Cunninghamia : A Journal of Plant Ecology for Eastern Australia, Volume 8, Issue 1 (2003)
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The flower structure of Pollia crispata (R.Br.) Benth. allows access by a taxonomically diverse assemblage of pollinating insects. Patterns of flower anthesis, and removal of pollen, suggest adaptation to diurnal flower visitors. Flowers are pollinated by insects, but Pollia crispata can produce viable seeds independent of insect pollination, and plants can reproduce and spread vegetatively subsequent to founding events. The composition of the pollinator fauna is dominated by syrphid flies, halictid bees and the apid bee Trigona carbonaria, but most insect visitors observed have broader recorded flower host ranges. In general, the insects recorded from Pollia crispata flowers are restricted to the understorey and ground strata of regional subtropical rainforests.
The vegetation of Peery Lake area, Paroo-Darling National Park (32°18’–32°40’S, 142°10’–142°25’E) in north western New South Wales was assessed using intensive quadrat sampling and mapped using extensive ground truthing and interpretation of aerial photograph and Landsat Thematic Mapper satellite images. 378 species of vascular plants were recorded from this survey from 66 families. Species recorded from previous studies but not noted in the present study have been added to give a total of 424 vascular plant species for the Park including 55 (13%) exotic species. Twenty vegetation communities were identified and mapped, the most widespread being Acacia aneura tall shrubland/tall open-shrubland, Eremophila/Dodonaea/Acacia open shrubland and Maireana pyramidata low open shrubland. One hundred and fifty years of pastoral use has impacted on many of these communities.
Twenty-two vascular plant communities occurring on, and adjacent to the Cumberland Plain and Hornsby Plateau, are defined using a multi-variate analysis of quantitative field survey data. Communities are described using structural features, habitat characteristics and diagnostic species. Diagnostic species are identified using a statistical fidelity measure. The pre–European spatial distribution of communities is estimated using a decision tree approach to derive relationships between community distribution and geological, climatic and topographical variables. Contemporary vegetation cover is estimated from 1:16 000 scale aerial photography (1997/98) and sorted into six categories based on cover of Eucalyptus species. These categories are only approximately related to vegetation condition: high Eucalyptus cover classes are most likely to contain high levels of floristic diversity, but areas with scattered cover or no cover at all may have either high or low diversity.
Map accuracy is assessed using independent field samples and is primarily limited by the accuracy of 1:100 000 geological maps. Patterns in overstorey composition were mapped at 1:16 000 scale but were less useful in delineating community boundaries than was hoped because few species are confined to a single community. The extent to which observer bias may influence estimates of the present extent of remnant vegetation is investigated by comparing the interpretations of two observers for a subset of the study area.
The community classification is interpreted in light of previous publications and the Endangered Ecological Communities listed under the NSW Threatened Species Conservation (TSC) Act (1995). Four communities listed under the TSC Act (1995) are represented by more than one unit in the new classification: Cumberland Plains Woodland (represented by Shale Plains Woodland, Shale Hills Woodland); Sydney Coastal River Flat Forest (Riparian Woodland, Riparian Forest, Alluvial Woodland); Shale/Sandstone Transition Forest (Shale/Sandstone Transition Forest low sandstone influence, high sandstone influence); and Sydney Turpentine-Ironbark Forest (Turpentine-Ironbark Forest, Turpentine-Ironbark Margin Forest). A further seven listed communities are described in this paper (Cooks River/Castlereagh Ironbark Forest, Shale/ Gravel Transition Forest, Castlereagh Swamp Woodland, Agnes Banks Woodland, Western Sydney Dry Rainforest, Moist Shale Woodland, and Blue Gum High Forest).
As a result of clearing, native vegetation cover on the Cumberland Plain has been reduced to only 13.1% (+ 1.7) of the pre- European extent. Despite high levels of fragmentation, the presence of exotic species and a history of extensive grazing, high numbers of native species were recorded in remnants of all sizes. A large proportion of species was recorded once only (22%), while nearly half of all species were recorded 5 times or less. This suggests that there is a high likelihood that further clearing will lead to a loss of floristic diversity. Two exotic species (Olea europea subsp. africana and Myrsiphyllum asparagoides) are identified as a major threat to the conservation of native flora due to their widespread distribution and ability to out-compete native species. Control of these species should be a high priority in conservation management.
Effect of pasture type on regeneration of eucalypts in the woodland zone of south-eastern Australia
(2003)
Although eucalypt regeneration is an uncommon event in the highly modified rural environments of southeastern Australia, it still occurs on some roadsides and even in grazed paddocks. A number of observations suggest that under grazing, regeneration is more likely to occur in native pastures than in those dominated by exotics. The apparently adverse effect of exotic pastures was investigated by monitoring growth and survival of eucalypt seedlings — either planted or from sown seed — on the Central Western Slopes of NSW. Survival of seedlings arising from direct drilled seed of Eucalyptus albens and/or Eucalyptus melliodora in exotic pastures was generally low. However, survival was higher for seedlings emerging in spring (but not at other times) in an annual exotic pasture than for those emerging in spring in a perennial exotic (Phalaris) pasture. Experimental plantings of Eucalyptus melliodora seedlings adjacent to annual exotics v. a perennial native grass plant showed no significant difference in seedling growth between the two microsites though there was a trend towards enhanced survival near the perennial grass.
Within the context of other work on the regeneration of woodland eucalypts, these results suggest that: (1) competition from annual exotics is a major limitation to the survival of eucalypt seedlings in their first year; (2) competition from a perennial exotic establishing at the same time as the eucalypt seedlings is particularly severe during the eucalypt's second year. In the absence of a major disturbance such as scalping of topsoil, regeneration of eucalypts in exotic pastures is unlikely.
Fresh seeds of the endangered Hakea dohertyi Haegi (Proteaceae) germinated at 15°C (with 12 hour light) within 14 days. At higher temperatures (20°, 25°C) seeds were slower to germinate. After 28 days only 5% of seeds germinated at 30°C, but when moved to 15°C, close to 100% of seeds germinated within 14 days. Having established optimum germination conditions, the effects of ex situ storage conditions and duration were examined. Storage at low moisture content appeared to have little effect on the germinability of Hakea dohertyi seeds and this species can be considered orthodox in that respect. Seeds stored at 4.5 or 9% moisture content, 5 or -20°C and tested after 1 and 7 years of storage achieved close to 100% germination. Issues relating to the in situ and ex situ conservation of Hakea dohertyi are discussed.
The vegetation of Ironbark Nature Reserve (1603 ha) and Bornhardtia Voluntary Conservation Agreement (704 ha), 75 km north west of Armidale, 30 km north east of Barraba (30°19’S, 150°53’E) in the Barraba Shire, in the Northern Tablelands Bioregion NSW, is described. Eleven communities are defined based on flexible UPGMA analysis of coverabundance scores of all vascular plant taxa. These communities are mapped based on ground truthing, air photo interpretation and substrate. All communities are simple in structure being primarily of woodlands or shrublands.
Communities described are: (1) Eucalyptus macrorhyncha (Red Stringybark) – Eucalyptus blakelyi (Red Gum) Woodlands, (2) Eucalyptus caleyi (Caley’s Ironbark) – Eucalyptus andrewsii (Western New England Blackbutt) Woodlands, (3) Eucalyptus prava (Orange Gum) – Eucalyptus andrewsii (Western New England Blackbutt) Woodlands, (4) Eucalyptus dealbata (Tumbledown Gum) – Eucalyptus caleyi (Caley’s Ironbark) Woodlands, (5) Eucalyptus prava (Orange Gum) – Eucalyptus blakelyi (Red Gum) Woodlands, (6) Eucalyptus quinniorum (Quinn’s Gum) – Eucalyptus prava (Orange Gum) Forests, (7) Angophora floribunda (Rough-barked Apple) – Eucalyptus blakelyi (Red Gum) Woodlands, (8) Casuarina cunninghamiana (River Oak) – Eucalyptus blakelyi (Red Gum) – Angophora floribunda (Apple) Forests, (9) Calytrix tetragona (Fringe Myrtle) – Ozothamnus obcordatus (Daisy Bush) Open Shrublands, (10) Homoranthus bornhardtiensis Open Shrublands and (11) Leptospermum polygalifolium (Tea-tree) Wetland.
All communities described here are inadequately represented in the conservation network with one (White-Box – Yellow-Box – Blakely's Red Gum Woodland) listed as endangered on the NSW TSC Act. Both conservation areas and neighbouring parcels of land contain extensive areas of little disturbed high quality "old growth". 38 species are of conservation significance of which one is listed as Vulnerable and one Endangered on the NSW TSC Act. The broader remnant is under increasing pressure for clearing for grazing production and the combined area of both reserves is considered to be inadequate to protect the significant features of the local region.
During the past two centuries massive land use changes in Australia have altered fire regimes, changed hydrology, increased soil salinity and nutrient levels, and altered abundance and distributions of animals with which native plants interact. Such changes to plant habitats may induce changes in range of indigenous plant species. We need to consider very carefully how to treat native species that naturalise outside their previous ranges. The spread of Pittosporum undulatum in the Sydney region provides a case study for considering approaches to this question.
Tetratheca juncea Smith (family Tremandraceae) is a terrestrial herbaceous plant now mainly found in the Lake Macquarie area of coastal NSW and listed as Vulnerable under Schedule 2 of the NSW Threatened Species Conservation Act 1995. This study carried out from July 2001 to June 2002 records the observation and identification of two species of native bee buzz-pollinating its flowers and describes a direct relationship between the first appearance of a pollinator and the commencement of seed set. Findings from this study with respect to the pollination ecology of Tetratheca juncea are:
• There is a strong flowering period from September to January, though a number of flowers can be found on some plants across the geographic range of the plant in all months of the year;
• Two species of native bee Lasioglossum convexum and Exoneura sp, were confirmed collecting pollen from the flowers by way of buzz pollination;
• Fruiting only occurred in coincidence with flower pollination by these bees;
• Flowering, seed set and seed release was a concurrent process while ever the bees were active;
• The bees are polylectic and the sexual reproductive process in Tetratheca juncea appears to be pollinator-limited.
Sand mining has been responsible for much of the degradation of the indigenous flora of sand dunes in New South Wales, to the extent that authentic foredune plant communities are now uncommon in much of NSW and southern Queensland. Dune heaths are very susceptible to invasion and infestation by the weed, bitou bush (Chrysanthemoides monilifera subsp. rotunda). This paper compares the floristic composition of dunes in 1941 (before sand mining) and 1997 & 1999 (after sand mining and invasion by bitou bush), at Bennetts Beach, Hawks Nest, on the lower north coast of NSW. The 1941 data provide a unique example of authentic foredune vegetation and is the first quantitative analysis of coastal dune vegetation in NSW. In 1941, 25 native species were recorded in the 0.5 ha site. Nine of these were considered to be characteristic of dune communities and eight of these nine were also recorded in a 1939 survey at Myall Lakes. Four other studies in the intervening 60 years contain species lists of dune vegetation in this general area (1986, 1995, 1997 and 1999). Of a total of 17 species considered to be strongly associated with dune habitats, five were reported in all of six surveys and 15 occurred in one or more of the more recent surveys (1986 and later); the two exceptions were Austrofestuca littoralis and Senecio spathulatus. Only one introduced weed was recorded in 1941 (Cakile edentula) and the only weeds recorded in 1939 were Cakile edentula and Oxalis corniculata, both cosmopolitan species. Thirteen additional weed species, the most abundant being Chrysanthemoides monilifera, were recorded in the more recent surveys. A set of 14 native species that are more typical of heath and eucalypt forest and woodland communities than of the dunes were absent in the 1939 and 1941 surveys but occurred in one or more of the post-mining surveys of 1995, 1997 and 1999. Detailed plant distribution and abundance were assessed in the same part of Bennetts Beach in 1941, 1997 and 1999. All show some patterns of zonation across the sand dune. However, clear phytosociological patterns of the dominant species that were obvious in 1941 were lacking in the 1997 and 1999 analyses. These contrasts suggest that post-mining revegetation has resulted in weed invasion, addition of native species from other communities, and a disruption of the distributions of typical dune species of species across the sand dunes that has been only partially recovered since sand mining and invasion of bitou bush.
Japan and south eastern Australia have a large exotic flora in common, in spite of contrasting histories, physiographies and land-use patterns. There are some 187 common invading species and at least 71 of these are widespread in both locations. Some 15 widespread exotic invaders in Japan have not been recorded in Australia and a number of native Japanese plants that could be introduced as ornamentals and escape cultivation are noted. The incursion of most exotic species to Japan has been historically recent. The lack of quarantine for plants (apart from parasitic plants and plants infected with disease) coupled with large importations of wheat and soybeans from north America and contaminated grain and fodder for farm animals has led to an exponential rate of plant invasion in Japan. The apparent lack of impact of woody invading species in Japanese forests and forests margins may be due simply to the relatively short time invading species (some with long juvenile periods) have been naturalised.