Abstract:
The seasonal climate drivers of the carbon cycle
in tropical forests remain poorly known, although these
forests account for more carbon assimilation and storage than
any other terrestrial ecosystem. Based on a unique combination
of seasonal pan-tropical data sets from 89 experimental
sites (68 include aboveground wood productivity measurements
and 35 litter productivity measurements), their associated
canopy photosynthetic capacity (enhanced vegetation
index, EVI) and climate, we ask how carbon assimilation
and aboveground allocation are related to climate seasonality
in tropical forests and how they interact in the seasonal
carbon cycle. We found that canopy photosynthetic capacity
seasonality responds positively to precipitation when rainfall
is < 2000mm/yr (water-limited forests) and to radiation
otherwise (light-limited forests). On the other hand, independent
of climate limitations, wood productivity and litterfall
are driven by seasonal variation in precipitation and
evapotranspiration, respectively. Consequently, light-limited
forests present an asynchronism between canopy photosynthetic
capacity and wood productivity. First-order control by
precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000mm/yr.
