Underground » Environment - Subsidence and Mine Water
Tetratheca juncea Smith (Tremandraceae) is a vulnerable species listed under the NSW Threatened Species Conservation Act (Schedule 2, TSC Act 1995), and in the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. The species occurs on the central coast of New South Wales in heath and sclerophyll vegetation communities, and is often found on land leased for coal?mining activities.
The long-term prospects for the conservation of T. juncea and planning and development in the region are impaired by a lack of ecological knowledge about the species. This makes effective sustainable management of the T juncea populations difficult and uncertain, while precautionary management practices may be limiting potential development in the region unnecessarily.
Prior to the project commencing, preliminary observations suggested that T juncea was not setting seed, and there was concern that nil or low levels of seed production could result in declining populations. Coal mining companies and other landholders required more information to assist with the management of their lands in a way that was not threatening the survival of this vulnerable species. The Australian Coal Association Research Program (ACARP) and three participating coal mines, (Oceanic Coal Limited, Powercoal Pty Ltd and Coal Operations Australia Limited) sponsored a research program to determine whether and why seed production and recruitment of in T. Juncea is poor. In?kind support also was provided by NSW National Parks & Wildlife, BHP Coal Pty Ltd and two local Councils (Lake Macquarie and Wyong). Researchers at the Universities of Queensland, New England and Newcastle established a collaborative research program to investigate the reproductive and establishment biology of T juncea. Breeding systems, seed biology and mycorrhizal associations were investigated to determine which factors, if any, were limiting the reproductive output of the species.
The breeding system was found to be self compatible, although automatic self production of seed was an uncommon event. Outcross pollination was identified as the preferred breeding system, meaning that a pollinator is required for high yields of seed. During the study it was determined that the floral structure of T. juncea dictates that the system must be worked by a special class of native bees capable of buzz pollination. Native bees were not detected on flowers despite over 100 hours of observation. Seed production occurred in all 25 study sites but it is not known whether these were automatically produced or effected by a pollinator.
Viability testing of the seeds found that at least a third of the seeds were viable. Seed germination and dormancy investigations found that the seeds germinated following exposure to smoke or scarification of the seed coat. Untreated seeds did not germinate during the preliminary study, although the proportion of viable seeds were still present at the conclusion of the experiment. The seeds are produced in late spring and mature from December to February. However, the longevity of the soil seed bank seems to be short, as no seeds germinated from soil collected in September, irrespective of the soil being treated by smoke, heat and fire. The research has revealed that the species tends to form arbuscular mycorrhizal associations, and typically grows in low nutrient soils of a moderate to strong acidic nature. The appropriate mycorrhizal fungi may therefore be need to be present in the soil for the species to survive.
The three key ramifications from this study of T. juncea's ecology is that: (1) a pollinator is required for high seed yields; (2) fire is required for germination; and (3) a mycorrhizal partner is required for plant longevity. These findings indicate that translocations of the species cannot be recommended as there is a lack of knowledge about many factors that are critical for the persistence of the species. Translocations will not be successful if any of a range factors are not present. The conservation implications of this are that habitats are the key management unit and not just the species. A fire management plan will need to cater for all obligate ecological requirements.
The findings and experience of the researchers in this study have been used to develop a flowchart for environmental officers on the biological procedures that need to be considered when a threatened flora species is found on a site. The results from this study are also considered to be a relevant guide for managing populations of other species of Tetratheca, many of which are also rare or threatened.