Abstract
Fens belong to the most threatened ecosystems in Europe. Maintaining a high water table through rewetting is an effective measure to rehabilitate many of their ecosystem functions. However, the impact of meteorological conditions such as vapor pressure deficit (VPD) and precipitation on water tables is still unclear for rewetted fens. Here, we compare the impact of meteorological factors on water table dynamics in a drained and a rewetted fen, using multiple regression with data from continuous high-resolution (temporal) water level monitoring and weather stations. We find that an increase in the daily mean VPD causes a higher drop in the water table at the drained and degraded fen compared to the rewetted fen. Precipitation contributes to recharge, causing the water table to rise higher at the drained site than at the rewetted site. We attribute the differential influence of meteorological conditions on water table dynamics to different soil specific yield values (i.e., water storage capacity) largely driven by lower water table position at the drained site. Our study underlines the importance of understanding how and why water tables in peatlands vary in response to meteorological factors for management decisions (e.g., rewetting). Continuous monitoring of water table and vegetation development in rewetted fen peatlands is advisable to ensure long-term success especially under climate change conditions and associated drought events.
Highlights
Over the past century, about 90% of minerotrophic peatlands in Central Europe have been degraded through artificial drainage and deforestation (Joosten and Couwenberg, 2001)
Receding water tables at both sites occur at times of rising daily maximum air temperatures and an absence of substantial rainfall (Figures 4, 5; for each site, an example of such a period has been indicated by a translucent pink band)
According to our regression analysis, precipitation and vapor pressure deficit (VPD) affect the water table at different magnitudes, depending on the drainage status of the fen, while the direction of the relationship between the meteorological variables and water levels were according to expectations
Summary
About 90% of minerotrophic peatlands (fens; groundwater-fed peatlands) in Central Europe have been degraded through artificial drainage and deforestation (Joosten and Couwenberg, 2001). Restoration of degraded peatlands is an important climate change mitigation measure, as peatlands store much of the global terrestrial carbon stock. Hydrological restoration of peatlands has been implemented throughout Europe and North America (Lamers et al, 2015), rewetted peatlands are under pressure from climate change (Levison et al, 2014). The impact of a changing climate on peatland ecohydrology through extreme weather events such as droughts is likely not uniform over different spatial scales and climatic zones. Part of this variability is due to a variation in local meteorological conditions and differences in land management
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