Storage and Turnover of Organic Matter in Soil

Torn, M. S.; Swanston, Christopher W.; Castanha, Cristina; Trumbore, Susan E.

doi:10.1002/9780470494950.ch6

“…This variation has a large effect on the calculated turnover times when soil carbon fractions cycling at different rates are averaged together (Trumbore, 2000). Although it is widely recognized that assumptions of homogeneity in decomposition kinetics are too simplistic to adequately model and predict soil carbon turnover (Trumbore, 1993;Davidson et al, 2000;Torn et al, 2009;Derrien and Amelung, 2011), in practice, it is difficult to adequately describe and model turnover of an immeasurable number of individual organic compounds. While there are models representing decomposing organic matter as a continuum of differentially behaving compounds (Ågren and Bosatta, 1987), more commonly ecosystem models operationally divide SOM into a limited number of pools.…”

Section: S Torn Et Al: a Dual Isotope Approach To Isolate Soil Cmentioning

confidence: 99%

“…We estimate turnover times based on a linear donorcontrolled model of soil carbon cycling (Trumbore, 1993;Gaudinski et al, 2000;Torn et al, 2009), meaning that the amount of carbon decomposed is the product of the carbon stock (C), a decomposition rate constant (k), and the time interval ( t). The turnover time (τ ) is the reciprocal of the decomposition rate (i.e., τ = 1/k).…”

Section: The Dual Isotope and Inverse Label Approachmentioning

confidence: 99%

“…Although models with a limited number of pools or SOM categories do a good job of predicting steady-state carbon stocks, they may not be adequate for predicting responses to perturbation or climate change Derrien and Amelung, 2011). Increasing the resolution of soil carbon turnover estimates is important for understanding biogeochemical cycling of carbon, nitrogen, and other SOM-related elements, as well as predicting the response to environmental change (Schimel et al, 1994;Trumbore, 2000;Torn et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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A dual isotope approach to isolate soil carbon pools of different turnover times

Torn

¹

,

Kleber

²

,

Zavaleta

³

et al. 2013

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Abstract. Soils are globally significant sources and sinks of atmospheric CO 2 . Increasing the resolution of soil carbon turnover estimates is important for predicting the response of soil carbon cycling to environmental change. We show that soil carbon turnover times can be more finely resolved using a dual isotope label like the one provided by elevated CO 2 experiments that use fossil CO 2 . We modeled each soil physical fraction as two pools with different turnover times using the atmospheric 14 C bomb spike in combination with the label in 14 C and 13 C provided by an elevated CO 2 experiment in a California annual grassland.In sandstone and serpentine soils, the light fraction carbon was 21-54 % fast cycling with 2-9 yr turnover, and 36-79 % slow cycling with turnover slower than 100 yr. This validates model treatment of the light fraction as active and intermediate cycling carbon. The dense, mineral-associated fraction also had a very dynamic component, consisting of ∼ 7 % fast-cycling carbon and ∼ 93 % very slow cycling carbon. Similarly, half the microbial biomass carbon in the sandstone soil was more than 5 yr old, and 40 % of the carbon respired by microbes had been fixed more than 5 yr ago.Resolving each density fraction into two pools revealed that only a small component of total soil carbon is responsible for most CO 2 efflux from these soils. In the sandstone soil, 11 % of soil carbon contributes more than 90 % of the annual CO 2 efflux. The fact that soil physical fractions, designed to isolate organic material of roughly homogeneous physico-chemical state, contain material of dramatically different turnover times is consistent with recent observations of rapid isotope incorporation into seemingly stable fractions and with emerging evidence for hot spots or micro-site variation of decomposition within the soil matrix. Predictions of soil carbon storage using a turnover time estimated with the assumption of a single pool per density fraction would greatly overestimate the near-term response to changes in productivity or decomposition rates. Therefore, these results suggest a slower initial change in soil carbon storage due to environmental change than has been assumed by simpler (one-pool) mass balance calculations.

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“…The dynamics of soil organic carbon (SOC), factors governing the turnover time of SOC, and variation with depth in many tropical regions are not clearly understood. It is believed that the turnover time of the organic carbon in tropical soils is less than that of boreal and temperate soils (Raich and Schlesinger 1992;Schimel et al 1994;Thompson et al 1996;Torn et al 2009). …”

Section: Introductionmentioning

confidence: 99%

Radiocarbon and Stable Carbon Isotopes in Two Soil Profiles from Northeast India

Laskar¹,

Yadava²,

Ramesh³

2012

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ABSTRACT. Two soil profiles from northeast India, one from Bakrihawar, an agricultural land, and the other from Chandipur, a virgin hilly area from Assam, are investigated to understand the organic carbon dynamics of the area. Due to frequent flooding, the Bakrihawar soil has accumulated a higher clay content than that of Chandipur. The carbon content is less than 1% by weight in both the sites. The higher clay content is responsible for relatively more soil organic carbon at Bakrihawar. The mean  13 C values at both sites reflect the values of the overlying vegetation. At Bakrihawar, both rice cultivation (C 3 ) and natural C 4 grasses contribute to higher mean enriched values of 13 C relative to Chandipur, where the surface vegetation is mostly of C 3 type. The turnover time of organic carbon, estimated using the residual radiocarbon content, depends strongly on the soil particle size distribution, especially the clay content (i.e. it increases with clay content). To the best of our knowledge, this is the first soil carbon dynamics study of its kind from northeast India.

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“…The dynamics of soil organic carbon (SOC), factors governing the turnover time of SOC, and variation with depth in many tropical regions are not clearly understood. It is believed that the turnover time of the organic carbon in tropical soils is less than that of boreal and temperate soils (Raich and Schlesinger 1992;Schimel et al 1994; Thompson et al 1996;Torn et al 2009). …”

Section: Introductionmentioning

confidence: 99%

Radiocarbon and Stable Carbon Isotopes in Two Soil Profiles from Northeast India

Laskar

¹

,

Yadava

²

,

Ramesh

³

2012

View full text Add to dashboard Cite

ABSTRACT. Two soil profiles from northeast India, one from Bakrihawar, an agricultural land, and the other from Chandipur, a virgin hilly area from Assam, are investigated to understand the organic carbon dynamics of the area. Due to frequent flooding, the Bakrihawar soil has accumulated a higher clay content than that of Chandipur. The carbon content is less than 1% by weight in both the sites. The higher clay content is responsible for relatively more soil organic carbon at Bakrihawar. The mean  13 C values at both sites reflect the values of the overlying vegetation. At Bakrihawar, both rice cultivation (C 3 ) and natural C 4 grasses contribute to higher mean enriched values of 13 C relative to Chandipur, where the surface vegetation is mostly of C 3 type. The turnover time of organic carbon, estimated using the residual radiocarbon content, depends strongly on the soil particle size distribution, especially the clay content (i.e. it increases with clay content). To the best of our knowledge, this is the first soil carbon dynamics study of its kind from northeast India.

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Storage and Turnover of Organic Matter in Soil

Cited by 131 publications

References 203 publications

A dual isotope approach to isolate soil carbon pools of different turnover times

A dual isotope approach to isolate soil carbon pools of different turnover times

Radiocarbon and Stable Carbon Isotopes in Two Soil Profiles from Northeast India

Radiocarbon and Stable Carbon Isotopes in Two Soil Profiles from Northeast India

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