The drivers of soil organic matter turnover across spatial scales and the effect of climate change on gaseous losses of C and N from heathland systems

Electronic versions


  • Robert Mills

    Research areas

  • PhD, School of Environment, Natural Resources and Geography


Understanding the turnover and storage of C and N in soils is central to the wider studyof biogeochemical cycles. The loss of C and N to the atmosphere can be monitored usingsimple analytical techniques both in the field and under laboratory conditions, with the loss of C (soil respiration) being one of the most studied components of terrestrial biogeochemistry. The sensitivity of these processes to climate change,and the general driving by edaphic, vegetation and climatic conditions are variable and still poorly understood. This thesis considers three issues in contemporary biogeochemistry; 1. How do warming and throughfall reduction (i.e. climate change) alter soil respiration in an upland heathland. 2. What are the drivers of gaseous losses of C (and N) over spatial scales. 3. What controls the turnover of long residence-time soil C on a national scale. Reduction in summer throughfall had a significant effect on soil respiration when monitored over a three year period. Passive night time warming also had a significant effect on soil respiration, and both treatments increased the temperature sensitivity of soil respiration. There was a strong seasonal element thoughwhich suggests a greater temporal resolution is needed to further understand the nature of these fluxes. Assessment of C fluxes on across a nationalscale suggested that the quantity (and possible quality)of Soil Organic Matter (SOM) was a major factor alongside vegetation type when explaining large-scale soil respiration rates under controlled conditions. Using radiocarbon to model the turnover of SOM on a national scale suggested a fundamental difference between vegetation types with regard to the storage of SOM on decadal or millennial timescales. These results reinforce the sensitivity of shorter-term processes,such as soil respiration,to fluctuations in prevailing climatic conditions, but suggest that vegetation type (and therefore litter inputquantity and quality) may be more important when considering the longer-residence time SOM stored in GB soils. Linking concepts across scales is therefore deemed the way forward in an attempt to integrate model predictions of the resilience of different pools of SOM to perturbations such as climate and land-use change.


Original languageEnglish
Awarding Institution
  • Bridgett A. Emmett (External person) (Supervisor)
  • David Jones (Supervisor)
Thesis sponsors
  • NERC
Award dateJan 2011