Floristic Patterns and Disturbance History in Karri Forest, South-Western Australia 1. Environment and Species Richness

We examined the influence of disturbance history on interactions between floristic composition and environmental factors in a single community type in karri forest (site type 10, after Inions et al., 1990) in south-western Australia. The relationship of six disturbance and site-based environmental variables, and three plant species richness variables (native, introduced and total vascular plant species) were compared using numerical taxonomic, regression and correlation approaches. Disturbance and site variables were highly intercorrelated, limiting the opportunity to directly attribute causes to observed floristic patterns. Nevertheless, management practices in karri forest are based on interrelated disturbances (e.g. high intensity slash burns were used to initiate regeneration for timber production), limiting the necessity to separate effects. Community types in karri forest have both, low alpha diversity (quadrat-based species richness) and species richness of the community in comparison with neighboring vegetation types. For community type 10, alpha diversity was negatively correlated with time-since-fire (P < 0.002) and time-since-regeneration (P < 0.004), but was lowest at intermediate times since disturbance (11-20 years). Although ordination revealed no discernable pattern of sites based on floristic composition, four plant assemblages defined a priori according to time-since-disturbance were significantly different from one another (P < 0.01 by ANOSIM). Time-since-fire (and other disturbance) influenced floristic composition more than the number of recent past fires in contrast to the more species-rich, but drier and nutrient-poor neighboring jarrah forest communities where the number of past fires is more influential. Under the current climatic regime, karri forest communities are likely to undergo less long-term change in floristic patterns following disturbance than neighboring vegetation types. This is primarily because of the greater intervals between disturbance events, the few transformer weeds in the area and the rapid recovery of native plant cover following disturbance. This study has demonstrated the resilience of karri forest to various discrete disturbances currently associated with these environments, although more profound changes are likely following continuing disturbance intervention such as clearing and grazing

Modelling the impacts of wildfire on the viability of metapopulations of the endangered Australian species of arboreal marsupial, Leadbeater's Possum

Catastrophic events such as intensive wildfires have a major effect on the dynamics of some wildlife populations. In this investigation, the computer package ALEX (Analysis of the Likelihood of EXtinction), was used to simulate the impacts of wildfires on the persistence of metapopulations of the endangered species Leadbeater's possum (Gymnobelideus leadbeateri) which is restricted to the montane ash forests of the Central Highlands of Victoria. A range of scenarios was examined. First, the response of G. leadbeateri to tires in hypothetical patches of old growth forest of varying size was modelled. Metapopulation dynamics were then modelled in four existing forest management areas: the O'Shannassy Water Catchment and the Steavenson, Ada and Murrindindi Forest Blocks using GIS-derived forest inventory data on complex spatial arrangements of potentially suitable old growth habitat patches. The impacts of different fire frequencies and the proportion of forest area that was burnt in the Steavenson Forest Block and the O'Shannassy Water Catchment were examined. Finally, the combined impacts of both wildfires and post-fire salvage logging operations on the persistence of populations of G. leadbeateri were assessed. Our analyses indicated that, even in the absence of wildfires, populations of G. leadbeateri are very susceptible to extinction within single isolated habitat patches of 20 ha or less. The probability of persistence approached 100% in patches of 250 ha. The incorporation of the effects of wildfire was predicted to have a major negative impact on isolated populations of G. leadbeateri. In these cases, the probability of population extinction remained above 60%, even when a single patch of 1200 ha of old growth forest was modelled. In the absence of wildfires, there was a low probability of extinction of G. leadbeateri in the O'Shannassy Water Catchment where very large patches of old growth forest presently exist. The risk of extinction of the species was significantly higher in the Murrindindi and Ada Forest Blocks where there are lower total areas of, and significantly smaller, suitable habitat patches. Wildfires resulted in an increase in the predicted probability of metapopulation extinction in the four areas that were targeted for study. An investigation of the Steavenson Forest Block and the O'Shannassy Water Catchment revealed that the predicted values for the probability of extinction were sensitive to inter-relationships between the frequency of fires and the proportion of habitat patches that were burnt during a given fire event. The probability of extinction of G. leadbeateri was predicted to be lowest when there were frequent fires that burnt only relatively small areas of a given forest block. Conversely, the results of our analyses suggested that populations of the species are vulnerable to infrequent but intensive conflagrations that burnt a large proportion of the forest. The results of the suite of analyses completed in this study suggest hat four management strategies will be important for the long-term conservation of G. leadbeateri. (1) Attempts to suppress wildfires should be maintained as even the largest remaining areas of old growth forest may be susceptible to being burnt by repeated widespread wildfires that could result in localised and/or global extinction of the species. (2) Because the probability of population persistence is greatest in those areas that support more extensive stands of old growth forest, it will be important to grow relatively large patches of existing regrowth forest (over 50 ha) through to ecological maturity. This will be particularly important in some wood production forest blocks where there are only limited areas of old growth forest. (3) Patches that are set aside for the conservation of G. leadbeateri should be spatially separated to minimise the risk that all of the reserved areas in a region are destroyed in a single major fire event. (4) Salvage logging operations should be excluded from stands of old growth forest and reserved areas that are burnt in a wildfire. This is because such activities can have a major negative impact of the development of suitable habitat for G. leadbeateri

Development of tree hollows in pedunculate oak (Quercus robur)

Many invertebrates, birds and mammals are dependent on hollow trees. For landscape planning that aims at persistence of species inhabiting hollow trees it is crucial to understand the development of such trees. In this study we constructed an individual-based simulation model to predict diameter distribution and formation of hollows in oak tree populations. Based on tree-ring data from individual trees, we estimated the ages when hollow formation commences for pedunculate oak (Quercus robur) in southeast Sweden. At ages of about 200–300 years, 50 % of the trees had hollows. Among trees 400-year-old trees had hollows. Hollows formed at earlier ages in fast-growing trees than in slow-growing trees, which may be because hollows are formed when big branches shed, and branches are thicker on fast-growing trees in comparison to slow-growing trees of the same age. The simulation model was evaluated by predicting the frequency of presence of hollows in relation to tree size in seven oak stands in the study area. The evaluation suggested that future studies should focus on tree mortality at different conditions. Tree ring methods on individual trees are useful in studies on development of hollow trees as they allow analysis of the variability in time for hollow formation among trees

Effects of High Light on Photosynthesis and Artemisinin Production for the Medicinal Plant, Artemisia annua.

Artemisia annua L., produces a secondary compound (artemisinin) that is currently one of the most effective drugs for combating malaria. Limitations in commercial production of artemisinin include the relatively low yield of the compound within the plant (usually 0.01-0.50% of the total dry weight) and the fact that, as yet, we do not understand the metabolic pathways that produce the compound well enough for artificial synthesis. High-yielding strains of A. annua have been produced using traditional breeding methods that yield up to 1.0% artemisinin (per total dry weight). Unfortunately, these strains are proprietary and not available to all farmers seeking to grow A. annua for Artemisnin production. We are working to determine the effect of high light and other environmental stresses such as drought and UV-B exposure on the production of artemisinin and photosynthetic productivity of low-yielding strains of A. annua. When plants are grown in moderate light (about ¼ full sunlight) and then treated with high light (full sunlight) for up to six hours, they experience some light-induced loss of photosynthetic efficiency, increased formation of compounds indicating oxidative stress (e.g. singlet oxygen, superoxide and hydrogen peroxide radicals) and increased in artemisinin production. This occurs without an appreciable loss to photosynthetic carbon assimilation indicating that treatment with high light prior to harvest may be an effective way to increase artemisinin production, even in non-proprietary, low-yielding strains of A. annua

Den use, home range and territoriality of the koomal (Trichosurus vulpecula hypoleucus) with implications for current forest management strategies

The koomal (Trichosurus vulpecula hypoleucus) is a declining subspecies ('near-threatened'), residing largely within the Western Australian jarrah forest, a forest managed for both conservation and for forestry (roughly half is available for logging). Information on the spatial dynamics of koomal is essential to evaluating whether logging prescriptions provide adequate protection for this threatened species. Here we describe the home range and territoriality of koomal, as well as the characteristics and use of their den trees, at multiple sites within the jarrah forest. We also compare the characteristics of den trees used by koomal against logging prescriptions and previous models that estimate availability of den trees. Results suggested that koomal home ranges varied between sites and sexes, with males having the larger home ranges. Koomal also maintained exclusive core territories, probably to protect their den trees from same-sex individuals. Den trees used by koomal had similar characteristics to those outlined in logging prescriptions, but also included two additional characteristics that may improve the retention of trees suitable for koomal: den trees were preferentially of marri (Corymbia calophylla) and wandoo (Eucalyptus wandoo) species, and had some level of canopy connectivity. Overall, findings from this study should help future evaluations of the effectiveness of logging prescriptions in providing adequate den availability for koomal