Contribution of Increasing CO
            <sub>2</sub>
            and Climate to Carbon Storage by Ecosystems in the United States

Schimel, David; Melillo, Jerry M.; Tian, Hanqin; McGuire, A. D.; Kicklighter, David W.; Kittel, T.G.F.; Rosenbloom, N. A.; Running, Steven W.; Thornton, P. E.; Ojima, Dennis S.; Parton, William J.; Kelly, Robert D.; Sykes, Martin T.; Neilson, Ronald P.; Rizzo, Brian

doi:10.1126/science.287.5460.2004

Cited by 531 publications

(367 citation statements)

References 22 publications

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“…If a Q 10 value of 2.4 is used as in BIOME-BGC, the heterotrophic respiration will increase by 0.78 Pg C yr − 1 . In contrast to the TEM result, the CASA model predicts that an increase in Q 10 from 2.0 to 2.1 results in a decrease of heteotrophic respiration by 0.15 Pg C yr − 1 , tripling the estimate by Schimel et al (2000). Again, the discrepancies between these two ecosystem models are due largely to the different reference temperatures.…”

Section: Effects Of Variations In Temperature Sensitivity Of Soil Rescontrasting

confidence: 39%

“…For example, based on three ecosystem process models (Biome-BGC, Century, and TEM), Schimel et al (2000) estimated that the conterminous USA was a net carbon sink during the period from 1980 to 1993, taking up 0.08 Pg C yr − 1 on average. This was in contrast with some previous estimates (Fan et al, 1998;Brown and Schoeder, 1999).…”

Section: Effects Of Variations In Temperature Sensitivity Of Soil Resmentioning

confidence: 99%

“…To avoid confounding effects with other factors such as soil moisture and litter quality, Kirschbaum (1995) selected laboratory-based measurements only, but obtained an even greater range of Q 10 from 2.5 at 20°C to 8 at 0°C. Although it has been well documented that Q 10 varies with temperature, this parameter has commonly been treated as a constant in ecosystem models (Heimann et al, 1989;Raich et al, 1991;Running and Hunt, 1993;Potter et al, 1993;Schimel et al, 2000). Due to the nonlinear nature of the relationship between Q 10 and respiration, small changes in Q 10 may cause significant differences in estimated soil respiration fluxes (Townsend et al, 1992;Holland et al, 1995;Kutsch and Kappen, 1997).…”

Section: Introductionmentioning

confidence: 99%

“…Despite the problems with the Q 10 model, it has been widely used in modeling the process of soil respiration (Heimann et al, 1989;Raich et al, 1991;Running and Hunt, 1993;Schimel et al, 2000). Unlike the Arrhenius equation and its modified form by Lloyd and Taylor (1994), the Q 10 model relates the rate of soil respiration to varying temperature through a parameter, Q 10 , which determines the rate of change of soil respiration with respect to temperature.…”

Section: Introductionmentioning

confidence: 99%

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Temperature sensitivity of soil respiration and its effects on ecosystem carbon budget: nonlinearity begets surprises

2002

Ecological Modelling

141

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Nonlinearity is a salient feature in all complex systems, and it certainly characterizes biogeochemical cycles in ecosystems across a wide range of scales. Soil carbon emission is a major source of uncertainty in estimating the terrestrial carbon budget at the ecosystem level and above. Due to the lack of consideration of the nonlinearity in temperature sensitivity of soil respiration, several commonly used ecosystem models produce substantially different estimates of soil respiration with the same or similar model input. In this paper we demonstrated that the response of soil respiration to changes in temperature sensitivity is nonlinear and, thus, that the oversimplified formulations may significantly reduce the accuracy of ecosystem models in predicting carbon fluxes. To alleviate this problem, we have developed a general model of temperature sensitivity of soil respiration that explicitly considers this nonlinearity. The model was supported by our field measurements from a forest ecosystem, and used to assess the uncertainty in estimating the soil CO 2 efflux with several commonly used ecosystem models. Our results indicated that the variations and nonlinearity of the soil respiration-temperature relationship and its dependence on moisture may have important implications for ecosystem carbon modeling at regional and global scales. In other words, 'small causes' may lead to 'large effects' in complex ecosystems in terms of carbon dynamics. In particular, when the variability in temperature sensitivity of soil respiration was incorporated in the several commonly used ecosystem models, the carbon source-sink relationship for terrestrial ecosystems under future global warming scenarios became dramatically different from those reported previously. Thus, we advocate that confidence limits are both necessary and feasible for simulated carbon budget from ecosystem models. Based on field measurements and model simulations, our study provides useful information for computing such confidence limits. In addition, our new model of temperature sensitivity of soil respiration seems more general and yet realistic, and can improve the accuracy of ecosystem models in predicting carbon fluxes at large scales.

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Section: Effects Of Variations In Temperature Sensitivity Of Soil Rescontrasting

confidence: 39%

Section: Effects Of Variations In Temperature Sensitivity Of Soil Resmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Temperature sensitivity of soil respiration and its effects on ecosystem carbon budget: nonlinearity begets surprises

2002

Ecological Modelling

141

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“…At face value, if CO 2 fertilization is not as strong as previously thought over temperate and boreal forests [Caspersen et al, 2000;Schimel et al, 2000], or if the mechanisms responsible for the current biotic or oceanic sink happen to saturate in the future, then we will not benefit from this ''buffering'' of the land-use amplifier effect. In response, CO 2 will be even higher, and we estimated using the E3-E2 difference, that in such a ''worst case,'' atmospheric CO 2 can be 28 ppm (B1) to 68 ppm (A2) higher as compared to the current treatment of landuse in IPCC-TAR.…”

Section: Discussionmentioning

confidence: 99%

Amplifying effects of land‐use change on future atmospheric CO₂ levels

Gitz

Ciais

2003

Global Biogeochemical Cycles

103

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[1] We constructed a model to analyze the interactions between land-use change and atmospheric CO 2 during the recent past and for the future. The primary impact of the conversion of forested lands to cultivated lands is to increase atmospheric CO 2 , via losses of biomass and soil carbon to the atmosphere. This increase is likely to continue in the next decades, but its magnitude can vary according to each land-use scenario. We show that this first-order effect is further amplified by the correlated diminution of terrestrial sinks, because when croplands replace forests, the turnover time of excess carbon in the biosphere decreases, and hence the sink capacity of terrestrial ecosystems decreases. This effect acts to further increase by up to 100 ppm the CO 2 level reached by 2100, and it is of the same order of magnitude, although smaller, than climate-carbon feedbacks. Uncertainties on the magnitude of this land-use induced effect are large, because of uncertainties in the sink role of terrestrial ecosystems in the future and because of uncertainties inherent to the modeling of land-use induced carbon emissions. Such an extra rise in atmospheric CO 2 is however partially offset by the ocean reservoir and by sinks operating over undisturbed, pristine ecosystems, suggesting that conserving pristine forests with long turnover times might be efficient in mitigating the greenhouse effect. Citation: Gitz, V., and P. Ciais, Amplifying effects of land-use change on future atmospheric CO 2 levels, Global Biogeochem.

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Impacts of inadequate historical disturbance data in the early twentieth century on modeling recent carbon dynamics (1951–2010) in conterminous U.S. forests

et al. 2015

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Stand age and disturbance data have become more available in recent years and can facilitate modeling studies that integrate and quantify effects of disturbance and nondisturbance factors on carbon dynamics. Since high‐quality disturbance and forest age data to support forest dynamic modeling are lacking before 1950, we assumed dynamic equilibrium (carbon neutrality) for the starting conditions of forests with unknown historical disturbance and forest age information. The impacts of this assumption on forest carbon cycle estimation for recent decades have not been systematically examined. In this study, we tested an assumption of disequilibrium conditions for forests with unknown disturbance and age data by randomly assigning ages to them in the model initial year (1900) and analyzed uncertainties for 1951–2010 carbon dynamic simulations compared with the equilibrium assumption. Results show that with the dynamic equilibrium assumption, the total net biome productivity (NBP) of conterminous U.S. forests was 188 ± 60 Tg C yr−1 with 185 ± 56 Tg C yr−1 in living biomass and 3 ± 23 Tg C yr−1 in soil. The C release due to disturbance on average was about 68 ± 55 Tg C yr−1. The disequilibrium assumption causes annual NBP from 1951 to 2010 in conterminous U.S. forests to vary by an average of 13% with the largest impact on the soil carbon component. Uncertainties related to nondisturbance factors have relatively small impacts on NBP estimation (within 10%), while uncertainties related to disturbances cause biases in NBP of 4 to 28%. We conclude that the dynamic equilibrium assumption for the model initialization in 1900 is acceptable for simulating 1951–2010 forest carbon dynamics as long as disturbance and age data are reliable for this later period, although caution should be taken regarding the prior‐1950 simulation results because of their greater uncertainties.

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Contribution of Increasing CO ₂ and Climate to Carbon Storage by Ecosystems in the United States

Cited by 531 publications

References 22 publications

Temperature sensitivity of soil respiration and its effects on ecosystem carbon budget: nonlinearity begets surprises

Temperature sensitivity of soil respiration and its effects on ecosystem carbon budget: nonlinearity begets surprises

Amplifying effects of land‐use change on future atmospheric CO₂ levels

Impacts of inadequate historical disturbance data in the early twentieth century on modeling recent carbon dynamics (1951–2010) in conterminous U.S. forests

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Contribution of Increasing CO 2 and Climate to Carbon Storage by Ecosystems in the United States

Cited by 531 publications

References 22 publications

Temperature sensitivity of soil respiration and its effects on ecosystem carbon budget: nonlinearity begets surprises

Temperature sensitivity of soil respiration and its effects on ecosystem carbon budget: nonlinearity begets surprises

Amplifying effects of land‐use change on future atmospheric CO2 levels

Impacts of inadequate historical disturbance data in the early twentieth century on modeling recent carbon dynamics (1951–2010) in conterminous U.S. forests

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Product

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Contribution of Increasing CO ₂ and Climate to Carbon Storage by Ecosystems in the United States

Amplifying effects of land‐use change on future atmospheric CO₂ levels