What determines the seasonal and interannual variation of carbon allocation and respiration in trees in a tropical forest during a drought? We explore this question with a novel high temporal resolution dataset of carbon allocation and respiration from a network of plots in South America, Africa and Asia.
Results/Conclusions -
The forests show strong seasonal variation in tree wood growth rates which are largely explained by shifts in carbon allocation, and not by shifts in total productivity. At some plots, there was a clear seasonal trade-off between wood and canopy NPP, while other plots showed a contrasting seasonal trade-off between wood and fine roots. Although a strong 2010 drought in the Amazon reduced photosynthesis, NPP remained constant and increased in the six month period following the drought, which indicates usage of significant non-structural carbohydrate stores. Following the drought, carbon allocation increased initially towards the canopy, and then in the following year, allocation increased towards fine root production. In many tropical forest ecosystems, we propose that changing tree growth rates are more likely to reflect shifts in allocation rather than changes in overall productivity. Only a whole NPP allocation perspective can correctly interpret the relationship between changes in growth and changes in productivity.