Vegetation and carbon gas dynamics under a changed hydrological regime in central European peatlands

Background: Northern peatlands are known for having significant stocks of terrestrial soil carbon (C). However, little is known about how peatlands function under various land uses and what impacts land-use change has on their functioning in central Europe. Aim: The objective of our study was to quantify the variability and controls of typical plant communities in terms of C gas dynamics on bogs and fens affected by a changed hydrological regime in the Bohemian Forest, Czech Republic. Methods: Carbon dioxide (CO2) exchange and methane emissions (CH4) were measured in bogs (pristine, drained, restored) and in fens (pristine, drained) during the 2009 growing season. We applied cluster analysis to define plant communities and non-linear response models to quantify the variation in CO2 dynamics among the communities. Results: Drainage had a strong impact on vegetation; forest and meadows species were dominant on drained peatland sites and the vascular green area was higher than on pristine sites. The net ecosystem CO2 exchange (NEE) varied from -27 to 241 g CO2-C m(-2) per growing season on the bogs and from 27 to 153 g m(-2) on the fens. The most-drained parts of the bog and fen with the most changed vegetation structure acted as both net C sources and very weak C sinks; however, areas dominated by Molinia caerulea acted as a strong C sink. Plant communities on the wetter parts of drained sites had a positive seasonal NEE, comparable with NEE on pristine sites. Seasonal CH4 emissions were relatively low (0-9 g CH4-C m(-2)) at all sites and did not influence net C balance, with the exception of pristine fen where CH4 emissions with average 90 g C m(-2) led to a negative total growing season C balance. Water regime restoration caused neither a significant change in plant composition nor any major changes, such as plant die-back or increased CH4 emissions during the first season after restoration. Conclusions: Our results showed that C gas fluxes, and in turn the C balance of the whole ecosystem, were largely determined by plant community type. Drainage did not necessarily lead to a negative ecosystem C balance; however, a significant change of species composition occurred on most drained areas. The less-drained parts on drained sites, where original peatland species and original functions are preserved, could facilitate future ecosystem restoration.