Soil carbon sensitivity to temperature and carbon use efficiency compared across microbial-ecosystem models of varying complexity

Global ecosystem models may require microbial components to accurately predict feedbacks between climate warming and soil decomposition, but it is unclear what parameters and levels of complexity are ideal for scaling up to the globe. Here we conducted a model comparison using a conventional model with first-order decay and three microbial models of increasing complexity that simulate short- to long-term soil carbon dynamics. We focused on soil carbon responses to microbial carbon use efficiency (CUE) and temperature. Three scenarios were implemented in all models: constant CUE (held at 0.31), varied CUE (−0.016 °C−1), and 50 % acclimated CUE (−0.008 °C−1). Whereas the conventional model always showed soil carbon losses with increasing temperature, the microbial models each predicted a temperature threshold above which warming led to soil carbon gain. The location of this threshold depended on CUE scenario, with higher temperature thresholds under the acclimated and constant scenarios. This result suggests that the temperature sensitivity of CUE and the structure of the soil carbon model together regulate the long-term soil carbon response to warming. Equilibrium soil carbon stocks predicted by the microbial models were much less sensitive to changing inputs compared to the conventional model. Although many soil carbon dynamics were similar across microbial models, the most complex model showed less pronounced oscillations. Thus, adding model complexity (i.e. including enzyme pools) could improve the mechanistic representation of soil carbon dynamics during the transient phase in certain ecosystems. This study suggests that model structure and CUE parameterization should be carefully evaluated when scaling up microbial models to ecosystems and the globe.

[1]  A. Heinemeyer,et al.  Effects of three years of soil warming and shading on the rate of soil respiration: substrate availability and not thermal acclimation mediates observed response , 2007 .

[2]  R. Schnur,et al.  Climate-carbon cycle feedback analysis: Results from the C , 2006 .

[3]  William R. Wieder,et al.  Global soil carbon projections are improved by modelling microbial processes , 2013 .

[4]  Jizhong Zhou,et al.  Microbial mediation of carbon-cycle feedbacks to climate warming , 2012 .

[5]  Michael J. Rogers,et al.  Long-term sensitivity of soil carbon turnover to warming , 2005, Nature.

[6]  J. Randerson,et al.  Causes of variation in soil carbon simulations from CMIP5 Earth system models and comparison with observations , 2012 .

[7]  A. Porporato,et al.  A theoretical analysis of nonlinearities and feedbacks in soil carbon and nitrogen cycles , 2007 .

[8]  G. Ågren,et al.  Reconciling differences in predictions of temperature response of soil organic matter , 2002 .

[9]  Steven D. Allison,et al.  The Michaelis–Menten kinetics of soil extracellular enzymes in response to temperature: a cross‐latitudinal study , 2012 .

[10]  Stephen W. Pacala,et al.  LINEAR ANALYSIS OF SOIL DECOMPOSITION: INSIGHTS FROM THE CENTURY MODEL , 1998 .

[11]  J. Schimel.  Soil carbon: Microbes and global carbon , 2013 .

[12]  David W. Kicklighter,et al.  Equilibrium Responses of Soil Carbon to Climate Change: Empirical and Process-Based Estimates , 1995 .

[13]  Matthew J. Smith,et al.  Oscillatory behavior of two nonlinear microbial models of soil carbon decomposition , 2013 .

[14]  J. Cole,et al.  BACTERIAL GROWTH EFFICIENCY IN NATURAL AQUATIC SYSTEMS , 1998 .

[15]  R. Koide,et al.  Acclimation to temperature and temperature sensitivity of metabolism by ectomycorrhizal fungi , 2008 .

[16]  J. Randerson,et al.  Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks: results from an atmosphere-ocean general circulation model , 2009 .

[17]  Eoin L. Brodie,et al.  Integrating microbial ecology into ecosystem models: challenges and priorities , 2012, Biogeochemistry.

[18]  J. Neff,et al.  Does adding microbial mechanisms of decomposition improve soil organic matter models? A comparison of four models using data from a pulsed rewetting experiment , 2009 .

[19]  B. Hawkins,et al.  A framework: , 2020, Harmful Interaction between the Living and the Dead in Greek Tragedy.

[20]  C. Quan,et al.  Acclimatization of soil respiration to warming , 2004 .

[21]  J. Six,et al.  The temperature response of soil microbial efficiency and its feedback to climate , 2013 .

[22]  W. Post,et al.  Development of microbial-enzyme-mediated decomposition model parameters through steady-state and dynamic analyses. , 2013, Ecological applications : a publication of the Ecological Society of America.

[23]  W. Parton,et al.  Analysis of factors controlling soil organic matter levels in Great Plains grasslands , 1987 .

[24]  M. Cannell,et al.  Soil Carbon Storage Response to Temperature: an Hypothesis , 2001 .

[25]  M. Garnett,et al.  Soil microbial respiration in arctic soil does not acclimate to temperature. , 2008, Ecology letters.

[26]  W. Parton,et al.  Dynamics of C, N, P and S in grassland soils: a model , 1988 .

[27]  Jianwei Li,et al.  Legacies of native climate regime govern responses of boreal soil microbes to litter stoichiometry and temperature , 2013 .

[28]  Mark A. Bradford,et al.  Soil-carbon response to warming dependent on microbial physiology , 2010 .

[29]  Andreas Richter,et al.  Environmental and stoichiometric controls on microbial carbon-use efficiency in soils. , 2012, The New phytologist.

[30]  Joshua P. Schimel,et al.  The implications of exoenzyme activity on microbial carbon and nitrogen limitation in soil: a theoretical model , 2003 .

[31]  A. V. Van Bruggen,et al.  Short-Term Wavelike Dynamics of Bacterial Populations in Response to Nutrient Input from Fresh Plant Residues , 2005, Microbial Ecology.

[32]  J. Melillo,et al.  Soil warming, carbon–nitrogen interactions, and forest carbon budgets , 2011, Proceedings of the National Academy of Sciences.

[33]  G. Ågren,et al.  What determines the temperature response of soil organic matter decomposition , 2007 .

[34]  Yiqi Luo,et al.  Acclimatization of soil respiration to warming in a tall grass prairie , 2001, Nature.

[35]  W. Post,et al.  A theoretical reassessment of microbial maintenance and implications for microbial ecology modeling. , 2012, FEMS microbiology ecology.

[36]  R. B. Jackson,et al.  THE VERTICAL DISTRIBUTION OF SOIL ORGANIC CARBON AND ITS RELATION TO CLIMATE AND VEGETATION , 2000 .

[37]  W. Horwath,et al.  Decomposition of rice straw and microbial carbon use efficiency under different soil temperatures and moistures , 2000 .

[38]  J. Aber,et al.  Soil warming and carbon-cycle feedbacks to the climate system. , 2002, Science.

[39]  John F. Morrison.  Michaelis–Menten Kinetics , 2002 .

[40]  A. Mariotti,et al.  The priming effect of organic matter: a question of microbial competition? , 2003 .

[41]  Stefano Manzoni,et al.  Carbon use efficiency of microbial communities: stoichiometry, methodology and modelling. , 2013, Ecology letters.

[42]  S. Frey,et al.  Thermal adaptation of soil microbial respiration to elevated temperature. , 2008, Ecology letters.

[43]  Y. Kuzyakov.  Priming effects : interactions between living and dead organic matter , 2010 .

[44]  E. Pendall,et al.  Does declining carbon‐use efficiency explain thermal acclimation of soil respiration with warming? , 2013, Global change biology.

[45]  J. Six,et al.  Bacterial and Fungal Contributions to Carbon Sequestration in Agroecosystems , 2006 .

[46]  R. Sinsabaugh,et al.  An enzymic approach to the analysis of microbial activity during plant litter decomposition , 1991 .

[47]  Francesca M. Hopkins,et al.  A framework for representing microbial decomposition in coupled climate models , 2012, Biogeochemistry.