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  Soil carbon cycling in a temperate forest: radiocarbon-based estimates of residence times, sequestration rates and partitioning of fluxes

Gaudinski, J. B., Trumbore, S. E., Davidson, E. A., & Zheng, S. H. (2000). Soil carbon cycling in a temperate forest: radiocarbon-based estimates of residence times, sequestration rates and partitioning of fluxes. Biogeochemistry, 51(1), 33-69. doi:10.1023/A:1006301010014.

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Gaudinski, J. B., Author
Trumbore, Susan E.1, Author           
Davidson, E. A., Author
Zheng, S. H., Author
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1External Organizations, ou_persistent22              

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Free keywords: carbon dynamics isotope disequilibrium radiocarbon soil respiration temperate forests northern hardwood forest gas diffusivity organic-matter fine roots nitrogen respiration dynamics co2 ecosystem turnover
 Abstract: Temperate forests of North America are thought to be significant sinks of atmospheric CO2. We developed a below-ground carbon (C) budget for well-drained soils in Harvard Forest Massachusetts, an ecosystem that is storing C. Measurements of carbon and radiocarbon (C-14) inventory were used to determine the turnover time and maximum rate of CO2 production from heterotrophic respiration of three fractions of soil organic matter (SOM): recognizable litter fragments (L), humified low density material (H), and high density or mineral-associated organic matter (M). Turnover times in all fractions increased with soil depth and were 2-5 years for recognizable leaf litter, 5-10 years for root litter, 40-100+ years for low density humified material and > 100 years for carbon associated with minerals. These turnover times represent the time carbon resides in the plant + soil system, and may underestimate actual decomposition rates if carbon resides for several years in living root, plant or woody material. Soil respiration was partitioned into two components using C-14: recent photosynthate which is metabolized by roots and microorganisms within a year of initial fixation (Recent-C), and C that is respired during microbial decomposition of SOM that resides in the soil for several years or longer (Reservoir-C). For the whole soil, we calculate that decomposition of Reservoir-C contributes approximately 41% of the total annual soil respiration. Of this 41%, recognizable leaf or root detritus accounts for 80% of the flux, and 20% is from the more humified fractions that dominate the soil carbon stocks. Measurements of CO2 and (CO2)-C-14 in the soil atmosphere and in total soil respiration were combined with surface CO2 fluxes and a soil gas diffusion model to determine the flux and isotopic signature of C produced as a function of soil depth. 63% of soil respiration takes place in the top 15 cm of the soil (O + A + Ap horizons). The average residence time of Reservoir-C in the plant + soil system is 8 +/- 1 years and the average age of carbon in total soil respiration (Recent-C + Reservoir-C) is 4 +/- 1 years. The O and A horizons have accumulated 4.4 kgC m(-2) above the plow layer since abandonment by settlers in the late-1800's. C pools contributing the most to soil respiration have short enough turnover times that they are likely in steady state. However, most C is stored as humified organic matter within both the O and A horizons and has turnover times from 40 to 100+ years respectively. These reservoirs continue to accumulate carbon at a combined rate of 10-30 gC m(-2) yr(-1). This rate of accumulation is only 5-15% of the total ecosystem C sink measured in this stand using eddy covariance methods.

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Language(s): eng - English
 Dates: 2000
 Publication Status: Issued
 Pages: -
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 Table of Contents: -
 Rev. Type: -
 Identifiers: Other: BEX438
DOI: 10.1023/A:1006301010014
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Title: Biogeochemistry
Source Genre: Journal
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Publ. Info: Dordrecht : M. Nijhoff/Dr W. Junk Publishers
Pages: - Volume / Issue: 51 (1) Sequence Number: - Start / End Page: 33 - 69 Identifier: ISSN: 0168-2563
CoNE: https://pure.mpg.de/cone/journals/resource/954925484702