DO ARCTIC PLANT-SOIL COMMUNITIES ACCLIMATE TO LONG TERM ELEVATED CO2 EXPOSURE?

Concentrations of greenhouse gases are rising as a result of continued industrial activity with consequences for our future climate. The biosphere has been suggested as a significant factor mitigating atmospheric change, through its capacity to respond to this change by sequestering additional carbon. Key to our understanding and evaluation of these processes is knowledge about the extent to which ecosystems acclimate to elevated CO2. Some research has indicated only short-term growth responses to elevated CO2, but these studies have often focussed on production responses ignoring more subtle shifts in whole ecosystem function. Even where acclimation has occurred, it is important to determine whether any new state of equilibrium results in altered ecosystem function, especially with regard to C loss or gain. Arctic ecosystems are of critical importance to global conservation and store up to one-third of global soil carbon reserves. Their stability under future atmospheric CO2 scenarios will have major influences on global biodiversity and warming. In this study we want to test whether arctic plant communities do not acclimate fully even with extended exposure to elevated CO2, that below-ground responses lag those above-ground and that exposure to elevated CO2 has a cumulative effect on ecosystem properties that influence ecosystem stability, resistance and resilience. As a result of anthropogenic gaseous emissions, the climate of Arctic regions is likely to alter, in particular with regard to temperature and precipitation. These changes, and other periodic perturbations will challenge the stability of current vegetation and soil microbial processes. Sub-arctic heath systems are also subject to periodic mass herbivory events, for example due to mass infestation by the moth Epirrita autumnata. We will therefore investigate field responses (leaf regrowth and soil respiration) to a simulated defoliation event. In a controlled environment facility, we will also investigate whether variations in soil temperature and moisture content will interact with the future capacity of Arctic soils to retain sequestered C under future elevated CO2. The information from this research programme is vital if we are to be able to make effective management decisions based on improved predictions from climate models. Specifically, the extent to which whole ecosystems acclimate to elevated CO2 is a key area of uncertainty in predicting and modelling future scenarios. Research findings will also significantly advance our understanding of the stability of Arctic ecosystems to perturbations under future climate change and important potential impacts on global biodiversity impacts.