Changes in Soil Carbon Storage After Cultivation

a b s t r a c tWidespread land degradation has strengthened the urgent need to restore overgrazing grasslands. China has implemented the program 'Returning Grazing Land to Grassland' (RGLG) through grazing exclusion by fence since 2003. Despite a lot of field experiments, there is still controversy on the effects of grazing exclusion on rangeland restoration, highlighting the need for synthetic analysis. We conducted a metaanalysis of 447 entries from 78 papers to analyze the spatiotemporal effects of grazing exclusion on plant diversity, productivity and soil carbon sequestration in the major RGLG-implemented provinces of China. Our results showed that, compared with the grazed sites, grazing exclusion significantly increased carbon stored in aboveground biomass, litter mass, belowground biomass and soils by 84.7%, 111.6%, 25.5% and 14.4%, respectively. Plant coverage, soil available nitrogen, soil available phosphorus and soil microbial biomass carbon increased by 52.0%, 21.7% 22.8% and 26.3%, respectively. However, grazing exclusion had little effects on recovering plant diversity in China's grasslands. Of the factors examined, climatic factors strongly modified the effects of grazing exclusion on ecosystem carbon stocks, for example, precipitation significantly amplified the positive effects. Grazing exclusion played a positive role in soil carbon sequestration in most grassland types except in temperate desert-steppe. But annual soil carbon sequestration rates decayed rapidly over time in both alpine meadow and temperate steppe. Short-term (≤5 years) grazing exclusion remarkably increased species richness, but not significantly in the long run. The threshold from neutral to negative effects of grazing exclusion on species evenness occurs after approximately ten years. Our findings provide evidence that grazing exclusion is an effective way to restore vegetation and sequestrate carbon in degraded grasslands, but not beneficial to plant diversity maintenance. The benefits of grazing exclusion are more effective in humid area than arid area. We suggest that grazing exclusion should be ceased after about six to ten years. Additionally, grazing exclusion should integrate with other appropriate management practices instead of operating on a stand-alone basis.

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“…Eq. (1) assumes that SOM is 58% SOC (Mann, 1986). The factor 0.45 was used to convert plant dry biomass to plant C stocks (Olson et al, 1983).…”

Section: Data Compilationmentioning

confidence: 99%

Effects of grazing exclusion on carbon sequestration and plant diversity in grasslands of China—A meta-analysis

Xiong

Shi

Zhang

et al. 2016

Ecological Engineering

173

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“…Also for grassland conversion into forest (afforestation) soils are commonly completely or party ploughed to prepare the seedbed for planted seedlings (Querejeta et al 2001;Thuille and Schulze 2006). Ploughing causes considerable disturbance which results in soil C losses of 20-50% (Guo and Gifford 2002;Mann 1986). Soil disruptions such as ploughing influence also DOC production and transport (Hornung et al 1986).…”

Section: Introductionmentioning

confidence: 99%

Controls on fluxes and export of dissolved organic carbon in grasslands with contrasting soil types

2008

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Export of dissolved organic carbon (DOC) from grassland ecosystems can be an important C flux which directly affects ecosystem C balance since DOC is leached from the soil to the groundwater. DOC fluxes and their controlling factors were investigated on two grassland sites with similar climatic conditions but different soil types (Vertisol vs. Arenosol) for a 2.5-year period. Parts of both grasslands were disturbed by deep ploughing during afforestation. Contrary to what was expected, ploughing did not increase DOC export but surface soil DOC concentrations decreased by 28% (Vertisol) and 14% (Arenosol). DOC flux from the soil profile was negatively influences by the clay content of the soil with seven times larger DOC export in the clay-poor Arenosol (55 kg C ha -1 a -1 ) than in the clay-rich Vertisol (8 kg C ha -1 a -1 ). At the Arenosol site, highest DOC concentrations were measured in late summer, whereas in the Vertisol there was a time lag of several months between surface and subsoil DOC with highest subsoil DOC concentrations during winter season. DOC export was not correlated with soil organic carbon stocks. Large differences in 14 C concentrations of 22-40 pMC between soil organic carbon and DOC in the subsoil indicated that both C pools are largely decoupled. We conclude that DOC export at both sites is not controlled by the vegetation but by physicochemical parameters such as the adsorption capacity of soil minerals and the water balance of the ecosystem. Only in the acidic sandy Arenosol DOC export was a significant C flux of about 8% of net ecosystem production.

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“…Because soils contain nearly twice as much carbon (C) as the vegetation, a better understanding of soil organic carbon (SOC) distribution and its stabilization mechanisms is important (Mann, 1986). Soil organic matter is often categorized into physico-chemically protected fractions, such as organo-mineral particles, and the occluded particulate organic matter in microaggregates, biochemically protected fractions, such as recalcitrant soil organic matter (SOM) compounds, and free particulate organic matter (Six et al, 2002;Peng et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Soil Organic Carbon and Its Fractions Across Vegetation Types: Effects of Soil Mineral Surface Area and Microaggregates

Wang

Ouyang

2009

Pedosphere

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Soil organic carbon (SOC) can act as a sink or source of atmospheric carbon dioxide; therefore, it is important to understand the amount and composition of SOC in terrestrial ecosystems, the spatial variation in SOC, and the underlying mechanisms that stabilize SOC. In this study, density fractionation and acid hydrolysis were used to assess the spatial variation in SOC, the heavy fraction of organic carbon (HFOC), and the resistant organic carbon (ROC) in soils of the southern Hulun Buir region, northeastern China, and to identify the major factors that contribute to this variation. The results showed that as the contents of clay and silt particles (0-50 μm) increased, both methylene blue (MB) adsorption by soil minerals and microaggregate contents increased in the 0-20 and 20-40 cm soil layers (P < 0.05). Although varying with vegetation types, SOC, HFOC, and ROC contents increased significantly with the content of clay and silt particles, MB adsorption by soil minerals, and microaggregate content (P < 0.05), suggesting that soil texture, the MB adsorption by soil minerals, and microaggregate abundance might be important factors influencing the spatial heterogeneity of carbon contents in soils of the southern Hulun Buir region.

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Changes in Soil Carbon Storage After Cultivation

Cited by 613 publications

References 0 publications

Effects of grazing exclusion on carbon sequestration and plant diversity in grasslands of China—A meta-analysis

Effects of grazing exclusion on carbon sequestration and plant diversity in grasslands of China—A meta-analysis

Controls on fluxes and export of dissolved organic carbon in grasslands with contrasting soil types

Soil Organic Carbon and Its Fractions Across Vegetation Types: Effects of Soil Mineral Surface Area and Microaggregates

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