Multi-annual carbon flux at an intensively cultivated lowland peatland in East Anglia, UK

Peatlands are an important store of carbon (C), accounting for an estimated third of global soil C despite only covering 3% of the land surface. Drainage of these soils for intensive cultivation has already led to considerable peat wastage, largely due to mineralisation of stored C, with associated carbon dioxide (CO₂) emissions. This thesis provides the first multi-annual measurements of CO₂ flux for a lowland deep peat soil in East Anglia, UK. Measurements of CO₂ exchange between an intensively cultivated field and the atmosphere were made for 3.5 years using the eddy covariance (EC) methodology. During this time two lettuce, a leek and a celery crop were cultivated, with intervening periods of fallow. Drivers of CO₂ exchange were investigated. Soil temperature was identified as a key driver of CO₂ flux during fallow periods while gross primary productivity (GPP), limited by high temperature and vapour pressure deficit, was the key driver of NEE during crop periods. There was some evidence that under a shallower WTD and higher SWC, temperature response was limited and net CO₂ flux was reduced. The annual C-CO₂ flux was 675.75 ± 101.45, 806.38 ± 88.75 and 797.18 ± 84.6 g C-CO₂ m-2 yr-1, for 2013, 2014 and 2015 respectively, averaged to 759.77 ± 91.6 g C-CO₂ m-2 yr-1. The import and export of C associated with crop management (planting and harvesting) resulted in a net gain of 20-30 g C m-2 for lettuce crops, however for crops with greater yields a net loss was estimated at 20-100 g C m-2. The first UK quantification of C flux, measured at field boundaries, due to wind erosion from peatland agriculture indicated a loss of 90 to 490 g C m-2 yr-1. C loss mitigation strategies should aim to reduce periods of bare soil and raise the water table whilst still enabling ongoing agricultural management. Better understanding of the consequences of mitigation strategies for C balance and agricultural productivity are required.