Response of ecosystem carbon and water dynamics to spring drought in Switzerland

Europe has experienced a number of exceptional weather events such as severe droughts and heat spells (2003 & 2010), disastrous flood events (2002 & 2005), and severe storms with wind throw (1999 & 2005) during the past decade that heavily disturbed the carbon and water balance of terrestrial ecosystems. For the future, regional climate models have predicted more intense and frequent extreme events. Our knowledge about the changes in ecosystem carbon and water dynamics in response to such extreme events is still limited. In Switzerland, spring 2011 was the warmest and among the driest since start of meteorological measurements following an exceptionally dry winter. This combination resulted in a pronounced spring with severe effects on ecosystem phenology, agricultural production and water supply. We synthesized data from the regional eddy covariance network Swiss FluxNet to assess the impact of this spring drought on ecosystem carbon dioxide and water vapour fluxes. Swiss FluxNet integrates the major plant functional types of deciduous and coniferous forest, grassland and cropland across elevation gradients in Switzerland. The objectives of our synthesis study were to evaluate (1) the phenological development of vegetation, (2) to assess the range and magnitude of ecosystem carbon and water fluxes, (3) to quantify carbon and water budgets, and (4) to investigate potential carry-over effects of the spring drought 2011 in Switzerland. Our results present the first synthesis study of the regional network Swiss FluxNet and provide an improved understanding of the ecosystem response to spring drought in temperate and alpine climates. We will finally discuss the implications of our results for ecosystem management and for further regional synthesis studies.