Changes in key climatic variables (e.g., atmospheric CO2, air temperature and water availability) are occurring at unprecedented rates and having substantial impacts on functionality, biodiversity and productivity of terrestrial ecosystems. Because forests dominate terrestrial net primary production and play a prominent role in the global carbon cycle, understanding the capacity of woody species to cope with simultaneously changing climatic variables is critical for the management of natural resources and the conservation of biodiversity. One fundamental way that plants may respond to rapid climate change in the short-term is to adjust their growth and physiology via phenotypic plasticity - the ability of a genotype to express multiple phenotypes in response to environmental change, which is thought to be particularly important for woody species with long generation times. For any given species, plant populations originating from different environments usually differ in their responses to the same environmental change, as evidence of intraspecific variation in phenotypic plasticity. Although some progress has been made on intraspecific variation in woody plant response to climate change, no studies have looked into the interactive effects of concurrently changing climatic variables on their intraspecific variation in phenotypic plasticity. Therefore, my PhD thesis was designed to assess the impacts of key climatic variables (i.e., [CO2], temperature, and water availability) on growth and physiology of woody plant populations originating from contrasting environments, with a focus on the intraspecific variation in their capacity to cope with climate change. Three Australian native woody species representing different taxa and functional groups were included in this research: Telopea speciosissima (Proteaceae; Shrub; open xvi woodland), Eucalyptus grandis (Myrtaceae; Tree; wet forest) and Eucalyptus tereticornis (Myrtaceae; Tree; dry forest), each of which consisted of two populations originating from climatically differentiated regions. Treatment levels (i.e., changes in [CO2], temperature, and water availability) in this research were chosen based on predicted climatic conditions within this century. My goal was to use these woody species to generate improve understanding of woody plant growth and physiological responses under future climatic scenarios. my PhD research addressed the main and interactive effects of changes in multiple climatic variables (i.e., [CO2], temperature, and water availability) on growth and physiology of three woody species representing different taxa and functional groups, with a focus on the intraspecific variation in their responses between populations originating from different environments. Results of this research were reported based on the treatment levels chosen for the experiments. Significant intraspecific variation in growth plasticity when responding to a constant mild warming (TE; ambient + 3.5-4.0 -°C) was found in all three species, and intraspecific variation in photosynthetic responses to a short-term heat stress (ambient + 8 -¦C) was observed in the two Eucalyptus species. In contrast, populations did not differ in their growth or photosynthetic responses to elevated [CO2] (CE) or to sustained drought in most cases for all three species. These results together suggest that temperature would be more effective than [CO2] or water availability in exposing intraspecific variation in phenotypic plasticity for woody plant populations under future climates. The relationships between phenotypic plasticity and source environment variability of plant populations differed among the three species. Results from the two Eucalyptus species confirmed the general prediction that greater levels of environmental variability will select for plants with greater phenotypic plasticity, while findings from T. speciosissima contradicted the paradigm, indicating that woody plant populations originating from more variable environments may not necessarily show greater phenotypic plasticity in response to climate change. In addition, TE negatively affected plant resistance to drought and heat stress exacerbated the negative effects of drought on plant responses, suggesting that temperature may influence the responses of woody plants to drought under future climates. Overall, my PhD work expands current knowledge regarding the interactive effects of simultaneously changing climatic variables on woody plant growth and physiology. More importantly, this research contributes valuable information on intraspecific variation in phenotypic plasticity of woody plant populations in response to changing climatic variables, as well as the association between phenotypic plasticity and source environment variability, which will assist in making robust predictions of the distribution and abundance of woody species under future climates.
Date of Award | 2016 |
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Original language | English |
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- woody plants
- biodiversity
- climatic factors
- climatic changes
- Australia
Differential response to climate change among populations for woody plant species : an ecological and physiological approach
Huang, G. (Author). 2016
Western Sydney University thesis: Doctoral thesis