Inverse analysis of coupled carbon–nitrogen cycles against multiple datasets at ambient and elevated CO2

Aims Carbon (C) sequestration in terrestrial ecosystems is strongly regulated by nitrogen (N) processes. However, key parameters that determine the degree of N regulation on terrestrial C sequestration have not been well quantified. Methods Here, we used a bayesian probabilistic inversion approach to estimate 14 target parameters related to ecosystem C and N interactions from 19 datasets obtained from Duke Forests under ambient and elevated carbon dioxide (Co2). Important Findings our results indicated that 8 of the 14 target parameters, such as C:N ratios in most ecosystem compartments, plant N uptake and external N input, were well constrained by available datasets whereas the others, such as N allocation coefficients, N loss and the initial value of mineral N pool were poorly constrained. our analysis showed that elevated Co2 led to the increases in C:N ratios in foliage, fine roots and litter. moreover, elevated Co2 stimulated plant N uptake and increased ecosystem N capital in Duke Forests by 25.2 and 8.5%, respectively. In addition, elevated Co2 resulted in the decrease of C exit rates (i.e. increases in C residence times) in foliage, woody biomass, structural litter and passive soil organic matter, but the increase of C exit rate in fine roots. our results demonstrated that Co2 enrichment substantially altered key parameters in determining terrestrial C and N interactions, which have profound implications for model improvement and predictions of future C sequestration in terrestrial ecosystems in response to global change.

[1]  R. B. Jackson,et al.  Fine root dynamics in a loblolly pine forest are influenced by free‐air‐CO2‐enrichment: a six‐year‐minirhizotron study , 2008 .

[2]  Shaun Quegan,et al.  Model–data synthesis in terrestrial carbon observation: methods, data requirements and data uncertainty specifications , 2005 .

[3]  Andrei P. Sokolov,et al.  Consequences of Considering Carbon–Nitrogen Interactions on the Feedbacks between Climate and the Terrestrial Carbon Cycle , 2008 .

[4]  Andrew D. Friend,et al.  Carbon and nitrogen cycle dynamics in the O‐CN land surface model: 1. Model description, site‐scale evaluation, and sensitivity to parameter estimates , 2010 .

[5]  R. B. Jackson,et al.  Progressive nitrogen limitation of ecosystem processes under elevated CO2 in a warm-temperate forest. , 2006, Ecology.

[6]  Philippe Ciais,et al.  Optimizing a process‐based ecosystem model with eddy‐covariance flux measurements: A pine forest in southern France , 2007 .

[7]  Yiqi Luo,et al.  Terrestrial C:N stoichiometry in response to elevated CO2 and N addition: a synthesis of two meta-analyses , 2011, Plant and Soil.

[8]  Christopher B. Field,et al.  Nitrogen and Climate Change , 2003, Science.

[9]  B. Hun.  Does deep soil N availability sustain long-term ecosystem responses to elevated CO 2 ? , 2009 .

[10]  Charles W. Cook,et al.  Re-assessment of plant carbon dynamics at the Duke free-air CO(2) enrichment site: interactions of atmospheric [CO(2)] with nitrogen and water availability over stand development. , 2010, The New phytologist.

[11]  Yiqi Luo,et al.  Main and interactive effects of warming, clipping, and doubled precipitation on soil CO2 efflux in a grassland ecosystem , 2006 .

[12]  W. K. Hastings,et al.  Monte Carlo Sampling Methods Using Markov Chains and Their Applications , 1970 .

[13]  Kenneth L. Denman Canada.  Couplings between changes in the climate system and biogeochemistry , 2008 .

[14]  B. Law,et al.  An improved analysis of forest carbon dynamics using data assimilation , 2005 .

[15]  R. Norby,et al.  Nitrogen uptake, distribution, turnover, and efficiency of use in a CO2-enriched sweetgum forest. , 2006, Ecology.

[16]  Christopher B. Field,et al.  Predicting responses of photosynthesis and root fraction to elevated [CO2]a: interactions among carbon, nitrogen, and growth* , 1994 .

[17]  B. Hungate,et al.  Does deep soil N availability sustain long‐term ecosystem responses to elevated CO2? , 2009 .

[18]  Li Zhang,et al.  Estimated carbon residence times in three forest ecosystems of eastern China: Applications of probabilistic inversion , 2010 .

[19]  R. B. Jackson,et al.  Potential nitrogen constraints on soil carbon sequestration under low and elevated atmospheric CO2. , 2006, Ecology.

[20]  W. Knorr,et al.  Inversion of terrestrial ecosystem model parameter values against eddy covariance measurements by Monte Carlo sampling , 2005 .

[21]  Charles W. Cook,et al.  Increased belowground biomass and soil CO2 fluxes after a decade of carbon dioxide enrichment in a warm-temperate forest. , 2009, Ecology.

[22]  Yiqi Luo,et al.  Carbon : nitrogen stoichiometry in forest ecosystems during stand development , 2011 .

[23]  Yiqi Luo,et al.  Elevated CO2 stimulates net accumulations of carbon and nitrogen in land ecosystems: a meta-analysis. , 2006, Ecology.

[24]  J. Nagy,et al.  A free‐air enrichment system for exposing tall forest vegetation to elevated atmospheric CO2 , 1999 .

[25]  Edward B. Rastetter,et al.  RESPONSES OF N‐LIMITED ECOSYSTEMS TO INCREASED CO2: A BALANCED‐NUTRITION, COUPLED‐ELEMENT‐CYCLES MODEL , 1997 .

[26]  Soil carbon sequestration in a pine forest after 9 years of atmospheric CO 2 enrichment , 2008 .

[27]  Li Zhang,et al.  Parameter identifiability, constraint, and equifinality in data assimilation with ecosystem models. , 2009, Ecological applications : a publication of the Ecological Society of America.

[28]  W. Parton,et al.  Progressive Nitrogen Limitation of Ecosystem Responses to Rising Atmospheric Carbon Dioxide , 2004 .

[29]  B. Hungate,et al.  Nitrogen cycling during seven years of atmospheric CO2 enrichment in a scrub oak woodland. , 2006, Ecology.

[30]  W. Schlesinger,et al.  The nitrogen budget of a pine forest under free air CO2 enrichment , 2002, Oecologia.

[31]  Peter A. Coppin,et al.  Parameter estimation in surface exchange models using nonlinear inversion: how many parameters can we estimate and which measurements are most useful? , 2001 .

[32]  Pierre Friedlingstein,et al.  Carbon and nitrogen cycle dynamics in the O‐CN land surface model: 2. Role of the nitrogen cycle in the historical terrestrial carbon balance , 2010 .

[33]  Lianhai Wu,et al.  ELEVATED CO2 DIFFERENTIATES ECOSYSTEM CARBON PROCESSES: DECONVOLUTION ANALYSIS OF DUKE FOREST FACE DATA , 2001 .

[34]  E. Davidson,et al.  Estimating parameters of a forest ecosystem C model with measurements of stocks and fluxes as joint constraints , 2010, Oecologia.

[35]  Shenfeng Fei,et al.  Ecological forecasting and data assimilation in a data-rich era. , 2011, Ecological applications : a publication of the Ecological Society of America.

[36]  S. Gerber,et al.  Nitrogen cycling and feedbacks in a global dynamic land model , 2010 .

[37]  D. Schimel,et al.  Concurrent and lagged impacts of an anomalously warm year on autotrophic and heterotrophic components of soil respiration: a deconvolution analysis. , 2010, The New phytologist.

[38]  W. Schlesinger,et al.  Soil–Nitrogen Cycling in a Pine Forest Exposed to 5 Years of Elevated Carbon Dioxide , 2003, Ecosystems.

[39]  P. Reich,et al.  Maintenance of leaf N controls the photosynthetic CO2 response of grassland species exposed to 9 years of free‐air CO2 enrichment , 2010 .

[40]  L. White,et al.  Probabilistic inversion of a terrestrial ecosystem model: Analysis of uncertainty in parameter estimation and model prediction , 2006 .

[41]  W. Schlesinger,et al.  EFFECTS OF FREE-AIR CO2 ENRICHMENT (FACE) ON BELOWGROUND PROCESSES IN A PINUS TAEDA FOREST , 2000 .

[42]  E. B. Rastetter,et al.  Changes in C storage by terrestrial ecosystems: How C-N interactions restrict responses to CO2 and temperature , 1992 .

[43]  R. Monson,et al.  Model‐data synthesis of diurnal and seasonal CO2 fluxes at Niwot Ridge, Colorado , 2006 .

[44]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

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

[46]  Qianlai Zhuang,et al.  A global sensitivity analysis and Bayesian inference framework for improving the parameter estimation and prediction of a process-based Terrestrial Ecosystem Model , 2009 .

[47]  Yiqi Luo,et al.  Relative Information Contributions of Model vs. Data to Constraints of Short- and Long-Term Forecasts of Forest Carbon Dynamics , 2010 .

[48]  E. Bernhardt,et al.  Enhanced root exudation induces microbial feedbacks to N cycling in a pine forest under long-term CO2 fumigation. , 2011, Ecology letters.

[49]  Ernst Linder,et al.  Estimating diurnal to annual ecosystem parameters by synthesis of a carbon flux model with eddy covariance net ecosystem exchange observations , 2005 .

[50]  Peter E. Thornton,et al.  Influence of carbon‐nitrogen cycle coupling on land model response to CO2 fertilization and climate variability , 2007 .

[51]  N. Metropolis,et al.  Equation of State Calculations by Fast Computing Machines , 1953, Resonance.

[52]  Benjamin Z. Houlton,et al.  Nitrogen constraints on terrestrial carbon uptake: Implications for the global carbon‐climate feedback , 2009 .

[53]  Josep G. Canadell,et al.  Sustainability of terrestrial carbon sequestration: A case study in Duke Forest with inversion approach , 2003 .

[54]  Atul K. Jain,et al.  Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors , 2009 .

[55]  S. Güsewell.  N : P ratios in terrestrial plants: variation and functional significance. , 2004, The New phytologist.

[56]  Colleen M. Iversen,et al.  Digging deeper: fine-root responses to rising atmospheric CO concentration in forested ecosystems. , 2010, The New phytologist.

[57]  Yiqi Luo,et al.  Relative information contributions of model vs. data to short- and long-term forecasts of forest carbon dynamics. , 2011, Ecological applications : a publication of the Ecological Society of America.

[58]  P. Reich,et al.  Carbon-Nitrogen Interactions in Terrestrial Ecosystems in Response to Rising Atmospheric Carbon Dioxide , 2006 .

[59]  R. B. Jackson,et al.  Soil carbon sequestration in a pine forest after 9 years of atmospheric CO2 enrichment , 2008 .

[60]  R. B. Jackson,et al.  Increases in the flux of carbon belowground stimulate nitrogen uptake and sustain the long-term enhancement of forest productivity under elevated CO₂. , 2011, Ecology letters.

[61]  R. B. Jackson,et al.  Increases in nitrogen uptake rather than nitrogen-use efficiency support higher rates of temperate forest productivity under elevated CO2 , 2007, Proceedings of the National Academy of Sciences.