Impacts of land cover and climate data selection on understanding terrestrial carbon dynamics and the CO&lt;sub&gt;2&lt;/sub&gt; airborne fraction

Abstract. Terrestrial and oceanic carbon cycle processes remove ~55 % of global carbon emissions, with the remaining 45 %, known as the "airborne fraction", accumulating in the atmosphere. The long-term dynamics of the component fluxes contributing to the airborne fraction are challenging to interpret, but important for informing fossil-fuel emission targets and for monitoring the trends of biospheric carbon fluxes. Climate and land-cover forcing data for terrestrial ecosystem models are a largely unexplored source of uncertainty in terms of their contribution to understanding airborne fraction dynamics. Here we present results using a single dynamic global vegetation model forced by an ensemble experiment of climate (CRU, ERA-Interim, NCEP-DOE II), and diagnostic land-cover datasets (GLC2000, GlobCover, MODIS). For the averaging period 1996–2005, forcing uncertainties resulted in a large range of simulated global carbon fluxes, up to 13 % for net primary production (52.4 to 60.2 Pg C a−1) and 19 % for soil respiration (44.2 to 54.8 Pg C a−1). The sensitivity of contemporary global terrestrial carbon fluxes to climate strongly depends on forcing data (1.2–5.9 Pg C K−1 or 0.5 to 2.7 ppmv CO2 K−1), but weakening carbon sinks in sub-tropical regions and strengthening carbon sinks in northern latitudes are found to be robust. The climate and land-cover combination that best correlate to the inferred carbon sink, and with the lowest residuals, is from observational data (CRU) rather than reanalysis climate data and with land-cover categories that have more stringent criteria for forest cover (MODIS). Since 1998, an increasing positive trend in residual error from bottom-up accounting of global sinks and sources (from 0.03 (1989–2005) to 0.23 Pg C a−1 (1998–2005)) suggests that either modeled drought sensitivity of carbon fluxes is too high, or that carbon emissions from net land-cover change is too large.

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Impacts of land cover and climate data selection on understanding terrestrial carbon dynamics and the CO2 airborne fraction

Biogeosciences Discussions ◽

10.5194/bgd-8-1617-2011 ◽

2011 ◽

Vol 8 (1) ◽

pp. 1617-1642 ◽

Cited By ~ 5

Author(s):

B. Poulter ◽

D. C. Frank ◽

E. L. Hodson ◽

N. E. Zimmermann

Keyword(s):

Land Cover ◽

Forest Cover ◽

Net Primary Production ◽

Carbon Fluxes ◽

Positive Trend ◽

Carbon Sinks ◽

Climate Data ◽

Terrestrial Carbon ◽

Dynamic Global Vegetation Model ◽

Global Carbon

Abstract. Terrestrial and oceanic carbon cycle processes remove ~ 55% of global carbon emissions, with the remaining 45%, known as the "airborne fraction", accumulating in the atmosphere. The long-term dynamics of the component fluxes contributing to the airborne fraction are challenging to interpret, but important for informing fossil-fuel emission targets and for monitoring the trends of biospheric carbon fluxes. Climate and land-cover forcing data for terrestrial ecosystem models are a largely unexplored source of uncertainty in terms of their contribution to understanding airborne fraction dynamics. Here we present results using a single dynamic global vegetation model forced by an ensemble experiment of climate (CRU, ERA-Interim, NCEP-DOE II), and diagnostic land-cover datasets (GLC2000, GlobCover, MODIS). Forcing uncertainties resulted in a large range of simulated global carbon fluxes, up to 13% for net primary production (52.4 to 60.2 Pg C a−1) and 19% for soil respiration (44.2 to 54.8 Pg C a−1). The sensitivity of contemporary global terrestrial carbon fluxes to climate strongly depends on forcing data (1.2–5.9 Pg C K−1 or 0.5 to 2.7 ppmv CO2 K−1), but weakening carbon sinks in sub-tropical regions and strengthening carbon sinks in northern latitudes are found to be robust. The climate and land-cover combination that best correlate to the inferred carbon sink, and with the lowest residuals, is from observational data (CRU) rather than reanalysis climate data and with land-cover categories that have more stringent criteria for forest cover (MODIS). Since 1998, an increasing positive trend in residual error from bottom-up accounting of global sinks and sources (from 0.03 (1989–2005) to 0.23 Pg C a−1 (1998–2005)) suggests that either modeled drought sensitivity of carbon fluxes is too high, or that the trend toward decreased net land-use fluxes (~ 0.5 Pg C) is overestimated.

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Estimating regional terrestrial carbon fluxes for the Australian continent using a multiple-constraint approach. I. Using remotely sensed data and ecological observations of net primary production

Tellus B ◽

10.1034/j.1600-0889.2003.00031.x ◽

2003 ◽

Vol 55 (2) ◽

pp. 270-289 ◽

Cited By ~ 16

Author(s):

YING PING WANG ◽

DAMIAN J. BARRETT2

Keyword(s):

Primary Production ◽

Net Primary Production ◽

Carbon Fluxes ◽

Remotely Sensed ◽

Terrestrial Carbon ◽

Remotely Sensed Data ◽

Australian Continent ◽

Multiple Constraint ◽

Constraint Approach

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Can we reconcile differences in estimates of carbon fluxes from land-use change and forestry for the 1990s?

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-3843-2008 ◽

2008 ◽

Vol 8 (1) ◽

pp. 3843-3893 ◽

Cited By ~ 2

Author(s):

A. Ito ◽

J. E. Penner ◽

M. J. Prather ◽

C. P. de Campos ◽

R. A. Houghton ◽

...

Keyword(s):

Climate Change ◽

Land Use ◽

Land Cover ◽

Land Cover Change ◽

Carbon Fluxes ◽

Terrestrial Carbon ◽

Co2 Fertilization ◽

Uncertainty Range ◽

Inverse Models ◽

The Usa

Abstract. The effect of Land Use Change and Forestry (LUCF) on terrestrial carbon fluxes can be regarded as a carbon credit or debit under the UNFCCC, but scientific uncertainty in the estimates for LUCF remains large. Here, we assess the LUCF estimates by examining a variety of models of different types with different land cover change maps in the 1990s. Annual carbon pools and their changes are separated into different components for separate geographical regions, while annual land cover change areas and carbon fluxes are disaggregated into different LUCF activities and the biospheric response due to CO2 fertilization and climate change. We developed a consolidated estimate of the terrestrial carbon fluxes that combines book-keeping models with process-based biogeochemical models and inventory estimates and yields an estimate of the global terrestrial carbon flux that is within the uncertainty range developed in the IPCC 4th Assessment Report. We examined the USA and Brazil as case studies in order to assess the cause of differences from the UNFCCC reported carbon fluxes. Major differences in the litter and soil organic matter components are found for the USA. Differences in Brazil result from assumptions about the LUC for agricultural purposes. The effects of CO2 fertilization and climate change also vary significantly in Brazil. Our consolidated estimate shows that the small sink in Latin America is within the uncertainty range from inverse models, but that the sink in the USA is significantly smaller than the inverse models estimates. Because there are different sources of errors at the country level, there is no easy reconciliation of different estimates of carbon fluxes at the global level. Clearly, further work is required to develop data sets for historical land cover change areas and models of biogeochemical changes for an accurate representation of carbon uptake or emissions due to LUC.

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Regional CO2 fluxes from 2010 to 2015 inferred from GOSAT XCO2 retrievals using a new version of the Global Carbon Assimilation System

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-1963-2021 ◽

2021 ◽

Vol 21 (3) ◽

pp. 1963-1985

Author(s):

Fei Jiang ◽

Hengmao Wang ◽

Jing M. Chen ◽

Weimin Ju ◽

Xiangjun Tian ◽

...

Keyword(s):

Carbon Assimilation ◽

Carbon Fluxes ◽

Atmospheric Co2 ◽

Interannual Variations ◽

Carbon Sinks ◽

Area Index ◽

Spatial Coverage ◽

The Impact ◽

Global Carbon ◽

Assimilation System

Abstract. Satellite retrievals of the column-averaged dry air mole fractions of CO2 (XCO2) could help to improve carbon flux estimation due to their good spatial coverage. In this study, in order to assimilate the GOSAT (Greenhouse Gases Observing Satellite) XCO2 retrievals, the Global Carbon Assimilation System (GCAS) is upgraded with new assimilation algorithms, procedures, a localization scheme, and a higher assimilation parameter resolution. This upgraded system is referred to as GCASv2. Based on this new system, the global terrestrial ecosystem (BIO) and ocean (OCN) carbon fluxes from 1 May 2009 to 31 December 2015 are constrained using the GOSAT ACOS (Atmospheric CO2 Observations from Space) XCO2 retrievals (Version 7.3). The posterior carbon fluxes from 2010 to 2015 are independently evaluated using CO2 observations from 52 surface flask sites. The results show that the posterior carbon fluxes could significantly improve the modeling of atmospheric CO2 concentrations, with global mean bias decreases from a prior value of 1.6 ± 1.8 ppm to −0.5 ± 1.8 ppm. The uncertainty reduction (UR) of the global BIO flux is 17 %, and the highest monthly regional UR could reach 51 %. Globally, the mean annual BIO and OCN carbon sinks and their interannual variations inferred in this study are very close to the estimates of CarbonTracker 2017 (CT2017) during the study period, and the inferred mean atmospheric CO2 growth rate and its interannual changes are also very close to the observations. Regionally, over the northern lands, the strongest carbon sinks are seen in temperate North America, followed by Europe, boreal Asia, and temperate Asia; in the tropics, there are strong sinks in tropical South America and tropical Asia, but a very weak sink in Africa. This pattern is significantly different from the estimates of CT2017, but the estimated carbon sinks for each continent and some key regions like boreal Asia and the Amazon are comparable or within the range of previous bottom-up estimates. The inversion also changes the interannual variations in carbon fluxes in most TransCom land regions, which have a better relationship with the changes in severe drought area (SDA) or leaf area index (LAI), or are more consistent with previous estimates for the impact of drought. These results suggest that the GCASv2 system works well with the GOSAT XCO2 retrievals and shows good performance with respect to estimating the surface carbon fluxes; meanwhile, our results also indicate that the GOSAT XCO2 retrievals could help to better understand the interannual variations in regional carbon fluxes.

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Monitoring Effects of Land Cover Change on Biophysical Drivers in Rangelands Using Albedo

Land ◽

10.3390/land8020033 ◽

2019 ◽

Vol 8 (2) ◽

pp. 33 ◽

Cited By ~ 5

Author(s):

Zahn Münch ◽

Lesley Gibson ◽

Anthony Palmer

Keyword(s):

Land Cover ◽

Land Cover Change ◽

Carbon Storage ◽

Water Use ◽

Satellite Data ◽

Management Practices ◽

Net Primary Production ◽

Seasonal Effects ◽

Positive Trend ◽

Normalised Difference Vegetation Index

This paper explores the relationship between land cover change and albedo, recognized as a regulating ecosystems service. Trends and relationships between land cover change and surface albedo were quantified to characterise catchment water and carbon fluxes, through respectively evapotranspiration (ET) and net primary production (NPP). Moderate resolution imaging spectroradiometer (MODIS) and Landsat satellite data were used to describe trends at catchment and land cover change trajectory level. Peak season albedo was computed to reduce seasonal effects. Different trends were found depending on catchment land management practices, and satellite data used. Although not statistically significant, albedo, NPP, ET and normalised difference vegetation index (NDVI) were all correlated with rainfall. In both catchments, NPP, ET and NDVI showed a weak negative trend, while albedo showed a weak positive trend. Modelled land cover change was used to calculate future carbon storage and water use, with a decrease in catchment carbon storage and water use computed. Grassland, a dominant dormant land cover class, was targeted for land cover change by woody encroachment and afforestation, causing a decrease in albedo, while urbanisation and cultivation caused an increase in albedo. Land cover map error of fragmented transition classes and the mixed pixel effect, affected results, suggesting use of higher-resolution imagery for NPP and ET and albedo as a proxy for land cover.

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Photoheterotrophy by aerobic anoxygenic bacteria modulates carbon fluxes in a freshwater lake

The ISME Journal ◽

10.1038/s41396-021-01142-2 ◽

2021 ◽

Author(s):

Kasia Piwosz ◽

Cristian Villena-Alemany ◽

Izabela Mujakić

Keyword(s):

Primary Production ◽

Net Primary Production ◽

Carbon Fluxes ◽

Photochemical Reactions ◽

Freshwater Lake ◽

Infrared Light ◽

Community Respiration ◽

New Paradigm ◽

Heterotrophic Microorganisms ◽

Global Carbon

AbstractLakes are a significant component of the global carbon cycle. Respiration exceeds net primary production in most freshwater lakes, making them a source of CO2 to the atmosphere. Driven by heterotrophic microorganisms, respiration is assumed to be unaffected by light, thus it is measured in the dark. However, photoheterotrophs, such as aerobic anoxygenic photoheterotrophic (AAP) bacteria that produce ATP via photochemical reactions, substantially reduce respiration in the light. They are an abundant and active component of bacterioplankton, but their photoheterotrophic contribution to microbial community metabolism remains unquantified. We showed that the community respiration rate in a freshwater lake was reduced by 15.2% (95% confidence interval (CI): 6.6–23.8%) in infrared light that is usable by AAP bacteria but not by primary producers. Moreover, significantly higher assimilation rates of glucose (18.1%; 7.8–28.4%), pyruvate (9.5%; 4.2–14.8%), and leucine (5.9%; 0.1–11.6%) were measured in infrared light. At the ecosystem scale, the amount of CO2 from respiration unbalanced by net primary production was by 3.69 × 109 g CO2 lower over these two sampling seasons when measured in the infrared light. Our results demonstrate that dark measurements of microbial activity significantly bias the carbon fluxes, providing a new paradigm for their quantification in aquatic environments.

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Holocene carbon emissions as a result of anthropogenic land cover change

The Holocene ◽

10.1177/0959683610386983 ◽

2010 ◽

Vol 21 (5) ◽

pp. 775-791 ◽

Cited By ~ 303

Author(s):

Jed O. Kaplan ◽

Kristen M. Krumhardt ◽

Erle C. Ellis ◽

William F. Ruddiman ◽

Carsten Lemmen ◽

...

Keyword(s):

Land Use ◽

Land Cover ◽

Land Cover Change ◽

Carbon Emissions ◽

Land Surface ◽

Simple Relationship ◽

Data Set ◽

Dynamic Global Vegetation Model ◽

The Holocene ◽

The World

Humans have altered the Earth’s land surface since the Paleolithic mainly by clearing woody vegetation first to improve hunting and gathering opportunities, and later to provide agricultural cropland. In the Holocene, agriculture was established on nearly all continents and led to widespread modification of terrestrial ecosystems. To quantify the role that humans played in the global carbon cycle over the Holocene, we developed a new, annually resolved inventory of anthropogenic land cover change from 8000 years ago to the beginning of large-scale industrialization (ad 1850). This inventory is based on a simple relationship between population and land use observed in several European countries over preindustrial time. Using this data set, and an alternative scenario based on the HYDE 3.1 land use data base, we forced the LPJ dynamic global vegetation model in a series of continuous simulations to evaluate the impacts of humans on terrestrial carbon storage during the preindustrial Holocene. Our model setup allowed us to quantify the importance of land degradation caused by repeated episodes of land use followed by abandonment. By 3 ka BP, cumulative carbon emissions caused by anthropogenic land cover change in our new scenario ranged between 84 and 102 Pg, translating to c. 7 ppm of atmospheric CO2. By ad 1850, emissions were 325–357 Pg in the new scenario, in contrast to 137–189 Pg when driven by HYDE. Regional events that resulted in local emissions or uptake of carbon were often balanced by contrasting patterns in other parts of the world. While we cannot close the carbon budget in the current study, simulated cumulative anthropogenic emissions over the preindustrial Holocene are consistent with the ice core record of atmospheric δ13CO2 and support the hypothesis that anthropogenic activities led to the stabilization of atmospheric CO2 concentrations at a level that made the world substantially warmer than it otherwise would be.

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