1. In-situ GHG measurements
To address HP4, in-situ chamber measurements of net undersorey CO2, CH4 and N2O fluxes and soil respiration will be made across the 12 (+2) fire disturbance chronosequence sites, the 15 N deposition gradient sites and 9 sites with natural fertility gradients during the peak growing season.
2. N fixation and carbon flux
To assess the direct link between N fixation and photosynthesis rates in feathermosses, we will use a transplant approach where moss microcosms (12 transplanted and 12 controls) from high fertility stands with low N fixation rates (and few or no cyanobacteria) will be transplanted into a low fertility stand with normally high rates of fixation (Year 1). This approach will allow us to evaluate the relative rates of photosynthesis in the presence or absence of cyanobacteria.
3. Mesocosm GHG flux
Iintact litter-soil cores (0-30 cm) will be taken from the fire and N deposition gradient field sites and transported to CEH Lancaster where controlled acetylene block incubations will be made to determine the relative contribution of nitrification and denitrification to N2O emissions after the addition of NO3.