Selective organic carbon losses from soils by sheet erosion and main controls
08 Feb 2017-
TL;DR: In this article, the impact of sheet erosion on the selective transportation of mineral soil particles has been widely investigated, but little is yet known about the specific mechanisms of organic carbon (OC) erosion, which constitutes an important link in the global carbon cycle.
Abstract: Although the impact of sheet erosion on the selective transportation of mineral soil particles has been widely investigated, little is yet known about the specific mechanisms of organic carbon (OC) erosion, which constitutes an important link in the global carbon cycle. The present study was conducted to quantify the impact of sheet erosion on OC losses from soils. Erosion plots with the lengths of 1- and 5-m were installed at different topographic positions along a hillslope in a mountainous South African region. A total of 32 rainfall events from a three years period (November 2010 up to February 2013), were studied and evaluated for runoff (R), particulate and dissolved organic carbon (POCL and DOCL). In comparison to the 0–0·05 m bulk soil, the sediments from the 1-m plots were enriched in OC by a factor 2·6 and those from the 5-m long plots by a factor of 2·2, respectively. These findings suggest a preferential erosion of OC. In addition, total organic carbon losses (TOCL) were incurred mainly in particulate form (~94%) and the increase in TOCL from 14·09 ± 0·68 g C m−1 yr−1 on 1-m plots to 50·03 ± 2·89 g C m−1 yr−1 on 5-m plots illustrated an increase in sheet erosion efficiency with increasing slope length. Both TOCL and sediment enrichment in OC correspondingly increased with a decrease in soil basal grass cover. The characteristics of rainstorms had no significant impact on the selectivity of OC erosion. The results accrued in this study investigating the links between sheet erosion and OC losses, are expected to be of future value in the generation of carbon specific erosion models, which can further help to inform and improve climate change mitigation measures.
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TL;DR: This review is a collation and synthesis of articles published in peer-reviewed journals and estimates of the historic depletion of SOC in world soils, 115-154 Pg C and equivalent to the technical potential or the maximum soil C sink capacity, need to be improved.
Abstract: The global magnitude (Pg) of soil organic carbon (SOC) is 677 to 0.3-m, 993 to 0.5-m, and 1,505 to 1-m depth. Thus, ~55% of SOC to 1-m lies below 0.3-m depth. Soils of agroecosystems are depleted of their SOC stock and have a low use efficiency of inputs of agronomic yield. This review is a collation and synthesis of articles published in peer-reviewed journals. The rates of SOC sequestration are scaled up to the global level by linear extrapolation. Soil C sink capacity depends on depth, clay content and mineralogy, plant available water holding capacity, nutrient reserves, landscape position, and the antecedent SOC stock. Estimates of the historic depletion of SOC in world soils, 115-154 (average of 135) Pg C and equivalent to the technical potential or the maximum soil C sink capacity, need to be improved. A positive soil C budget is created by increasing the input of biomass-C to exceed the SOC losses by erosion and mineralization. The global hotspots of SOC sequestration, soils which are farther from C saturation, include eroded, degraded, desertified, and depleted soils. Ecosystems where SOC sequestration is feasible include 4,900 Mha of agricultural land including 332 Mha equipped for irrigation, 400 Mha of urban lands, and ~2,000 Mha of degraded lands. The rate of SOC sequestration (Mg C ha-1 year-1 ) is 0.25-1.0 in croplands, 0.10-0.175 in pastures, 0.5-1.0 in permanent crops and urban lands, 0.3-0.7 in salt-affected and chemically degraded soils, 0.2-0.5 in physically degraded and prone to water erosion, and 0.05-0.2 for those susceptible to wind erosion. Global technical potential of SOC sequestration is 1.45-3.44 Pg C/year (2.45 Pg C/year).
367 citations
TL;DR: In this article, the authors proposed a watershed-level approach to assess the impacts of erosional processes on decomposition of soil organic carbon, gaseous emission, and the soil/ecosystem C budget for diverse soils and management systems in global biomes/ecoregions.
Abstract: Soil erosion, physical transport of soil over the landscape by alluvial and aeolian processes as source of energy, has a strong impact on the global carbon cycle (GCC). Being a light fraction (bulk density of 0.6–0.8 Mg/m 3 ) and concentrated in vicinity of soil surface, soil organic carbon (SOC) is preferentially removed by water and wind erosion. The process of erosion and the attendant transport of SOC are accelerated by conversion of natural to agroecosystems. Whereas the human-induced acceleration of soil erosion has depleted the SOC stock of agroecosystems, the fate of SOC transported over the landscape and that deposited in depressional sites is not understood. While a fraction of SOC transported to and buried under aquatic ecosystems (e.g., flood plains, lakes, ocean) may be protected because of limited microbial activity, labile fractions of SOC being transported over the landscape enroute to the depositional site are vulnerable to decomposition. Depending on the site-specific conditions with regards to the hydrothermal regimes and the degree of aeration, the decomposition may lead to emission of CO 2 under aerobic environments, CH 4 under anaerobic conditions, and N 2 O under both situations. The process of soil erosion, especially that by water, is a 4-stage process: (i) detachment, (ii) splash, (iii) transport and redistribution, and (iv) deposition. Breakdown of aggregates, during the first three stages, exposes the hitherto encapsulated SOC to microbial processes and exacerbates its vulnerability to decomposition. Thus, the fate of SOC subject to erosion must be assessed for all landscape positions and integrated over the watershed. Lack of credible data regarding the fate of SOC at different erosional stages is a major cause of uncertainties. Thus, well-planned research at a watershed-level is needed to assess the impacts of erosional processes on decomposition of SOC, gaseous emission, and the soil/ecosystem C budget for diverse soils and management systems in global biomes/ecoregions. The data on global C budget is incomplete without consideration of the impact of erosion on SOC and the attendant gaseous emissions.
121 citations
TL;DR: The role of soil erosion in global C cycle remains a topic of debate as discussed by the authors, especially for the mineralization and sequestration of eroded organic carbon upon erosion, transport and deposition.
77 citations
TL;DR: In this article, the effects of erosion degree and rainfall intensity on erosion process and sediment transport mechanism were investigated on pre-wetted bare fallow Ultisols (derived from quaternary red clay) under four erosion degrees (no, moderate, severe, and very severe) and two rainfall intensities (60 and 120mm−h−1).
41 citations
TL;DR: Li et al. as mentioned in this paper examined variation in soil bacterial communities across eroding slopes and depositional zones with three slope gradients (5°, 10° and 20°) on the Loess Plateau of China (2015-2017).
35 citations
References
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01 Jan 1986
TL;DR: In this article, the authors describe methods of particle-size analysis for soils, including a variety of classification schemes and standard methods for size distributions using pipet and hydrometer techniques.
Abstract: Book Chapter describing methods of particle-size analysis for soils. Includes a variety of classification schemes. Standard methods for size distributions using pipet and hydrometer techniques are described. New laser-light scattering and related techniques are discussed. Complete with updated references.
8,997 citations
TL;DR: In this article, the authors proposed a sustainable management of soil organic carbon (SOC) pool through conservation tillage with cover crops and crop residue mulch, nutrient cycling including the use of compost and manure, and other management practices.
2,931 citations
"Selective organic carbon losses fro..." refers background in this paper
...Hence, by having the potential to offset the current influx of anthropogenic CO2 emissions (Lal, 2004), soils, through their sequestration properties, could provide a possible solution for global warming....
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TL;DR: With the addition of a quarter of a million people each day, the world population's food demand is increasing at a time when per capita food productivity is beginning to decline.
Abstract: Soil erosion is a major environmental threat to the sustainability and productive capacity of agriculture. During the last 40 years, nearly one-third of the world's arable land has been lost by erosion and continues to be lost at a rate of more than 10 million hectares per year. With the addition of a quarter of a million people each day, the world population's food demand is increasing at a time when per capita food productivity is beginning to decline.
2,589 citations
"Selective organic carbon losses fro..." refers background in this paper
...For instance, soil organic matter (SOM), which soil organic carbon (SOC) constitutes the bulk of, provides the soil with essential plant nutrients, improves soil texture, acts as a natural buffer against compaction, enhances soil water retention capacity and provides energy for soil biota (Pimentel et al., 1995; Biggelaar et al., 2001; Lal, 2003)....
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...…organic carbon (SOC) constitutes the bulk of, provides the soil with essential plant nutrients, improves soil texture, acts as a natural buffer against compaction, enhances soil water retention capacity and provides energy for soil biota (Pimentel et al., 1995; Biggelaar et al., 2001; Lal, 2003)....
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01 Jan 2002
TL;DR: In this article, the authors describe methods of particle-size analysis for soils, including a variety of classification schemes and standard methods for size distributions using pipet and hydrometer techniques.
Abstract: Book Chapter describing methods of particle-size analysis for soils. Includes a variety of classification schemes. Standard methods for size distributions using pipet and hydrometer techniques are described. New laser-light scattering and related techniques are discussed. Complete with updated references.
1,701 citations
TL;DR: In this paper, the authors provide a brief review for policymakers who are concerned that changes in soil respiration may contribute to the rise in CO2 in Earth's atmosphere, while simultaneously leaving a greater store of carbon in the soil.
Abstract: Soil respiration is the primary path by which CO2fixed by land plants returns to the atmosphere. Estimated at approximately 75 × 1015gC/yr, this large natural flux is likely to increase due changes in the Earth's condition. The objective of this paper is to provide a brief scientific review for policymakers who are concerned that changes in soil respiration may contribute to the rise in CO2in Earth's atmosphere. Rising concentrations of CO2in the atmosphere will increase the flux of CO2from soils, while simultaneously leaving a greater store of carbon in the soil. Traditional tillage cultivation and rising temperature increase the flux of CO2from soils without increasing the stock of soil organic matter. Increasing deposition of nitrogen from the atmosphere may lead to the sequestration of carbon in vegetation and soils. The response of the land biosphere to simultaneous changes in all of these factors is unknown, but a large increase in the soil carbon pool seems unlikely to moderate the rise in atmospheric CO2during the next century.
1,646 citations
"Selective organic carbon losses fro..." refers background in this paper
...Soils, which sequester atmospheric carbon (CO2), by means of retaining and absorbing the plant residue of photosynthesizing plants, have been shown to contain more than half the carbon in terrestrial ecosystems (Schlesinger and Andrews, 2000)....
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