Slow Growth Rates of Amazonian Trees: Consequences for Carbon Sequestration and Forest Management.
Abstract
Growth rates for tropical forest trees estimated from radiocarbon ages and dendrometer measurements illustrate differences in forest age and structure among three sites located in the eastern, central and western Amazon basin. Although growth rates vary dramatically among individual trees overall the slowest growing trees (averaging \sim0.1mm yr-1 as opposed to 0.3mm yr-1 diameter increment) are found in the central Amazon. Small individuals (DBH \<30cm) have slower growth rates than larger diameter trees, and trees in this size class with radiocarbon ages >500 yr are encountered at all sites. Only \sim2MgC ha-1 year-1, or \SIM7% of annual photosynthesis, is allocated to growth of living wood at the eastern and central Amazon sites. Rates of C allocation to stem growth are similar across the three sites we studied because slowest growth occurs at the central Amazon site that has highest stem density and greatest biomass. Extrapolating our growth increment data to forest stand, we estimate the mean age of individual trees is \SIM350 years in the central Amazon but \SIM200\-250 years in the other two areas. The mean age of C making up the trees has a smaller range of \SIM250\-310 years, because of the greater fraction of biomass in larger individuals in the eastern and western Amazon sites. These residence times for C are longer than those of 100\-180 years obtained by simply dividing the total biomass C by the rate of C allocation to new wood for the same reason. We estimate that >20% of trees at all sites should have ages >300 years, and that maximum tree ages of >1000 years, though not common, are in accord with the growth rates we find. The fact that many Amazon trees attain ages greater than several centuries should be accounted for in management practices in these forests.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFM.B41C..01V
- Keywords:
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- 1800 HYDROLOGY;
- 1600 GLOBAL CHANGE (New category);
- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0400 Biogeosciences