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Harvard Forest REU Symposium Abstract 2005
- Title: Root Respiration and Nitrogen Concentration: An excised root study of three tree species
- Author: Emily E Austin (University of Tennessee at Knoxville)
- Abstract:
Carbon dioxide, the product of soil respiration, is an important greenhouse gas. Global climate change will affect the contributions of autotrophic and heterotrophic components to soil respiration. Reported contributions of autotrophic respiration to total soil respiration vary widely (5-85%). There is a correlation between root respiration and nitrogen concentration, [N], across species and ecosystems. This correlation may be used in the future to estimate root respiration at ecosystem level based on tree species composition and nitrogen availability.
The objective of this study was to examine the relationship between root respiration and root [N] among tree species and root size classes. I sampled roots in three size classes: medium (2-4mm), fine (1-2mm), and very fine (<1mm) from three trees of each species: Quercus rubra, Betula lenta, and Tsuga canadensis for a total of 27 samples. I measured the respiration in a closed chamber system circulating air from the chamber headspace to an Infrared Gas Analyzer and % nitrogen using a total carbon and nitrogen analyzer. Decreasing root size showed significant increase in both root respiration (p=0.002) and nitrogen concentration (p=0.000). Tree species had a significant effect on root respiration (p=0.026), there was no relationship with root [N]. My data shows a significant correlation of increased respiration with increased nitrogen concentration (figure 1). Using average root respiration data and published root biomass data from the Harvard Forest, I estimated the autotrophic contribution to total soil respiration in hardwood plots (≈28 %). These data confirm the correlation between root respiration and root [N]. - Research Category:
