Carbon Balance and Management

BackgroundThe amount of carbon dioxide in the atmosphere steadily increases as a consequence of anthropogenic emissions but with large interannual variability caused by the terrestrial biosphere. These variations in the CO2 growth rate are caused by large-scale climate anomalies but the relative contributions of vegetation growth and soil decomposition is uncertain. We use a biogeochemical model of the terrestrial biosphere to differentiate the effects of temperature and precipitation on net primary production (NPP) and heterotrophic respiration (Rh) during the two largest anomalies in atmospheric CO2 increase during the last 25 years. One of these, the smallest atmospheric year-to-year increase (largest land carbon uptake) in that period, was caused by global cooling in 1992/93 after the Pinatubo volcanic eruption. The other, the largest atmospheric increase on record (largest land carbon release), was caused by the strong El Niño event of 1997/98.ResultsWe find that the LPJ model correctly simulates the magnitude of terrestrial modulation of atmospheric carbon anomalies for these two extreme disturbances. The response of soil respiration to changes in temperature and precipitation explains most of the modelled anomalous CO2 flux.ConclusionObserved and modelled NEE anomalies are in good agreement, therefore we suggest that the temporal variability of heterotrophic respiration produced by our model is reasonably realistic. We therefore conclude that during the last 25 years the two largest disturbances of the global carbon cycle were strongly controlled by soil processes rather then the response of vegetation to these large-scale climatic events.

[1]  C. Tucker,et al.  Climate-Driven Increases in Global Terrestrial Net Primary Production from 1982 to 1999 , 2003, Science.

[2]  I. C. Prentice,et al.  Climatic Control of the High-Latitude Vegetation Greening Trend and Pinatubo Effect , 2002, Science.

[3]  W. Wagner,et al.  Evaluation of the agreement between the first global remotely sensed soil moisture data with model and precipitation data , 2003 .

[4]  Richard G. Derwent,et al.  Radiative forcing in the 21st century due to ozone changes in the troposphere and the lower stratosphere , 2003 .

[5]  E. Davidson,et al.  Temperature sensitivity of soil carbon decomposition and feedbacks to climate change , 2006, Nature.

[6]  Christopher B. Field,et al.  Satellite‐derived increases in net primary productivity across North America, 1982–1998 , 2002 .

[7]  R. Reynolds,et al.  Global surface air temperature in 1995: Return to pre‐Pinatubo level , 1996 .

[8]  R. Sepanski,et al.  TRENDS '90: A compendium of data on global change , 1991 .

[9]  I. Fung,et al.  CO2 seasonality indicates origins of post‐Pinatubo sink , 2004 .

[10]  C. Potter,et al.  Interannual covariability in Northern Hemisphere air temperatures and greenness associated with El Niño‐Southern Oscillation and the Arctic Oscillation , 2003 .

[11]  Fire emissions from C3 and C4 vegetation and their influence on interannual variability of atmospheric CO2 and δ13CO2 , 2005 .

[12]  Jonathan A. Foley,et al.  An equilibrium model of the terrestrial carbon budget , 1995 .

[13]  J. Randerson,et al.  Continental-Scale Partitioning of Fire Emissions During the 1997 to 2001 El Niño/La Niña Period , 2003, Science.

[14]  M. Mcphaden,et al.  Genesis and evolution of the 1997-98 El Nino , 1999, Science.

[15]  Dennis D. Baldocchi,et al.  Response of a Deciduous Forest to the Mount Pinatubo Eruption: Enhanced Photosynthesis , 2003, Science.

[16]  J. Houghton,et al.  Climate change 2001 : the scientific basis , 2001 .

[17]  R. Houghton.  Carbon Flux to the Atmosphere from Land-Use Changes: 1850 to 1990 , 2001 .

[18]  M. Keller,et al.  Carbon in Amazon Forests: Unexpected Seasonal Fluxes and Disturbance-Induced Losses , 2003, Science.

[19]  Pang-Ning Tan,et al.  Continental-scale comparisons of terrestrial carbon sinks estimated from satellite data and ecosystem modeling 1982–1998 , 2003 .

[20]  J. Berry,et al.  A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species , 1980, Planta.

[21]  J. Lloyd,et al.  On the temperature dependence of soil respiration , 1994 .

[22]  Benjamin Smith,et al.  Using a generalized vegetation model to simulate vegetation dynamics in northeastern USA , 2004 .

[23]  G. Collatz,et al.  Coupled Photosynthesis-Stomatal Conductance Model for Leaves of C4 Plants , 1992 .

[24]  W. Lucht,et al.  Terrestrial vegetation and water balance-hydrological evaluation of a dynamic global vegetation model , 2004 .

[25]  P. Jones,et al.  REPRESENTING TWENTIETH CENTURY SPACE-TIME CLIMATE VARIABILITY. , 1998 .

[26]  J. Townshend,et al.  Global land cover classi(cid:142) cation at 1 km spatial resolution using a classi(cid:142) cation tree approach , 2004 .

[27]  I. C. Prentice,et al.  Evaluation of ecosystem dynamics, plant geography and terrestrial carbon cycling in the LPJ dynamic global vegetation model , 2003 .

[28]  P. Ciais,et al.  Multiple constraints on regional CO2 flux variations over land and oceans , 2005 .

[29]  Two decades of ocean CO2 sink and variability , 2003 .