LAUSR

Global change is affecting terrestrial carbon balances. The effect of climate on ecosystem carbon balance has been largely explored, but the roles of other concurrently changing factors, such as diversity and nutrient availability, remain elusive. We used eddy-covariance carbon-flux measurements from 62 ecosystems from which we compiled information on climate, ecosystem type, stand age, species abundance and foliar concentrations of N and P of the main species, to assess their importance in the ecosystem carbon balance. Climate and productivity were the main determinants of ecosystem C balance and its stability. In P-rich sites, increasing N was related with increased gross primary production and respiration and vice versa, but reduced net C uptake. Our analyses did not provide evidence for a strong relation between ecosystem diversity and their productivity and stability. Nonetheless, these results suggest that nutrient imbalances and, potentially, diversity loss may alter future global carbon balance.