Article

Ecosystems

, Volume 7, Issue 5, pp 498-512

First online:

Production, Respiration, and Overall Carbon Balance in an Old-growth Pseudotsuga-Tsuga Forest Ecosystem

  • Mark E. HarmonAffiliated withDepartment of Forest Science, Oregon State University Email author 
  • , Ken BibleAffiliated withCollege of Forest Resources, University of Washington
  • , Michael G. RyanAffiliated withRocky Mountain Research Station, USDA Forest Service
  • , David C. ShawAffiliated withCollege of Forest Resources, University of Washington
  • , H. ChenAffiliated withDepartment of Forest Science, Oregon State University
  • , Jeffrey KlopatekAffiliated withDepartment of Plant Biology, Arizona State University
  • , Xia LiAffiliated withDepartment of Biology, Stanford University

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Abstract

Ground-based measurements of stores, growth, mortality, litterfall, respiration, and decomposition were conducted in an old-growth forest at Wind River Experimental Forest, Washington, USA. These measurements were used to estimate gross primary production (GPP) and net primary production (NPP); autotrophic respiration (Ra) and heterotrophic (Rh) respiration; and net ecosystem production (NEP). Monte Carlo methods were used to calculate uncertainty (expressed as ± 2 standard deviations of 200–400 calculations). Live carbon (C) stores were 39,800 g C m−2 (34,800–44,800 g C m−2). The store of C in detritus and mineral soil was 22,092 g C m−2 (20,600–23,600 g C m−2), and the total C stores were 61,899 g C m−2 (56,600–67,700 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 1309 g C m−2 y−1 (845–1773 g C m−2 y−1), indicating a GPP of 1906 g C m−2 y−1 (1444–2368 g C m−2 y−1). Rh, including the respiration of heart rots in tree boles, was 577 g C m−2 y−1 (479–675 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 (a) undetected biomass increases, (b) underestimates of NPP, (c) unmeasured losses, and (d) 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)