Impact of precipitation, air temperature and abiotic emissions on gross primary production in Mediterranean ecosystems in Europe

Mediterranean ecosystems are significant carbon sinks and are particularly sensitive to climate change. However, the carbon dynamics in such ecosystems are still not fully understood. An improved understanding of the drivers of carbon fixation by vegetation is needed to better predict how these ecosystems will respond to climate change. In this study, a large dataset collected through the FLUXNET network is used to estimate how the gross primary production (GPP) of different Mediterranean ecosystems was affected by air temperature and precipitation between 1996 and 2013. We showed that annual precipitation and temperature were not significant drivers of annual GPP. However, inter-annual variations of GPP seemed largely controlled by the precipitation during early spring (March-April). Late spring and early summer temperature also had a positive effect on annual GPP. We furthermore show that GPP may also have been influenced by both summer rainfall pulses and abiotic emissions due to carbonates precipitation/dissolution. Finally, the sensitivity of GPP in the Mediterranean region to climate drivers seemed not to be ecosystem-type dependent. Our results can provide general information for modeling exercises and improve future biomass projections on a regional scale.