DOCSLIB.ORG

Global Soil Organic Carbon Removal by Water Erosion Under Climate Change and Land Use Change During AD 1850–2005

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Global Soil Organic Carbon Removal by Water Erosion Under Climate Change and Land Use Change During AD 1850–2005 Biogeosciences, 15, 4459–4480, 2018 https://doi.org/10.5194/bg-15-4459-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Global soil organic carbon removal by water erosion under climate change and land use change during AD 1850–2005 Victoria Naipal1, Philippe Ciais1, Yilong Wang1, Ronny Lauerwald2,3, Bertrand Guenet1, and Kristof Van Oost4 1Laboratoire des Sciences du Climat et de l’Environnement, CEA CNRS UVSQ, Gif-sur-Yvette 91191, France 2Department of Geoscience, Environment and Society, Université Libre de Bruxelles, Brussels, Belgium 3Department of Mathematics, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK 4Université catholique de Louvain, TECLIM – Georges Lemaître Centre for Earth and Climate Research, Louvain-la-Neuve, Belgium Correspondence: Victoria Naipal ([email protected]) Received: 8 December 2017 – Discussion started: 23 January 2018 Revised: 29 June 2018 – Accepted: 9 July 2018 – Published: 20 July 2018 Abstract. Erosion is an Earth system process that transports mospheric CO2 and LUC. This additional erosional loss de- carbon laterally across the land surface and is currently ac- creases the cumulative global carbon sink on land by 2 Pg of celerated by anthropogenic activities. Anthropogenic land carbon for this specific period, with the largest effects found cover change has accelerated soil erosion rates by rainfall and for the tropics, where deforestation and agricultural expan- runoff substantially, mobilizing vast quantities of soil organic sion increased soil erosion rates significantly. We conclude carbon (SOC) globally. At timescales of decennia to mil- that the potential effect of soil erosion on the global SOC lennia this mobilized SOC can significantly alter previously stock is comparable to the effects of climate or LUC. It is estimated carbon emissions from land use change (LUC). thus necessary to include soil erosion in assessments of LUC However, a full understanding of the impact of erosion on and evaluations of the terrestrial carbon cycle. land–atmosphere carbon exchange is still missing. The aim of this study is to better constrain the terrestrial carbon fluxes by developing methods compatible with land surface mod- els (LSMs) in order to explicitly represent the links between 1 Introduction soil erosion by rainfall and runoff and carbon dynamics. For this we use an emulator that represents the carbon cycle of a Carbon emissions from land use change (LUC), recently esti- − LSM, in combination with the Revised Universal Soil Loss mated as 1:0±0:5 Pg C yr 1, form the second largest anthro- Equation (RUSLE) model. We applied this modeling frame- pogenic source of atmospheric CO2 (Le Quéré et al., 2016). work at the global scale to evaluate the effects of potential However, their uncertainty range is large, making it difficult soil erosion (soil removal only) in the presence of other per- to constrain the net land–atmosphere carbon fluxes and re- turbations of the carbon cycle: elevated atmospheric CO2, duce the biases in the global carbon budget (Goll et al., 2017; climate variability, and LUC. We find that over the period Houghton and Nassikas, 2017; Le Quéré et al., 2016). The AD 1850–2005 acceleration of soil erosion leads to a total absence of soil erosion in assessments of LUC is an impor- potential SOC removal flux of 74 ± 18 Pg C, of which 79 %– tant part of this uncertainty, as soil erosion is strongly con- 85 % occurs on agricultural land and grassland. Using our nected to LUC (Van Oost et al., 2012; Wang et al., 2017). best estimates for soil erosion we find that including soil ero- The expansion of agriculture has accelerated soil ero- sion in the SOC-dynamics scheme results in an increase of sion by rainfall and runoff significantly, mobilizing around 62 % of the cumulative loss of SOC over 1850–2005 due 783 ± 243 Pg of soil organic carbon (SOC) globally over the to the combined effects of climate variability, increasing at- past 8000 years (Wang et al., 2017). Most of the mobilized SOC is redeposited in alluvial and colluvial soils, where it Published by Copernicus Publications on behalf of the European Geosciences Union. 4460 V. Naipal et al.: Global soil organic carbon removal by water erosion is stabilized and buried for decades to millennia (Hoffmann carbon dynamics models at different spatial and temporal et al., 2013a, b; Wang et al., 2017). Together with dynamic scales. Some studies coupled process-oriented soil erosion replacement of removed SOC by new litter input at the erod- models with carbon turnover models calibrated for specific ing sites, and the progressive exposure of carbon-poor deep micro-catchments on timescales of a few decades to a mil- soils, this translocated and buried SOC can lead to a net car- lennium, (Billings et al., 2010; Van Oost et al., 2012; Nadeu bon sink at the catchment scale, potentially offsetting a large et al., 2015; Wang et al., 2015a; Zhao et al., 2016; Bouchoms part of the carbon emissions from LUC (Berhe et al., 2007; et al., 2017). Other studies focused on the application of par- Bouchoms et al., 2017; Harden et al., 1999; Hoffmann et al., simonious erosion–SOC-dynamics models using the Revised 2013a; Lal, 2003; Stallard, 1998; Wang et al., 2017). Universal Soil Loss Equation (RUSLE) approach together On eroding sites, soil erosion keeps the SOC stocks below with sediment transport methods at regional or continental a steady state (Van Oost et al., 2012) and can lead to substan- spatial scales (Chappell et al., 2015; Lugato et al., 2016; Yue tial CO2 emissions in certain regions (Billings et al., 2010; et al., 2016; Zhang et al., 2014). However, the modeling ap- Worrall et al., 2016; Lal, 2003). CO2 emission from soil ero- proaches used in these studies apply erosion models that still sion can take place during the breakdown of soil aggregates require many variables and data input that is often not avail- by erosion and during the transport of the eroded SOC by able at the global scale or for the past or the future time pe- runoff and later also by streams and rivers. riod. These models also run on a much higher spatial reso- LUC emissions are usually quantified using bookkeeping lution than LSMs, making it difficult to integrate them with models and LSMs that represent the impacts of LUC activ- LSMs. The study of Ito (2007) was one of the first studies to ities on the terrestrial carbon cycle (Le Quéré et al., 2016). couple water erosion to the carbon cycle at the global scale, These impacts are represented through processes leading to using a simple modeling approach that combined the RUSLE a local imbalance between net primary productivity (NPP) model with a global ecosystem carbon cycle model. How- and heterotrophic respiration, ignoring lateral displacement. ever, there are several unaddressed uncertainties related to his Currently, LSMs consider only the carbon fluxes following modeling approach, such as the application of the RUSLE at LUC resulting from changes in vegetation, soil carbon, and the global scale without adjusting its parameters. sometimes wood products (Van Oost et al., 2012; Stocker et Despite all the differences between the studies that cou- al., 2014). The additional carbon fluxes associated with the pled soil erosion to the carbon cycle, they all agree that soil human action of LUC from the removal and lateral transport erosion by rainfall and runoff is an essential component of of SOC by erosion are largely ignored. the carbon cycle. Therefore, to better constrain the land– In addition, the absence of lateral SOC transport by ero- atmosphere and the land–ocean carbon fluxes, it is neces- sion in LSMs complicates the quantification of the human sary to develop new LSM-compatible methods that explic- perturbation of the carbon flux from land to inland waters itly represent the links between soil erosion and carbon dy- (Regnier et al., 2013). Recent studies have been investigat- namics at regional to global scales and over long timescales. ing the dissolved organic carbon (DOC) transfers along the Based on this, our study introduces a 4-D modeling ap- terrestrial–aquatic continuum in order to better quantify CO2 proach that consists of (1) an emulator that simulates the car- evasion from inland waters and to constrain the lateral car- bon dynamics like in the ORCHIDEE LSM (Krinner et al., bon flux from the land to the ocean (Lauerwald et al., 2017; 2005), (2) the Adjusted Revised Universal Soil Loss Equa- Regnier et al., 2013). They point out that an explicit repre- tion (Adj.RUSLE) model that has been adjusted to simulate sentation of soil erosion and transport of particulate organic global soil removal rates based on coarse-resolution data in- carbon (POC) – in addition to DOC leaching and transport put from climate models (Naipal et al., 2015), and (3) a spa- – in future LSMs is essential to be able to better constrain tially explicit representation for LUC. This approach repre- the flux from land to ocean. This is true, since the transfer of sents explicitly and consistently the links between the pertur- POC from eroded SOC forms an important part of the carbon bation of the terrestrial carbon cycle by elevated atmospheric inputs to rivers. CO2 and variability (temperature and precipitation change), The slow pace of carbon sequestration by soil erosion and the perturbation of the carbon cycle by LUC, and the effect deposition (Van Oost et al., 2012; Wang et al., 2017) and of soil erosion at the global scale. the slowly decomposing SOC pools require the simulation The main goal of our study is to use this new modeling of soil erosion at timescales longer than a few decades to approach to determine the potential effects of long-term soil fully quantify its impacts on the SOC dynamics.
Load more

Recommended publications
  • Effects of Erosion Control Practices on Nutrient Loss
    Effects of Erosion Control Practices on Nutrient Loss George F. Czapar, University of Illinois John M. Laflen, Iowa State University Gregory F. McIsaac, University of Illinois Dennis P. McKenna, Illinois Department of Agriculture Elements of Soil Erosion Soil erosion by water is the detachment of soil particles by the direct action of raindrops and runoff water, and the transport of these particles by splash and very shallow flowing water to small channels or rills. Detachment of soil particles also occurs in these rills due to the force exerted by the flowing water. When rills join together and form larger channels, they may become gullies. These gullies can be either temporary (ephemeral) or permanent (classical). Non-erodible channels might be grassed waterways, or designed channels that limit flow conditions so that channel erosion does not occur. Gross erosion includes sheet, rill, gully and channel erosion, and is the first step in the process of sediment delivery. Because much eroded sediment is deposited in or near the field of origin, only a fraction of the total eroded soil from an area contributes to sediment yield from a watershed. Sediment delivery is affected by a number of factors including soil properties, proximity to the stream, man made structures-including sediment basins, fences, and culverts, channel density, basin characteristics, land use/land cover, and rainfall-runoff factors. Coarse- textured sediment and sediment from sheet and rill erosion are less likely to reach a stream than fine-grained sediment or sediment from channel erosion. In general, the larger the area, the lower the ratio of sediment yield at the watershed outlet or point of interest to gross erosion in the entire watershed, defined as the sediment delivery ratio (SDR).
    [Show full text]
  • Agricultural Soil Compaction: Causes and Management
    October 2010 Agdex 510-1 Agricultural Soil Compaction: Causes and Management oil compaction can be a serious and unnecessary soil aggregates, which has a negative affect on soil S form of soil degradation that can result in increased aggregate structure. soil erosion and decreased crop production. Soil compaction can have a number of negative effects on Compaction of soil is the compression of soil particles into soil quality and crop production including the following: a smaller volume, which reduces the size of pore space available for air and water. Most soils are composed of • causes soil pore spaces to become smaller about 50 per cent solids (sand, silt, clay and organic • reduces water infiltration rate into soil matter) and about 50 per cent pore spaces. • decreases the rate that water will penetrate into the soil root zone and subsoil • increases the potential for surface Compaction concerns water ponding, water runoff, surface soil waterlogging and soil erosion Soil compaction can impair water Soil compaction infiltration into soil, crop emergence, • reduces the ability of a soil to hold root penetration and crop nutrient and can be a serious water and air, which are necessary for water uptake, all of which result in form of soil plant root growth and function depressed crop yield. • reduces crop emergence as a result of soil crusting Human-induced compaction of degradation. • impedes root growth and limits the agricultural soil can be the result of using volume of soil explored by roots tillage equipment during soil cultivation or result from the heavy weight of field equipment. • limits soil exploration by roots and Compacted soils can also be the result of natural soil- decreases the ability of crops to take up nutrients and forming processes.
    [Show full text]
  • Dynamics of Carbon 14 in Soils: a Review C
    Radioprotection, Suppl. 1, vol. 40 (2005) S465-S470 © EDP Sciences, 2005 DOI: 10.1051/radiopro:2005s1-068 Dynamics of Carbon 14 in soils: A review C. Tamponnet Institute of Radioprotection and Nuclear Safety, DEI/SECRE, CADARACHE, BP. 1, 13108 Saint-Paul-lez-Durance Cedex, France, e-mail: [email protected] Abstract. In terrestrial ecosystems, soil is the main interface between atmosphere, hydrosphere, lithosphere and biosphere. Its interactions with carbon cycle are primordial. Information about carbon 14 dynamics in soils is quite dispersed and an up-to-date status is therefore presented in this paper. Carbon 14 dynamics in soils are governed by physical processes (soil structure, soil aggregation, soil erosion) chemical processes (sequestration by soil components either mineral or organic), and soil biological processes (soil microbes, soil fauna, soil biochemistry). The relative importance of such processes varied remarkably among the various biomes (tropical forest, temperate forest, boreal forest, tropical savannah, temperate pastures, deserts, tundra, marshlands, agro ecosystems) encountered in the terrestrial ecosphere. Moreover, application for a simplified modelling of carbon 14 dynamics in soils is proposed. 1. INTRODUCTION The importance of carbon 14 of anthropic origin in the environment has been quite early a matter of concern for the authorities [1]. When the behaviour of carbon 14 in the environment is to be modelled, it is an absolute necessity to understand the biogeochemical cycles of carbon. One can distinguish indeed, a global cycle of carbon from different local cycles. As far as the biosphere is concerned, pedosphere is considered as a primordial exchange zone. Pedosphere, which will be named from now on as soils, is mainly located at the interface between atmosphere and lithosphere.
    [Show full text]
  • Soil Carbon Science for Policy and Practice Soil-Based Initiatives to Mitigate Climate Change and Restore Soil Fertility Both Rely on Rebuilding Soil Organic Carbon
    comment Soil carbon science for policy and practice Soil-based initiatives to mitigate climate change and restore soil fertility both rely on rebuilding soil organic carbon. Controversy about the role soils might play in climate change mitigation is, consequently, undermining actions to restore soils for improved agricultural and environmental outcomes. Mark A. Bradford, Chelsea J. Carey, Lesley Atwood, Deborah Bossio, Eli P. Fenichel, Sasha Gennet, Joseph Fargione, Jonathan R. B. Fisher, Emma Fuller, Daniel A. Kane, Johannes Lehmann, Emily E. Oldfeld, Elsa M. Ordway, Joseph Rudek, Jonathan Sanderman and Stephen A. Wood e argue there is scientific forestry, soil carbon losses via erosion and carbon, vary markedly within a field. Even consensus on the need to decomposition have generally exceeded within seemingly homogenous fields, a Wrebuild soil organic carbon formation rates of soil carbon from plant high spatial density of soil observations is (hereafter, ‘soil carbon’) for sustainable land inputs. Losses associated with these land therefore required to detect the incremental stewardship. Soil carbon concentrations and uses are substantive globally, with a mean ‘signal’ of management effects on soil carbon stocks have been reduced in agricultural estimate to 2-m depth of 133 Pg carbon8, from the local ‘noise’11. Given the time soils following long-term use of practices equivalent to ~63 ppm atmospheric CO2. and expense of acquiring a high density of such as intensive tillage and overgrazing. Losses vary spatially by type and duration observations, most current soil sampling is Adoption of practices such as cover crops of land use, as well as biophysical conditions too limited to reliably quantify management and silvopasture can protect and rebuild such as soil texture, mineralogy, plant effects at field scales9,10.
    [Show full text]
  • Agricultural Soil Carbon Credits: Making Sense of Protocols for Carbon Sequestration and Net Greenhouse Gas Removals
    Agricultural Soil Carbon Credits: Making sense of protocols for carbon sequestration and net greenhouse gas removals NATURAL CLIMATE SOLUTIONS About this report This synthesis is for federal and state We contacted each carbon registry and policymakers looking to shape public marketplace to ensure that details investments in climate mitigation presented in this report and through agricultural soil carbon credits, accompanying appendix are accurate. protocol developers, project developers This report does not address carbon and aggregators, buyers of credits and accounting outside of published others interested in learning about the protocols meant to generate verified landscape of soil carbon and net carbon credits. greenhouse gas measurement, reporting While not a focus of the report, we and verification protocols. We use the remain concerned that any end-use of term MRV broadly to encompass the carbon credits as an offset, without range of quantification activities, robust local pollution regulations, will structural considerations and perpetuate the historic and ongoing requirements intended to ensure the negative impacts of carbon trading on integrity of quantified credits. disadvantaged communities and Black, This report is based on careful review Indigenous and other communities of and synthesis of publicly available soil color. Carbon markets have enormous organic carbon MRV protocols published potential to incentivize and reward by nonprofit carbon registries and by climate progress, but markets must be private carbon crediting marketplaces. paired with a strong regulatory backing. Acknowledgements This report was supported through a gift Conservation Cropping Protocol; Miguel to Environmental Defense Fund from the Taboada who provided feedback on the High Meadows Foundation for post- FAO GSOC protocol; Radhika Moolgavkar doctoral fellowships and through the at Nori; Robin Rather, Jim Blackburn, Bezos Earth Fund.
    [Show full text]
  • Measuring Soil Carbon Change
    Measuring soil carbon change Peter Donovan version: October 2013 This guide can be freely copied and adapted, with attribution, no commercial use, and derivative works similarly licensed. Contents What this guide is about, and how to use it iv 1 The work of the biosphere 1 1.1 Technology . 1 1.2 The carbon cycle . 2 1.3 Let, not make . 3 1.4 Monitoring: a strategic and creative choice . 4 2 Measuring soil carbon 7 2.1 Purpose, result, and uncertainty . 7 2.2 Change . 9 2.3 Organic and inorganic soil carbon . 11 2.4 Laboratory tests . 12 2.5 Getting started . 14 3 Site selection and sampling design 15 3.1 Mapping your site . 15 3.2 Stratification . 15 3.3 Locating plots . 17 3.4 Sampling tools . 17 3.5 Sampling intensity within the plot . 17 4 Sampling and field procedures 20 4.1 Lay out a transect and mark the plot center . 20 4.2 Soil surface observations . 23 4.3 Lay out the plot . 23 4.4 Use probe to take samples . 24 4.5 Soils with abundant rocks, gravel, or coarse fragments . 24 4.6 Characterize the soil . 25 4.7 Bag the sample . 26 4.8 Going deeper . 26 4.9 Sampling for bulk density . 27 4.10 Resampling . 29 4.11 Correcting for changes in bulk density . 29 ii 5 Getting your samples analyzed 31 5.1 Sample preparation . 31 5.2 Storing samples . 32 5.3 Split sampling to test your lab . 32 5.4 U.S. labs that do elemental analysis or dry combustion test .
    [Show full text]
  • Progressive and Regressive Soil Evolution Phases in the Anthropocene
    Progressive and regressive soil evolution phases in the Anthropocene Manon Bajard, Jérôme Poulenard, Pierre Sabatier, Anne-Lise Develle, Charline Giguet- Covex, Jeremy Jacob, Christian Crouzet, Fernand David, Cécile Pignol, Fabien Arnaud Highlights • Lake sediment archives are used to reconstruct past soil evolution. • Erosion is quantified and the sediment geochemistry is compared to current soils. • We observed phases of greater erosion rates than soil formation rates. • These negative soil balance phases are defined as regressive pedogenesis phases. • During the Middle Ages, the erosion of increasingly deep horizons rejuvenated pedogenesis. Abstract Soils have a substantial role in the environment because they provide several ecosystem services such as food supply or carbon storage. Agricultural practices can modify soil properties and soil evolution processes, hence threatening these services. These modifications are poorly studied, and the resilience/adaptation times of soils to disruptions are unknown. Here, we study the evolution of pedogenetic processes and soil evolution phases (progressive or regressive) in response to human-induced erosion from a 4000-year lake sediment sequence (Lake La Thuile, French Alps). Erosion in this small lake catchment in the montane area is quantified from the terrigenous sediments that were trapped in the lake and compared to the soil formation rate. To access this quantification, soil processes evolution are deciphered from soil and sediment geochemistry comparison. Over the last 4000 years, first impacts on soils are recorded at approximately 1600 yr cal. BP, with the erosion of surface horizons exceeding 10 t·km− 2·yr− 1. Increasingly deep horizons were eroded with erosion accentuation during the Higher Middle Ages (1400–850 yr cal.
    [Show full text]
  • What Is Soil Erosion? Soil Erosion by Wind Or Water Is the Physical Wearing Away of the Soil Surface
    Do you have a problem with: • Low yields • Time & expense to repair and gullies • Small rills and channels in your fields • Soil deposited at the base of slopes or along fence lines • Sediment in streams, lakes, and reservoirs Soil Erosion May be the Problem! Erosion from cropland What is soil erosion? Soil erosion by wind or water is the physical wearing away of the soil surface. Soil material and nutrients are removed in the process. Why be concerned? • Erosion reduces crop yields • Erosion removes topsoil, reduces soil organic matter, and destroys soil structure Signs of Erosion – Sediment entering river • Erosion decreases rooting depth • Erosion decreases the amount of water, air, and nutrients available to plants • Nutrients and sediment removed by water erosion cause water quality problems and fish kills • Blowing dust from wind erosion can affect human health and create public safety hazards • Increased production costs Erosion removes our richest soil. How much does it cost? • Technical assistance to assess and plan erosion control systems from NRCS is free • No till and mulch till may require special tillage equipment or planters if this equipment is not al- ready available • Vegetative barriers may cost $50-$100 per mile of barrier • Cover crops may cost between $10 and $40 per acre depending on the type of seed used Controlling Soil Erosion Signs of Erosion – Small rills and channels on the soil Dust clouds & “dirt devils” such as the one pictured surface are a sign of water erosion here are signs of wind erosion. How to Reduce Erosion: The key to reducing is erosion is to keep the soil covered as much as possible for both wind and water ero- sion concerns.
    [Show full text]
  • How Do Newly-Amended Biochar Particles Affect Erodibility and Soil Water Movement?—A Small-Scale Experimental Approach
    Article How Do Newly-Amended Biochar Particles Affect Erodibility and Soil Water Movement?—A Small-Scale Experimental Approach Steffen Seitz * , Sandra Teuber , Christian Geißler, Philipp Goebes and Thomas Scholten Department of Geosciences, Soil Science and Geomorphology, University of Tübingen, Rümelinstrasse 19–23, 72070 Tübingen, Germany; [email protected] (S.T.); [email protected] (C.G.); [email protected] (P.G.); [email protected] (T.S.) * Correspondence: steff[email protected]; Tel.: +49-7071-29-77523 Received: 16 July 2020; Accepted: 23 September 2020; Published: 6 October 2020 Abstract: Biochar amendment changes chemical and physical properties of soils and influences soil biota. It is, thus, assumed that it can also affect soil erosion and erosion-related processes. In this study, we investigated how biochar particles instantly change erodibility by rain splash and the initial movement of soil water in a small-scale experiment. Hydrothermal carbonization (HTC)-char and Pyrochar were admixed to two soil substrates. Soil erodibility was determined with Tübingen splash cups under simulated rainfall, soil hydraulic conductivity was calculated from texture and bulk soil density, and soil water retention was measured using the negative and the excess pressure methods. Results showed that the addition of biochar significantly reduced initial soil erosion in coarse sand and silt loam immediately after biochar application. Furthermore, biochar particles were not preferentially removed from the substrate surface, but increasing biochar particle sizes partly showed decreasing erodibility of substrates. Moreover, biochar amendment led to improved hydraulic conductivity and soil water retention, regarding soil erosion control. In conclusion, this study provided evidence that biochar amendments reduce soil degradation by water erosion.
    [Show full text]
  • Age of Soil Organic Matter and Soil Respiration: Radiocarbon Constraints on Belowground C Dynamics
    April 2000 BELOWGROUND PROCESSES AND GLOBAL CHANGE 399 Ecological Applications, 10(2), 2000, pp. 399±411 q 2000 by the Ecological Society of America AGE OF SOIL ORGANIC MATTER AND SOIL RESPIRATION: RADIOCARBON CONSTRAINTS ON BELOWGROUND C DYNAMICS SUSAN TRUMBORE Department of Earth System Science, University of California, Irvine, California 92697-3100 USA Abstract. Radiocarbon data from soil organic matter and soil respiration provide pow- erful constraints for determining carbon dynamics and thereby the magnitude and timing of soil carbon response to global change. In this paper, data from three sites representing well-drained soils in boreal, temperate, and tropical forests are used to illustrate the methods for using radiocarbon to determine the turnover times of soil organic matter and to partition soil respiration. For these sites, the average age of bulk carbon in detrital and Oh/A-horizon organic carbon ranges from 200 to 1200 yr. In each case, this mass-weighted average includes components such as relatively undecomposed leaf, root, and moss litter with much shorter turnover times, and humi®ed or mineral-associated organic matter with much longer turnover times. The average age of carbon in organic matter is greater than the average age predicted for CO2 produced by its decomposition (30, 8, and 3 yr for boreal, temperate, and tropical soil), or measured in total soil respiration (16, 3, and 1 yr). Most of the CO2 produced during decomposition is derived from relatively short-lived soil organic matter (SOM) components that do not represent a large component of the standing stock of soil organic matter. Estimates of soil carbon turnover obtained by dividing C stocks by hetero- trophic respiration ¯uxes, or from radiocarbon measurements of bulk SOM, are biased to longer time scales of C cycling.
    [Show full text]
  • Interpreting, Measuring, and Modeling Soil Respiration
    Biogeochemistry (2005) 73: 3–27 Ó Springer 2005 DOI 10.1007/s10533-004-5167-7 -1 Interpreting, measuring, and modeling soil respiration MICHAEL G. RYAN1,2,* and BEVERLY E. LAW3 1US Department of Agriculture-Forest Service, Rocky Mountain Research Station, 240 West Pros- pect Street, Fort Collins, CO 80526, USA; 2Affiliate Faculty, Department of Forest, Rangeland and Watershed Stewardship and Graduate Degree Program in Ecology, Colorado State University Fort Collins, CO 80523, USA; 3Department of Forest Science, Oregon State University, 328 Richardson Hall, Corvallis, OR 97331, USA; *Author for correspondence (e-mail: [email protected]) Key words: Belowground carbon allocation, Carbon cycling, Carbon dioxide, CO2, Infrared gas analyzers, Methods, Soil carbon, Terrestrial ecosystems Abstract. This paper reviews the role of soil respiration in determining ecosystem carbon balance, and the conceptual basis for measuring and modeling soil respiration. We developed it to provide background and context for this special issue on soil respiration and to synthesize the presentations and discussions at the workshop. Soil respiration is the largest component of ecosystem respiration. Because autotrophic and heterotrophic activity belowground is controlled by substrate availability, soil respiration is strongly linked to plant metabolism, photosynthesis and litterfall. This link dominates both base rates and short-term fluctuations in soil respiration and suggests many roles for soil respiration as an indicator of ecosystem metabolism. However, the strong links between above and belowground processes complicate using soil respiration to understand changes in ecosystem carbon storage. Root and associated mycorrhizal respiration produce roughly half of soil respiration, with much of the remainder derived from decomposition of recently produced root and leaf litter.
    [Show full text]
  • Global Status, Processes and Trends in Soil Erosion
    Status of the World’s Main Report Soil Resources Chapter 6 Global soil status, processes and trends © FAO | Giuseppe Bizzarri © FAO INTERGOVERNMENTAL TECHNICAL PANEL ON SOILS Disclaimer and copyright Recommended citation: FAO and ITPS. 2015. Status of the World’s Soil Resources (SWSR) – Main Report. Food and Agriculture Organization of the United Nations and Intergovernmental Technical Panel on Soils, Rome, Italy The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views or policies of FAO. ISBN 978-92-5-109004-6 © FAO, 2015 FAO encourages the use, reproduction and dissemination of material in this information product. Except where otherwise indicated, material may be copied, downloaded and printed for private study, research and teaching purposes, or for use in non-commercial products or services, provided that appropriate acknowledgement of FAO as the source and copyright holder is given and that FAO’s endorsement of users’ views, products or services is not implied in any way.
    [Show full text]