Climate change implications for grassland ecosystems: a biodiversity approach

Grassland species assemblages are vulnerable to changes in rainfall patterns, with consequences of change including less species-rich communities, and changes in carbon, nitrogen and hydrological cycles. Research has indicated that increasing species diversity can lead to better resource and water use efficiency, and experiments are now targeted at identifying species characteristics that can modify ecosystem responses to climate change. This thesis aimed to evaluate the extent plant functional diversity can modify the effect of climate change in a field experiment on acid grassland in South-East England. Other climate scenarios, namely spring and summer drought, and highly variable rainfall were tested concurrently, and a modelling technique was developed to predict ecosystem functions from abiotic and plant trait-based variables. Climate change treatments generally decreased rates of ecosystem processes such as mineralisation and ecosystem respiration. Plots dominated by perennial plant species exhibited lower rates of processes such as net ecosystem CO2 exchange and soil respiration under climate stress. Results suggest annual plants are adapted to take advantage of very small rainfall input, and are less affected by climate change, thus generally maintaining overall ecosystem function through times of drought. A spring and summer drought regime was associated with slowing of ecosystem processes. This treatment was more deleterious to ecosystem function than increasing rainfall variability, where process rates did not differ discernibly from ambient, although plants suffered a higher level of dieback in general. While climate change could have detrimental effects on all aspects of ecosystem function, using information regarding species traits which are more resistant to climate change may aid grassland management in order to preserve more vulnerable species. Experiments such as these are vital to further understanding of the links between plant community composition and ecosystem function in order to target management schemes and policy to reduce the effects of climate change