| Summary: | © 2009 Dr. Liubov Vladimirovna Volkova Publications arising from thesis: Volkova, L., Bennett L. T., & Tausz, M. (2009). Effects of sudden exposure to high light on two tree fern species Dicksonia antarctica (Dicksoniaceae) and Cyathea australis (Cyatheaceae) acclimated to different light intensities. Australian Journal of Botany, 57(7), 562-571. DOI:10.1071/BT09153 Volkova, L., Tausz, M., Bennett, L. T., & Dreyer, E. (2009). Interactive effects of high irradiance and moderate heat on photosynthesis, pigments, and tocopherol in the tree fern Dicksonia antarctica. Functional Plant Biology, 36(12), 1046-1056. DOI:10.1071/FP09098 Volkova, L., Bennett, L. T., Merchant, A., & Tausz, M. (2010). Shade does not ameliorate drought effects on the tree fern species Dicksonia antarctica and Cyathea australis. Trees, 24(2), 351-362. DOI:10.1007/s00468-009-0405-1 Volkova, L., Bennett, L. T., & Tausz, M. (2011). Diurnal and seasonal variations in photosynthetic and morphological traits of the tree ferns Dicksonia antarctica(Dicksoniaceae) and Cyathea australis (Cyatheaceae) in wet sclerophyll forests of Australia. Environmental and Experimental Botany, 70(1), 11-19. DOI:10.1016/j.envexpbot.2010.06.001 Predictions of global warming and associated climate change indicate widespread increases in light intensities, temperatures, and the frequency and severity of droughts in south-eastern Australia. Understanding the ability of plants to respond and acclimate to these events is essential to predict species survival and potential impacts on biodiversity. This study focuses on two tree fern species – Dicksonia antarctica and Cyathea australis – two iconic understorey species of south-east Australian forests. These tree ferns belong to different families and are of contrasting origins, yet often grow together in south-eastern Australia, typically in shade, often along waterways. Their ecological importance is evident in the high epiphytic diversity on their trunks (ferns, mosses, bryophytes, liverwort etc), and the provision of nursery sites for many tree and shrub species. Both species are decreased by timber harvesting practices such as clearcut logging, with deaths continuing for up to five years in the post-harvest environment. Understanding the relative roles of changing light, water, and temperature in these ongoing declines is essential to conserving both tree fern populations and their dependent biota. The Thesis encompasses three controlled experiments and a field study. In the controlled experiments, the tree ferns were acclimated to contrasting growth light environments (shade or moderate light) and then exposed to an environmental stress (i.e. light, heat, water deficit). The field study examined relationships between environmental variables (i.e. light, temperature, plant water status) and photosynthetic capacity parameters of the tree ferns in their natural environment. Stress responses and acclimation potential of photosynthetic traits, water relation parameters, and frond traits of the tree ferns were studied using infrared gas analysis, pigment determination techniques, and stable isotope methods. It was hypothesised that, consistent with their contrasting origins and microsite preferences, the two tree fern species would possess different physiological characteristics and therefore respond differently to environmental stresses. It was also hypothesised that plants grown under contrasting light environments would have different reactions to and recoveries from environmental stresses. Overall, plants were able to sustain and recover from high light stress, while interactive effects of high light and heat were most detrimental to tree fern performance. Both species were susceptible to water stress, either alone or in combination with high light. The hypothesised different responses of the two species (associated with their different origins) were not confirmed, and reaction to and recovery from stress was mainly unaffected by growth light environment. Both species had low acclimation potential to any of the applied environmental stresses. Overall, findings from this study indicate that combined effects of high light and heat most likely cause ongoing decline of tree ferns in post-harvest environments, and that the distribution of tree ferns will most likely contract under future climate scenarios of higher light, increased temperatures, and decreased water availability.
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