Ecohydrological resilience to short-term warming in a high-altitude peatland under different water table levels

Peatland function and ecosystem services are increasingly at risk from climate and land-use change. At high altitudes climate warming is enhanced, while large peatland areas have undergone drainage, yet there is little knowledge of their interaction. Such information is essential for informing future management and restoration decisions. To address this gap, we investigated the effects of warming on ecohydrological function of intact (wet) and drained (dry) high-altitude peatlands. Our experiment compared the response of water table, pore-water chemistry, litter decomposition and vegetation composition to drainage and warming in a factorial experiment, utilising open top chambers to simulate warming. Our results showed that shallow peat (8 cm depth) warmed by 0.75 °C and 0.17 °C in the dry and wet site respectively, over one year of warming. However, we found limited effects of warming on peatland function, attributed to the short-term nature of the experiment, where the ecosystem showed a certain resilience to one-year of increased temperatures. Drainage significantly affected ecosystem function. A mean difference of 10.2 cm in water table level between the dry and wet sites, increased shallow pore-water dissolved organic carbon in the dry site with a greater contribution from recent shallow peat decomposition. Further, drainage also enhanced litter decomposition rates and altered vegetation composition, increasing graminoid abundance. We found small differences in water table have large impacts on function, therefore rewetting drained high-altitude peatlands by restoration, may help improve ecosystem services, while enhancing resilience to warming.