Cunninghamia : A Journal of Plant Ecology for Eastern Australia, Volume 11, Issue 2 (2009)
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A vegetation survey was undertaken within Columbey National Park (32° 35’S, 151° 44’E) near Clarence Town in the lower Hunter Valley of New South Wales. Multivariate cluster analysis and non-metric multi-dimensional scaling were carried out on plot-based data to classify the vegetation into twelve native communities (one plantation), and each compared with a larger regional dataset. A vegetation map was also prepared, based heavily on extensive ground-data supplemented with aerial photographic interpretation. Although small in size, this reserve conserves good examples of the endangered Lower Hunter Spotted Gum-Ironbark Forest (475 ha) and River-Flat Eucalypt Forest on Coastal Floodplains (124 ha), together with a small parcel of Hunter Lowlands Redgum Forest (3.7 ha). Collectively, these Endangered Ecological Communities occupy approximately 70% of the 870 ha reserve. Small populations of the threatened and previously unreserved orchid, Pterostylis chaetophora are present in the reserve, together with the Endangered Corybas dowlingii and the regionally significant cycad, Macrozamia flexuosa. An historical record of Eucalyptus glaucina could not be substantiated during the current survey, and may have been recorded in error. A total of 349 vascular plant taxa were recorded, including 25 weed species. The vegetation present within Columbey National Park bears strong resemblance to that in the Cessnock region of the Hunter Valley (Bell 2004; DECC 2008), a feature attributed to similar rainfall and soil types. Vegetation communities common between the two areas include Lower Hunter Spotted Gum – Ironbark Forest, Red Ironbark Scrub-Forest, Paperbark Soak Forest, Floodplain Redgum-Box Forest and Gully Rainforest. Unlike the Cessnock area, however, Columbey has not been subject to illegal rubbish dumping to any great degree.
The resprouting response of plant species to fire is a key life history trait that has profound effects on post-fire population dynamics and community composition. This study documents the post-fire response (resprouting and maturation times) of woody species in six contrasting formations in the New England Tableland Bioregion of eastern Australia. Rainforest had the highest proportion of resprouting woody taxa and rocky outcrops had the lowest. Surprisingly, no significant difference in the median maturation length was found among habitats, but the communities varied in the range of maturation times. Within these communities, seedlings of species killed by fire, mature faster than seedlings of species that resprout. The slowest maturing species were those that have canopy held seed banks and were killed by fire, and these were used as indicator species to examine fire immaturity risk. Finally, we examine whether current fire management immaturity thresholds appear to be appropriate for these communities and find they need to be amended.
The population diversity of Doranthes excelsa Corrêa (Doryanthaceae) was measured from nine distinct geographic populations across eastern Australia, using random amplified polymorphic DNA (RAPD) markers. An UPGMA dendrogram of individuals was derived from squared Euclidian distances based on the Dice (1945) algorithm. Three clusters corresponding to populations at Somersby, Newfoundland and Kremnos Creek populations were found to be distinct from the remainder of the sampled individuals. A ΦST value of 0.443 indicated that a significant diversity between geographic populations existed; this appeared to be a product of geographical distance and isolation between some of the populations. (PCR = Polymerase Chain Reaction; RAPD = Random Amplified Polymorphic DNA) The results suggest that there is lesser gene flow between the‘northern’ populations (Kremnos Creek and Newfoundland) when compared to the ‘southern’ populations and that they have a significant level of genetic isolation. The two ‘northern’ populations should therefore be regarded as being of considerable value for conservation authorities and the commercial breeding sector and should be given priority for conservation. The plants there appear to exhibit a smaller phenotype but confirming this requires further quantification.
The New South Wales Seedbank (at Mount Annan Botanic Garden) stores seeds of both common and threatened species for conservation, research and restoration or revegetation projects. The value of the collections depends on our ability to germinate seeds once they have been retrieved from storage. The collection includes 129 collections representing 93 taxa in the family Rutaceae, but seed viability in Rutaceae is variable, germination cues are poorly-understood and problems are likely to arise in trying to grow plants from seed. In this study we quantified seed fill and/or viability and germination for 112 species in the Rutaceae family. For many of the species, this is the first time that these seed characteristics have been recorded. We found that seed fill (0–100%) and seed viability (0–97%), were highly variable, with 80% of collections having low viability (<75%). There was also a trend for threatened species to have lower seed fill than common species, while viability and germination were similar. This review reaffirms the need for further study of seed characteristics in Rutaceae.
For the successful long-term management of biodiversity in conservation reserves, science and management need to work together. In 2008 we resampled two transects in a small urban reserve in northern Sydney under longterm conservation management. The transects were established in 1976 and recorded again in 1987 and 1998 (by other workers). We looked at plant species changes by growthforms, family (Fabaceae) and conservation-significance. Over the 30-year period the structure of the understorey has changed markedly, and despite ongoing weeding programs, the frequency of species identified as significant for conservation has continued to decrease. Despite periodic recommendations for ecological burning since 1987, supported by the monitoring data, this has not been attempted. We discuss the lessons for ecology, monitoring and management evident in this long-term monitoring study.
Hexham Swamp (32° 52’ S, 151° 41’ E), the largest wetland on the floodplain of the lower Hunter River, New South Wales (ca. 2500 ha in area), historically supported extensive areas of estuarine wetlands. Substantial vegetation changes have occurred following the 1971 construction of floodgates on the main creek draining the swamp. Previous areas of mangroves have been reduced from180 ha to 11 ha, and saltmarsh from 681 ha to 58 ha. Phragmites australis reedswamp has expanded from 170 ha to 1005 ha. Much of the mangrove loss (ca. 130 ha) was a result of clearing, and the remainder has gradually died off. The factors contributing to the dieback are likely to be a combination of drying of the soil, and, at times, waterlogging. Field sampling indicates that a reduction in soil salinity has been an important factor initiating successional change from saltmarsh to Phragmites reedswamp. The data also suggest that increased waterlogging has been an important factor in vegetation change. The initial effect of the floodgates was expected to have been a drying of the swamp, followed over time by an increasing wetness(floodgates and associated drainage are generally intended to reduce the flooding of wetlands). The apparently paradoxical result is likely to have resulted from occlusion of drainage lines by sediment and reeds.
A preliminary analysis has recorded the cushion lifeform in 60 taxa from lowland southern Australia (i.e. latitudes south of 26° S) encompassing six morphological forms from open, non-peat-accumulating species (58 taxa) to hard, dense cushions more typical of alpine and subalpine areas (2 taxa). Only two species appear to be obligate cushions. All but six cushion-forming species are endemic to southern Western Australia. Most species occur in the Transitional Rainfall Zone rather than the High Rainfall Zone or the more arid interior, with only one species being endemic to the arid zone. In Western Australia cushion-forming species occur on exposed coasts, granites, edges of salt lakes and sandplains; almost half of the species also commonly occur across a number of other habitat types. The few plant communities dominated by cushion plants are generally restricted to small areas of a specific habitat type such as Borya herblands on shallow soils around outcropping granites. Lowland cushion species in Western Australia do not appear to be restricted to the most stressful habitats.
We establish a methodology and present baseline data for a long-term grassy woodland restoration study that commenced in 2007 in two nature reserves (Mulligans Flat, Goorooyarroo (35° 9–13’ S; 149° 9–12’ E)) totalling 1386 ha on the northern boundary of Canberra, in the Australian Capital Territory in south eastern Australia. The experimental infrastructure comprises 96 × 1 ha sites established in Eucalyptus blakelyi / Eucalyptus melliodora dominated woodland. These are being subjected to varying kangaroo grazing pressure and augmentation with logs, while burning treatments are planned. One reserve (Mulligans Flat) has been fenced for feral predator control and contains half the sites, forming a companion experiment to Goorooyarroo. Our baseline floristic study comprised estimates, at the site level, of ground layer biomass, species biomass, ground cover types and soil (0–10 cm) properties. From these data we conclude that the groundlayer vegetation is dominated by Joycea pallida, Austrodanthonia spp., Themeda australis and Aristida ramosa. These grasses varied in abundance according to differences in soil pH, phosphorus and to a lesser extent nitrates. Forb frequencies were highly sensitive to nitrate levels with annual exotic forbs dominating at high nitrate sites. More generally, soil nutrient levels and exotic species in some sites indicated areas of previous pasture improvement activities. Biomass estimates indicated extremely high grazing pressure, sufficient to negatively affect the habitat quality for ground-dependent fauna and some soil processes. These data will provide an important basis for examining rates of ecosystem recovery under different restoration strategies.
Phormium tenax (New Zealand flax) was one of the first plants found on Norfolk Island by Cook’s expedition in 1774, and its potential value to the British navy was considered so significant that it appears to be one of the main reasons Norfolk Island (lat 29° 02’S; long 167° 57’E), about 780 km north of New Zealand, was colonised in March 1788. Phormium tenax has always been considered native to Norfolk Island, despite the realisation that Polynesian settlers had been there before the British. The absence of any records of it on nearby Phillip Island until 1967 however, contrasts with its reported abundance on Norfolk Island in the 1700s. If Phormium had been present on Norfolk earlier than about 15,000 years ago it would be expected to have colonised Phillip Island, particularly in habitats similar to those it occupied on Norfolk, because the two islands (now 6 km apart) were then part of a single, much larger island. The absence of Phormium pollen from fossilised pollen recently collected on Norfolk Island suggested to researchers that flax had been introduced to Norfolk Island by Polynesian settlers and should therefore not be regarded as native or indigenous. The lack of any recorded distribution of Phormium on Phillip Island before 1967 and its distribution there in 1978 provide evidence reinforcing this conclusion.