Effects of summer drought on temperate grassland performance

摘要

Climate models predict that summers in temperate regions will be drier in the future. The prognosis for Switzerland is for about 20% less summer precipitation in 2050. Since about a quarter of the Swiss area is covered by grasslands, we need detailedinformation about the consequences of such summer droughts to be able to develop adaptation strategies that ensure ecosystem services. Using transparent rain-out shelters, we simulated pronounced summer droughts in three Swiss grasslands at different altitudes and assessed the impacts on productivity, community structure and plant ecophysiology. We found that the reaction to drought was strongly dependent on grassland type. While reducing precipitation created water stress for the alpine grassland site,the effects were less clear in pre-alpine and lowland grasslands. At the pre-alpine site, a positive effect of drought on biomass productivity was observed. At the lowland site, grasses were more affected by drought than forbs, leading to a change in competitive interactions between plant functional types, favouring the weed species Rumex obtusifolius. Thus, our results indicate relevant consequences of climate change for grassland management, particularly in terms of productivity and weed pressure.