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Title: Impacts of climate change on ecosystem functioning : linking above-ground and below-ground responses
Author: Pierce, Sarah
ISNI:       0000 0004 6420 9954
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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Climate change is expected to include changes to rainfall patterns. For southern England, this is likely to include decreased summer and increased winter rainfall patterns by the end of the 21st century. The aim of this research was to investigate the effects of altered precipitation patterns on ecosystem properties both above- and below-ground using a grassland experimental system in southeast England. The DIRECT experiments were established in 2008 and continued through 2013. This included three experiments assessing the effects of rainfall change on ecosystem functioning. The first crossed a summer rainfall reduction/winter rainfall increase scenario with plant functional trait diversity. The second considered the effects of two more extreme rainfall change scenarios, one an extended drought and one a shorter, more severe drought with occasional downpours. The third crossed rainfall change with increased nitrogen deposition in line with current levels experienced in parts of Europe. By concurrently measuring a broad range of above- and below-ground properties during the 2012 and 2013 growing seasons, I assessed the effects of changes in annual precipitation patterns. Drought during the growing season was linked to increased grass dominance and reduced ecosystem respiration, photosynthesis, and net ecosystem exchange, despite increases in winter precipitation. Effects on ecosystem functioning were most severe under extreme drought scenarios. Plant functional trait identity and diversity influenced response to drought, with increased diversity linked to higher plant cover in drought conditions. Increased nitrogen appeared to magnify the effects of drought on plant cover, while moderating the effects on CO2 flux. These results suggests that the levels of precipitation change predicted for England will negatively affect biodiversity and carbon cycling in grasslands, but factors such as trait diversity and nutrient inputs must be taken into account to understand the range of possible outcomes for ecosystem functioning.
Supervisor: Bell, Thomas ; Power, Sally Sponsor: Imperial College London ; Natural Environment Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral