ARS | Publication request: How do variations in the temporal distribution of rainfall events affect ecosystem fluxes in seasonally water-limited Northern Hemisphere shrublands and forests?

Submitted to: Biogeosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2012
Publication Date: March 13, 2012
Citation: Ross, I., Mission, L., Rambal, S., Arneth, A., Scott, R.L., Carrara, A., Cescatti, A., Genesio, L. 2012. How do variations in the temporal distribution of rainfall events affect ecosystem fluxes in seasonally water-limited Northern Hemisphere shrublands and forests?. Biogeosciences. 9:1007-1024. doi:10.5194/bg-9-1007-2012.

Interpretive Summary: During the 20th century, there has been change in global patterns of precipitation. Likewise, climate change in this century is expected to result in fewer and larger rainfall events in many temperate regions of the world. There are few and contradictory conclusions about how this change will affect ecosystem productivity. Data from a global network of sites that measure carbon dioxide exchange between the land and the atmosphere were analyzed to investigate the effects of differences in rainfall distribution on the carbon balance of seasonally water-limited shrubland and forest sites. Results show that sites where rainfall events are larger but more widely spaced have significantly lower gross vegetation productivity, slightly lower respiration rates, and consequently a smaller net ecosystem productivity. With the forecasted changes in climate of less, more spread out, rain events, these results imply poor consequences for ecosystem productivity.

Technical 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.