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Little research has been undertaken on the conservation value of natural and derived native grasslands within the Hunter Valley region of New South Wales. In part, this is due to a lack of rigorous survey and classification of grassland habitats, but also because of the ease with which past studies have deferred to the concept of 'derived grasslands' to describe grassland areas. Given the extent of European occupation of the Hunter Valley over the past 200 years, all grasslands have been impacted upon in one way or another by agricultural activities, and hence all can be considered 'derived'. For one site in the upper Hunter Valley, classification and mapping of grasslands was undertaken using data collected over three Spring seasons from 2009 to 2011, encompassing over 1,000 ha of derived grassland habitat within a wider mosaic of forest and woodland. Numerical classification of 168 sampling plots (each 0.01ha in size) delineated 17 floristic groups (16 communities, one with two sub-communities). Based on the composition of component taxa, 8 of these can be considered primarily of exotic origin, while the remaining 9 are predominantly native. All grasslands have been shaped by past agricultural activities, and all have been collectively referred to previously as derived grasslands. Plant species of significance within the grasslands include the threatened terrestrial orchids Diuris tricolor and Prasophyllum petilum, the threatened forbs Swainsona recta and Thesium australe, and the rare but localised grass Bothriochloa biloba. An additional 19 taxa occur at or extend known distributional limits. The lack of an appropriate existing framework with which to assign conservation value to grasslands in the Hunter complicates any assessment of significance. However, considerable diversity is present within grasslands collectively referred to as 'derived', and effort should be applied in future studies to elucidate community patterns more satisfactorily. Within State and Federal threatened species legislation, there are 30 grassland or derived grassland communities, but only one of these (White Box - Yellow Box – Blakely's Red Gum Grassy Woodland and Derived Native Grassland: EPBC Act) potentially include the grasslands under study here.
A review has been undertaken of herbarium records, point location and full floristic data to assess the distribution, habitat and conservation status of Macrozamia flexuosa (Zamiaceae), a rare cycad endemic to the Hunter Region of New South Wales. Spatial analysis of all records (n=588) showed that the species is most prevalent on Permian-aged sediments but also occurs on older Carboniferous sediments and younger Triassic Narrabeen and Quaternary substrates. Point records intersect with a wide range of annual average rainfall bands (<700 to 1400 mm/yr), suggesting either that the species is tolerant of a variety of soil moisture gradients, or that current distribution may be representative of a differing climatic environment. Interpolation of database records (n=397) across 175,000 hectares of high-resolution vegetation mapping showed Macrozamia flexuosa to most frequently occur within the Lower Hunter Spotted Gum-Ironbark Forest (41%), followed by Kurri Sands Swamp Woodland (16%), Coastal Foothills Spotted Gum-Ironbark Forest (15%) and Coastal Plains Smooth-barked Apple Woodland (13%). Numerical analysis of full floristic plot data (n=86) largely supported these results, with the addition of Hunter Valley Moist Forest to these four regional communities. A revised assessment of the conservation significance of Macrozamia flexuosa suggests that the existing conservation risk code of 2K be amended to 3RCa (distributional range >100km; rare but not immediately threatened; adequately conserved in at least 14 conservation reserves). An extent of occurrence of 6,319 km2 and an area of occupancy of 696 km2 have been determined for the species, and an estimated population size of between 1,740,000 and 43,500,000 individuals has been calculated. Under IUCN threat criteria, a code of NT (Near Threatened) is here considered appropriate for Macrozamia flexuosa, recognising uncertainties applicable to the assessment of Criteria A and B. It is noted, however, that Macrozamia flexuosa may currently be in slow decline due to as yet unknown limitations in flowering, pollination and/or dispersal mechanisms over a long period of time (many decades), with the longevity of individual specimens confounding any observable trends. A lack of demographic data relevant to these life traits limits comprehensive assessment, and further research to address these data gaps is recommended.
A rare flowering event in a stand of Acacia pendula (Weeping Myall) (family Fabaceae, Mimosoideae) from the Hunter Valley of New South Wales is documented. This species flowers poorly in the region and (with the exception of horticultural specimens) has not been observed to fruit and develop viable seed for over a decade. One stand of this threatened Hunter Valley population of Acacia pendula was monitored over a seven month period (January to July 2018) to investigate this poor reproductive output. Despite copious bud production in January and February, the extent and condition of these, and all subsequent flowers rapidly declined, and none progressed to fruit.
Primary reasons for reproductive failure were postulated to be a combination of mass desiccation of capitula following extended dry conditions, infestation by native flower- and phyllode-galling midges and thrips (Asphondylia sp., Dasineura glomerata, Kladothrips rugosus), fungal galls (Uromycladium sp.), caterpillars (Ochrogaster lunifer), and mistletoe (Amyema quandang). Collectively, these stressors appear to be eliminating seed production from the study
population; survival is maintained only by the copious root-suckering observed around most plants, particularly after the pressure from stock grazing (cattle, sheep) has been removed. The age of trees studied, based on measures of girth and comparison with growth rates reported for other semi-arid Acacia, was inferred to be between 50 and 150 years. The level of Amyema quandang (mistletoe) infestation on Acacia trees was independent of tree size, and there was no evidence to suggest that mistletoe density alone influenced flowering progress.
Consequences of these observations on future management of Acacia pendula in the Hunter Valley are briefly discussed.