SOIL MICROBIAL ECOLOGY
Our understanding of the role of microbes in the function of soil remains incomplete. Diverse communities support soil functions, but we do not know the extent of these communities, or the variety of contributions they may make. We have used molecular techniques to establish the diversity of microbes in different soils, but these studies tell us that many unknown taxa are present in low frequencies. Thus we have turned to examining specific groups of microbes and specific functions in order to clarify important questions.
AM Fungi:
We have developed a much deeper understanding of arbuscular mycorrhizal (AM) fungi. AM fungi are associated with plant uptake of minerals and they are especially important in the poor soils found across much of Australia. Indeed, AM fungi may aid plant tolerance of toxic metals and other compounds. AM fungi also contribute to the development of structure of soil. Thus we are concerned about the loss of diversity of these fungi due to erosion and degradation. Diversity of mycorrhizal fungi is directly related to plant diversity and productivity and this becomes important when severely degraded soils are rehabilitated. We are currently examining the specific interactions between AM fungi and their abiotic environment with the goal of developing a more predictive process to select inoculants in restoration. Sporocarpic members of Glomalean fungi are an important part of forested plant communities, and we are starting to clarify why these fungi are so apparently sensitive to disturbance. We are also interested in better understanding the importance of sporocarpic fungi in the diet of small mammals.
Trichocomaceae: We have also examined members of the Trichocomaceae. This taxon is represented by a huge number of unidentified species in Australia. We have characterised their nutritional physiology and are now examining their interaction with fungi that initiate plant disease. Some species appear to be involved with soil aggregation, and they may have a role in the formation of biofilms.
Chytrids: This poorly studied group of fungi has recently undergone a revolution; the fungi belong in many Phyla, not one, they have diverse interactions with other organisms, and they appear to be important regulators of other organisms. However, they are a difficult group of fungi to study. We still lack clear methods to isolate and grow many species, their ecology is poorly understood, and their physiology is much more complicated than is apparent from published studies. We now have limited data on a suite of species from three Phyla, and are examining their functions in extreme environments.
Specific Functions: We are examining a number of functions of importance to soil during restoration. Many microbes express metabolites that aid soil aggregation, aeration, CEC and water storage capacity of soil. Increased metabolite content would reduce the need for fertilisers and increase efficiency of water use. Microbes compete with potential soil-borne plant pathogens. We predict high diversity of fungi that express inhibitory compounds will reduce the capacity of pathogens to cause disease. Microbes contribute to the carbon cycle; they degrade and transform carbon, leading to the possibility that sequestration of recalcitrant carbon is possible.
ENDOPHYTIC FUNGI IN THE CONTROL OF PESTS AND PATHOGENS
Endophytic fungi interact with the other organisms that use the plant for nutrition. Insect herbivory and pathology of plants have serious economic consequences, and their current treatments often have untoward ecological consequences. The goal of our research is to determine the mechanisms underlying the interactions between endophytes, their host plant, and deleterious organisms such as pests and pathogens. To date we have shown complex mechanisms of interaction, including induction of host responses.
RESTORATION OF ECOSYSTEMS
Many human activities place ecosystems under stress. Restoration of these systems requires application of various approaches in concert. For instance, soil-borne and endophytic fungi are critical to plant establishment, survival and growth, provide nutrition to small animals, and remove organic toxins from the environment. Our current research aims to better understand the influence of fungi in these processes in severely disturbed and nutrient depauporate habitats. We seek restored ecosystems that have resilience to perturbation, and resistance to change. One collaboration is working to improve approaches to revegetation of mine sites, and we have a second goal of establishing vegetation in soils contaminated by heavy metals.
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