The response of carbon assimilation and storage to long-term drought in tropical trees is dependent on light availability

1) Whether tropical trees acclimate to long-term drought stress remains unclear. This uncertainty is amplified if drought stress is accompanied by changes in other drivers such as the increases in canopy light exposure that might be induced by tree mortality or other disturbances.

2) Photosynthetic capacity, leaf respiration, non-structural carbohydrate (NSC) storage and stomatal conductance were measured on 162 trees at the world’s longest running (15 yr) tropical forest drought experiment. We test whether surviving trees have altered strategies for carbon storage and carbon use in the drier and elevated light conditions present following drought-related tree mortality.

3) Relative to control trees, the surviving trees experiencing the drought treatment showed functional responses including: i) moderately reduced photosynthetic capacity; ii) increased total leaf NSC; and iii) a switch from starch to soluble sugars as the main store of branch NSC. This contrasts with earlier findi...