Bergh (1968) has shown that arithmetic increases and decreases, on which earlier analyses were based, are only likely to approach equality when the yields obtained in monoculture are similar. McGilchrist and Trenbath (1971) re-analysed the data obtained by Wi lliams (1962) and compared it with the earljer approach of McGilchrist

(1965). They reported that the data " are fj tted somewhat better by the present statistical model [but] experience has shown that this is not a 1ways the case'i.

In the present study, the yield data were analysed by a three way analysis of variance (species x soil treatment x competition treatment).

Monoculture yields were halved for comparison with the competition yields per species; height data were log transformed since variables were proportional to means (see Williams 1962) and subjected to a split plot analysis in time (Steel and Torrie 1960). Such a straight forward analysis would seem appropriate as a first approach. Furthermore the clear non­ significance of some effects (see results) did not warrant more refined analyses such as those outlined by Langer (1973) and HcGilchrist and

Trenbath (1971).

Replacement series diagrams (de Wit and van den Bergh 1965) were constructed for dry weight data using mean total shoot dry weight per pot for monocultures, and mean total shoot dry weight per species for mixed cultures. The relative yield totals were calculated using the formula given in Burdon and Pryor (1975). The occurrence of competitive inter- c

... ~

I A B "45~ i I I ~~ i '~1 I I I I I I ~ l'4Q~ ~ ..- 40 pr ~ " ..- ,. / 1 ! ..- j / ..- " I / ~ I ! ~ " " / " " I / ". " / ~ I i I 35 / 1 / 35 I :5. " 1I " l .. / / I I / "" / I ..:l I / / I / / I I / I / I I d / i I o E. vimlnali. I I r:f 1301 / 130~ • E. camaldillensi$ I / I i i / - monoculture I I i • --- mlled tultull i i I I '// I "II " " I I 12 14 16 18 20 12 14 16 18 20 Weeks

Fig. 11. Height growth of E. viminalis and E. camaldulensis on two in monoculture and mixed culture. (a) on E. camaldulensis topsoi I, E. viminalis topsoil. Confidence limits are not shown as few means are significantly different.

1;,1',.:1." (bl 2 (bl ~J"': o E. villin ....

O...L...-'--- E. ClIMldullnsis soil E. viminllis soil

Fig. 12. Shoot dry weights of E. viminalis and E. camaldulensis grown two topsoils in (a) monoculture and (b) mixed culture. Vertical bar ( confidence limits.) allows comparison of species and treatments (Schef tes t) . 35

action was indicated by the slope of the lines in the replacements diagram.

Where the slope exceeded 45 0 competitive interaction between the two species

resulted in suppression of the yield of one species and enhancement of the

other (Etherington 1975).

Resu Its

Analysis of the height growth data (Table 8) showed that the signif-

icance of the main effect, species, was time dependent, as was the species

x soil interaction. The competition effect was not significant. Figure

, 11 shows that E. viminalis was the taller of the two species on both soils !O and for both monoculture and competition treatments immediately prior to

harvest. Species differences were more pronounced after 20 weeks growth

on the E. camaldulensis soil. However, shoot dry weights provide a

) lIs different picture, being significantly larger for E. camaldulensis than >n for E. viminalis (Table 8, Fig. 12). Shoot dry weight production by

E. viminalis tended to be greater in monoculture than in mixed culture

conditions; this trend was reversed for E. camaldulensis. Suppression of

E. viminalis growth in mixed culture suggests that competition with

E. camaldulensis may have been taking place, however this effect was not

statistically significant.

The replacement series diagrams (Fig. 13a,b) indicates that competition

did not occur; the slope of the lines being close to 45°. The displacement

of the E. camaldulensis slope above E. viminalis (Fig. 13) represents I different growth rates. The relative yield totals close to 1.0 indicates

that there is no inhibition nor stimulation of growth when the two species

are grown together.

The preliminary experiment carried out by Ashton showed a more marked

species difference in height growth, with E. viminalis suppressing

E. camaldulensis. However, E. viminalis did not overtop E. camaldulensis

until seedlings were twelve months old. It was suggested that a growing a

A o RYT-'-O' RYT -0-89

v+C "~ _____~o-----~

12

V v+C C V Vw+C C B E ~ AYT-'-Q4 RYT "1'05

., 8. ~ .. ~ i'~. - ,~. 'iii ~ 12 ')

~Vl (' ... I, . >- i .i -0 ';, c (1) V V+c Va Q) c \fe+C C " . -~) .. ' :2 :1 ~:'l' - . ,. ~ ", C F RYT", "'3 RYT "0-89

5 12 ~. ___ _

v V+C v

Fig. 13. Replacement diagrams for competition trials between E. viminaZis and E. camaZduZensis. A, yields from E. camaZduZensis topsoil; B, yields from E. viminaZis topsoil - experiment one. C, yields from alluvial soils - experiment two. D-F, yields from E. viminaZis 'Westerfolds', E. viminaZis 'Eltham' and E. camaZduZensis grown on alluvial soils - experiment three. Relative yield total (RYT) values above diagrams relate to yields in mixed culture.

" 36

Table 8. Analyses of variance of data from seedling growth on two topsoils (Experiment 1).

Source of Variation df MS F p

(a) Height, 10910 transformed. Split plot analysis in time.

Species 0.00581 O. 12 NS Soi Is 0.04030 0.80 NS Spp. x Soils 0.02223 0.44 NS Competition 0.00259 0.05 NS Spp. x Competition 0.01043 0.21 NS Soils x Competition 0.01311 0.26 NS Spp. x Soils x Camp. 0.01546 0.31 NS Res i dua 1 a 64 0.05037

Time 2 0.2214 160.43 Spp. x Time 2 0.00754 5.46 Soi Is x Time 2 0.00089 0.64 NS Spp. x So i 1s x Time 2 0.00494 3.58 Camp. x Time 2 0.00236 1. 71 NS Spp. x Camp. x Time 2 0.00146 1.06 NS Soils x Camp. x Time 2 0.002 1. 45 NS Spp. x Soils x C. x T. 2 0.00224 1.62 N5 Residual b 128 0.00138

(b) Shoot dry weight

Species 3.69014 9.10 ** 50 i 1s 0.03294 0.08 NS Spp. x 50 i Is 0.24267 0.60 N5 Competition 0.05120 0.13 NS Spp. x Camp. 0.70409 1. 74 N5 Soils x Compo 0.01389 0.03 N5 Spp. x Soils x Compo 0.00036 0.001 N5 Residual 64 0.40534

*. :'::': ***, significant at p = 0.5, 0.1, 0.001 respectively; N5, not significant at p 0.5. --~------

',8

-0- ~------0 --'" I(a) I (b)

1'1 I I I I I I o E. viminllis / I I I • E. CIImlldulensis I I / / monoculturl f 1·0 I ----- mixed culture / I '.' I •I

t I 1 1 t 1 1 6 8 12 16 20 24 28 Weeks

Fig. 14. Height growth of E. viminalis and E. aamaldulensis in monoculture mixed culture. Vertical bars indicate 95% confidence limits, allowing compari of (a) anyone species/treatment combination over time, (b) species and trea at anyone time.

(b)

6

5 -CD (8) .!: 4 CD I 'w 3: (b) .c>- J C; : ~ .,g 2 ";'"< '"

v v c c

Fig. 15. Shoot dry weights of E. viminaZis (V) and E. camaZduZensis (C) culture (a) and in mixed culture (b). Vertical bar allows comparison be species and treatments. 37

period of 20 weeks may have been too short for any similar reversal in

growth rates to occur. Direct comparison between the two experiments

is difficult since Ashton used soil of a different texture and ferti lity,

and grew seedl ings in larger pots for a longer period. However a second

experiment was established to examine this possibil ity.

A Comparison of Seedling Growth Rates on Alluvial Soil

Methods

Topsoi I of fine, loamy sand from the river bank where stands of both

E. viminalis and E. camaldulensis occur at Westerfolds was sieved coarsely

and placed in 15.2 cm pots. Four pinches of seed (of one species for mono­

culture, two of each species for mixed culture) collected from Westerfolds

were germinated on the soil surface in the pots. After germination,

seedlings were thinned to four per pot, and following four weeks growth

the tallest two seedl ings were selected. Pots were randomised in a block

design with 2 species x 11 replicates in monoculture and mixed culture.

Pots were watered daily, heights were measured at regular intervals and

growth continued in a heated glasshouse unti I July 1977. Harvesting was

carried out after 28 weeks as seedl ing height growth for both species appeared to have ceased. Shoots were oven-dried and weighed; height and dry weight data were anlysed as for the first experiment.

Results

Analysis of the height data (Table 9) indicated a significant difference between the species which was maintained over time. Figure

14 shows that E. camaldulensis,which did equally well in monoculture and mixed culture, grew taller than E. viminalis. The competition effect was not significant.

There was also a significant species difference in dry weight production (Table 9), and the species x competition interaction was significant. Dry weight production by E. camaldulensis was significantly 38

Table 9. Analyses of variance of data from seedling growth in

competition (Experiment 2).

Source of Variance df MS F p

(a) Height, 10910 transformed. Split plot analysis in time.

Spec i es 0.11228 5.34 * Competition o .02211 1.05 NS

Species x Competition 0.00018 0.01 NS

Residual a 40 0.021008

Time 4 5.65103 281 . 17

Species x Time 4 0.07552 3.76

Competition x Time 4 0.00054 0.03 NS

Species x Compo x Time 4 0.01738 0.86 NS

Res i dua I b 160 0.020098

(b) Shoot dry weights

Species 52.40728 20.32 *.,,:*

Competition 0.36728 O. 14 NS Species x Competition 14.54750 5.64 * Residual 40 2.57953

* **. *** significant at p : 0.5,0.01,0.001 respectively; NS, not significant at p : 0.5.

,i'., 39 greater than that of E. vimiY'..o.lis (Fig. 15), and was largest under mixed culture conditions. Shoot dry weights \"lere smallest for E. viminalis seedlings growing in mixed culture, indicating that E. camaldulensis was suppressing the growth of E. viminalis.

The slope for E. camaldulensis on the replacement series diagram

(Fig. 13c) is convex, whi 1st that for E. viminalis is concave, suggesting that the growth of E. camaldulensis was enhanced in mixed culture, and that of E. viminalis suppressed.

Comvarativec Growth Rates of _E. camaldulensis and Two Provenances of

E. vimina lis

The yield results for the first and second experiments suggested that growth for E. camaldulensis was greater than that for E. viminalis, and that in mixed culture the presence of E. camaldulensis may suppress

E. viminaZis growth. In view of the results of the preliminary experiments,

it was decided to investigate the possibility of ecotypic variation within

E. viminalis in the Yarra Valley. An experiment was established to examine the growth rates of E. viminalis and E. camaldulensis from

Westerfolds and E. viminalis from Eltham (the seed source for the pre-

liminary experiment). No seed was available for the Heidelberg provenance of E. camaldulensis used in the preliminary experiment.

Methods

E. viminalis and E. camaldulensis from Westerfolds, and E. viminalis

seed collected from tall forest form E. viminalis growing along Diamond

Creek, Eltham (hereafter called E. viminalis 'Eltham ' ), was germinated

as for the first experiment. Fine loamy sand topsoil was collected from

the riverbank at Westerfolds, sieved. coarsely and placed into 15.5x15 em

drained plastic buckets. Seedlings were planted out, eight per bucket,

in monoculture and mixed culture combinations two weeks after germination.

Buckets were randomly assigned to blocks, the experimental design being a

A 1·8 -.-----. .. ------. T 1·8 : I _.0- _ - ______0------0 i 1 la) Ibj o E v,m,nalis 'Westertolds" 1·4 4 E .,m,nalos "Eltham" • E camaldulen ...

monocuJture ,,2 mlud culrur~

) ii r ;I~ ;/, '. ~ B - ., c t '-8 ,~ 1'81 T I .:.. -~ 'II "6 1'6~ ,.------: -0 la) i i I I rl Ib) I ___ ::Z::: ::::: :S::-:·::_:'A til) (bI :I i I -i! '·4 1-41 - - '"i IP--~/- ,I }/ ;:s./ 1/" 'I ~ I I I' I f I I I -,( 1'21 f'l h /,// : .!J I; , I I " II 1/I I ,- Ii ,,0 !!p' I,oi I ' . . . '. .. ~. d / "I" '?' , ·n I I .:l

• "II i i , '"'-1I-,o'---''''''2-14''''---'1~--18'---2O'''''i -2"1"'2--"24--'28 " i i I i TO 12 14 18 18 20 22 24 26 " Weeks

Fig. 16. Heights of E. viminaZis 'Westerfolds ' • E. viminalis 'Eltham ' and E. aamaldulensis grown in monoculture and mixed culture. Vertical bars represent 95% confidence limits for the comparison of (a) any species/treatmen combination over time. (b) species or treatments at anyone time_ A. E. viminaZis 'Westerfolds ' x E. aamaldulensis. B. E. viminalis 'Eltham ' x E. aamaZdulensis. C. E. viminalis 'Westerfolds ' x E. viminalis 'Eltham'. 40

3 'species'x2 treatments x 3 replicates. Plants were grown under glass-

house conditions for 27 weeks (August 1977 - February 1978), and heights

were measured each month. Plants were harvested in February after both

species had developed purple tinged leaves, lower leaf abscission was

occurring and height growth rates had slowed down. Shoots were oven-dried

and weighed. Dry weights and heights were analysed as for the previous

experiments. Seed sources or 'species' were analysed in pairs (hence three

analyses).

Resul ts

There were significant differences in height between E. viminaZis

'Westerfolds' and E. camaldulensis (Table 10). After 11 weeks growth

E. camaldulensis had overtopped E. viminalis 'Westerfolds' in both mono-

culture and mixed culture treatments (Fig. 16a); at 20 weeks

I E. camaldulensis was significantly taller (error bar (b)) than E. viminalis Ibl 'Westerfolds'. However the competition effect was not significant.

A comparison of the mean heights of E. viminalis 'Eltham' and

E. camaldulensis indicates that the significance of this species difference

was dependent on time (Table 10), after 23 weeks E. camalduZensis was

significantly taller (Fig. 16b). E. viminalis 'Eltham', like E. viminaZis

'Westerfolds ' , showed reduced height growth when grown in competition with E. camaZduZensis, whose height growth was greatest in mixed cultures,

although this competition effect again was not significant. There were

no significant differences between the mean heights of E. viminalis d atment 'Westerfolds ' and E. viminaZis 'Eltham' , but treatment effects were significant (Table 10). Both populations showed reduced height growth

in mixed culture (Fig. 16c). Shoot dry weights (Fig. 17) showed a

similar pattern to height growth, with E. camaldulensis having a greater

yield than either E. viminalis populations. Although the competition

effect was not statistically significant, E. camaZduZensis tended to have

a greater yield in mixed culture than in monoculture. There were no 10 ~S\ ~t(, I ~ f»., I :;: ~ ~~l .'iii" t:·/~ I [",~:y" I i,.. 5 n, I .." I i 1 1 I Q n 0 ~~1 .c I t,~';\ i tF§ 1' I I I I I '" I t\;i\ I ! I I I ~~. ~,(i:.~', I .:.:.,.... i I~ 0 ~~ IIw C Vw~C II. e Vt' C IIw lit Vwxll.

Fig. 17. Shoot dry weights for E. viminalis 'Westerfolds ' (Vw), E. viminalis 'Eltham' (Ve) and E. camaldulensis (C) grown in monoculture and mixed culture (Vw x C. Ve x C. Vw x Ve). Vertical bars represent 95% confidence limits.

\: ·1 "I.

I J, \ ~.

f ,." "~I, ~ 41

Table 10. Analyses of variance for growth trials with two populations

of E. viminalie and E. camaldulqnsis (Experiment 3).

Source of Variation df MS F p

(a) Height growth, 10910 transformed. Split plot analysis in time.

1. E. viminalis Westerfolds x E. ccunaldulensis

Blocks 7 0.16797 6.56 :,,** Species 0.46511 18. 17 -;1:;':* Competition 0.01750 0.68 NS Species x Camp. 0.05622 2.2 NS Residual a 21 0.0255919

Time 4 2.59252 277.34 *** Species x Time 4 0.11310 12. 1 *-1:* Competition x Time 4 0.00271 0.29 NS f Spp. x Camp. x Time 4 0.00962 1.03 NS 1 Res i dua 1 b 112 0.0093478

2. E. viminalis Eltham x E. camaldulensis Blocks 7 0.20965 3.02 * Species 0.21962 3.16 NS Competition 0.04121 0.59 NS Species x Camp. 0.05135 0.74 NS 'e Residual a 21 0.0694133

Time 4 2.87576 642.71 :':::':'* Species x Time 4 0.08313 18.58 ;'c** Competition x Time 4 0.00101 0.22 NS Spp. x Camp. x Time 4 0.00864 1.93 NS Residual b 112 0.0044744

----_..

(cant. ) 42

Table 10 (cont.)

3. E. viminalis Westerfolds x E. viminalis Eltham Blocks 7 0.26343 10.0 *** Species 0.00228 0.09 NS Competition 0.31767 12.06 ** Species x Compo 0.06282 2.38 NS Residual a 21 0.0263371

Time 4 2.06787 547. 14 *** Species x Time 4 0.00252 0.67 NS Compo x Time 4 0.00082 0.22 NS Spp. x Compo x Time 4 0.00123 0.32 NS Res i dua I b 112 0.0037794

(b) Shoot dry weight.

1. E. viminalis Westerfolds x E. camaldulensis Blocks 7 66.83777 3.15 ** Species 180.83265 8.53 ** Competition 1 .30815 0.06 NS Spp. x Competition 31.34340 1.48 NS Residual 21 21.202455

2. E. viminalis Eltham x E. camaldulensis Blocks 7 55.13296 3.74 ** Species 249.03540 16.88 *** Competition 6.39925 0.43 NS Spp. x Competition 37.47615 2.54 NS Residual 21 14.751577

3. E. viminalis Westerfolds x E. viminalis Eltham Blocks 7 37.82098 3.88 ** Speci es O. 10125 0.01 NS Competition 3.36701 0.35 NS Spp. x Competition 2.22605 0.25 NS Residual 21 9.7392347

*, **, ***, significant at p = 0.5, 0.01, 0.001 respectively; NS, not significant at p = 0.5. N N N N N PIN} P1N2 P1N3 P2 N} P2 2 P2 3 P3 I P3 2 P3 3

;t~ 2.0 2.0 2.0 B.O B.o B.o P as KH2P04 0.5 0.5 0.5 48.0 3.0 12.0 4B.0 3.0 12.0 48.0 N as NH4N03 3.0 12.0 9.84 9.84 9.84 9.84 9.84 9.84 9.84 K as KH2P04 + K2 S0 4 9.84 9.84 10.0 10.0 10.0 10.0 10.0 10.0 Ca as CaCl2 10.0 10.0 10.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 Hg as HgS04 7H20 20.0 20.0 O. 1 O. 1 0.1 0.1 0.1 0.1 Hn as HnS04 H2 O O. 1 0.1 0.1 0.05 0.05 0.05 0.05 0.05 0.05 Ho as Ho (NH1\)6 H07024 4H2 0 0.05 0.05 0.05 O. 1 0.1 0.1 0.1 0.1 0.1 0.1 Zn as ZnS047H20 0.1 0.1 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 B as H3 BO 3 0.2 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Cu as CUS04 5H20 0.02 0.02 2.B 2.B 2.B 2.8 2.8 2.8 Fe as Fe EDTA 2.0 2.8 2.8

5. 1 5.0 4.B 4.9 4.9 pH of solution 5.5 5. 1 5. 1 5.5

* Analytical grade reagents used.

. .. ~~

--.C~;:~~·::t::c-;os;.1~'!;'::':'f~.;..::::r...::._., ...... :~~_._~~~_ :..._ .. __ ~_: ._.....,-. - "-_ . ~-'---~--.----:- ... -~ ...... ~~.~.~ . __~: .. :~±. ':"'~ ·-':"i.t.-~·": ,. .i.~~~ 43

significant differences in the dry weight production of E. viminalis

'Westerfolds ' and E. viminalis 'Eltham' (Table 10).

The replacement series diagram for the E. viminalis 'Eltham' x - E. camaldulensis combination suggests that some competitive interaction may have been taking place, as the slope deviates slightly from 45°, but

the major effect is the different growth rates of the two species. The I• -'"', relative yield total of 0.89 for the E. viminalis 'Westerfolds ' x g E. viminalis 'Eltham' suggests some inhibition of both forms when grown .,.o :J in mixed culture, the statistical analysis also indicated that the ...,.C competition effect was significant. -G ..:J •o Growth at Various Phosphorus and Nitrogen Levels -...c The experiment was established to examine the responses of

E. viminalis and E. camaldulensis over a range of nutrient conditions,

and to assess the relative nutrient requirements of the species. gn ~ ~: Methods ...., III ... E. viminalis and E. camaldulensis seed collected from Westerfolds o ~ III was germinated as for the first experiment. Two week old seedlings were

planted out, four per pot, into 12.5 cm plastic pots containing a 2:1

mixture of acid-washed sand and perlite, which was added to improve drainage.

Pots were placed on saucers and arranged randomly in blocks, the experimental

design being 2 species x 9 treatments x 7 replicates. The treatments

consisted of three levels of phosphorus, each of which was applied at three

levels of nitrogen. The composition of the treatments and their nomen-

clature is given in Table 11.

Seedlings were watered daily with 100 mls of distilled water during

the first week, followed by 50 mls 12.5% P1N1 for one week. When seedlings were four weeks old the strength of the solution was doubled, and at five

weeks the amount increased to 100 mls. During the sixth week plants were

given 100 mls of 50% P1Nl. at week seven full strength P1Nl solution was A N,

18l --A

1-6 T

.. J ...... 1 :t ' /~/ ' .~ -' /" o E vlminalis • ///" ,'P' --/ I H~ • E. camaldulensis I //'fr ~/ ---Pi -- P ------P , ,II z J .,I I I l2l / ~ .. I II 0 '/ 1- 1 Ij j E... ,; L;/ I I I .E 12 14 16 'Q;"" --= = B NZ ....""Q 1-6 I T 1-6 1

14 , ,, ,, '·2 ,, " ,·2

,. '·0

? tH---,i-----ri------~I-- LH----~I------r-----~i-- 12 14 16 12 14 16

Weeks

Fig. 18. Effect of increasing levels of phosphorus at three levels of nitrogen on height growth of E. viminaZis and E. camaZduZensis seedlings. Vertical bar allows comparison of species or treatments at anyone time, and o.f anyone species/treatment combination over time. Arrow indicates commencement of full strength treatment. 44

applied. Nine week old seedlings, which were at the four leaf pair stage,

were thinned to three per pot prior to the commencement of full scale

treatment. Treatment solutions were appl ied at the rate of 100 mls daily

and once a week pots were watered with 100 mls of distilled water to

prevent possible accumulations of salts.

Seedling heights were measured and the experiment was harvested

after a total of 16 weeks growth in the glasshouse. Leaves were detached

from all three plants in five pots of each species in each treatment, and

leaf area was measured using a Paton Leaf Area Planimeter. Leaf area was

estimated from regression equations for the remaining pots. Oven dry

weights of roots and shoots were determined, seedling heights, leaf area,

total dry weights and root/shoot ratios were subjected to analyses of

variance. The heights and dry weights were log transformed prior to

analysis since variances appeared proportional to the means. The height

data were subjected to a split plot analysis in time.

Results

1. Heights

All single factors. species. phosphorus and nitrogen and their

interactions were significant except for phosphorus x nitrogen; however

the phosphorus x nitrogen interaction was significant over time (Table 12).

E. camaldulensis generally grew taller than E. viminalis; it showed

an increased height growth in response to phosphorus at Nl (Fig. 18a),

but for N2 and N3 treatment differences were time dependent, being

insignificant at 14 and 16 weeks. For the highest level of N (N3, Fig.

l8c) there was a trend for the rate of height growth to decline with the rogen bar highest level of phosphorus. E. viminalis showed a similar response to

full phosphorus at N3 (Fig. 18c), but at lower levels of nitrogen, the reaction of E. viminaZis to phosphorus was different from that of E. camaZduZensis. 45

Table 12. Analyses of variance of data from seedling response to varying levels of phosphorus and nitrogen.

Source of Variation df MS F P

(a) Heights, 10910 transformed. Split plot analysis in time.

Blocks 6 0.02621 2.54 Species 3.23357 313.33 *** Phosphorus 2 5.96366 577.87 Species x Phosphorus 2 0.27021 26. 18 Nitrogen 2 0.33413 32.38 *** Species x Nitrogen 2 0.06958 6.74 ** Phosphorus x Nitrogen 4 0.02413 2.34 NS Species x Phos. x Nit. 4 0.02872 2.78 Residual a 102 0.01032

Time 2 0.11827 9.84 *** Species x Time 2 0.04584 3.81 -:. Phosphorus x Time 4 0.05184 4.31 ** Species x Phos. x Time 4 0.00765 0.64 NS Nitrogen x Time 4 0.05069 4.22 ** Species x Nit. x Time 4 0.00522 0.43 NS Phos. x Nit. x Time 8 0.04032 3.35 ** Spp. x Phos. x Nit. x Time 8 0.00093 0.08 NS Residual b 192 0.012021

(b) Dry we i ghts. log 10 transformed. Blocks 6 0.02591 1.68 NS Species 3.02172 195.56 *** Phosphorus 2 0.53016 34.31 *** Species x Phosphorus 2 0.10125 6.55 Nitrogen 2 0.20516 13.28 *** Species x Nitrogen 2 0.05086 3.29 * Phosphorus x Nitrogen 4 0.04091 2.65 * Species x Phos. x Nit. 4 0.00500 0.32 NS Residual 102 0.015452

(cont.) 46

Table 12 (cont.)

( c) Leaf area

Blocks 6 10.54073 3. 14 ** Species 74.29018 22. 13 '1:*'1:

Phosphorus 2 183.27744 54.60 -;~*~r: Species x Phosphorus 2 7.95721 2.37 NS Nitrogen 2 101.99558 30.38 **1. Species x Nitrogen 2 16.32363 4.86 *"1, Phosphorus x Nitrogen 4 6.05313 1.80 NS Species x Phos. x Nit. 4 2.64994 0.79 NS Residual 102 3.356729

(d) Root/shoot rat i os

Blocks 6 0.00907 1.28 NS Speci es 0.07975 11 .21 -h:* Phosphorus 2 0.25617 36.01 *** Species x Phosphorus 2 0.03454 4.85 ~':* Nitrogen 2 0.00408 0.57 NS Speci es x Nitrogen 2 0.01582 2.22 NS Phosphorus x Nitrogen 4 0.00927 1. 30 NS Species x Phos. x Nit. 4 0.01201 1.69 NS Residual 102 0.007114

*, **, *** significant at p = 0.5,0.01,0.001 respectively; NS, not significant at p = 0.5. 48 it continued to increase in response to increased nitrogen supply even when phosphorus levels were high (compare P3 NI. P3 N2. P3 N3). Both species produced their maximum leaf areas at P3 N3.

4. Root/shoot ratios

Species. phosphorus as main effects and their interaction significantly affected root/shoot ratios (Table 12). E. viminalis root/shoot ratios generally decreased in response to increasing levels of phosphorus, whi 1st those for E. camaldulensis were not so affected, and in fact at N3 its root/shoot ratios increased with increasing levels of phosphorus.

Seedling Growth in the Field

Method

A preliminary field trial was established in December 1975 as soon as fences were erected to exclude stock. E. camaldulensis seed1 ings were grown from seed collected at Westerfolds, however the E. viminalis seed used was from Kyneton, as capsules collected at Westerfolds contained only chaff that year. 6y mid-January many of the E. viminalis and some of the E. camaldulensis seedlings had died of drought stress, by early

February almost all seedlings on both sites were dead.

For the second field trial seed was collected from 8-10 mature specimens of E. viminalis and E. camaldulensis at Westerfolds, germinated in a constant temperature (230 C) room in petri dishes and planted out into small plastic pots (8 em diameter x 7 em depth) fi lIed with one part sand, one part krasnozem soil and growth continued in the glasshouse for a further five weeks. After an eight week hardening off period outside the glass­ house, 18 seedlings of each species were transplanted to each of the field sites (6 and C) at Westerfolds. Seedlings were planted in a random block design 35 cm apart within 30x30 m wire, rabbit-proof enclosures. During the following 12 months (June 1976-July 1977) seedl ing heights were recorded every two months and measured again in April 1978; heights were A 100 a E. vi.in,li,

• E. CI.. ,ldu ... i. ~,O ,- ,- --- E. villli.llis soil ,------E. Clllllld_sis soil ,- ,- " ,-" 80 " ,- " ,- " ,- ,- ,- ~ " ,fJ " / ,- ... " ....

0 II r 20 30 40 50 60 70 80 90 100 110 t t w..b t .' t June 1978 Jlttuary 1977 JUI'II 1977 , ,t , .

I B 80 E. villljnllil , < 0 ! 60 "#. ~ E. Cllllliduflftlil :I ~ 40 -S• c! f 20 : .' i,

" 0 I E. villliOliis soil E. CI"'lklu.sis soil t ~ I! ~.' ; f f I Fig. 20. A, Height growth rates of E. viminaZis and E. camaZduZensis ~ for field trials at E. viminaZis and E. camaldulensis sites at Westerfolds. Arrow indicates time at which most deaths (29.6%) occurred. B, Percentage death rate after 22 months of E. viminalis and E. camaldulensis field trials grown at E. viminalis and E. camaZdulensis sites. 49 measured to the top of the growing shoot, and deaths were recorded.

Hei,ght data were subjected to analyses of variance.

Res ul ts

A significant difference in height growth between the species was evident (Table 13); Fig. 20a indicates that E. viminalis, taller than

E. camaldulensis when planted, grew better than E. camaldulensis on both plots unti I the summer of 1977. Subsequently there was a high death rate amongst E. viminalis on the E. viminalis plot, and remaining seedlings grew

.~ slowly" E. viminalis on the E. camaldule~~is plot continued to grow much faster than any other group. The mean height growth of E. camaldulensis was similar for both sites.

Percentage death rate for E. viminalis on the E. viminalis plot was

72% (Fig. 20b) , and most of these seedlings died from drought stress in summer. Twenty-eight percent of the E. camaldulensis seedlings on this plot also died, the survivors tending to be the larger, better established plants. Only two E. viminaZis seedlings (11%) died on the E. camaldulensis plot, but 39% of the E. camaldulensis died, 28% during summer. By Apri I

1978 E. viminalis seedlings were dominating the E. camaldulensis plot; although E. camaldulensis replicates were as tall as the E. viminalis, their dry weights and leaf areas would be much smaller (Plate 4a). On the E. viminaZis plot, less than 30% of the E. viminalis had survived, but

-'. "The decrease in height shown in Fig. 20 reflects the inclusion of dead seedl ings as zero height since a measure of the success of the species was required. The zero values did not affect the analysis greatly, since analysis of variance is somewhat robust and a non-parametric test showed similar significant results (p,Y. Ladiges, pers. comm.). 50

Table 13. Analyses of variance of height growth data for field trials.

Source of Variation df MS F p

(a) Ti me 1

Species 1104.5 72.02 ~I:*"i': Treatment 6.72222 0.46 NS Species x Treatment 4.01389 0.27 NS Residual 68 14.72263

(b) Time 2 Species 1116.28125 49.37 *** Treatment 50.83681 2.25 NS Species x Treatment 12.92014 0.57 NS Residual 68 22.60927

(c) Time 3 Species 1196.42014 27.25 *** Treatment 129.33681 2.94 NS Species x Treatment 103.92014 2.37 NS Residual 68 43.90870

(d) Time 4 Species 1417.78125 14.23 *** Treatment 14]1.53125 14.77 *** Species x Treatment 452.50347 4.54 * Residual 68 99.61254

(e) Time 5 Species 589.38889 1.97 NS Treatment 5724.5 19.12 ,~fd. Species x Treatment 4802.0 16.04 *** Residual 68 299.38399

(con t.) 51

Tab 1e 13 (con t. )

( f) Time 6

Species 220.5 0.44 NS Treatment 6593.34722 13 .24 -h** Species x Treatment 5512.5 11 .07 *-;'t-;I:; Residual 68 497.87214

(g) Time 7

Species 533.55556 0.77 NS Treatment 9706.88889 14.0 **-ir. Species x Treatment 8320.5 12.0 '1:** Residual 68 693.14216

(h) Time 8

Species 180.5 0.10 NS Treatment 18304.22222 10.0 *** Sp-cies x Treatment 1 28163.55556 15.37 *** Residual 68 1832.35784

*. **. ***. significant at p = 0.5. 0.01. 0.001 respectively; NS, not significant at p 0.5. '\" i

. ),;

8

r 1 \ PLATE 4

A. Seedling growth on the E. camalduZensis field trial plot at Westerfolds, April 1978. Note greater size of E. viminalis seedlings.

f-;"\." .•. B. Seedling growth on, the E. viminalis field trial plot at Westerfolds, April 1978. Ranging pole indicates, scal~, each band is 30 em high.

--...:.!"" 52

E. camaZdulensis height growth was slightly better here than on the

E. camaldulensis plot. Seedlings of both species were subject to insect attack on the E. viminaZis plot, and plants appeared depauperate (Plate

4b) .

DISCUSSION

The results of the four glasshouse trials indicated significant differences in the growth rates of E. viminalis and E. camaldulensis.

Height growth (except in experiment one) and dry weight production was significantly greater for E. camaldulensis. The effects of competition on the growth rates of the two species were not significant, except in the second experiment where E. viminalis dry weights were significantly depressed in mixed culture. There was a trend for the height growth and shoot dry weights of E. viminalis to be depressed in culture, whilst those of E. camaldulensis tended to increase. The replacement series diagrams provided a similar, but visual picture, of the results of the analyses of variance.

The response of E. viminalis and E. camaldulensis in both the mono­ culture and mixed cultures of experiments one, two and three were at variance with those obtained in the preliminary experiment, even when similar seed sources (experiment three) were used. It is suggested that the structure of the soil used in these experiments is an important factor affecting growth. Topsoil collected from the riverbank at Westerfolds for use in experiments two and three was very fine-textured; after several weeks of daily watering during the growth trials it set into solid blocks in the pots. Soils collected from the field trial sites for experiment one also tended to compact in the pots to some extent.

Beadle (1962) noted that the physical structure of the soil, which

affects such properties as pore space, drainage, aeration and waterlogging,

is destroyed when soils are collected and sieved. Thus where physical 53 properties of the soil are influencing the distribution of species, extrapolation from pot trials to field conditions may be misleading.

The ability of E. camaldulensis to grow in heavy soi Is has been noted by Jacobs (1955). and is further discussed in Chapter 5. It is suggested that in the present study E. camaldulensis grew better because of the superior abi lity of its root system to grow in heavy soils, and

its higher root/shoot ratio which enabled it to exploit the restricted volume of the pot quickly. Height growth of E. viminaZis was greater than that of E. camaldulensis in both monoculture and mixed culture when the species were grown in well-structured garden soil used in the preliminary experiment by Ashton. and in the field trials planted on alluvial deposits of the E. camaldulensis field trial plot. I t is suggested that the physical structure of the soil may be an important factor influencing the distribution of the two species.

Field observations support this hypothesis, but the results of the percentage disaggregation analysis (Table 5) show that soils at site A, which support E. camaldulensis, had a slightly better structure than soils at the other sites. However the method employed was not entirely satis­ factory. The structure of the complete profile appears to be an important

factor, particularly in controlling drainage, and in a floodplain environ­ ment where depositional lenses of material may occur sporadically in the

profi Ie, two samples at 0-10 cm and 50-60 cm are unlikely to be sufficiently

representative.

The results of the field trials indicated that E. viminaZis was able

to grow faster than E. camaldulensis on well-drained, comparatively well­

structured soils. It is thought that the slow growth rate and death of many E. viminalis seedlings in the E. viminalis field trial plot was the

result of winter waterlogging of the soil. Waterlogging may have

differentially affected the development of E. viminalis and E. camaldulensis

root systems, so that poorly establ ished E. viminalis seedlings were highly 54 susceptible to drought stress when the topsoil dried out during summer.

The effect of waterlogging on the root systems of E. viminalis and

E. eamaldulensis is further discussed in Chapter 5.

The glasshouse results were often difficult to correlate with field observations, and it is felt that pot experiments (as competition experiments) may not give a real istic view. The present study has shown that when the physical structure of the soil affects seedling growth, it is particularly difficult to relate the performance of species in pot trials to their behaviour in the field, and it is suggested that the limited volume of soil avai lable for exploitation in the pots used may further decrease the validity of such pot trials. The high root/shoot ratio of E. eamaldulensis may have allowed it to rapidly exploit the

I imited volume of the pots to the detriment of E. viminalis. \.Jhere soi 1 volumes are less limiting, as in field situations, E. eamaldulensis may not gain such an initial advantage. Harper (1977) has also pointed out that in competition experiments it is difficult to know whether the interaction between plants is taking place above or below ground.

E. camaldulensis overall grew faster than E. viminaZis in sand culture but responses to phosphorus and nitrogen differed. The root/shoot ratios of E. viminalis declined with increasing levels of nutrients, whilst those for E. eamaZdulensis increased. Ladiges (197~) found that root/ shoot ratios of E. viminaZis seedlings from five populations generally decreased as nutrient levels were increased, and suggested that as a result E. viminaZis may be more susceptible to drought on fertile sites.

E. viminaZis continued to respond to increased applications of nitrogen

(N2 to N3) and may have a higher optimum for some nutrients than

E. camaZdulensis. It is suggested that the levels of phosphorus applied

(0.5, 2, 8 mg/l) may have been too low to el icit optimum responses from both species, since dry weights continued to increase as nutrient levels

increased. However, these values are realistic in terms of available phosphorus levels measured for soi Is. Upper values of 50 mg/l used by others (eg. Attiwill 1964) seem high, although it is still difficult to determine rates of appl ication for sarod culture experiments.

As in the present study, and that of Attiwill (1964), Parsons (1968b) was unable to establish optimum levels of response for three mallee eucalypts to phosphorus over a range of levels, 0-15 mg/l whilst nitrogen was varied concurrently (5-300 mg/l), although the highest nutrient application apparently represented higher nitrogen and phosphorus levels than those found in the soils supporting the species.

Studies by Moore and Keraitis (1971) on the effect of nitrogen source on the growth of eucalypts in sand culture have shown that the form of nitrogen suppl ied affects the growth rates of eucalypt species, and thus may mask the effects of factors being tested. Woodland species tested made maximum growth where ammonium did not exceed one half of the total nitrogen treatment, whilst forest species behaved quite differently. However there were some differences within these groupings, and it was not possible to predict the preferred nitrogen source for a eucalypt species from its taxonomic classification or ecological habitat. In the present study nitrogen was supplied as ammonium nitrate, but it was difficult to be sure that the optimum forms or concentrations for E. viminaZis and

E. camaZduZensis were suppl ied.

Limited studies of the soil nutrient status carried out at the four field localities provided no conclusive evidence for any differences in soil fertility which could have influenced the distribution of the two species in the Yarra Valley. In addition, there was no significant difference in the growth rate of each species on the topsoils collected from beneath E. viminaZis abd E. camaZduZensis stands at Westerfolds

(experiment one). However grazing and top dressing at sites A, Band C may have substantially altered the soil fertility. 56

Mueller-Dombois and Ellenberg (1974) have emphasized that the competitive capacity of a species varies with habitat factors. In the present study the competitive abi lity of E. viminalis and

E. camaldulensis appears to be dependent on the physical structure of the soil, which may thus influence the distribution of the two species.

Further experimental work will be carried out to examine this possibility.

SUMMARY

The results of the pot trials indicated that E. camaldulensis has a faster growth rate than E. viminalis in both monoculture and mixed culture.

However field trials Support the hypothesis that E. viminalis is able to out-compete E. camaldulensis on well-drained, well-structured soils. From the limited soil analysis undertaken it appears that soi 1 fertil ity is not an important factor in determining the distribution of the two species.

It is suggested that the physical characteristics of the soi I may influence local distribution. 57

CHAPTER 4

SEEDLING TOLERANCE TO DROUGHT

INTRODUCTION

In the Yarra Valley area the forest form of E. viminalis is generally riparian, and extends from the foothi 11s zone of the Great Dividing Range to about the 700 mm isohyet. Woodland forms of this species may also occur on the duplex and gradational soils of Teriary sandy cappings, and on krasnozem basalt soils where M.A.R. is between 700 and 800 mm.

E. aamaldulensis dominates the riparian environment where rainfall is less than 700 mm per annum. It extends onto undulating Silurian topography, and onto the heavy soils of the basalt plains where-M.A.R. is 550-700 mm. At

Westerfo1ds the two species cohabit on the alluvial flats and are found to a limited extent on Silurian mudstone topography.

The death of six-month-01d, hardened seedlings planted out as a field trial at Westerfo1ds (Chapter 3) suggested that seedling tolerance to limiting soil moisture conditions may be an important factor in the establish­ ment of trees, and may confine E. viminalis to soils which are relatively well drained, yet have a high water holding capacity.

The influence of limiting soil moisture conditions on the distribution of eucalypt species has been studied by a number of workers. Specht and

Perry (1948) correlated the distribution of some tree species in the Mt.

Lofty Ranges of S.A. with the water retaining capacities of soils. Holland and Moore (1962) related the distribution of some species in the Bollon

District (Qld.) to soil moisture status, and Florence (1964) has suggested that the vegetational pattern in Australian east coast forests is influenced by physical properties of the soil, including soil moisture availability.

Pook, Costin and Moore (1966) correlated observed drought damage of eucalypt 58

species with soil texture and depth and resultant differences in moisture

storage, suggesting that occasional severe droughts may be a contributory

factor in the distribution of eucalypt communities. Lamb and Florence

(1973) have shown that the distribution of E. fas~igata in the A.C.T. may

be delimited by smal I variations in soil properties influencing root move­ ment and penetration of light summer rainfall. Ashton, Bond and Morris

(1975) related the distribution of dominant species along a moisture gradient

to their relative tolerance to droughted conditions. Parsons (1969) has

shown that competition for water under I imiting soil moisture conditions may influence the distribution of E. socialis and E. incrassata, and

Kirkpatrick (1970) has suggested that the distribution of E. sideroxyZon and E. gZobulus x bicostata in the Otways region may be related to competition and the relative drought tolerance of these two species.

In the present study pot trials were established to compare the

behaviour of E. viminalis and E. camaldulensis seedlings under drought

stress. Habitat differences were examined by the description of soil

profiles and measurement of soil moisture conditions over a 12 month period.

HETHODS

Soil Moisture Characteristics

Soil samples were collected from the E. viminaZis field trial plot on an upper slope and from the E. camaZduZensis site located on lower

terrace deposits at Westerfolds for the gravimetric determination of soil moisture from June 1976 to July 1977. Five replicates were collected from each site at depths of 0-10 em and 50-60 em.

Seedling Behaviour under Drought Stress

Seed of E. viminaZis and E. camaZdulensis collected at Westerfolds

in the Yarra Valley was germinated in petri dishes in a constant temperature 59 room. Due to fungal attack additional seed was germinated six days later, and seedl ings from both germinations were initially established in si liceous sand to which was added a full nutrient solution (Aquasol. at the rate of

50 mls of 0.125 g/Aquasol/l, then 50 mls of 1 9 Aquasol/l). After four weeks growth seedlings were pricked out and transferred to plastic pots of

12.5 cm diameter, containing a 1:1 mixture of loam and sand. Growth in the glasshouse continued for a further three months, during which seedlings were thinned to one per pot. Pots were then moved outside to harden off for five weeks.

Twenty seedlings (aged five months) of each species were returned to the glasshouse and watered until the soil was near field capacity. The pots were then sealed to prevent direct waterloss from the soil, and placed

inside larger earthenware pots to prevent overheating of the soil (Ladiges

1974). Each species was divided into two groups: water was withheld from those to be droughted, whilst the control pots received as much water daily as was necessary to maintain their initial weight. The daily transpiration rate of each plant was measured over six days by weighing the pots each morning at 7 am, measurements were expressed as waterloss in g/24 hours/dm2 leaf area. Regression equations for leaf area/weight relationships were calculated for five seedlings of each species and each treatment separately.

This enabled leaf area estimates to be made for the remaining plants, particularly severely drought damaged plants whose dead leaves were difficult to measure directly. Daily transpiration rates were subjected to an analysis of variance.

Leaf water potentials were estimated on days four and six of the experiment, using the Wescor Model C-51 Sample Chamber combined with the

Dew Point Microvoltmeter (Campbell. Campbell and Barlow 1973). Five to six plants per population x treatment unit were sampled. With this method reduction in leaf area during transpiration measurements was minimal, since A I E. vimlnaiis soil I 2°1 I E. camaldulensis soil I I

15,

/ / / T / / ... I ( I I I I I T 1 I I r 10"'; (a) I I 1 T .l- ! r 1 I I I I I I f , I f ... r f i "" \ T 1 I I ! I T .-J I .- ---X 1 .- .- I Ibl , "'" .... I ~ V ... 5-- ... : I "- ... ' T r T r \.\. ..---.. \ I ,.. I .... I I I - , , ... I ... r .I- ... T '\, .I. 1 .I. ... .I- "- , ,! ...I '- ° J J A S 0 N 0 J F M A M J J 1976 1977 *Cll '\ '- .....~ T a'" I E B '0 I I rr T I en 1 1 2°1 r i I I I (a) I I 1 15 1 , / I / • I I I i I / I I I 10 / T / f / t / ; / j / T .... " / I I r I ! I /\ 'T I f , • f I I / \ 5 T '\ f I r / I "- / \ I I .... .- .... "- / , I I - r ;/ \ I "- / \ I I ~-.-~~.- "- I / \ I -- I -J. 1 '-' I \._--- \ ! , I I T r r (bl I .... r r I ..L I I T :::: .L " I I I .L J. ..L .L ::: -'-

J J A S 0 N 0 J F M A M J J 1976 1977

Fig. 21. Percentage soil moisture for soils from E. viminaZis (Site C) and E. camaZduZensis (Site B) field trial plots at \~esterfolds. At 0-10 em depth; S, 50-60 em depth. Bars indicate ± standard error. Where there are no error bars fewer than five replicates were used. 60

only one disc ( 0.8 cm diameter) was removed from anyone plant.

After the sixth day of treatment all plants were rewatered and left

to recover for three days. The shoots of each plant were harvested, and

the leaves cut into dead and alive areas, oven dried and weighed. Drought

damage was estimated by calculating the percentage of dead leaf material.

Percentages were subjected to a T test, normality and homogeneity of the

variance being assumed.

RESULTS

Soil Moisture Characteristics

Descriptions of soil profiles at the Westerfolds E. viminalis and

E. camaldulensis plots are given in Table 1 (see Chapter 3). Soil moisture

contents throughout the year were generally higher at the E. viminalis site

(Fig. 21), although differences in the topsoi 1 were not as marked as those

at 50-60 cm depth. Examination of the percentage soil moisture values for

the field trial sites over a 12 month period (Fig. 21) indicated that

both the topsoil (except in spring 1976) and subsoil of theE. viminalis

site generally contained more moisture than the soils of the E. camaldulensis

site. The high variability in subsoil replicates is attributed to changes

in the depth and distribution of clay across the study sites. The pF values

(Fig. 10 , Chapter 3) indicated that the slightly sandier E. viminalis top-

soil would contain less available water than the topsoi 1 of the

E. camaldulensis site, however the E. viminalis plot is situated'on a

slow draining 'slope and is waterlogged during winter. The nature of the

subsoil at the E. camaldulensis site is very variable; the alluvial soils

although deep are sandy, whilst the clay subsoils derived from Silurian

parent material are comparatively shallow. Both subsoils at this site

would have less available water than the E. viminalis subsoil, and probably

:h; dry out more rapidly in summer. )r 61

Table 14. Analyses of variance of transpiration data.

Day Source of Variance df MS F P<

Species 59.29225 3.74 NS Treatment 193.16025 12.19 0.01 Species x Treatment 10·30225 0.65 NS Residual 36 15.84081

2 Species 0.55225 0.03 NS Treatment 4. i 6025 0.22 NS Species x Treatment 0.65025 0.03 NS Residual 36 19.21625

3 Species 10.00000 1. 05 NS Treatment 921 .60000 96.63 0.001 Species x Treatment 22.80100 2.39 NS Residual 36 7.74378

4 Species 0·93025 0.17 NS Treatment 809.10025 151 .79 0.001 Species x Treatment 8.74225 1.64 NS Residual 36 5.33047

5 Species 0.67600 o. 16 NS Treatment 1449.61600 333.36 0.001 Species x Treatment 1.44400 0.33 NS Res i dua I 36

6 Species 5.11225 0.78 NS T reatmen t 2032.05025 312.42 0.001 Species x Treatment 6.00625 0.92 NS Residual 36 , 20 A " o E. viminllil 18 • E. Clmllduleflsis 16 control pllnts ,. , ... ,- EI ,. drought.d pllntl ...... 14 ,. ,. , 0 ~ ..Iff:. '" ". --,. ~ -- ...... IN --- -"-...d ...... 12 :! ...... ' .. '0"'

~ 10 . ~ :! .g .. 8 .Q.~.. ..• ~ 6

4

2

0 2 3 5 6

B .•...... -...... m8Jlimum ...•. , 30 ...... " ..•.. ' . rnHn daily ...... _-- minimum t54-____~---~-~~~~-~-~~~-~-~-r~--~~--~ 2 3 4 5 6 C

90 "l/I. " _-----.. mean daily X :...... -~. C 70

50 minimum 2 3 4 5 6

Fig. 22. A. Transpiration rates for control and droughted plants of E. viminaZi8 and E. camaZduZensis; B, air temperature; C, relative ""' humidity of glasshouse. i 62

Seedling Behaviour

No significant differences were observed in the transpiration rates of E. viminalis and E. camaldulensis (Table 14, Fig. 22 ). On day one of the experiment, the transpiration rates of the droughted plants of both species were higher than those for the controls (possibly a sampling effect), but thereafter they decreased abruptly. The more rapid decrease in the transpiration rates of droughted E. camaldulensis suggests that it was able to more quickly control transpiration by stomatal closure.

Increases in the rates of transpiration of the controls occurred after day four, paralleling increases in glasshouse temperature. This increased rate of water loss was also reflected in the decrease in the leaf water potential of control plants (Table 15) observed between days four and six.

Table 15. Leaf water potential (bars) for droughted and freely watered plants on days 4 and 6 of experiment. Values for day 4 are calculated from 5 replicates, those for day 6 on 6 replicates.

Day 4 I Day 6 I

E. viminalis (control) -17.3 -23.2

E. v imina lis (droughted) -37.9 -43.5

E. camaldulensis (control) -15.5 -25.0

E. camaldulensis (droughted) -39.2 -46.0

Droughtedreplicates of both species began to show signs of wilting on the second day, the onset of wilting appeared to be related to plant size. By the fourth day all the droughted E. camaldulensis and some droughted E. viminalis were wilted, and by the sixth day all droughted plants of both species were wilted. Plants wilted from the tips initially, 63

however tissue death was more extensive In the lower leaves. Death of the

lower leaves was more marked in Z. camaldulensis, and leaf abscission had

begun by the sixth day. Measurements of leaf water potential (Table 15)

suggest that droughted E. camaZdulensis may have been subject to greater water stress, however with the limitation of only one sample chamber

insufficient replicates were sampled for these measurements to be statist-

ically significant.

Table 16 shows that the root/shoot ratio, total dry weight, total leaf

area and percentage leaf death of droughted seedl ings was significantly

greater for E. camaZduZensis than for E. viminalis. Since E. camaZdulensis

seedlings were 66% larger and had a greater transpirational area, yet were

grown in the same sized pots, they were therefore probably subject to

earlier drought stress than the E. viminaZis seedlings. The lower leaf water potentials recorded for E. camalduZensis give some indication of this.

Table 16. Means and standard errors (parenthesis) of leaf area, dry weight and root/shoot ratios for droughted seedlings. Means significantly

different at p '" 0.5 (*), .001 ('b·~"'~).

Root/Shoot Total Dry Total Leaf % Dead Ratio Wt. (g) Area (dm2 ) Leaves

E . viminaZis 0.33 5.48 3.76 51.0

(0.04) (0.63) (0.61) (9.70)

E. camaZduZensis 0.41 9. 11 5.68 71.8

*** ,'d~* ...':-;':-/- "1: ..

DISCUSSION

The transpiration responses of the droughted seedlings are in agree­

ment with those reported by Lubrano and Tarsia (1973). When water was

withheld successively from groups of potted E. viminalis and E. camaldulensis

seedlings aged 1t, 3t, 5. 6t, 7t and 10 months, no significant species

differences in transpi ration rates, water saturation deficits or plant

moisture contents were observed.

As reported for the present study, Quraishi and Kramer (1970) found

that E. camalduZensis when droughted, suffered severe injury. In a

comparison of the effects of soil water stress on potted seedlings of

E. rostrata (E. camaZdulensis)~ E. polyanthemos and E. sideroxylon, they

found that E. camaldulensis which had a relatively high transpiration rate

under non-limiting moisture conditions, depleted soil moisture reserves

more quickly than the other species when water was withheld. They attributed

the greater injury suffered by E. camaldulensis to its later stomatal

closure and higher rate of cuticular transpiration. In the present study,

the rate of decrease in transpiration losses indicated that stomatal closure

probably occurred earlier in E. camaldulensis, and that cuticular trans­

piration was slightly lower than for E. viminaZis. Pot experiments

investigating the water relations of E. camaldulensis and E. globulus

(Pereira and Kozlowski 1976) indicated that E. camaZdulensis was less

drought resistant than E. globulus,a species which throughout its

range would occasionally be subject to moderate summer drought, but in

general occurs in higher rainfall zones. Under droughted conditions plant

water stress increased more rapidly in E. camaZduZensis, its higher trans­

piration rate was associated with larger numbers of stomata on both leaf

surfaces. Extensive development of the E. camaldulensis root system in

the restricted volume of soil in the pots also induced greater water

deficits than developed in E. globulus. However, when seedlings of both

species were grown in long plastic tubes with an unrestricted soil volume,

. ~ / .. ,' 65 water stress did not develop more rapidly in Z. camalduZensis than in

E. giobulus, indicating that a major factor in the drought avoidance of

E. camaZdulensis was the capacity to produce a deep, extensive root

system capable of obtaining water from deep soil layers after the topsoil

has dried out.

The development of a deep root system probably enables E. camaldulensis

to survive prolonged periods of drought in the field. Levitt (1972) has

suggested that certain species are able to avoid drought in spite of high

transpiration rates "by extracting larger quantities of water from the soil

per unit time and leaf surface". A high root/shoot ratio provides a high

ratio of water absorbing to water evaporating surface, and may enable

exploitation of deeper water reserves in the soil.

Zimmer and Grose (1958) have correlated the possession of high root/

shoot ratios in eucalypts with certain habitat factors; species with high

root/shoot ratios generally occur in dry areas where summer temperatures

are very high. Furthermore, Parsons (1969) has suggested that the larger

root/shoot ratio of E. socialis may be a consistent genotypic difference

which can be expected to confer superior drought avoidance. Jacobs (1955)

has suggested that the high root/shoot ratio typical of E. camaldulensis

permits the development of a deep, foraging root system before the shoot

becomes too large. and Awe et al. (1976) have demonstrated that the ability

of E. camaldulensis to establish successfully in a drying soil profile is

largely dependent on its capacity to produce a massive root system very

quickly.

Additionally, the -abscission of the lower leaves observed in

E. camaldulensis under droughted conditions by Pereira and Kozlowski (1976),

and in the present study in the glasshouse and field trials. may indicate

an adaptive response. The ability of a plant to survive drought may be

enhanced by a reduction in surface area (Levitt 1972). Field trial observ- 66

ations indicate that E. camaldulensis is able to p~oduce new foliage quickly once soil is rewetted.

The greater damage suffered by E. camaldulensis in the present study resulted from mo~e rapid depletion of soil moisture by its larger root system and transpi~ation losses from its significantly larger leaf area.

In the field the higher ~oot/shoot ratio of E. camaldulensis should enable it to tolerate limiting soil moisture conditions more readily than

E. viminalis. At the Westerfo1ds field trial site the extensive root system of E. camaldulensis would assist in the establ ishment and survival of seed1 ings on the sandier soil profiles where subsoil moisture reserves are smaller during the summer period.

Comparison of species is also complicated by population variation.

Population differences in the drought resistance of forest and woodland forms of E. viminalis have been demonstrated by Ladiges (1974, 1975, 1976); the most tolerant population occurring in a low rainfall area on a shallow soil with poor available water storage. In the Yarra Valley, since the forest form of E. viminalis is essentially riparian, it may be more suscept­

ible to drought under field conditions in drier sites, particularly if there is competition with E. camaldulensis for scarce moisture resources.

SUMMARY

Pot trials indicated no significant difference in the transpiration rates of droughted E. viminalis and S. camaldulensis, and limiting soil moisture conditions induced greater injury in E. camaldulensis. It is concluded that the purported advantage of E. camaldulensis over E. viminalis, to produce an extensive root system able to maintain water supply under droughted conditions, was obscured by the use of pots in which the soil volume was limited. In the field it is expected that the high root/shoot

ratio of E. camaldulensis would result in superior drought avoidance. 67

CHAPTER 5

THE RELATIVE TOLERANCES OF E. VIMINALIS AND

E. CAMALDULENSIS TO WATERLOGGING

INTRODUCTION

As indicated in Chapter 1, E. viminaZis and E. camaZduZensis occur

over a wide range of soil and rainfall conditions. However, each species

shows habitat preferences - most forms of E. viminaZis occur on moist well­

drained sites, whilst E. camaZduZensis is usually found on heavy soi Is

subject to periodic waterlogging. In the riparian environment of the

Yarra Val ley, E. camaZduZensis tends to occur in localities which by virtue

of their topography and/or soil structure tend to be more frequently water­

logged. The hypothesis that E. camaZduZensis is more tolerant than

E. viminaZis of such soil conditions was tested in a pot experiment. The

effects of waterlogging on soil conditions and plant distribution are reviewed.

THE EFFECTS OF WATERLOGGING ON SOILS AND PLANTS

The extent to which plants are able to tolerate waterlogged soil

conditions is dependent on the relative tolerance of the species or local

population, on edaphic factors, and on the timing, depth and duration of flooding.

Changes in SoiZ Conditions

Changes in soi 1 conditions associated with the onset of flooding or

waterlogging may result in a habitat which can only be occupied by plants

tolerant of these conditions. Waterlogging may result from inundation of

the soil by flood waters, poor soil permeability. the presence of an

~~~~~------:---~"."<'''''.''''':-~''''''''''-''_OQ_------68 impervious layer in the profile, or a high water table (Ponnamperuma 1972).

An excess of water in the soil displaces air from the non-capillary pore space, and slows down the rate of gaseous diffusion between the soil and the atmosphere, which results in the onset of anaerobic conditions.

Within a few hours, soil micro-organisms reduce almost all the molecular oxygen present (Ponnamperuma 1972). Soil microbes capable of anaerobic respiration now reduce combined forms of oxygen or other electron acceptors, often producing substances toxic to plants. According to Russell (1973), the principal inorganic reductions are nitrate to nitrite, manganic salts and manganese dioxide to manganous ions, ferric hydroxide to ferrous ions, hydrogen ions to hydrogen gas and sulphates to sulphites and sulphides. In the early stages of flooding, anaerobic decomposition of organic matter results in the production of nitrogen and nitrous oxide, hydrogen gas and a range of low molecular weight hydrocarbons, including methane and ethylene.

Toxic substances formed in waterlogged soils include methane, methyl compounds and complex aldehydes; ferrous ions, nitrites, sulphides and manganous ions may also accumulate to toxic levels (Kramer and Kozlowski

1960). Ethylene production also increases, and many plant responses to flooding have been attributed to its accumulation (Russell 1973, Kawase 1974,

Jackson and Campbell 1975, 1976).

Edaphic factors which may influence plant responses to waterlogging

include soil textures, structure and the supply of decomposable organic matter. Heavy soils with limited pore space normally have low rates of oxygen diffusion, so that soils with a high clay content are likely to have a greater degree of root anaerobiosis. Accumulation of toxic products also tends to be more acute in heavy textured soi Is (Gill 1970). The presence of hardpans or impermeable layers in soils also impedes the diffusion of gases and prevents water from draining out of the soil surface layers (Kramer and

Kozlowski 1960). The nature and content of soil organic matter has some , '.::: , ,.,' 69

influence on the course, rate and degree of reduction (Ponnamperuma 1972),

the effects of waterlogging being more marked in soils with a high organic

matter content, since greater microbial activity is possible (Russell 1973).

Smith and Dowdell (1974) have suggested that under some conditions the

availabil ity of substrates for microbial activity may be the limiting

factor controlling the production of ethylene.

Plant Responses

Interspecific differences in the waterlogging tolerance of mature

woody species have been reported by Green (1947). Parker (1950) and Hosner

(1958, 1959. 1960); and for seedl ings of woody species by Boden (1963),

Bannister (1964). Ladiges and Kelso (1977) and Pereira and Kozlowski (1977).

Significant differences in tolerance have also been observed between popu-

lations of a single species (Karschon and Zohar 1972, 1975; Ladiges and

Kelso 1977). Reasons for such observed differences are thought to be

related to structural differences which result in a better oxygen supply to

the roots of some species, or to physiological differences in cell toleration

of the products of anaerobic respiration or a combination of these (Kramer 1969) .

The timing of the onset of waterlogged conditions influences the

response of some plants. Many conifers and deciduous species are relatively

insensitive to waterlogging during their dormant season (Gill 1970). Plants

also differ in their ability to tolerate varying degrees of waterlogging,

from soil saturation, partial inundation of the shoot to total submergence.

Demaree (1932) reported that total submergence of Taxodium seedlings resulted

in death; however,seedlings half submerged in the cotyledon stage were able

to produce leaves. Dexter (1967) found that differential survival of flooded

E. camalduZensis seedlings was related to seedling height, and depth and

duration of flooding. The duration of waterlogging has also been shown to

affect seedling survival (Karschon and Zohar 1972); Hosner (1958) has

recorded differential species survival dependent on the duration of sub- 70 mergence. Kawase (1974) has established a quantitative relationship between degrees of flood damage symptoms and duration of flooding.

Initial reactions of the plant to poor soil aeration include decreased absorption capacity of the root, due to a reduction in its permeability to water because of oxygen deficiency or carbon dioxide excess (Kramer 1969).

Decreased absorption results in water deficits, wilting, decreased nutrient uptake, a reduced transpiration rate (Parker 1950, Kramer 1951, Bannister 1964), and a decrease in photosynthesis (Regehr, Bazzaz and Boggess 1975).

The Effects of Waterlogging on Root Systems

The long term effects of inadequate aeration on root systems is

reduction in size (Parsons 1968) or even death (Kramer 1969). Changes in

root distribution of plants under waterlogged conditions have also been observed (Parsons 1968, Wample and Reid 1975), including a strong development of surface rooting systems (Williams and Barber 1961, Boden 1963), and neg­ ative geotropism of surface roots (Clucas 1977, Pereira and Kozlowski 1977).

The formation of adventitious roots, usually from the stem, is a common

response to flooding recorded for a wide variety of species (Kramer 1951,

Boden 1963, Kawase 1974, Jackson and Campbell 1975, Clemens and Pearson

1977, Ladiges and Kelso 1977). It is thought that adventitious root formation may be an adaptive characteristic, providing the plant with an auxilIary

root system in a relatively aerobic zone where they can respire and so

fulfill their absorptive functions (Gill 1970). Resumption of shoot growth

in waterlogged tomatoes has been recorded following the development of adventitious roots (Kramer 1951). However, Gill (1975) was unable to

demonstrate any overriding importance of adventitious roots to the flooding

tolerance of Al.nus gl.utinosa, and Pereira and Kozlowski (1977) found 1 ittle

correlation between the capacity for adventitious root production and

tolerance to flooding. Kramer (1969) has suggested that blockage of down­ ward translocation of carbohydrate and auxins stimulat~the growth of 71 adventitious roots, whilst Abeles (1973) and Kawase (1974) suggest that ethylene production also stimulates such development.

Uptake by roots of toxic substances including divalent iron and manganese from waterlogged soils has been recorded by Jones and Etherington

(1970) and Jones (19 72a), a 1though a decrease in manganese was noted by

Ladiges and Kelso (1977). However, Somers and Shive (1942) considered that the relative proportions of these ions were likely to be more significant than absolute concentrations. Studies of plants growing under waterlogged conditions have indicated a greater concentration of iron in the root systems than in the shoot, suggesting that there is some immobilisation of this substance in the former. Increase was particularly marked in the roots of plants which do not normally grow on waterlogged sites (Jones and

Etherington 1970, Jones 1972a). Precipitation of iron in the intercellular spaces (Armstrong and Boatman 1967) and cell walls (Green and Etherington

1977) has been noted in some flood tolerant species.

Plants tolerant of waterlogged soils must be able to maintain sufficient root oxygen supplies for metabolic functioning and to prevent the accumulation of toxic substances from the soil. Diffusion of atmospheric oxygen from the shoots down to the roots and out into the rhizosphere (Armstrong 1964) results in an oxygen sheath which surrounds the roots. The larger oxygen sheaths of flood tolerant species afford better protection against toxic substances which must pass through this oxidising zone to reach the root surface (Armstrong 1970). The presence of an enzymatic component in addition to the diffused oxygen is thought to account for the high root oxidising activities observed in some bog species (Armstrong 1967a).

The presence of aerenchymatous tissue in roots has been correlated with the ability of roots to survive in poorly aerated environments (Cannon 1940) and of some species to grow under waterlogged conditions (Martin 1968).

Martin (1968) has suggested that although the development of extensive 72

intercellular air spaces in roots may be superfluous in supplying oxygen for

normal respiration (Williams and Barber 1961), it may be regarded as an

adaptation to provide for an oxidising environment around the root, as

described by Armstrong (1970). The development of intercellular air spaces

reduces the amount of tissue requiring oxygen in the root. and allows

oxygen diffusion into the rhizosphere, enabling oxidation of toxic reduced

substances. Aerenchyma is also thought to act as an oxygen reservoir during

periods of prolonged stomatal closure (Conway 1937 • Armstrong 1967b).

The Effects of Waterlogging on the Shoot

Morphological responses of the shoot system to waterlogging include

downward roll ing of leaf laminae (Jackson and Campbel I 1975) which may

preceed petiole epinasty (Kramer 1951, Kramer and Jackson 1954, Kawase 1974,

Jackson and Campbell 1975, 1976; Clemens and Pearson 1977) and leaf chlorosis

(Kramer 1951, Kramer and Jackson 1954, Kawase 1974, Clemens and Pearson 1977),

which may be followed by abscission of flowers, fruits and leaves, particularly

of the lower leaves (Kramer 1951. Parsons 1968, El-Beltagy and Hall 1974.

Clemens and Pearson 1977. Ladiges and Kelso 1977. Pereira and Kozlowski 1977).

The appearance of these symptoms may be followed by accelerated senescence.

The development of basal stem hypertrophy. enlargement of the cortical

cells and intercellular spaces soon after the onset of waterlogged conditions

has also been recorded for a variety of species (Kramer 1951. Boden 1963,

Kawase 1974, Clemens and Pearson 1977. Clucas 1977. Ladiges and Kelso 1977).

Retardation in shoot growth rates is also common (Kramer and Jackson 1954,

Boden 1963, EI-Beltagy and Hall 1974, Kawase 1974. Clemens and Pearson 1977,

Ladiges and Kelso 1977). Increased synthesis of ethanol, abscissic acid

and ethylene, and reduced levels of giberellins and cytokinins have been

implicated in the production of morphological changes in the shoots of

flooded plants (Wample and Reid 1975 and references therein).

-----.=,,,.,-'-"....., =-_.=-- =_._=._-----~------~. 73

ihus morphological changes in waterlogged plants seem to be induced by a complex set of interactions between the soi 1 environment and various plant hormones. These changes have been classified by Wample and Reid (1975): dwarfing, leaf chlorosis and petiole epinasty result from root anaerobiosis, but stem hypertrophy and adventitious root development are induced merely by an excess of water around the roots and hypocotyl. Although some authors have correlated certain morphological responses, such as the developments of adventitious roots, with tolerance to waterlogging (Boden 1963, Gill

1970), it is not clear which responses have adaptive significance.

Intolerant species often display the same symptoms as those shown by plants tolerant of waterlogging, but these are indicative of senescence (Clucas

1977) .

Metabolic Responses to Waterlogging

Under anaerobic conditions, the rate of glycolysis in plants sensitive to waterlogging is accelerated when pyruvate is decarboxylated to produce carbon dioxide and acetaldehyde. The acetaldehyde is reduced directly to .. ethanol by the enzyme alcohol dehydrogenase. McManmon and Crawford (1971) found a highly significant correlation between alcohol dehydrogenase activity and plant sensitivity to waterlogging. Plants intolerant of flooding are unable to control the rate of glycolysis which increases with the onset of anaerobiosis, and results in the accumulation of toxic products including carbon dioxide, ethanol and acetaldehyde (Crawford 1966). Flood tolerant species are able to avoid such an acceleration, producing a wide range of non-toxic end products.

Accumulation of organic acids including malate (Crawford and Tyler 1969) and succinate (Crawford 1967) have been noted in some waterlogged plants.

Other organic acids such as shikimic may be produced as intermediate metab-

01 ites (Boulter, Coult and Henshaw 1963). Tolerant species may undergo a

metabo Ii c swi tch from ethano I to ma 1ate product i on (C rawford and Ty 1er 1969). 74

Waterlogging also induces the degradation of protein, resulting in an increase in the concentration of free amino acids in roots and shoots

(van der Heide, de Boer-Bolt and van der Raalte 1963). Garcia-Nova and

Crawford (1973) suggest that this response may be an adaptation to such conditions. Associated changes in the nitrate metabolism of flood tolerant species result in the provision of alternative electron acceptors and a means for disposal of hydrogen ions - increasing the capacity of the plant to with­ stand waterlogged conditions.

THE INFLUENCE OF WATERLOGGING ON PLANT DISTRIBUTION

The local distribution of certain species has been correlated with the presence of anaerobic conditions, and the subsequent accumulation of elements in toxic concentrations which results from waterlogging of the soil

(Bannister 1964, Crawford 1966, Armstrong and Boatman 1967, Martin 1968).

High levels of ferrous ions (Martin 1968, Jones and Etherington 1970,

Jones 1972a) and manganous ions (Jones 1972b) have been shown to exclude some species from waterlogged sites. Some species tolerant of periodic water­ logging which results in reduced growth rate, show better growth on freely draining soils (Boden 1963, Parsons 1968, Clucas 1977, Ladiges and Kelso

1977). This suggests that interspecific competition may be an important facto'r in influencing the distribution of species under waterlogged conditions (Boden 1963, Bannister 1964).

Eucalypts are typically species of well-drained sites, with only a small percentage occurring in areas subject to waterlogging for long periods.

Eucalyptus robusta (Clemens and Pearson 1977) and E. camphora, species known to be tolerant of flooding, are largely confined as adult trees to swampy areas which are waterlogged for most of the year (Boden 1963). Comparatively few studies have been carried out on the role of waterlogging in influencing the distribution of eucalypt species. Boden (1963) related the performance 75 of z. ~~~nora and ~. daZrumpZeana under waterlogged conditions to observed field distributions; however, Parsons (1~68a) obtained no conclusive evidence that waterlogging was important in control 1 ing the distribution of three south-east Austral ian mal lee eucalypts.

Species able to grow On sites subject to seasonal waterlogging include

E. aggregata~ E. camaZduZensis~ E. incrassata~ E. ovata~ E. rodwayi~ E. rudis~

E. steZZuZata and Z. yarraensis. However, these species are not necessarily confined to such sites, and may be found on well-drained soils (Clucas

1977). Other species generally confined to well-drained sites tolerate occasional waterlogging, and these include E. blakeZyi~ E. rubida and

E. viminalis (Boden 1963). Ecotypic variation in the tolerance of eucalypts to waterlogging also occurs (Karschon and lohar 1972, 1975; Ladiges and

Kelso 1977).

THE DISTRIBUTION OF E. VIMINALIS AND E. CAMALDULENSIS WITH REFERENCE

TO WATERLOGGING

Previous workers (Patton 1930, Gibbons and Downes 1964) have described

E. viminalis as a species of well-drained sites. According to Boden (1963), it may occur on sites subject to occasional waterlogging for short periods.

Populations have been recorded on seasonally waterlogged soils at a number of sites, and intraspecific variation in tolerances to such conditions has been observed (Karschon and lohar 1972, Ladiges and Kelso 1977).

E. camalduZensis commonly occurs on sites which may be subject to periodic waterlogging for a prolonged time (Boden 1963). as the result of flooding or poor permeability of heavy soils, and seedlings are even able to tolerate periods of total immersion (Dexter 1967). Karschon and lohar (1975) have reported differences in the flooding tolerance of various provenances of

E. camaZduZensis, which they related to contrasting ecological conditions at the seed source.

- "." '---.... -,-·'··'~ ... ,.~··,·· ... ·r('''· '" .~.~I\I...... ,~.:-•.•.. '. 1 76

Since field observations in the Yarra Valley had suggested that water-

logging may be a discriminating factor in the distribution of E. viminaZis

and E. camaldulensis, pot trials were established to investigate the effects

of waterlogging on the growth of seedlings from the local populations under

consideration in the Yarra Valley.

METHODS

Seed was collected from six trees of E. vi~:nalis and E. camaldulensis

at Templestowe (Westerfolds), and germinated (in mid-September 1976) in o petri dishes under 1 ight at a constant temperature of 25 C. Seedlings were

planted in 60 pots (13 cm diameter) containing topsoil (0-10 em) from

Westerfolds which had been passed through a 1 cm sieve. Drainage holes in

the pots were plugged with foam rubber in an attempt to prevent root growth

outside the pots.

After four weeks growth in the glasshouse (during which seedlings were

thinned to two per pot), the seedlings were hardened off outside for two

weeks, then randomly placed in plastic-lined wooden troughs for waterlogging

in the glasshouse.

The experimental treatments used were the same as those of Parsons (1968a)

and Ladiges and Kelso (1977). Ten pots of each species were fully water-

logged with the water level maintained just above the soil surface, and

another ten pots were half waterlogged, the water level being kept at

approximately half pot height. The remainder were used as controls and

watered daily. Seedling heights were measured throughout the treatment

period, which began in October, and was continued until May 1977 when all

plants were harvested for dry weight estimation. A 0 2- 1

1Sj r I ,; Species 0-----0 E vlmlnalls j ; :~I; I ~ 1-0 -----. E. camaldulensis ! I • " treatment commenced

0-5~

··Il >; oi 5 10 15 20 25 30 35

1'l 1 E {i u .1., ~ It = ;;; '

1-0~. .$ -".

f I I 0-51 0-5~ • I

0+1--~--~--~--~--~--~,r- O~I----~--~--~----~---r--~-- 5 10 15 20 25 30 35 5 10 15 20 25 30 35 Weeks

Fig. 23. Height growth of E. viminaZis andE. camaldulensis seed! ings under A, control conditions; e, half-waterlogged; C, fully waterlogged. The vertical bars allow comparison of the two species at anyone time, or a comparison of heights at the one time for either species (Scheffe's test).

. __ . .. , .. , ... _-- --- 77

Statis-c~caZ ~4nc:.:yses

Data were subject to analyses of variance. Root/shoot ratios were

arcsine transformed prior to analysis since a wide range of values had

been recorded. The height measurements were log transformed since the

variances were proportional to the means (Sokal and Rohlf 1969, p.369),

and subject to a spl it plot analysis in time (Steel and Torrie 1960).

RESULTS

Height

The height data indicated that there was a significant difference

between the two species (Table 17). Interactions between treatment and

time, and species, treatment and time were highly significant. Three

weeks after treatment began, E. camaldulensis had reached a greater height

than E. viminalis in all treatments. E. camalduZensis was not affected by

the waterlogging treatment but height growth in E. viminalis was reduced

(Fig. 23).

Dry Weight

One of the seedlings in two pots of E. viminalis and E. camaZduler$is

under fully waterlogged conditions died during the experiment. Yield was

recorded as total dry weight per pot, irrespective of whether one or two

plants survived. The species and treatment effects on yield were significant,

as was the species x treatment interaction (Table 17). Yield for E. viminaZis

was severely decreased by the fully waterlogged treatment; E. camaldulensis

tended to grow best under half waterlogged conditions, althought the

difference was not statistically significant, and performed equally well

under waterlogged as under control conditions (Fig. 24). :a I ~. \ i~ {

E. viminalis E. c..... ldulenli. 15 15 I

10 10

0 ...... o:t. m

~ Q; 5 >= 5

0""---- c w Wltlrlogging treatment

Fi g. 24. Yields of seedl ings subjected to control (c), half water-

logged (tw) and fully waterlogged (w) conditions. Vertical bars

represent 95% confidence limits for comparison of treatments. 78

Table 17. Analyses of variance of data from waterlogging experiment.

Source of va ria t ion df MS F P

(a) He i gh t, 10910 trans formed. Sp 1 i t plot analysis in time

Species 1 0.13891 6.85 }~

Treatment 2 0.00589 0.29 NS

Species x Treatment 2 0.00008 0.004 NS Residual a 54 0.02029

Time 6 1.51682 238.64 1': ":,I~-:::.

Species x Time 6 0.14236 0.0004 NS

Treatment x Time 12 2.02903 319.23 ";,'~.}:';,I:

Species x Treatment x Time 12 0.15258 24.01 ~I:*;I:

Res i dua 1 b 324 0.006356

(b) Dry weight

Species 1 360.83633 40.04 *i~i'~ Treatment 2 61.34809 6.81 ** Species x Treatment 2 32.45305 3.6 0'< Residual 54 7.04044

I ( c) Root/shoot ratio, arcsine transformed

Species 1 3.96499 11 .69 ,'r>:

Treatment 2 0.59227 1. 74 NS Species x Treatment 2 1.6]268 4.93 ..}; Residual 54 0.42203

* 0':7. 0':** SIGNIFICANT AT P '" 0.5,0.1,0.001 respectively;

NS not significant at p 0.05. 79

~oot/Shoot Ratio

Root/shoot ratios were very variable in both species, but a significant

interaction between species and treatment was noted (Table 17).

E. camaZduZensis had a larger root/shoot ratio in al I treatments, and the

ratio increased, as the total root weight increased in response to water-

logging (Table 18). The root/shoot ratios of ~. viminaZis did not differ

significantly between treatments (Table 18), but that for fully waterlogged

plants was lower than for E. camaZduZensis.

Table 18. Mean oven dry weights of roots (g) and the calculated root/

shoot ratios (R/S)'~'

Control Half Waterlogged Fully Waterlogged

Roots R/S Roots R/S Roots R/S

C E. viminaZis 3.60 0.50 3.66 0.54 1.92 0.46 A 6 ABC E. camaZduZensis 4.59 0.54 5.64 0.59 I 5.71 0.78

*back transformed means

Means with same superscript are significantly different at p < 0.5

(S che ffes tes t) .

MorphoZogy

Both species showed similar morphological responses to waterlogging in

the development of surficial root systems and basal stem hypertrophy.

Surficial roots occurred occasionally in half waterlogged pots, and frequently

in fully waterlogged pots. Some root death WaS observed in waterlogged pots

of both species, but was more extensive in E. viminaZis. Stem hypertrophy

was common in both species under fully waterlogged conditions.

i j PLATE 5

The effect of waterlogging on the roots of E. camaldulensis seedl ings. ,, ,j 80

I However, the extent of root development under fully waterlogged

I! conditions was very different for the t\-JO species. Root growth in most of the fully waterlogged E. viminalis was confined to the top 9 cm of the

pot, whereas almost all other replicates were pot-bound at the conclusion

of the experiment. In spite of the foam rubber packing in drainage holes.

roots of fully waterlogged grew out of the pots and up to E. camaldulensis.. the surface in the troughs (Plate 5 ) less than 8 weeks after treatment

began. These extra-pot roots were subsequently harvested and included in

dry weight measurements, but similar root systems grew again. Extra-pot

roots developed in one repl icate of fully waterlogged E. viminalis, but were

very short. Two fully waterlogged E. camaldulensis seedlings also developed

small adventitious roots arising from their stems.

DISCUSSION

The results indicate that E. camaldulensis is more tolerant of water-

logged conditions than E. viminalis. Waterlogging induced some similar

morphological responses in both species; however, the different responses

of the root systems may account for the observed interspecific differences.

The growth of E. camaldulensis roots through the drainage holes of the pots

may have provided a pathway for the absorption of some oxygen directly from

the surrounding water, thus mitigating to some extent the effects of water-

logging. The abil ity of E. camaldulensis to produce massive root systems

quickly has been noted by Awe et al. (1976), and Karschon and Zohar (1975)

reported strong development of floating adventitious roots following dieback

of the main taproot in some more flood sensitive provenances of

E. camaldulensis.

High root/shoot ratios have also been reported for E. camaldulensis

(Jacobs 1955, Zirrrner and Grose 1958), and Jacobs (1955) suggested that they

assist E. camaldulensis to penetrate heavy, unaerated floodplain soils and 81

reach better-aerated soils below. Significantly greater root/shoot ratios

were recorded for fully waterlogged E. camaldulensis in the present study

indicating the abil ity of seedling root systems to penetrate waterlogged I ~ soils. It is thoughtthat the difference in root/shoot ratios was induced ) ! by treatment. j I I Although there were significant differences in the growth rates of

waterlogged E. viminalis and E. camaldulensis. they were not as large as

might be expected. Measurements of oxygen flux and redox potential made j in a similar experiment (Ladiges and Kelso 1977). suggested that substantially less oxygen was available to fully waterlogged plants than to freely draining

controls; however, some oxygenation may have taken place during the

frequent topping up of water levels. This may have reduced root anaerobiosis

for both species to some extent.

Experimental evidence (Karschon and Zohar 1972. Ladiges and Kelso 1977)

suggests that seedlings of some populations of E. viminalis can survive

waterlogging for up to 220 days when flooded to just above the soil surface.

However, under these conditions growth rates are reduced. In a competitive

situation not only survival but the degree of growth rate retardation may

be critical. The effect of total or partial submergence of the shoot on

the survival of E. viminalis seedlings has not been examined. E. viminalis

may prove more sensitive to shoot submergence than E. camaldulensis.

The development of stem-borne adventitious roots has been reported for

E. camaldulensis (Jacobs 1955) and other eucalypts (Boden 1963), although

not for E. viminalis. In the field they appear to be restricted to

inundated sections of trunks or stems. In the present study, two waterlogged

E. camaldulensis produced these structures, although stems were not sub-

merged. In a flooding environment, adventitious roots may be important in

survival where sedimentation is taking place around the butts of trees.

J~ _____ 82

In the Yarra Valley, ~. viminalis generally occurs on well-drained

sites, a I though occas i ona I stan ds occu r on some s 10\oJ d ra i n i ng te rraces and

slopes where the water table may only be 15 cm below the soil surface during

winter. Most sites occupied by E. camaldulensis are probably not subject

to prolonged waterlogging, since catchment management has changed the

flooding regime of the river. Floods now usually recede after several days.

Most of the floodplain has been cleared of trees, and stands of

E. camaldulensis are now largely restricted to areas which drain fairly

quickly, such as the banks of rivers and bi llabongs. However, swampy

depressions on the floodplain probably supported E. camaldulensis prior to

clearing.

E. camaldulensis was found to be more tolerant of experimentally

induced waterlogged conditions than E. viminaZis. Growth rate retardation

occurred in both species subjected to waterlogging, but was significantly

greater in E. vi~nalis. It is suggested that this difference may be

reflected in the competitive abil ity of these species on waterlogged sites.

sd 83

CHAPTER 6

DISCUSSION AND CONCLUSIONS

., .~ The distributions of E. viminalis and E. camaldulensis in Victoria

overlap in the region of the 1000 mm isohyet in the north east and at

the 700 mm isohyet south of the Divide and in western Victoria. It is

suggested that the occurrence of the ecotone between the two species at

different mean annual rainfalls north and south of the Divide is the

result of the effectiveness of the rainfall in these areas.

The variation in form observed in E. camaldulensis in Victoria,

from tall forest to woodland. appears to be related to soil moisture

gradients. The occurrence of various forms in E. viminalis has been

related to both soil moisture and soil nutrient status.

In the north east and on the northern slopes of the Divide. ecotones

between the smooth-barked forest form of E. viminalis and the riparian

form of E. camaldulensis occur on streambank and floodplain sites where

floodplains interdigitate with spurs of the north east highlands. South

of the Divide riparian ecotones between the two species occur at the

700 mm isohyet. Ecotones also occur between the woodland forms of these

species in the region south of the Divide and including the Western

District of Victoria in the 600-700 mm rainfall belt on undulating

topography where the soil nutrient status is fair to good. Here

E. viminalis generally occurs on the better drained sites. In the lower

rainfall region south of the Divide E. viminalis has been able to exploit

a wide range of soil types, including acid and calcareous sands (Ladiges

and Ashton 1977), whilst E. oamaldulensis tends to be confined to heavy

cl ay so i 1s. , ; 84

It appears that the geographic extent of E. viminaZis and

E. camaZduZensis in Victoria is strongly influenced by mean annual

rainfall, and that E. viminaZis has a preferece for higher rainfall

I oca lit i es .

A survey of the Australian distribution of E. viminaZis and

E. camaZduZensis in Chapter 1 indicated that both species occupy a

comparatively wide range of habitats with respect to altitude, topography.

rainfall and soil type, although E. viminaZis is largely restricted to

one climatic zone (Cfb - humid mild-winter climate of Koppen) whilst

E. camaZduZensis,because it is riparian and depends on flooding or the

watertable for moisture, occurs across a range of climatic types, from

humid tropical through semi-arid climates of inland Australia to the

humid mild-winter climates of south eastern Australia.

Ladiges and Ashton (1974) suggested that the ability of E. viminaZis

to occupy such a variety of habitats may be related to the occurrence of

ecotypic variation within the species. Genetic differences between

populations growing in central Victoria have been demonstrated by field

transplants and pot trials. They included differences in seedling

establishment and growth rate, tolerance to drought (Ladiges and Ashton

1974, Ladiges 1974a, 1974b) and tolerance of waterlogged conditions

(Ladiges and Kelso 1977). Population differences in growth rate and

drought tolerance have been related to differences in edaphic factors,

and it has been suggested that differential selection pressures have

primarily been responsible for the establishment of such population

differences (Ladiges 1976).

Some ecotypic variation has also been demonstrated for

E. camaZduZensis in pot trial comparisons of tropical and subtropic~l

populations. Such population differences have been recorded in seedling

.... -"".--;-.--- -.' "."- .- .. ,~- ...-" --'~. ~ -'"' -- ••- ---,-_•••• - •• ,- •••• ", "!;." ;.' - ""'," "I:~'~:"":.:r-";>' ~I' ••. " 85

height (Pryor and Byrne 1969), response to lOW temperatures (Pryor and

Byrne 1969. Karschon 1971, Awe and Shepherd 1975) and tolerance to

flooding and salinity (Karschon and Zohar 1975). In Victorian populations

there is some morphological variation, but variation of the scale

demonstrated by E. viminalis has not been observed, nor extensively

studied, although Laurie (1976) has suggested that there are genotypic

differences in the seedling growth rate and rate of root penetration of

forest and woodland forms of E. camalduZensis growing under different

flooding regimes in the Barmah Forest.

At the junctions between the species ranges in Victoria, E. viminalis

and E. camaldulensis, like most species capable of interbreeding. rarely

form mixed stands (Pryor 1953). Where the species occur in close

proximity they tend to occupy separate habitats, with both the woodland

and forest forms of E. viminalis on the better drained sites. However

some hybridization between the species has been recorded (Pryor 1955,

Penfold and Willis 1961, Willis 1972), and intermediates have been noted

at Westerfolds and near Eildon.

The distribution of E. viminaZis and E. camaldulensis in the Yarra

Valley mirrors the patterns observed throughout Victoria, the tall smooth-

barked form of E. viminalis occurring as tal I open-forest in the upper

catchment where M.A.R. exceeds 1000 mm and fringing the Yarra and its

tributaries downstream to the 700 mm isohyet, where it gives way to

E. camaldulensis. The woodlal;d form of E. viminalis occurs on Tertiary

basalts and flat sites on sandy cappings towards the drier limits of

the E. viminaZis range, whilst woodland E. camaldulensis occupies heavy

clay soils on the gently undulating topography of Silurian slopes and

Quaternary basalt plains down to the 500 mm isohyet.

------.-~=------86

?ryor (1959a, 1959b) has suggested that the factors which control

the local distribution of wide ranging eucalypt species are I ikely to

be different from those which restrict them at their geographic limits.

He thought that competition. nutrition and the effects of microclimate

may be, factors contributing to the observed local distributions. In

the present study evidence suggests that in the Yarra Valley where M.A.R.

exceeds 700 mm and soils are well-drained and comparatively well-

structured. the faster growth rates of the forest form of E. viminaZis

may result in the exclusion of E. camaldulensis from such sites by

competition. In addition. floods favor the downstream dispersal of

E. viminalis which has occasionally been noted growing amongst

E. camaZduZensis on steep. sheltered south facing banks as far downstream

as Richmond.

At the upper limits of its range in the Yarra catchment (eg.

Hurstbridge and upstream from Westerfolds) • E. camaZdulensis occurs on

flood plain margins. but does not extend far up the valley slope where

soils tend to be shallow and often very stony! It does not occupy

E. viminaZis sites closer to the river. The woodland form of

E. camaldulensis which occurs on undulating topography away from the

river banks and floodplain may prove to be a more drought tolerant I ecotype of E. camaZduZensis. However, it is suggested that soil volume 1 may be a critical factor in the tolerance of E. camalduZensis to drought; soils derived from basalt and Silurian bedrock near Melbourne are

I relatively deep and frequently have a clay subsoil which tends to have

a high moisture retaining capacity.

Field observations and some experimental results indicate that

under certain conditions E. viminalis is able to grow faster than

E. camaldulensis and that E. camaldulensis is more tolerant of water-

logging and limiting soil mositure conditions. Differences between the 87

two species which may influence their gr~vth rates and success in the

Yarra Valley habitats include seed size and root/shoot ratios.

E. viminalis seeds are typically larger than those of

E. camaldulensis (Grose and Zimmer 1958 ) and it is suggested that this

may give E. viminalis an advantage over E. camaldulensis providing

germination rates do not differ markedly, and providing soil structure

and nutrient levels are favorable to the growth of E. viminalis.

In the present study the root/shoot ratios of E. camalduZensis were

consistently higher than those of E. viminaZis, and it was suggested

that they may confer greater drought avoidance on E. camalduZensis.

Previous studies have shown that there is a correlation between the

root/shoot ratios of eucalypts and site water availabil ity, and both

interspecific and intraspecific comparisons have demonstrated a decrease

from high to low root/shoot ratios with increasing wetness of provenance

site (Zimmer and Grose 1953, Hopkins 1964, Parsons 1968b). Consequently

it has been suggested that a high root/shoot ratio represents an

adaptation to drought conditions (Zimmer and Grose 1958), although low

nutrient levels may also be a selective factor (eg. Ladiges and Ashton

1977) .

There was also a differential species response of root/shoot ratios

to increasing levels of phosphorus and nitrogen, the root/shoot ratio

of E. viminalis tended to decrease when nutrient levels were increased,

whilst root/shoot ratios of E. camaldulensis showed little change. These

results suggest that on more fertile soils in lower rainfall areas some

ecotypes of E. viminalis may be more susceptible to drought stress.

Parsons (1968c) has suggested that there may be a positive correlation

between soil fertility and drought susceptibility, and Ladiges (1974a)

noted that lower root/shoot ratios were a feature of tall forest

populations of E. viminalis found on wetter sites.

J 38

It is not known what role the very high root/shoot ratio observed

in the fully waterlogged plants of E. camaldulensis (Chapter 5) may

play in the waterlogging tolerance of this species, however Jacobs (1955)

has suggested that, on the heavy floodplain soils of the Murray River

system, the high root/shoot ratio of E. camaldulensis helps penetration

of heavy gley layers of soils to reach better aerated layers beneath.

SUMMARY

It is concluded that,while average annual rainfall strongly

influences the geographic extent of E. viminalis and E. camaldulensis,

at the local level the effects of competition interacting with soil

moisture and soil structural properties determine the distribution of

the two species. Interpretation of distribution patterns is complicated

by intraspecific variation, particularly in E. viminalis.

J 89

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Minerva Access is the Institutional Repository of The University of Melbourne

Author/s: Barson, Michele Mary

Title: The distribution of Eucalyptus viminalis and Eucalyptus camaldulensis in Victoria

Date: 1978

Citation: Barson, M. M. (1978). The distribution of Eucalyptus viminalis and Eucalyptus camaldulensis in Victoria. Masters Research thesis, School of Botany, The University of Melbourne.

Publication Status: Unpublished

Persistent Link: http://hdl.handle.net/11343/35599

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