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Production, respiration, and overall carbon balance in an old-growth Pseudotsuga-Tsuga forest ecosystem


Harmon, Mark E.; Bible, Ken; Ryan, Michael G.; Shaw, David C.; Chen, H.; Klopatek, Jeffrey; Li, Xia. 2004. Production, respiration, and overall carbon balance in an old-growth Pseudotsuga-Tsuga forest ecosystem. Ecosystems. 7: 498-512.

Ground-based measurements of stores, growth, mortality, litterfall, respiration, and decomposition were conducted in an old-growth forest at Wind River Experimental Forest, Washington. These measurements were used to estimate: Gross (GPP) and Net Primary Production (NPP); autotrophic (Ra) and heterotrophic (Rh) respiration; and Net Ecosystem Production (NEP). Monte Carlo methods were used to calculate uncertainty (expressed as ±2 SD of 200-400 calculations). Live C-stores were 39,800 g C m-2 (34,800 to 44,800 g C m-2). The store of C in detritus and mineral soil was 22,100 g C m-2 (20,600 to 23,600 g C m-2) and the total C-stores were 61,900 g C m-2 (56,600 to 67,700 g C m-2). Total NPP was 597 g C m-2 y-1 (453 to 741 g C m-2 y-1). Ra was 1,309 g C m-2 y-1 (845 to 1,773 g C m-2 y-1) indicating a GPP of 1,906 g C m-2 y-1 (1,444 to 2,368 g C m-2 y-1). Rh, including the respiration of heart-rots in tree boles, was 577 g C m-2 y-1 (479 to 675 g C m-2 y-1). Long-term NEP was estimated to be +20 g C m-2 y-1 (-116 to +156 g C m-2 y-1), indicating this stand might be a small sink. These estimates contrast with the larger sink estimated at the same site using eddy flux methods. Several hypotheses to explain this discrepancy were explored including: 1) undetected biomass increases, 2) underestimates of NPP, 3) unmeasured losses, and 4) a temporal mismatch between the two sets of measurements. The last hypothesis appears the most likely.

Keywords: autotrophic respiration; carbon flux; carbon stores; decomposition; gross primary production (GPP); heterotrophic respiration; net ecosystem production (NEP); net primary production (NPP)


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Title: RMRS Other Publications: Production, respiration, and overall carbon balance in an old-growth Pseudotsuga-Tsuga forest ecosystem
Electronic Publish Date: April 7, 2006
Last Update:
April 7, 2006

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