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Non-structural carbohydrate pools in a tropical forest.
Mirjam K R Würth1, Susanna Peláez-Riedl, S Joseph Wright
1Institute of Botany, University of Basel, Schönbeinstrasse 6, 4056 Basel, Switzerland.
Oecologia
|December 4, 2004
Summary
Tropical trees store more non-structural carbohydrates (NSC) in the dry season due to drought limiting growth, not carbon supply. This indicates robust carbon reserves, with water availability, not carbon, limiting dry season expansion.
Area of Science:
- Plant physiology
- Forest ecology
- Tropical biology
Background:
- Non-structural carbohydrates (NSC) represent a balance between carbon uptake and use in trees.
- Seasonal variations in NSC concentrations are expected to reflect source-sink dynamics within forest ecosystems.
- Understanding NSC dynamics is crucial for predicting forest responses to environmental changes.
Purpose of the Study:
- To investigate seasonal variations in NSC concentrations across tree organs in a Panamanian tropical forest.
- To estimate the total NSC pool size for the entire forest ecosystem.
- To determine the factors limiting tree growth during the dry season.
Main Methods:
- Conducted a 22-month study of NSC concentrations (starch, glucose, fructose, sucrose) in various tree tissues.
- Utilized the Smithsonian canopy crane for intensive sampling in a semi-deciduous tropical forest.
- Estimated forest biomass and NSC pool size based on intensive species data.
Main Results:
- NSC concentrations were significantly higher in the dry season compared to the wet season across all studied species and organs.
- Increased NSC levels were primarily due to higher starch content, suggesting drought-constrained growth.
- The total forest NSC pool was estimated at approximately 16 t ha⁻¹, with the majority stored in stems and branches.
Conclusions:
- The tropical forest exhibits a high carbon supply status, with ample NSC reserves.
- Dry season growth is primarily limited by water availability, not by carbon supply.
- Water shortage directly restricts new tissue formation, overriding potential CO2 fertilization effects.