Sensitivity of carbon gas fluxes to weather variability on pristine, drained and rewetted temperate bogs

Climate change is considered to alter the functioning of boreal peatland ecosystems, but the vulnerability of pristine, rewetted and drained peatlands to climate change in temperate regions is unknown. We measured carbon (C) gas exchange during wet (2009) and dry (2010) growing periods in pristine, drained and rewetted sites in mountain bogs in the Bohemian Forest (Czech Republic). Wetter lawns with sedges and drier habitats dominated by ericaceous shrubs were distinguished and studied at each site. Methane (CH4) emissions, which decreased in the order pristine > rewetted > drained, were generally lower during the 2010 growing period than in 2009 as a consequence of a drought. During the drought in 2010, photosynthesis (PG) in the drier habitats with shrub vegetation increased on pristine and rewetted sites, while total respiration (RECO) remained the same. Communities dominated by sedges maintained similar rates of PG and RECO during both growing periods. Generally, this led to higher C accumulation during the drought on pristine and rewetted bogs. At the drained bog site, the decreased water table (WT) during the drought led to increased PG and RECO, such that the net C accumulation was similar in the two years. Drained peatlands may be more threatened by future climate change than pristine or rewetted peatlands because of their limited buffering capacity for decreased WT. In the case of further decreases in WT, they could lose the peatland vegetation and functions that have partly persisted through decades of drainage.