Cunninghamia : A Journal of Plant Ecology for Eastern Australia, Volume 21 (2021)
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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.
The small mallee Eucalyptus cunninghamii Sweet (family Myrtaceae) is restricted to the upper Blue Mountains of New South Wales with an outlier at Wanganderry Walls, 64 km south of Katoomba. It occurs in isolated clusters confined to windswept cliffs facing south and west, with average annual rainfall of at least 1300 mm, slopes of at least 200, and a narrow altitudinal range of 790–940 m. We investigated 38 occurrences, 16 in the Grose Valley north of Katoomba (including the five largest), and 21 in the Jamison Valley, south of Katoomba. We estimated there to be approximately 1560 trees, 75% in the Grose Valley and 25% in the Jamison Valley. Trees in the Grose are significantly shorter (0.8 m high), with more, but thinner trunks than those in the Jamison Valley (2.3 m high). There are about 12 short trees at the Wanganderry outlier. The Extent of Occurrence (EOO) (excluding the Wanganderry outlier) is about 200 km2. The Area of Occupation (AOO) for all 38 occurrences is 9420 m2, or less than one hectare, though despite its limited occurrence Eucalyptus cunninghamii could not be considered Vulnerable against IUCN Criteria at present. Leaf morphology measurements showed that Intramarginal Vein Ratio, Secondary Vein Angle and Oil Gland Density were approximately constant across the upper Blue Mountains. Fire history, bud development and flowering times, and pollination vectors were recorded. Leaf longevity is about 3 years. Flower buds emerge in spring (November) to early summer (December) and develop over a period of 18 months before flowering in late autumn (May). Fruits mature in spring. The time taken to reach flowering from germination and for regrowth after fire is about 5 years, but nearly 7 years to fruit maturity.
The 2019–20 bushfires in eastern New South Wales were intensive and extensive, with 62% of the native vegetation of the south coast region burnt in a series of large fires. Many of the listed threatened plant species in the region were significantly impacted, including most of the regionally endemic species. This study investigated the responses of two locally endemic mallee species, Eucalyptus langleyi and Eucalyptus sturgissiana (family Myrtaceae) to the fire in the northern Shoalhaven region. A six-month study post-fire found that both species recovered well by vegetative means but recruitment from seedling was apparently absent. A loss 1 – 3% of plants due to fire was recorded from monitored populations. The importance of such a loss to the long-term viability of these species is unknown, especially given the likelihood of more frequent and intense fires in the future.
Survey of rare mallee Eucalyptus dissita in Gibraltar Range National Park, NSW Northern Tablelands
(2021)
Remote sensing of pattern, texture and colour using high resolution ADS40 aerial photograph imagery identified 30 known and potential polygons of the listed Vulnerable mallee eucalypt Eucalyptus dissita (Myrtaceae) in Gibraltar Range National Park in the NSW New England Tablelands Bioregion. Targeted field surveys confirmed Eucalyptus dissita in 14 mapped polygons, covering a mapped extent of 7.6 hectares, with an estimated population of 2400–4600 mallee/ tree stems, including two new populations in remote locations along tributaries of Dandahra Creek and proposed as newly named management sites (Dragonfly Swamp and Valley of the Mallees) under the NSW Saving our Species Program. Populations of Eucalyptus dissita were burnt in a November 2014 hazard reduction burn, and again in the extensive December 2019 wildfire. After the 2014 fire, basal resprouting was observed and minimal mortality of pre-fire plants recorded, but no seedling recruitment observed. In May 2019, 4.5 years post-fire, five of 20 tagged individuals at Surveyors Creek were forming floral buds but are likely to require another year to seed production. All of these individuals were burnt again in the December 2019 fire. Full floristic data analysis using hierarchical agglomerative clustering revealed that Eucalyptus dissita forms a quantitatively distinct vegetation assemblage that groups with the vegetation of swamps and rocky riparian areas, adjoining granite hills.