DOI: 10.5061/dryad.vdncjsxs5
title: The response of carbon assimilation and storage to long-term drought in tropical trees is dependent on light availability

description: 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 findings at
 this experiment of no change in photosynthetic capacity or NSC storage.
 The changes detected here only occurred in the subset of drought-stressed
 trees with canopies exposed to high radiation and were absent in trees
 with less-exposed canopies, and also in the community average. In contrast
 to previous results acquired through less intensive species sampling from
 this experiment, we also observe no species-average drought-induced change
 in leaf respiration. 4) Our results suggest that long-term responses to
 drought stress are strongly influenced by a tree’s full-canopy light
 environment and therefore that disturbance-induced changes in stand
 density and dynamics are likely to substantially impact tropical forest
 responses to climate change. We also demonstrate that, while challenging,
 intensive sampling is essential in tropical forests to avoid sampling
 biases caused by limited taxonomic coverage.
description: This file contains all of the data for the 163 trees used to
 create the results for the above paper. We list these trees alongisde
 their taxonomic identity, size and a series of triats. The file contains
 the following fields: Plot: Whether the tree is located
 on the control or experimental plot (TFE) Tree Code:
 Tree number on the plot Genus: Tree genus
 Species: Tree species DBH..Cm.: Tree diameter
 at breast height (cm) Tree light score: The canopy
 light index assigned to each tree Min. gs: Minimum
 stomatal conductance (mol m-2 s-1) Max.gs: Maximum
 stomatal conductance (mol m-2 s-1) vm25: Maximum
 carboxylation rate corrected to 25⁰C (micromols m-2 s-1)
 jm25: Maximum rate of electron transport corrected to 25⁰C
 (micromols m-2 s-1) rd25: Dark respiration rate
 corrected to 25⁰C (micromols m-2 s-1) Sucrose_branch:
 Sucrose branch content (%) Starch_branch: Starch branch
 content (%) Total_NSC_branch: Total branch
 non-structural carbohydrate content (%) Sucrose_leaf:
 Sucrose leaf content (%) Starch_leaf: Starch leaf
 content (%) Total_NSC_leaf: Total leaf non-structural
 carbohydrate content (%) leaf_n: Leaf Nitrogen content
 (g m-2) leaf_P: Leaf Phosphorus content (g
 m-2) LMA: Leaf mass per area (g m-2)
 Light category: Whether the tree light score translates into a
 high or low light category