Estimating Limiting Foliar Biomass in Conifer Plantations from Allometric Relationships and Self-Thinning Behavior
Abstract:The ability of forest stands to sustain increasing amounts of foliage biomass is related in a positive manner to both aboveground woody biomass and to site productivity. Knowledge of the limit to sustainable foliar biomass at a given level of photosynthetically active radiation and under minimum environmental stress would have important implications for modeling primary forest productivity. Theoretical analysis and limited experimental data collected on even-aged plant populations that are undergoing self-thinning indicate that total stand foliar biomass should achieve a nearly constant value for a given species and site. Average diameter-plant density relations for various conifers species coupled with available foliage mass-stem diameter equations were used to approximate the maximum amount of foliage which could be sustained. Sources of bias and effects due to changes in specific leaf area are evaluated. The maximum foliage biomass calculated in this manner was subject to positive bias, but estimates at low densities correspond to values obtained empirically for mature stands growing under very favorable environmental conditions. Calculated estimates suggest that maximum sustainable foliage biomass increases slightly with decreasing plant density along the self-thinning line, in contrast to expectations. The magnitude of the increase depends upon the relative value of the self-thinning exponent compared to the exponent of the allometric equation. Changes in light distribution in relation to crown architecture, particularly crown depth and foliage clustering, may account for this effect. For. Sci. 37(1):296-307.
Document Type: Journal Article
Affiliations: Project Leader, Soils Productivity Research, USDA Forest Service, Research Triangle Park, NC
Publication date: March 1, 1991
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