How do variations in the temporal distribution of rainfall events affect ecosystem fluxes in seasonally water-limited Northern Hemisphere shrublands and forests?
1CEFE-CNRS, 1919 route de Mende, 34000 Montpellier, France
2Department of Earth and Ecosystem Sciences, Lund University, Sweden
3Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research/Atmospheric Environmental Research, Garmisch-Partenkirchen, Germany
4USDA ARS, SW Watershed Research Center, Tucson, AZ 85719, USA
5Fundación CEAM, Paterna 46980, Spain
6European Commission, Joint Research Centre, Institute for Environment and Sustainability, Ispra, Italy
7Institute of Biometeorology (IBIMET), National Research Council (CNR), Via Caproni 8, 51045 Firenze, Italy
Abstract. Rainfall regimes became more extreme over the course of the 20th century, characterised by fewer and larger rainfall events. Such changes are expected to continue throughout the current century. The effect of changes in the temporal distribution of rainfall on ecosystem carbon fluxes is poorly understood, with most available information coming from experimental studies of grassland ecosystems. Here, continuous measurements of ecosystem carbon fluxes and precipitation from the worldwide FLUXNET network of eddy-covariance sites are exploited to investigate the effects of differences in rainfall distribution on the carbon balance of seasonally water-limited shrubland and forest sites. Once the strong dependence of ecosystem fluxes on total annual rainfall amount is accounted for, results show that sites with rainfall distributions characterised by fewer and larger rainfall events have significantly lower gross primary productivity, slightly lower ecosystem respiration and consequently a smaller net ecosystem productivity.