Soil Inorganic Carbon Storage Research Articles

Leguminous forage introduction and returning reduced soil inorganic carbon loss on the Loess Plateau

Despite evidence from experiments that no-till and stubble retention promote soil organic carbon accumulation, it is not yet clear if this is the case for soil inorganic carbon (SIC), particularly in the arid and semiarid Loess Plateau. Based on field observations from 2001 to 2020, we methodically characterized the spatial–temporal dynamics of SIC and driving factors in a forage-crop rotation system. The results showed that 19 years continuous application of no-till or stubble retention practices resulted in SIC loss at the 0–10 cm soil depth at rates of 0.01–0.07 g kg−1 yr−1, the introduction of leguminous forages reduced the loss rate. The effects on SIC were greater at the 60–500 cm soil depth than at the 0–60 cm soil depth, SIC accumulated significantly in the deeper layer, and leaching and re-precipitation mainly occurred in the 60–200 cm layer. When performed on average over the 0–500 cm soil profile, no-till and stubble retention increased the SIC storage by 1.87–4.78 t ha−1 after maize harvest, while reduced by 1.04–1.20 t ha−1 after vetch harvest. The effects on SIC were mainly influenced by soil organic carbon according to the structural equation model. We concluded that leguminous forage introduction and returning to the field reduced the SIC loss in the rotation systems. The results highlight the importance of better understanding SIC dynamics when predicting the soil carbon budget.

Uranium-series and strontium isotope systematics in soil carbonates from dryland Critical Zones: Implications for soil inorganic carbon storage and transformation

Soil carbonates are dominantly present in dryland Critical Zone (CZ) and their formation could lead to important long-term carbon sequestration in arid to semiarid soils if the Ca ions were derived from silicate weathering or other non-carbonate sources. In managed CZ systems such as agricultural areas converted from natural drylands, irrigation has profound effects on the dryland CZ inorganic carbon storage, especially by modifying dissolution and precipitation dynamics of soil carbonates via controls of irrigation intensity and water chemistry, soil properties, and hydrological flow paths. These processes could lead to transformation of inorganic carbon in soils and groundwater aquifers underneath drylands. One key knowledge gap in studying soil carbonates from managed dryland CZ systems is to detect the formation of soil carbonates under irrigated conditions and distinguish them effectively from soil carbonates formed under natural conditions.Here, we explore the potential of using U-series and strontium isotopes to investigate the formation timescales and conditions of soil carbonates in both natural and managed dryland CZ in Chihuahua Desert of American Southwest. We obtained new U-series and Sr isotope ratios from mature stage V natural soil carbonates in the Jornada Basin of southern New Mexico and compared to previously published U-series and Sr isotope results for younger Jornada soil carbonates as well as irrigation impacted soil carbonates from the Rio Grande floodplains in west Texas. Specifically, we applied the U-series dating method (238U-234U-230Th) to estimate the timescales of soil carbonate formation under both natural climatic conditions and impacts of modern agriculture irrigation. In addition, we showed that the initial (234U/238U) activity ratios recorded in these soil carbonates reflect the systematic changes of soil infiltration rates in both natural and managed dryland CZ. We also utilized Sr isotope ratios (87Sr/86Sr) in soil carbonates, dust, and irrigation water to trace the Ca sources in soil carbonates from natural and managed dryland CZ. Soil carbonates from both settings were characterized by slightly radiogenic 87Sr/86Sr ratios, consistent with their potential of long-term carbon storage in drylands.U-series and Sr isotope systematics characterize important differences in soil carbonates from natural and managed dryland CZ with respect to their Ca sources, timescales of carbonate formation and transformation, and availability of soil moisture. Soil carbonates formed, accumulated, and transformed in natural drylands with long time scales but under irrigated arid agricultural areas its formation is significantly modified by irrigation and other agriculture practices, with implications for long- and short-term inorganic carbon sequestration in both systems of drylands.

Soil Inorganic Carbon as a Potential Sink in Carbon Storage in Dryland Soils—A Review

Soil organic carbon (SOC) pool has been extensively studied in the carbon (C) cycling of terrestrial ecosystems. In dryland regions, however, soil inorganic carbon (SIC) has received increasing attention due to the high accumulation of SIC in arid soils contributed by its high temperature, low soil moisture, less vegetation, high salinity, and poor microbial activities. SIC storage in dryland soils is a complex process comprising multiple interactions of several factors such as climate, land use types, farm management practices, irrigation, inherent soil properties, soil biotic factors, etc. In addition, soil C studies in deeper layers of drylands have opened-up several study aspects on SIC storage. This review explains the mechanisms of SIC formation in dryland soils and critically discusses the SIC content in arid and semi-arid soils as compared to SOC. It also addresses the complex relationship between SIC and SOC in dryland soils. This review gives an overview of how climate change and anthropogenic management of soil might affect the SIC storage in dryland soils. Dryland soils could be an efficient sink in C sequestration through the formation of secondary carbonates. The review highlights the importance of an in-depth understanding of the C cycle in arid soils and emphasizes that SIC dynamics must be looked into broader perspective vis-à-vis C sequestration and climate change mitigation.

Distribution and storage of soil organic and inorganic carbon in steppe riparian wetlands under human activity pressure

Soil organic carbon (SOC) and soil inorganic carbon (SIC) are key components of the global wetland soil carbon pool, which plays a crucial role in carbon cycling. However, research on carbon storage in riparian wetland soils, especially in inland steppe river environments impacted by human activities, is relatively scarce. Thus, we evaluated the SOC and SIC distributions and storage in riparian wetland soils under the pressure of human activities in the Xilin River Basin (XRB). We collected surface and profile soil samples, determined the SOC and SIC contents, aboveground biomass, and soil physicochemical properties, and calculated the SOC and SIC storage (SOCs and SICs) values. The surface soil SOC content decreased substantially from the upstream to the downstream zones (mean value range: 76.30–3.18 g/kg), and the SIC content showed the opposite trend (mean value range: 0.08–34.38 g/kg). The SIC content of the riparian wetlands along the permanently flowing stretch of river was much lower than that in the wetlands along the intermittently flowing stretch. In the XRB, the SOCs was primarily affected by vegetation coverage, soil water content, and soil pH, whereas the SICs was greatly affected by soil texture. A dry lake zone was markedly affected by wetland degradation, indicating a potential increase in the decomposition rate of the surface soil SOC; however, the SOC in the deep soils was relatively stable. The high SIC content most likely resulted from weathering, resuspension, and carbonate rock reprecipitation. Compared to different steppe grassland types, riparian wetlands appear to be potential hotspots of SOCs and SICs in the Inner Mongolian region. Riparian wetland SOCs in the upstream zones was substantially greater than in adjacent terrestrial locations. However, the SOCs in the downstream wetlands was similar to that in the grasslands. Under the impact of human activities, the water and soil environments in the downstream zone of the Xilin River were substantially modified, leading to severe wetland degradation, which most likely caused the carbon storage function of the riparian wetlands to weaken and carbon loss to accelerate. The mean SOCs in the riparian wetland soils decreased from 33.3 kg/m2 in the upstream area to 16.2 kg/m2 downstream, and the mean SICs increased from 2.3 kg/m2 to 34.6 kg/m2. Therefore, urgent measures are needed to restore the carbon sink function of river wetlands for long-term climate change mitigation.

Long-term vegetation restoration increases deep soil carbon storage in the Northern Loess Plateau

Afforestation plays an important role in soil carbon storage and water balance. However, there is a lack of information on deep soil carbon and water storage. The study investigates the effect of returning farmland to the forest on soil carbon accumulation and soil water consumption in 20-m deep soil profile in the hilly and gully region of the Chinese Loess Plateau. Four sampling sites were selected: Platycladus orientalis (Linn.) Franco forest (PO: oriental arborvitae), Pinus tabulaeformis Carr. Forest (PT: southern Chinese pine), apple orchard (AO) and farmland (FL, as a control). Soil organic carbon (SOC) and soil inorganic carbon (SIC) content were measured in 50-cm sampling intervals of 20-m soil profiles, as well as the associated factors (e.g. soil water content). The mean SOC content of PT was the highest in the 1–5 m layer and that of FL was the lowest (p < 0.05). Compared with FL, the SOC storages of PO, PT and AO increased by 2.20, 6.33 and 0.90 kg m−2 (p > 0.05), respectively, in the whole profile. The SIC content was relatively uniform throughout the profile at all land-use types and SIC storage was 9–10 times higher than SOC storage. The soil water storage of PO, PT and AO was significantly different from that of FL with a decrease of 1169.32, 1161.60 and 1139.63 mm, respectively. After the 36-yrs implementation of the “Grain for Green” Project, SOC in 20 m soil profiles increased as a water depletion cost compared with FL. Further investigation is still needed to understand the deep soil water and carbon interactions regarding ecological restoration sustainability in the Northern Loess Plateau.

Spatial variability of soil carbon and water storage across loess deposit catenas in China’s Loess Plateau region

The impact of hillslope vegetation restoration on the distribution and variability of carbon and water storage was studied across two catenary sequences of soils in the Liudaogou watershed of China’s Loess Plateau. Soil organic carbon storage (SOCS) under different land uses in the two catenas decreased significantly in the upper soil layers (&lt;50 cm) but was relatively stable in the deeper soil layers (&gt;50 cm). However, soil inorganic carbon storage (SICS) in the two catenas fluctuated (two maxima) with increasing soil depth. There was no significant difference of SOCS within the 200 cm soil profile between forestlands (FO) and grasslands (GR) at the catenary scale (p &gt; 0.05). However, SICS in the 0–200 cm soil profile differed markedly between FO and GR (p &lt; 0.05) in both catenas due to different degrees of root-facilitated CaCO3 redistribution. Based on the coefficient of variance (CV), soil water storage (SWS) was divided into three layers: active layer (0–100 cm, CV = 20%–30%), subactive layer (100–200 cm, CV = 10%–20%), and stable layer (200–500 cm, CV &lt; 10%). The SWS in the 0–500 cm soil profile was slightly higher in GR than in FO on the two slopes because of the higher water consumption under tree plantation than native grasses. SOCS, SICS, and SWS can be predicted by multiple regression equations using different soil properties. The study demonstrated that SOCS, SICS, and SWS respond differently to vegetation restoration at the catenary scale, which must be taken into account for improving ecosystem model predictions of soil carbon and water fluxes in sloping lands.

Determining the Value of Soil Inorganic Carbon Stocks in the Contiguous United States Based on the Avoided Social Cost of Carbon Emissions

Carbon sequestered as soil inorganic carbon (SIC) provides a regulating ecosystem service, which can be assigned a monetary value based on the avoided social cost of carbon (SC-CO2). By definition, the SC-CO2 is a measure, in dollars, of the long-term damage resulting from the emission of a metric ton of carbon dioxide (CO2). Therefore, this dollar figure also represents the value of damages avoided due to an equivalent reduction or sequestration of CO2. The objective of this study was to assess the value of SIC stocks in the contiguous United States (U.S.) by soil order, soil depth (0–20, 20–100, 100–200 cm), land resource region (LRR), state, and region using information from the State Soil Geographic (STATSGO) database together with a reported SC-CO2 of $42 (U.S. dollars). With this approach, the calculated monetary value for total SIC storage in the contiguous U.S. was between $3.48T (i.e., $3.48 trillion U.S. dollars, where T = trillion = 1012) and $14.4T, with a midpoint value of $8.34T. Soil orders with the highest (midpoint) values for SIC storage were: 1) Mollisols ($3.57T), 2) Aridisols ($1.99T), and 3) Alfisols ($841B) (i.e., $841B is 841 billion U.S. dollars, where B = billion = 109). When normalized by land area, the soil orders with the highest (midpoint) values for SIC storage were: 1) Vertisols ($3.57 m−2), 2) Aridisols ($2.45 m−2), and 3) Mollisols ($1.77 m−2). Most of the SIC value was associated with the 100–200 cm depth interval, with a midpoint value of $4T and an area-normalized value of $0.54 m−2. The LRRs with the highest (midpoint) values of SIC storage were: 1) D—Western Range and Irrigated Region ($1.77T), 2) H—Central Great Plains Winter Wheat and Range Region ($1.49T), and 3) M—Central Feed Grains and Livestock Region ($1.02T). When normalized by land area, the LRRs were ranked: 1) I—Southwest Plateaus and Plains Range and Cotton Region ($5.36 m−2), 2) J—Southwestern Prairies Cotton and Forage Region ($4.56 m−2), and 3) H—Central Great Plains Winter Wheat and Range Region ($2.56 m−2). States with the highest (midpoint) values for SIC storage were: 1) Texas ($2.96T), 2) New Mexico ($572B), and 3) Montana ($524B). When normalized by land area, the states were ranked: 1) Texas ($4.47 m−2), 2) Utah ($2.77 m−2), and 3) Minnesota ($2.17 m−2). Lastly, regions with the highest (midpoint) values for SIC storage were: 1) South Central ($3.13T), 2) West ($1.98T), and 3) Northern Plains ($1.62T). When normalized by land area, the regions were ranked: 1) South Central ($2.90 m−2), 2) Midwest ($1.32 m−2), and 3) West ($1.02 m−2). Results from this study demonstrate a new approach for assigning monetary values to SIC stocks at various scales based on their role in providing ecosystem services for climate regulation and carbon sequestration.

Desertification control on soil inorganic and organic carbon accumulation in the topsoil of desert grassland in Ningxia, northwest China

Soil carbon is an essential part of the terrestrial carbon pool, which includes soil organic carbon (SOC) and soil inorganic carbon (SIC). Soils contain a huge amount of inorganic carbon in arid and semiarid regions, which may be a potential source of CO2 emitted to the atmosphere. Neglecting soil inorganic carbon could result in erroneous or misleading interpretations of the soil carbon pool of arid and semiarid ecosystems. Nevertheless, only a few studies have focused on variations of SIC, or have further used the soil stable carbon isotope to explore the inherent mechanism of SIC variations in semiarid regions. The study was designed to estimate the dynamic of SOC and SIC with the development of desertification in the topsoil. Here, four desertification stages were chosen, including potential desertification (PD), light desertification (LD), severe desertification (SD), and very severe desertification (VSD) stages, to evaluate the horizontal and vertical distributions of SOC and SIC, and the stable carbon isotope (δ13C) of SOC and SIC with the desertification development in the topsoil (0–30 cm soil layer). The SOC and SIC contents and storage changed significantly with desertification development. The PD stages had the highest SOC (21.01 mg/hm2) and SIC (11.60 mg/hm2) storage at 0–30 cm, while the contrary result for VSD stages, with the average of SOC and SIC, was 8.27 mg/hm2 and 6.15 mg/hm2, respectively. The vertical distribution of SIC and SOC has varied sharply with soil depth. The δ13C-SIC within the 0–30 cm soil profile in the PD stages were more negative than those in other desertification stages and gradually increased with desertification development. In contrast, the δ13C-SOC generally decreased with desertification progress. The entire data (108 soil samples) exhibited that δ13C-SIC were significantly and negatively correlated with δ13C-SOC and SIC content, while SIC storage was significantly and positively correlated with SOC storage. The results demonstrated that an increase of SOC might be related to enhancing accumulation of SIC. The results of this study provide information about the variation of SIC and SOC with the desertification development and contribute to our understanding of the important role of SIC in estimating the carbon sequestration capacity in the degraded grassland ecosystems in arid and semiarid regions.

Accounting for soil inorganic carbon in the ecosystem services framework for United Nations sustainable development goals

Soil inorganic carbon (SIC) is currently not included in the list of key soil properties related to ecosystem services (e.g., provisioning, regulating, cultural, and supporting services). Soil inorganic carbon is a dynamic key soil property used in soil classification, taxonomy and fertility, therefore its inclusion in the framework of ecosystem services is important. With soils rapidly changing due to human use and climate change, the ecosystem services framework should include not only soil organic carbon (SOC), but SIC as well since it is of global importance to soil fertility and the long-term carbon (C) cycle, especially in semiarid and arid climates where SIC comprises the largest C pool. The objective of this study is to assess the value of SIC in the 12 soil orders of Soil Taxonomy at the country scale (continental United States (U.S.)) and at the farm scale (the Cornell University Research Farm) within the context of ecosystem services, specifically provisioning and supporting services. At the country scale, the total estimated midpoint value of SIC storage within the upper two meters of soil is $5.17 T (i.e., 5.17 trillion U.S. dollars). The soil orders having the highest total value of SIC storage (based on an average 2014 price of $10.42 per U.S. ton of CaCO3 lime in the U.S.) are: 1) Mollisols ($2.22 T), 2) Aridisols ($1.23 T), 3) Alfisols ($523B, i.e., 523 billion U.S. dollars), and 4) Entisols ($489B). In terms of SIC content (i.e., value per square meter), the soil orders are ranked: 1) Vertisols ($2.22 m−2), 2) Aridisols ($1.52 m−2), 3) Mollisols ($1.10 m−2), and 4) Inceptisols ($0.49 m−2). At the farm scale, based on variable measured and reported soil sample depths, the soil orders having the highest total value of SIC (based on an average 2014 price of $10.88 price per U.S. ton of CaCO3 for the State of New York (NY)) were: 1) Alfisols, 2) Inceptisols, and 3) Entisols. However, the farm-scale estimates varied greatly depending on whether the values were based on field-derived vs. SSURGO-derived data. The results of this study begin to provide an estimated value of the importance of SIC when assessing ecosystem services. The potential impacts on society from this research include adding SIC into the ecosystem services framework for the United Nations (UN) Sustainable Development Goals. Future research should identify and quantify other important ecosystem services that SIC may provide on a variety of spatial and temporal scales, as well as the potential need of including total C (TC) and interactions between SIC and SOC pools.

Vertical distribution and storage of soil organic and inorganic carbon in a typical inland river basin, Northwest China

Knowledge of soil carbon (C) distribution and its relationship with the environment can improve our understanding of its biogeochemical cycling and help to establish sound regional models of C cycling. However, such knowledge is limited in environments with complex landscape configurations. In this study, we investigated the vertical distribution and storage of soil organic carbon (SOC) and soil inorganic carbon (SIC) in the 10 representative landscapes (alpine meadow, subalpine shrub and meadow, mountain grassland, mountain forest, typical steppe, desert steppe, Hexi Corridor oases cropland, Ruoshui River delta desert, Alxa Gobi desert, and sandy desert) with contrasting bioclimatic regimes in the Heihe River Basin, Northwest China. We also measured the 87Sr/86Sr ratio in soil carbonate to understand the sources of SIC because the ratio can be used as a proxy in calculating the contribution of pedogenic inorganic carbon (PIC) to total SIC. Our results showed that SOC contents generally decreased with increasing soil depth in all landscapes, while SIC contents exhibited more complicated variations along soil profiles in relation to pedogenic processes and parent materials at the various landscapes. There were significant differences of C stocks in the top meter among different landscapes, with SOC storage ranging from 0.82 kg C/m2 in sandy desert to 50.48 kg C/m2 in mountain forest and SIC storage ranging from 0.19 kg C/m2 in alpine meadow to 21.91 kg C/m2 in desert steppe. SIC contributed more than 75% of total C pool when SOC storage was lower than 10 kg C/m2, and the proportion of PIC to SIC was greater than 70% as calculated from Sr isotopic ratio, suggesting the critical role of PIC in the C budget of this region. The considerable variations of SOC and SIC in different landscapes were attributed to different pedogenic environments resulted from contrasting climatic regimes, parent materials and vegetation types. This study provides an evidence for a general trade-off pattern between SOC and SIC, showing the compensatory effects of environmental conditions (especially climate) on SOC and SIC formation in these landscapes. This is largely attributed to the fact that the overall decrease in temperature and increase in precipitation from arid deserts to alpine mountains simultaneously facilitate the accumulation of SOC and depletion of SIC.

Inorganic carbon sequestration capacity and soil carbon assimilation pathway of deserts in arid region

The inorganic carbon sequestration capacity of deserts in an arid region is now still questioned for their accuracy. The key question is whether the result of CO2 absorption from aboveground flux observation can be reflected in the soil carbon pool or not. In the arid region of northwest China, desert is divided into three types based on the landscape and vegetation characteristics, namely gravel desert (Gobi), sand desert, and silt desert. By measuring and analyzing the soil particle composition, total salt content, organic carbon and inorganic carbon content, the changes in soil organic carbon (SOC) and soil inorganic carbon (SIC) density and their storage in different type deserts were studied, and then they were compared with that in the alpine ecosystem of southwest China. The results showed that the average SIC densities in 0–30 cm surface soil layer and 1 m soil depth in different type deserts were 2.8 and 10.1 kg C m−2, respectively. Comparatively, the SIC density of silt desert was the highest, and the value over 12 kg C m−2 in 1 m soil depth. In our study, the average total carbon densities in 0–30 cm desert soil layer was 3.5 kg C m−2, and in 1 m soil depth was 12.1 kg C m−2. According to the value of 100 g C m−2 a−1 to calculate, the carbon accumulation in 0–30 cm surface soil layer and 1 m soil depth need 35 years and 121 years, respectively. If the value is less than 100 g C m−2 a−1, a longer period is required, showed that it will take a long time for the formation of desert inorganic carbon pool. In terms of material content, the average bulk density in 1 m soil depth was 1.52 g cm−3, and the total carbon accumulated in desert soil accounted for 0.8% of soil mass in 121 years, of which the inorganic carbon accounted for 0.7% of soil mass. For the soil absorption and inorganic sequestration to CO2, we proposed the concept of soil carbon assimilation. Carbon sequestration in desert ecosystems is plant carbon assimilation and soil carbon assimilation, which is a combination of organic and inorganic processes. The SIC density and storage of desert soil are five times that of SOC. The pathway of soil carbon assimilation can be divided into three stages: the reaction stage between CO2 and H2O, the reaction stage between CO2 or weak carbonic acid and soil solution cation, and the stage that is the dissolved and precipitated carbonates which attached to soil particles and downward deposition. The soil carbon assimilation capacity was enhanced by increasing the soil organic carbon, salt content, water content, and soil silt and clay content. To recovering and conservation of desert vegetation, the desert is reclaimed into farmland under the carrying capacity of water resources, the SOC density was not only increased, the soil carbon assimilation capacity, SIC density and storage are also enhanced greatly. Under conditions of future climatic warming, soil inorganic carbon sequestration capacity will be increased and carbon sequestration capacity of the desert ecosystem will be enhanced with increasing precipitation in the arid region. The development of irrigated agriculture in the arid desert region will be beneficial to a collaborative improvement in production and ecological functions in the arid region.

On the rocks: Quantifying storage of inorganic soil carbon on gravels and determining pedon-scale variability

The storage and flux of carbon from soils, the planet's third largest carbon pool, strongly influence the global carbon cycle and are essential, but poorly constrained, parameters for global climate models. An estimated 40% of all soil carbon is stored as inorganic carbonate minerals. Despite a recognition of the importance of soil inorganic carbon (SIC) in soil carbon storage, few studies have quantified pedon-scale variability in SIC storage. We examine different stages of carbonate development and accumulation rates between gravelly and non-gravelly soils. Studies often ignore carbonate coatings on gravels in measurements of soil inorganic carbon (SIC). By quantifying and differentiating the fine (<2mm) and coarse (>2mm) fractions of SIC in the Reynolds Creek Experimental Watershed in southwestern Idaho, we show that gravel coatings contain up to 44% of total SIC at a given site. Among the 26 soil sites examined throughout the watershed, an average of 13% of the total SIC is stored as carbonate coatings within in the gravel fraction. We measured a high level of pedon-scale field variability (up to 220%) among the three sampled faces of 1m3 soil pits. Analytical error associated with the modified pressure calcimeter (0.001–0.014%) is considerably less than naturally occurring heterogeneities in SIC within the soil profile. This work highlights and quantifies two sources of uncertainty in studies of SIC needed to inform future research. First, in gravelly sites, the >2mm portion of soils may store a large percentage of SIC. Second, SIC varies considerably at the pedon-scale, so studies attempting to quantify carbon storage over landscape scales need to consider this variability.

Organic and inorganic carbon storage in soils along an arid to dry sub-humid climosequence in northwest of Iran

The importance of soil carbon in different biomes of the earth is well understood. Most of the studies on terrestrial carbon cycle have been focused on the surface horizon of soils, but deeper soils have rarely been considered. The effects of arid, semi-arid and dry sub-humid climates on soil organic carbon (SOC), soil inorganic carbon (SIC) and soil total carbon storage (STC) along a soil climosequence, on basaltic underlying rocks were investigated. SOC and SIC content and storage showed reverse trends with increasing soil depth. STCs increased by increasing mean annual precipitation (MAP) from 3.75 and 6.28kg m−2 in the arid and semi-arid regions, respectively to 11.32kgm−2 in the dry sub-humid. Despite lower SOC in the soils of arid region, the highest SICs/SOCs ratio was obtained in the arid climate, which indicates the importance of climate on SIC storage compared to the SOC content. The average times to store SIC in the dry sub-humid, semi-arid and arid regions were calculated as 15,400, 23,100 and 26,000years, respectively; this indicates that SIC is stored more rapidly in wetter climates due to more weathering. SICs constituted the dominant proportion of STCs which decreased by increasing MAP from in the arid region in comparison with other wetter regions (65%, 74.4% and 84.8% in the semi-arid, dry sub-humid and arid regions, respectively).

Distribution of soil carbon in different grassland types of the Qinghai-Tibetan Plateau

Accurate estimate of soil carbon storage is essential to reveal the role of soil in global carbon cycle. However, there is large uncertainty on the estimation of soil organic carbon (SOC) storage in grassland among previous studies, and the study on soil inorganic carbon (SIC) is still lack. We surveyed 153 sites during plant peak growing season and estimated SOC and SIC for temperate desert, temperate steppe, alpine steppe, steppe meadow, alpine meadow and swamp, which covered main grassland in the Qinghai Plateau during 2011 to 2012. The results showed that the vertical and spatial distributions of SOC and SIC varied by grassland types. The SOC amount mainly decreased from southeast to northwest, whereas the SIC amount increased from southeast to northwest. The magnitude of SOC amount in the top 50 cm across grassland types ranked by: swamp > alpine meadow > steppe meadow > temperate steppe > alpine steppe > temperate desert, while the SIC amount showed an opposite order.There was a great deal of variation in proportion of SOC and SIC among different grassland types (from 55.17 to 94.59 for SOC and 5.14 to 44.83 for SIC). The total SOC and SIC storage was 5.78 Pg and 1.37 Pg, respectively, in the top 50 cm of soil in Qinghai Province. The mixed linear model revealed that grassland types was the predominant factor in spatial variations of SOC amount while grassland types and soil pH accounted for those of SIC amount. Our results suggested that the community shift of alpine meadow towards alpine grassland induced by climate warming would decrease carbon sequestration capacity by 6.0 kg C m2.

Reassessing carbon sequestration in the North China Plain via addition of nitrogen

Soil inorganic carbon (SIC) exerts a strong influence on the carbon (C) sequestered in response to nitrogen (N) additions in arid and semi-arid ecosystems, but limited information is available on in situ SIC storage and dissolution at the field level. This study determined the soil organic/inorganic carbon storage in the soil profile at 0–100cm depths and the concentration of dissolved inorganic carbon (DIC) in soil leachate in 4N application treatments (0, 200, 400, and 600kgNha−1yr−1) for 15years in the North China Plain. The objectives were to evaluate the effect of nitrogen fertilizer on total amount of carbon sequestration and the uptake of atmospheric CO2 in an agricultural system. Results showed that after 15years of N fertilizer application the SOC contents at depths of 0–100cm significantly increased, whereas the SIC contents significantly decreased at depths of 0–60cm. However, the actual measured loss of carbonate was far higher than the theoretical maximum values of dissolution via protons from nitrification. Furthermore, the amount of HCO3− and the HCO3−/(Ca2++Mg2+) ratio in soil leachate were higher in the N application treatments than no fertilizer input (CK) for the 0–80cm depth. The result suggested that the dissolution of carbonate was mainly enhanced by soil carbonic acid, a process which can absorb soil or atmosphere CO2 and less influenced by protons through the nitrification which would release CO2. To accurately evaluate soil C sequestration under N input scenarios in semi-arid regions, future studies should include both changes in SIC storage as well as the fractions of dissolution with different sources of acids in soil profiles.

Soil carbon dynamics during grass restoration on abandoned sloping cropland in the hilly area of the Loess Plateau, China

Secondary vegetation succession on abandoned cropland significantly influences soil C-pool dynamics in arid and semi-arid region. Much work on soil C-pool dynamics has been focused on soil organic carbon (SOC), whereas considerably less attention has been given on soil inorganic carbon (SIC). Moreover, the relationship between SOC and SIC during natural succession is unclear. The objective of this research was to investigate SOC and SIC storage dynamics in natural restored grassland following cropland abandonment. We measured SOC and SIC content in paired grassland and cropland sites in the Gaoqiao watershed on the Loess Plateau, China. The grassland sites were established on cropland abandoned for 5, 13, 24, and 32years. Top soil OC was significantly higher after 10-year restoration, especially in the 0–5cm soil depths; deeper soil OC was lower in younger grasslands (<20yr), and significantly higher in older grasslands (>20yr). SIC was significantly higher after abandonment, but varied largely among successional grasslands. SOC storage (SOCs) decreased in the younger grassland (5yr), and SOCs (0–100cm) was significantly higher after 10-year restoration. SIC storage (SICs) increased after abandonment in the 0–100cm soil depth, but showed various magnitudes among restored grasslands. SIC storage (SICs) originally contained most part of STC storage (STCs), and grass restoration after cropland abandonment led to higher SOCs/STCs ratio and lower SICs/STCs ratio. Our results indicate that grass restoration enhanced the accumulation of SOC and SIC storages, but with inverse proportional contributions to STC storage. We suggest that SIC should be as much focused as SOC during grass restoration in the arid Loess Plateau.

Profile distribution of soil inorganic carbon along a chronosequence of grassland restoration on a 22-year scale in the Chinese Loess Plateau

Understanding the distribution of soil inorganic carbon (SIC) is meaningful and necessary for assessing soil carbon sequestration. However, changes in SIC following vegetation restoration are still not well studied in the Chinese Loess Plateau (CLP), which has undergone extensive changes from farmland to grassland. Here, we chose three study sites, farmland (FL), grassland restored for 12years (RG-1) and grassland restored for 22years (RG-2). The changes of SIC storage were determined under the conversion from a farmland ecosystem to extensively used grassland during the past twenty years. Results showed that the SIC content decreased with vegetation restoration, which averaged 18.5, 13.2 and 11.8gkg−1 in FL, RG-1 and RG-2, respectively. The SIC content was significantly lower in the top 80cm in RG-1 and RG-2 than in FL, but showed little variance at depths of 80–200cm among the study sites. It illustrated that the portion of carbonate was most likely released to the atmosphere as CO2 temporarily due to soil acidification and the increase of soil moisture in restored grassland. The lower δ13C value of SIC in RG-1 and RG-2 than in FL was most likely due to the soil carbonate exchanging with more soil respired CO2, with increasing vegetation coverage in restored grassland. Our results indicate that the SIC storage deceases in the restored grassland in situ probably due to the decrease of soil pH and the increase in soil water content. The SIC plays an important role when assessing the capacity of carbon sequestration with vegetation restoration in the semi-arid CLP.

青海省高寒草地土壤无机碳储量空间分异特征

PDF HTML阅读 XML下载 导出引用 引用提醒 青海省高寒草地土壤无机碳储量空间分异特征 DOI: 10.5846/stxb201301250156 作者: 作者单位: 中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所,中国科学院西北高原生物研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（41030105）；中国科学院战略性先导科技专项（XDA05050404）（固碳现状、速率、机制和潜力）项目 The variation feature of soil inorganic carbon storage in alpine grassland in Qinghai province Author: Affiliation: Northwest Institute of Plateau biology, Chinese Academy of Sciences,,,,,,,,Northwest Institute of Plateau biology, Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以青海省主要高寒草地类型即温性草原、高寒草原、草甸草原以及高寒草甸为研究对象，进行其土壤无机碳（SIC）储量分异特征研究。结果表明，在取样剖面内四类草地SIC储量依次为温性草原 >高寒草原 >草甸草原 >高寒草甸，其值分别为16.51、16.48 、3.37 kgC/m2和0.12 kgC/m2，温性草原与高寒草原土壤是高寒草地无机碳的主要储蓄库。温性草原与高寒草原50-100cm SIC储量分别占0-100cm总储量的60.2%和 51.8%，而草甸草原与高寒草甸30-50cmSIC储量分别占0-50cm总储量的50.1%和55.8%，说明土体下部是高寒草地无机碳储蓄的主要场所。四类草地SIC含量随土层深度的变化过程各异，其碳酸钙富集层与野外剖面调查所得碳酸钙盐酸泡沫检验结果相吻合。SIC储量与土壤容重和土壤pH均呈显著正相关关系，与地下生物量呈显著负相关关系。 Abstract:The warm steppe, alpine steppe, alpine meadow steppe and alpine meadow are the main grassland types which widely distribute in Qinghai-Tibetan plateau. It's widely distribution and diverse development environments make it play an important role in the ecosystem: supporting regional economic development, guaranteeing water conservation of the plateau, maintaining biodiversity, fixation of carbon, etc. A quantitative survey of the variation feature of soil inorganic carbon(SIC)stored in warm steppe, alpine steppe, alpine meadow steppe and alpine meadow were carried out in Qinghai province. Results showed that the total storage of SIC in the four types grassland appeared to be warm steppe> alpine steppe> meadow steppe> alpine meadow, and the values were 16.51kgC/m2,16.48 kgC/m2,3.37 kgC/m2 and 0.12 kgC/m2, respectively. One-Way ANOVA analysis indicated that warm steppe、alpine steppe had a significant difference with alpine meadow steppe and alpine meadow(P < 0.05)while no significant difference between warm steppe and alpine steppe as well as alpine meadow steppe and alpine meadow(P > 0.05). The warm steppe and alpine steppe grassland are the main reserve pool of SIC in alpine grassland. The SIC stored in 50-100cm accounted separately for 60.2% and 51.8% of the total storage in 0-100cm profile of the warm steppe and alpine steppe, while in alpine meadow steppe and alpine meadow, it occupied 50.1% and 55.8% respectively of the 30-50cm in 0-50cm. Deep soil layer is the main place of SIC storing in alpine grassland. Soil depth has an important effect on SIC storage in alpine grassland. In 0-50cm depth of the soil, SIC storing in the four types grassland were 6.57 kgC/m2,7.95 kgC/m2,3.37 kgC/m2 and 0.12 kgC/m2, respectively. The change of SIC content with soil depth were different in the four types grassland. It increased with soil depth in warm steppe and alpine meadow steppe, but increased at first then decreased in alpine meadow steppe and alpine meadow. The calcium carbonate enrichment layer in the soil tallied with the foam examination by hydrochloric acid in the soil profile investigation. The calcium carbonate accumulate in the deep soil of steppe, but enrich rather shallow in meadow. SIC storage in the four types of grassland had a significantly positive correlation with soil bulk density and pH value but a significantly negative correlation with underground biomass. The SIC storage increased from south to north in the grassland of Qinghai province and the total SIC storage of the four types grassland reached 1.34 Pg in the profile. The SIC storage in the alpine meadow is very small and it mainly distributed in the south of Qinghai province. Warm steppe which has the largest SIC storage mainly distributed nearby the Qinghai Lake. Climate change and human activity may affect the capacity and distribution of the carbon storage which would bring the ecological risk to the inorganic carbon fixation. 参考文献 相似文献 引证文献

Storage/Turnover Rate of Inorganic Carbon and Its Dissolvable Part in the Profile of Saline/Alkaline Soils

Soil inorganic carbon is the most common form of carbon in arid and semiarid regions, and has a very long turnover time. However, little is known about dissolved inorganic carbon storage and its turnover time in these soils. With 81 soil samples taken from 6 profiles in the southern Gurbantongute Desert, China, we investigated the soil inorganic carbon (SIC) and the soil dissolved inorganic carbon (SDIC) in whole profiles of saline and alkaline soils by analyzing their contents and ages with radiocarbon dating. The results showed that there is considerable SDIC content in SIC, and the variations of SDIC and SIC contents in the saline soil profile were much larger than that in the alkaline profile. SDIC storage accounted for more than 20% of SIC storage, indicating that more than 1/5 of the inorganic carbon in both saline and alkaline soil is not in non-leachable forms. Deep layer soil contains considerable inorganic carbon, with more than 80% of the soil carbon stored below 1 m, whether for SDIC or SIC. More importantly, SDIC ages were much younger than SIC in both saline soil and alkaline soil. The input rate of SDIC and SIC ranged from 7.58 to 29.54 g C m-2 yr-1 and 1.34 to 5.33 g C m-2 yr-1 respectively for saline soil, and from 1.43 to 4.9 g C m-2 yr-1 and 0.79 to 1.27 g C m-2 yr-1respectively for alkaline soil. The comparison of SDIC and SIC residence time showed that using soil inorganic carbon to estimate soil carbon turnover would obscure an important fraction that contributes to the modern carbon cycle: namely the shorter residence and higher input rate of SDIC. This is especially true for SDIC in deep layers of the soil profile.

English

&nbsp; A study was conducted to assess the soil carbon distribution in cold desert high altitude region of Ladakh in India at different altitudes and their correlation patterns with the altitude. The role of carbon dynamics in the exchange of CO2&nbsp;between the terrestrial biosphere and the atmosphere has important implications in this study of global climate change. The present study was done in Ladakh region of India from where soil samples were collected on the basis of different altitudes range and thereafter samples were analyzed for organic carbon and calcium carbonate content. Results of our study show that the soil organic carbon (SOC) content and storage increased significantly with the increase in the altitude where as when compared with the altitude of 10000 ft amsl, soil inorganic carbon (SIC content and its storage decreased significantly (P&lt; 0.05) at an altitude of 11000 ft up to 12000 ft amsl. The SOC content and storage were observed positively (P&lt;0.01) correlated with altitude, while soil inorganic carbon storage and contents were negatively (P&lt;0.05) correlated with altitude. Hence, our study indicates that very harsh and unique climatic conditions in Ladakh influences storage and distribution pattern of soil carbon along the altitudes or elevation gradients. So investigations along altitude gradients is a useful approach to the study of environmental change and its effect on the soil processes, which can complement data obtained from controlled, large scale field studies as well as other practical and theoretical approaches to climate change research. &nbsp; Key words: Cold desert, high altitude, carbon distribution pattern, altitudinal variation, soil carbon, micro-climate.