Plants of Western Australian granite outcrops



Yüklə 368.42 Kb.
PDF просмотр
səhifə1/6
tarix24.08.2017
ölçüsü368.42 Kb.
  1   2   3   4   5   6

Journal of the Royal Society of Western Australia, 80(3), September 1997

141


© Royal Society of Western Australia 1997

Granite Outcrops Symposium, 1996

Journal of the Royal Society of Western Australia, 80:141-158, 1997

Plants of Western Australian granite outcrops

S D Hopper

1,

 A P Brown



2

 & N G Marchant

3

1

Kings Park and Botanic Garden, West Perth WA 6005



email:  steveh@kpbg.wa.gov.au

2

Western Australian Threatened Species & Communities Unit,



Department of Conservation and Land Management, PO Box 51, Wanneroo WA 6065

email:  andrewbr@calm.wa.gov.au

3

Western Australian Herbarium, Department of Conservation and Land Management,



PO Box 104, Como WA 6152

Abstract

Outcropping granite rocks in Western Australia span a considerable climatic range, from the

mediterranean south-west to inland desert and northern arid subtropics and tropics. At least 1320,

and possibly 2000, plant taxa occur on Western Australian granite outcrops. Outcrop plant life is

most diverse in the South West Botanical Province, with individual outcrops having up to 200

species, including many endemics not found in surrounding habitats. Species richness and local

endemism declines with increasing aridity, to the point where Kimberley and Pilbara outcrops

show little discontinuity in species from the surrounding landscape matrix. Outcrops are dominated

by woody and herbaceous perennials, especially of the Myrtaceae, Orchidaceae, and Mimosaceae,

and have an unusually rich diversity of annuals (Asteraceae, Stylidiaceae, Poaceae,

Amaranthaceae etc.) compared with the flora as a whole. An unusual life form is found in

resurrection plants capable of extreme desiccation and rehydration (e.g. Borya, Cheilanthes).

Among woody perennials, bird pollination is frequent, and some outcrops harbour a high

proportion of obligate seeder species due to the refuge from fire provided by bare rock barriers.

The diversity of microhabitats and soil moisture regimes on outcrops has enabled the persistence

of species beyond their main range in the face of climatic fluctuations. It has also facilitated the

evolution of many endemics in the south-west. Major threatening processes facing outcrop plant

communities include weed invasion, grazing by stock and feral animals, too-frequent fire,

clearing, loss of shrub layer, salinity, and dieback. Conservation of these rich rare habitats needs

the support of local communities.



Introduction

Western Australia is the largest Australian State,

extending 2 391 km north-south and 1 621 km east-west,

and occupying 2 525 500 km

2

, or about a third of the



nation. Climates range from temperate and

mediterranean in the south-west to the monsoonal

tropics in the extreme north, with arid conditions

prevailing over much of the State from the Nullarbor

Plain north through the inland deserts to the north-west

Pilbara and Kimberley regions.

Most of the State is a plateau 300-600 m above sea

level, with the highest point (Mt Meharry) only 1 251 m.

Western Australia’s numerous granite inselbergs and

outcrops, consequently, are significant landscape

features, even though most emerge less than 100 m

above surrounding terrain.

Granite (or granitoid) rocks are mainly found on the

Yilgarn and Pilbara Cratons, which together occupy

about a third of the State’s landmass, and along adjacent

south coastal and Kimberley orogens (Myers 1997). The

outcrops thus span a considerable climatic range, from

the mediterranean south-west to inland desert and

northern arid subtropics and tropics.

Western Australian outcrops vary in area from about

one tenth of a hectare to many hectares. While most are

clearly isolated and disjunct, sometimes separated from

the next outcrop by tens of kilometres, others are part of

extensive inselberg systems covering several square

kilometres (e.g. outcrop systems in Cape Le Grand,

Porongurups and Cape Arid National Parks on the south

coast, at Oudabunna Station near Paynes Find, and at

Woodstock Station in the Pilbara). Peak Charles, 100 km

north-west of Esperance, stands highest above

surrounding country among the State’s inselbergs,

reaching 500 m from a low plain.

While the Kimberley, Pilbara and desert granites are

in regions with depauperate floras not unlike those of

much of tropical and arid Australia, the granite of the

Yilgarn Craton underlies one of the world’s regions

richest in plant life, the South West Botanical Province

(Marchant 1973; Hopper 1979, 1992; Beard 1980, 1981,

1990). As many as 8000 vascular plant species occur in

this region, with about 75% endemism. Consequently,

the botanical exploration of south-western inselbergs has

been particularly rewarding, and much remains to be

done.


Here, we provide an overview of current knowledge

of plant life on Western Australian granite outcrops. Our

aim was to compile a baseline, including a preliminary list

of plants (vascular and cryptogam) collected from

Western Australian outcrops, and a list of key references,

to inform future research and provide a context for more

specific studies. We conclude with some thoughts on the


142

Journal of the Royal Society of Western Australia, 80(3), September 1997

conservation of this special component of Western

Australian plant life.



Botanical Exploration

Western Australian granite outcrops have been

important to aboriginal people ever since they occupied

the land, but little has been documented of this long-

standing relationship (Bindon 1997). Recorded European

knowledge of granite outcrop plants in the State

commenced with Archibald Menzies, surgeon and

naturalist aboard the HMS Discoveryunder the

command of Captain George Vancouver. The Discovery

was anchored in King George’s Sound from September

28 to October 11, 1791.

Menzies made a “copious collection of ... vegetable

productions, principally the genus Banksia, which are

here very numerous” from various sites onshore in the

vicinity of present-day Albany (Maiden 1909). Given the

prominence of granite headlands, hills and islands at

Albany, Menzies undoubtedly collected from them, but

details are difficult to trace.

European botanists first named granite outcrop plants

from Western Australia in 1800. The Frenchman Jacques J

H de Labillardiere was naturalist on Admiral Bruny

d’Entrecasteaux’s expedition to Australia, which sought

refuge from a storm near the modern town of Esperance

over the period 9-17 December 1792. Labillardiere’s

specimens included a plant he named in 1800 as

Eucalyptus cornuta, collected from the granite Observatory

Island on 13 December 1792. E. cornuta occupies the apron

and deeper soil pockets on granite outcrops throughout

the Esperance area and adjacent islands, extending

westwards to the Cape Naturaliste area (Fig 1).

Labillardiere named other granite outcrop plants from

the expedition, including the bizarre genus Borya (Fig 4),

a pincushion lily and resurrection plant, named in 1805

and typified by the species B. nitida which occurs on

shallow soils on outcrops along the south coast from

Albany to east of Esperance.

Robert Brown, on the expedition to circumnavigate

Australia led by Matthew Flinders in the Investigator,

anchored at King George’s Sound on December 8, 1801,

and collected extensively until January 5, 1802. Between

January 10-18, the expedition also explored and collected

near Esperance, landing at Lucky Bay (in the present-day

Cape Le Grand National Park) for five days, and on

islands in the Recherche Archipelago. Brown (1810) also

named many granite outcrop plants, including another

species of Borya (B. spaherocephala) that occurs with B.

nitida on several south coast outcrops.

The arrival of James Drummond at the Swan River

with Captain Stirling’s colonising party on the Parmelia

in 1829 heralded a major advance in knowledge of the

south-west’s flora, including that of granite outcrops

(Erickson 1969). Drummond, a Scot and keen

nurseryman with an excellent eye for new taxa,

collected widely throughout the forests and present day

wheatbelt, his specimens destined for subscribers in

Great Britain and Europe. He was followed by many

others up to modern times. Beard (1981) provides a

useful historical review. The floral wealth of the south-

west is such that significant numbers of new taxa

continue to be discovered and described each year

(Green 1985; Hopper 1992), including granite outcrop

endemics.

The ecology and biogeography of Western Australian

granite outcrop plants were observed by the earliest

collectors, but drew specific mention by the plant

geographer Ludwig Diels (1906), who noted the

“dwarflike” vegetation. Smith (1962) provided an account

of the vegetation of the granite Porongurup Range, and

many others have mentioned granite outcrop plants in

broader vegetation surveys in the south-west (e.g. Beard

1981; Newbey & Hnatiuk 1985; Newbey et al. 1995;

Wardell Johnson & Williams 1996; Brooker & Margules

1996).

Main (1967) gave a delightful account of the natural



history of Yorkrakine Rock through an annual cycle.

Marchant (in Erickson et al. 1973) summarised botanical

features of south-western outcrops in an essay for a

general readership.

Schweinfurth (1978) described the vegetation of

exposed granite headlands along the south coast, while

Abbott & Watson (1978) and Abbott (1980) explored

these headlands and adjacent islands in greater detail,

showing the flora of most islands had a depauperate

subset of that found onshore, and displayed little

endemicity nor genetic differentiation from mainland

populations.

Hopper (1981) highlighted the importance of winter-

flowering woody perennials as a nectar resource used by

a diversity of honeyeaters in the central wheatbelt (Fig

3). Pate & Dixon (1982) gave a comprehensive account of

the biology of tuberous and cormous plants, including

many found on granite.

Ornduff (1987) documented the flora of herbfields

including, and centrewards from, the Borya zone on nine

outcrops near Perth and Hyden. Burgman (1987) sampled

five outcrops inland from Esperance and explored aspects

of rarity in granite communities. Hopper et al. (1990)

illustrated 29 endangered endemics of granite outcrops

and highlighted conservation issues.  Pignatti & Pignatti

(1994) reported on herbfields from shallow seasonally

wet soils on a selection of south-west outcrops.

Ohlemüller (1997) documented plants in shallow soil

depressions on 26 outcrops throughout the south-west

and goldfields.

In parallel with these ecological investigations, genetic

studies of Western Australian granite outcrop plants were

pioneered by James (1965), who’s penetrating work on

the herb Isotoma petraea (Lobeliaceae) has become a classic

in the literature on plant evolution (Bussell & James 1997).

Studies on the population genetics of endemic granite

outcrop eucalypts have also provided useful insights into

the evolution of highly fragmented small populations

(Moran and Hopper 1983; Sampson et al. 1988). The

breeding systems of granite outcrop endemics have been

documented for Villarsia (Menyanthaceae; Ornduff 1986,

1996) and Anthocercis gracilis (Solanaceae; Stace 1995).



Sampling Methods

Rather than laboriously search the increasing number

of botanical publications that include plant taxa recorded


Journal of the Royal Society of Western Australia, 80(3), September 1997

143


on Western Australian granite outcrops, we compiled the

plant list from specimens housed in the Western

Australian Herbarium. The database WAHERB stores full

label details of 413 000 specimens of vascular plants and

cryptogams collected throughout the State, and afforded

an opportunity to list those taxa for which habitat details

on labels included the words “granite outcrop”. Initial

trials indicated that searching on “granite” or “granitic”

alone picked up too many taxa that occupied regions

underlain by granite rock, but favoured deep soils well

removed from rock outcrops.

In our list, taxa are mainly species, but infraspecific

subspecies, varieties and forms, together with hybrids,

are all counted. This ensures that all named plant

biodiversity is included, and allows for discrepancies in

assigning rank among taxonomists.

The above approach to listing plant taxa was based on

an understanding that most authors involved in botanical

survey of Western Australian granite outcrops have

collected voucher specimens and deposited them in the

Western Australian Herbarium (e.g. Ornduff 1987;

Burgman 1987; Hopper 1981; Hopper et al. 1990; Hopper

& Brown, unpublished orchid research; Newbey & Hnatiuk

1985; Newbey et al. 1995). In addition, as an independent

check, the senior author has compiled field herbaria in

notebooks for ca 150 outcrops throughout Western

Australia over the past two decades. Most outcrops

sampled occur in the South West Botanical Province (e.g.

Fig 1) and adjacent pastoral region, while a few have

been examined in the Pilbara (e.g. Fig 2) and Kimberley.

Precisely defining the boundaries of a granite outcrop

is difficult, especially for mobile components of the biota

(Main 1997). However, the sedentary nature of adult

plants, especially perennials, affords a reliable and

measurable biological indicator of the limits of the

outcrop system.

In fieldwork, we have used the distribution of plants

that are locally endemic to outcrops to define the extent

of outcrop communities sampled. Thus, all species

centrewards from the outermost individuals of granite

outcrop local endemics were included as present on an

outcrop. This approach ensures that all endemics are

sampled, but has the effect of picking up some species

from surrounding deeper soils that do not extend onto

soil pockets on the outcrop itself. Other authors have

restricted their sampling to such soil pockets (e.g. Houle

1990; Porembski et al. 1995; Ohlemuller 1997), or only to

herbfields (e.g. Ornduff 1987). Experience showed that

perennial vegetation fringing the base of Western

Australian outcrops had to be sampled to ensure a

comprehensive inventory (see below).

We followed Newbey and Hnatiuk (1985) and

Newbey et al. (1995) in collecting on random walks

stratified by microhabitat rather than within quadrats i.e.

the random stratified walk technique. A comparison of the

senior author’s data with the quadrat-based data of

Burgman (1987) for Mt Ney inland from Esperance

showed that four 5m x 5m quadrats spaced at 25 m

intervals on NE scree slope and sheet rock yielded 61

taxa, whereas 192 taxa were documented through

random stratified walks covering cardinal compass

points.


Microhabitats recognised and deliberately searched

for on random stratified walks included bare rock,

cryptogamic crusts, gnammas (rock pools or weather

pits, seasonal and permanent), soil-filled crevices, caves/

tafoni/shade of boulders or exfoliated slabs, herbfields

on shallow well-drained soil, herbfields on shallow

seasonally waterlogged soil (ephemeral flush vegetation),

shrublands and woodlands on deep well-drained soil,

shrublands, woodlands and forests on deep seasonally

waterlogged soil, permanent springs, major

watercourses, and salt lakes.

Floristics

A total of 1320 Western Australian granite outcrop

plant taxa were represented and labelled as such in the

collections of the Western Australian Herbarium in May

1996 (Appendix 1). Of these, 1097 taxa (83.0%) were

described, 94 (7.1%) were undescribed but well-delimited

with manuscript names, and 129 (9.9%) were of uncertain

taxonomic delimitation. Only 4 (0.3%) were hybrids, well

below the proportion (4%) estimated for the whole WA

flora (Hopper 1995). The list includes 11 macrofungi, 34

lichens, 46 mosses, 9 liverworts, 9 ferns, 7 fern allies, 2

cycads, 2 conifers, and 1200 angiosperms (284

monocotyledons, 916 dicotyledons).

While these statistics provide a useful baseline, it is

pertinent to note that sampling of most cryptogam

groups is poor. For example, we recorded only 34 lichens

with vouchered granite outcrop specimens for the whole

of WA, whereas Pigott & Sage (1997) list 36 lichen taxa

for Yilliminning Rock alone. Macrofungi undoubtedly are

orders of magnitude more diverse than presently known.

The moss flora is comparatively better documented at

the species level (Stoneburner et al. 1993; Stoneburner &

Wyatt 1996), but much more collecting is needed to fill in

knowledge of distribution and ecology.

Some confidence may be placed in the list of vascular

plant taxa, which accounts for 1220 (92.4%) of the total of

1320. Based on our knowledge of rock outcrop floras

across the State, the majority of south-western vascular

plant taxa on granite outcrops are listed. However, some

conspicuous omissions of taxa that are common (e.g.



Hakea petiolarisCorymbia calophylla), uncommon (e.g.

Grevillea magnifica, Phylloglossum drummondii and Isoetes

drummondii) and rare (e.g. Drummondita hassellii var

longifolia, Hibbertia bracteosa, Villarsia calthifolia,

Pleurophascum occidentale) indicate that revision upwards

is required. Moreover, a comparison of the list of 187

taxa for Yilliminning Rock near Narrogin (Pigott & Sage

1997) with Appendix 1 shows that 78 Yilliminning taxa

(42%) are not present in our list for the State. This

discrepancy would be even more so for northern

outcrops. For example, absent from the present list are

the dominant spinifex hummock grasses on granite

outcrops (Triodia spp), as well as common lemon grasses

(Cymbopogon spp), and scattered but widespread

subtropical woody shrubs and small trees such as

Terminalia canescens. It would be no surprise to us,

consequently, if the number of vascular plant taxa on

Western Australian granite outcrops approached 2000 in

the future.

In the present list, major vascular plant families include

the Myrtaceae (162 taxa), Orchidaceae (159), Mimosaceae



144

Journal of the Royal Society of Western Australia, 80(3), September 1997

(82), Asteraceae (72), Papilionaceae (66), Proteaceae (54),

and Stylidiaceae (33). Genera richest in taxa on granite

outcrops include Acacia (82 taxa), Caladenia (70),

Eucalyptus (44), Stylidium (28), Melaleuca (26), Grevillea

(25), Drosera (21), Verticordia (20), Eremophila (18) and



Thelymitra (16).

Thus, woody perennial shrubs and trees of myrtles,

wattles, peas and Proteaceae are taxon-rich on WA

granite outcrops, reflecting trends in the flora as a whole

(Green 1985; Hopper et al. 1996). However, the granite

woody perennials are depauperate in Epacridaceae,

which is rich in other habitats. The granite outcrop flora

is clearly divergent from the flora at large in the

unusually high taxon richness of groups such as the

tuberous perennial terrestrials (orchids, sundews, lilies),

and herbaceous, often annual, daisies and triggerplants.

Systematic sampling of shallow-soil herbfields on

south-western outcrops by Ornduff (1987) and

Ohlemüller (1997) yields a useful comparison with our

data on herbaceous families. Ornduff recorded 160 taxa

belonging to 37 families (he didn’t sample Orchidaceae

for conservation reasons), of which the largest were

Asteraceae, Poaceae, Liliaceae sens. lat., and Stylidiaceae.

Ohlemüller recorded 134 species from 42 families, with

the largest being Asteraceae, Orchidaceae, Poaceae,

Apiaceae, Stylidiaceae and Centrolepidaceae.

Major herbaceous families in our list are Orchidaceae

(Fig 5), Asteraceae, Stylidiaceae, Anthericaceae (or

Liliaceae sens. lat.), Poaceae, Droseraceae, Cyperaceae,

Goodeniaceae, Amaranthaceae and Centrolepidaceae.

The Amaranthaceae is a family richest in the north of

Western Australia, so it is not surprising that Ornduff

(1987) and Ohlemüller (1997) found it to be depauperate

in their south-west study areas. Orchidaceae

undoubtedly emerges as the most taxon-rich herbaceous

family in our list because two of us (SH and AB) have

made a detailed and prolonged study of granite outcrop

orchids, and found that repeat surveys over different

seasons and years are needed to develop comprehensive

orchid inventories for individual rocks. Other differences

between our ranking and those of Ornduff (1987) and

Ohlemüller (1997) are minor. This general concordance

suggests that major trends and statistics for the vascular

plants in Appendix 1 are accurate, at least for south-west

outcrops.



Plants of Special Interest

Granite outcrop habitats have elicited remarkable

parallel evolution in many plants and animals (Porembski

et al. 1997; Wyatt 1997; Mares 1997). The combination of

high solar radiation, rapid runoff of rainfall, and shallow

soils on a rocky substrate provide microhabitats of

accentuated seasonal and diurnal stresses. Conditions

may vary over a few metres from cool permanently

moist shaded caves with water seepage to drought-

afflicted shallow soils and rock surfaces fully exposed to

all the elements.

Few organisms can tolerate the harshest of these rock-

surface habitats, which tend to be occupied by

cryptogamic crusts of cosmopolitan cyanobacteria,

lichens and mosses such as Grimmia laevigata. Western

Australian outcrops conform to this trend. However, on

south-west outcrops experiencing high rainfall, moss

cushions become prominent, with the luxuriant brown

carpets of Breutelia affinis and the verdant green



Campylopus bicolor and C. australis noteworthy.

Coping with seasonal or unpredictable drought is,

undoubtedly, the most significant survival strategy faced

by granite outcrop plants. Among Western Australian

herbaceous perennials on outcrops, pincushion lilies

(Borya spp, Boryaceae) are abundant and remarkable in

their capacity as resurrection plants (Gaff 1981) to

withstand desiccation to less than 5% of normal leaf

moisture content, turning orange in the process, and

rehydrating to normal green leaves within a day of

rainfall (Fig 4). There are at least six species of Borya in

the South West Botanical Province (B. sphaerocephala is a

variable taxon awaiting detailed study and possible

subdivision). These plants do not extend to the Pilbara

outcrops. Other resurrection plants commonly seen on

WA granites include the rock ferns Cheilanthes spp and



Pleurosorus rutifolius.

Persisting underground as a tuber during drought is a

common strategy among Western Australian granite

outcrop herbs in the south-west and adjacent pastoral

regions, especially lilioids (e.g. Wurmbea spp,

Colchicaceae), orchids (Caladenia, Thelymitra, Pterostylis,



Diuris, Prasophyllum) and sundews (Drosera), as well as

the unusual fern ally Phylloglossum (Pate & Dixon 1982).

On northern outcrops, tuberous Cyperaceae tend to

occupy this niche.

Succulence is not prominent in the Western Australian

granite outcrop perennial floras, but has evolved in a few

taxonomically-unrelated species e.g. Spiculaea ciliata

(Orchidaceae; Fig 5), Carpobrotus spp (Aizoaceae). Some

perennial shrubs of south coast granites have unusually

thick leaves (e.g. Hakea clavata, Proteaceae; Anthocercis



viscosa, Solanaceae), and at least one has tuberous roots

(Calothamnus  tuberosus, Myrtaceae). Sclerophyllous

leaves characterise the vast majority of woody perennials

found on granite outcrops, as well as in the Western

Australian flora at large.

The graminoid habit has evolved in several unrelated

groups in the south-west, with common perennials

forming tussocks including diverse Cyperaceae

(especially Lepidosperma spp), blind grass (Stypandra spp,

Phormiaceae), the sedge-like grass Spartochloa scirpoidea

(Poaceae) and lemon grass Cymbopogon spp (Poaceae).

Desert, Pilbara and Kimberley outcrops are dominated

by uniquely Australian hummock grasses with inrolled

pungent leaves (Triodia spp, Poaceae).

Drought avoidance through an annual life history is a

major feature of Western Australian granite herbs in

families such as the Asteraceae, Stylidiaceae, Poaceae,

Goodeniaceae, Amaranthaceae and Centrolepidaceae.

Most of these annuals have relatively small inconspicuous

flowers suggestive of inbreeding (Ornduff 1987), but

some are brightly coloured and adundant. Most outcrops

in southern Western Australia are bedecked with

colourful swards of annual triggerplants (Stylidium,

Stylidiaceae) and everlastings (e.g. Rhodanthe, Waitzia,

Asteraceae) that enliven the herbfields. Succulence is a

feature of some annuals, especially those that occupy the

dry spectrum of shallow soils (e.g. Calandrinia spp,

Portulacaceae; Crassula spp, Crassulaceae).



Journal of the Royal Society of Western Australia, 80(3), September 1997

145


123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

123456789012345678901234567890121234567890123

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

12345678901234567890123456789012123456789012

1. Coastal granite outcrops east of Albany on Two Peoples Bay

Nature Reserve, with Eucalyptus cornuta (pale canopy),

described in 1800 by French scientific explorer Labillardiere.

Photograph by SD Hopper.

2. Granite sheet, boulders and distant inselbergs in the arid

Pilbara, Spear Hill, south-west of Marble Bar. Photograph by

SD Hopper.

3. Bird-pollinated plants are a feature of south-west Australian

granite outcrops - New Holland Honeyeater on Eucalyptus

caesia, Boyagin Rock, north-west of Pingelly. Photograph by SD

Hopper.


4. The resurrection plant, pincushion lily Borya constricta, with

leaves 1 cm long desiccated (orange) but rehydrating (green)

following rain at the end of summer drought, Chiddarcooping

Rock, north-east of Merredin. Photograph by SD Hopper.

5. Terrestrial orchids are the second most species-rich plant

family on Western Australian granite outcrops. Here, flowers

of the elbow orchid (Spiculaea ciliata) 1 cm long splay from the

succulent stem that feeds them in early summer, and a male

thynnid wasp attempts to copulate with the flower’s sexual

decoy, an insectiform hinged labellum, Boulder Rock,

Brookton Highway. Photograph by BA & AG Wells.

6. Arguably the rarest Western Australian granite outcrop plant,

the annual aquatic millfoil Myriophyllum lapidicola in full flower

(with round floating leaves), and known from just two

gnammas (rock pools), alongside the invasive aquatic South

African weed, Crassula natans var minus. Photograph by SD

Hopper.


146

Journal of the Royal Society of Western Australia, 80(3), September 1997

Annuals are also found commonly in seasonally

waterlogged shallow soils or ephemeral flush

communities (Pignatti & Pignatti 1994). These annuals

include species of Centrolepidaceae (Centrolepis  and



Aphelia), Apiaceae (Hydrocotyle), Juncaginaceae

(Triglochin), Cyperaceae (Schoenus, Isolepis, Cyperus),

Asteraceae (Quinetia, Millotia, Rutidosis, Siloxerus,

Toxanthes, Hyalosperma, Podotheca etc.) and Stylidiaceae

(Stylidium, Levenhookia).

Deeper soils enable survivorship of woody perennials,

of which the largest on Western Australian outcrops

include eucalypts (Eucalyptus and  Corymbia, Myrtaceae),

wattles (Acacia, Mimosaceae), she-oaks (Allocasuarina,

Casuarinaceae), and rock figs (Ficus, Moraceae). A

noteworthy feature of the woody perennials is the high

proportion of bird-pollinated species (Hopper 1981; Fig

3) in families such as Myrtaceae (e.g. Eucalyptus,



Calothamnus, Melaeuca, Verticordia), Proteaceae (Grevillea,

Hakea, Banksia), Myoporaceae (Eremophila), Papilionaceae

(Kennedya, Crotolaria), Viscaceae (Amyema, Lysiana) and

Sterculiaceae (Brachychiton). Also, south-western outcrops

have an unusually high number of woody perennials that

are obligate seeders - plants that are killed by fire and

recruit only from seed. For example, 77% of the

perennials in a granite community at Chiddarcooping

Nature Reserve north-east of Merredin were obligate

seeders (Hopper et al., unpubl.).

Gnammas on Western Australian outcrops have a

unique flora comprising annual species of quillworts

(Isoetes, Isoetaceae), mudmats (Glossostigma,

Scrophulariaceae), millfoils (Myriophyllum, Haloragaceae;

Fig 6) and others, including the introduced South African

annual Crassula natans (Crassulaceae).

  1   2   3   4   5   6


Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur ©azkurs.org 2016
rəhbərliyinə müraciət

    Ana səhifə