Role of tree size in moist tropical forest carbon cycling and water deficit responses

Drought disproportionately affects larger trees in tropical forests, but implications for forest composition and carbon (C) cycling in relation to dry season intensity remain poorly understood. In order to characterize how C cycling is shaped by tree size and drought adaptations and how these patter...

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Bibliographic Details
Published in:The New phytologist 2018-08, Vol.219 (3), p.947-958
Main Authors: Meakem, Victoria, Tepley, Alan J, Gonzalez-Akre, Erika B, Herrmann, Valentine, Muller-Landau, Helene C, Wright, S Joseph, Hubbell, Stephen P, Condit, Richard, Anderson-Teixeira, Kristina J
Format: Article
Language:English
Subjects:
Adaptation
biomass
Carbon cycle
Climate
Composition
Data processing
Drought
drought adaptation
Dry season
Dynamics
El Nino
El Nino phenomena
El Niño
Forest ecosystems
Forests
Herbivores
Moisture
Moisture gradient
Mortality
Stems
Temporal variations
tree mortality
tree size
Trees
Tropical climate
Tropical forests
tropical moist forest
Water deficit
woody productivity
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Summary:Drought disproportionately affects larger trees in tropical forests, but implications for forest composition and carbon (C) cycling in relation to dry season intensity remain poorly understood. In order to characterize how C cycling is shaped by tree size and drought adaptations and how these patterns relate to spatial and temporal variation in water deficit, we analyze data from three forest dynamics plots spanning a moisture gradient in Panama that have experienced El Niño droughts. At all sites, aboveground C cycle contributions peaked below 50-cm stem diameter, with stems ≥ 50 cm accounting for on average 59% of live aboveground biomass, 45% of woody productivity and 49% of woody mortality. The dominance of drought-avoidance strategies increased interactively with stem diameter and dry season intensity. Although size-related C cycle contributions did not vary systematically across the moisture gradient under non-drought conditions, woody mortality of larger trees was disproportionately elevated under El Niño drought stress. Thus, large (> 50 cm) stems, which strongly mediate but do not necessarily dominate C cycling, have drought adaptations that compensate for their more challenging hydraulic environment, particularly in drier climates. However, these adaptations do not fully buffer the effects of severe drought, and increased large tree mortality dominates ecosystem-level drought responses.
ISSN:0028-646X
1469-8137
DOI:10.1111/nph.14633