Age-related decline of stand biomass accumulation is primarily due to mortality and not to reduction in NPP associated with individual tree physiology, tree growth or stand structure in a Quercus-dominated forest

Xu, Cheng-Yuan and Turnbull, Matthew H. and Tissue, David T. and Lewis, James D. and Carson, Rob and Schuster, William S. F. and Whitehead, David and Walcroft, Adrian S. and Li, Jinbao and Griffin, Kevin L. (2012) Age-related decline of stand biomass accumulation is primarily due to mortality and not to reduction in NPP associated with individual tree physiology, tree growth or stand structure in a Quercus-dominated forest. Journal of Ecology, 100 (2). pp. 428-440. ISSN 0022-0477


Age-related reductions in stand biomass accumulation are frequently observed in old-growth forests. The phenomenon may be caused by reduced production, increased mortality or both. The relative importance of production and mortality is not well studied, so the mechanisms controlling age-related decline of stand biomass accumulation remain unclear. In this study, conducted in a Quercus-dominated deciduous forest in the Northeastern USA, we examined whether age-related decline in stand above-ground biomass (AGB) accumulation could be explained by reduction of above-ground net primary production (NPP) (growth of surviving trees) that may be associated with (i) physiological constraints within individual trees or (ii) changes in stand structure, or by (iii) age-related, increasing tree mortality in stands up to 135years old. Few previous studies have tested these hypotheses simultaneously within the same forest. We did not find evidence for a reduction in individual tree growth associated with age-related physiological constraints, in terms of foliar carbon assimilation capacity, photosynthesis/respiration balance, nitrogen availability or hydraulic constraints on carbon gain. Over the period of 1937-2006, we did not observe alterations in stand structure, and the above-ground NPP of the Quercus forest was generally stable. However, we did find that the primary mechanism driving age-related decline of stand AGB accumulation was biomass loss due to the death of large, dominant trees. Our results indicate that shifts in mortality from the loss of small trees to the loss of large trees, rather than changes in above-ground NPP, drives age-related decline in stand AGB accumulation in this forest. Synthesis.We found that within the range of stand development stages analysed, the age-related decline of stand AGB accumulation in a Quercus-dominated forest was primarily due to mortality of large, dominant trees and not due to changes in above-ground NPP associated with tree physiology, individual tree growth or stand structure. This result indicates that tree demography and the influence of climate change on disturbances may need to be integrated into models to predict the change of above-ground carbon stock of some old-growth forests.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Publisher: Wiley-Blackwell Publishing Ltd.
Item Status: Live Archive
Additional Information (displayed to public): Permanent restricted access in accordance with the copyright policy of the publisher (Wiley-Blackwell).
Depositing User: epEditor USQ
Faculty / Department / School: Historic - Faculty of Sciences - Department of Biological and Physical Sciences
Date Deposited: 12 Dec 2012 09:57
Last Modified: 18 Aug 2014 06:38
Uncontrolled Keywords: carbon sequestration; disturbance; ecophysiology; growth dominance; hydraulic limitation; net primary productivity; nitrogen; photosynthesis; respiration; temperate deciduous forest
Fields of Research (FoR): 06 Biological Sciences > 0607 Plant Biology > 060705 Plant Physiology
05 Environmental Sciences > 0503 Soil Sciences > 050301 Carbon Sequestration Science
07 Agricultural and Veterinary Sciences > 0705 Forestry Sciences > 070502 Forestry Biomass and Bioproducts
Socio-Economic Objective (SEO): D Environment > 96 Environment > 9603 Climate and Climate Change > 960303 Climate Change Models
Identification Number or DOI: doi: 10.1111/j.1365-2745.2011.01933.x

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