Effects of Rest Grazing on Organic Carbon Storage in Stipa grandis Steppe in Inner Mongolia, China

This study was aimed to evaluate the potential effects of rest grazing on organic carbon storage in Stipa grandis steppe of Inner Mongolia, China. Using potassium dichromate heating method, we analyzed the organic carbon storage of plant and soil in Stipa grand＆ steppe after rest grazing for 3, 6, and 9 yr. The results indicated that as the rest grazing ages prolonged, the biomass of aboveground parts, litter and belowground plant parts （roots） of the plant communities all increased, meanwhile the C content of the biomass increased with the rest grazing ages prolonging. For RG0, RG3a, RG6a, and RG9a, C storage in aboveground vegetation were 60.7, 76.9, 82.8 and 122.2 g C m2, respectively; C storage of litter were 5.1, 5.8, 20.4 and 25.5 g C m^-2, respectively; C storage of belowground roots （0-100 cm） were 475.2, 663.0, 1 115.0 and 1 867.3 g C m^-2, respectively; C storage in 0-100 cm soil were 13.97, 15.76, 18.60 and 32.41 kg C m^-2, respectively. As the rest grazing ages prolonged, the organic C storage in plant communities and soil increased. The C storage ofbelowground roots and soil organic C was mainly concentrated in 0-40 cm soil body. The increased soil organic C for RG3a accounted for 89.8% of the increased carbon in vegetation-soil system, 87.2% for RG6a, and 92.6% for RG9a. From the perspective of C sequestration cost, total cost for RG3a, RG6,, and RG9a were 2 903.4, 5 806.8 and 8 710.2 CNY haq, respectively. The cost reduced with the extension of rest grazing ages, 0.15 CNY kg^-1 C for RG3a, 0.11 CNY kg-~ C for RG6a and 0.04 CNY kg℃ for RG9a. From the growth characteristics of grassland plants, the spring was one of the two avoided grazing periods, timely rest grazing could effectively restore and update grassland vegetation, and was beneficial to the sustainable use of grassland. Organic C storage for RG9a was the highest, while the cost of C sequestration was the lowest. Therefore, spring rest grazing should be encouraged because it was proved to be a very efficient grassland use pattern.

Estimation of soil organic carbon storage and its fractions in a small karst watershed

With few available soil organic carbon(SOC)profiles and the heterogeneity of those that do exist, the estimation of SOC pools in karst areas is highly uncertain.Based on the spatial heterogeneity of SOC content of 23,536 samples in a karst watershed, a modified estimation method was determined for SOC storage that exclusively applies to karst areas. The method is a "soil-type method" based on revised calculation indexes for SOC storage. In the present study, the organic carbon contents of different soil types varied greatly, but generally decreased with increasing soil depth. The organic carbon content decreased nearly linearly to a depth of 0–50 cm and then varied at depths of 50–100 cm. Because of the large spatial variability in the karst area, we were able to determine that influences of the different indexes on the estimation of SOC storage decreased as follows: soil thickness > boulder content > rock fragment content > SOC content > bulk density. Using the modified formula, the SOC content in the Houzhai watershed in Puding was estimated to range from 3.53 to 5.44 kg m^(-2), with an average value of 1.24 kg m^(-2) to a depth of 20 cm, and from 4.44 to 14.50 kg m^(-2), with an average value of 12.12 kg m^(-2) to a depth of 100 cm. The total SOC content was estimated at 5.39*10^(5) t.

Organic carbon storage in trees within different Geopositions of Chittagong （South） forest division, Bangladesh

The organic carbon storage in trees and organic carbon flow with geoposition of trees was estimated in the forest area of Chittagong （South） Forest Division within geo-position 91°47′ and 92°15′ East longitude and 21°45′ and 22°30′ North latitude. The study was conducted through stratified random sampling by identifying each sampling point through Global Positioning System （GPS）. It was found that above ground organic carbon storage （t/hm^2）, below ground organic carbon （t/hm^2） and total biomass organic carbon （t/hm^2） was respectively the highest in Dipterocarpus turbinatus （Garjan） （7.9, 1.18 and 9.08 t/hm^2） followed by Tectona grandis （Teak） （5.66, 0.85 and 6.51 t/hm^2）, Artocarpus chaplasha （Chapalish） （2.32, 0.34 and 2.66 t/hm^2）, Artocarpus lacucha （Batta） （1.97, 0.29 and 2.26 t/hm^2） and Artocarpus heterophyllus （Jackfruit） （1.7,0.25 and 2.26 t/hm^2）. From the study it was revealed that organic carbon stock was the highest （142.7 t/hm^2） in the geo-position 22° Latitude and 92° Longitude and was the lowest （4.42 t/hm^2） in the geo-position 21° 50′ Latitude and 92° 2.5′ Longitude. The forest of the study area is a good reservoir of organic carbon so has a good capacity to sequester organic carbon from the atmosphere. Sustainable forest management may help to sequester more organic carbon so that economic benefit for the country and environmental benefit in the international arena are possible from the study area.

Soil organic carbon storages and bacterial communities along a restored mangrove soil chronosequence in the Jiulong River Estuary:From tidal flats to mangrove afforestation

Among many ecological services provided by mangrove ecosystems,soil organic carbon(SOC)storages have recently received much attention owing to the increasing atmospheric partial pressure of dissolved CO_(2)(pCO_(2)).Bacteria are fundamental to ecosystem functions and strongly influence the coupling of coastal carbon,nitrogen,and sulfur cycling in soils.The SOC storage and bacterial communities along a restored mangrove soil chronosequence in the Jiulong River Estuary were explored using the 16S rDNA sequencing technique.The results showed the SOC storage in the 100 cm soil profile was 103.31±5.87 kg C m^(−2)and 93.10±11.28 kg C m^(−2)for mangroves with afforestation ages of 36 and 60 years,respectively.The total nitrogen(TN)and total sulfur(TS)contents exhibited significant correlations with the SOC in the mangrove soils,but only TN and SOC showed significant correlation in tidal flat soils.Although the tidal flats and mangroves occupied the contiguous intertidal zone within several kilometers,the variations in the SOC storage along the restored mangrove soil chronosequence were notably higher.The Functional Annotation of Prokaryotic Taxa(FAPROTAX)database was used to annotate the metabolic functions of the bacteria in the soils.The annotation revealed that only four metabolic functions were enriched with a higher relative abundance of the corresponding bacteria,and these enriched functions were largely associated with sulfate reduction.In addition,the specifically critical bacterial taxa that were associated with the SOC accumulation and nutrient cycling,shaped the distinct metabolic functions,and consequently facilitated the SOC accumulation in the mangrove soils with various afforestation ages.The general homogenization of the microbial community and composition along the intertidal soil chronosequence was primarily driven by the reciprocating tidal flows and geographical contiguity.

Estimation of Storage and Density of Organic Carbon in Peatlands of China

Based on the results of the National Survey of Peat Resources(1983-1985) and the investigation results on the peatlands of China,the storage and density of the organic carbon in the peatlands of China were estimated.The total organic carbon storage(OCS) of the peatlands in China,including bare peatlands and buried peatlands,are 1.503 × 109 t,unevenly distributed over 30 provincial level administrative units and 16 climatic zones.Peatland organic carbon storage(POCS) in Sichuan(6.45 × 108 t) and Yunnan provinces(2.91 × 108 t) is the highest,accounting for 62.29% of the total POCS.Humid zone of plateau has the highest POCS of 7.14 × 108 t,especially in the Zoigê Plateau,where the POCS is 6.30 × 108 t,accounting for 41.92% of the total POCS of China.The organic carbon density(OCD) of the peatlands in China mostly ranges from 80 kg/m3 to 140 kg/m3,and the range of the maximum is 270-360 kg/m3,and the minimum is less than 80 kg/m3.Divided by the Yanshan Mountain,Taihang Mountains and Hengduan Mountains,the peatland oganic carbon density(POCD) is lower on the northwestern side than that on the southeastern side.Jiangxi Province has the highest POCD due to the ancient buried peatlands.The OCD of the bare peatlands is mostly in the range of 60-150 kg/m3,and that of the buried peatlands is more than 100 kg/m3.In the bare peatlands,the OCD generally increases from the surface layer to the below surface layer,and then decreases with the depth.Although the peatlands area in China is small,the OCS per unit area is far higher than the other soil types,so peatlands protection can effectively mitigate climate change.

Characteristics of soil organic carbon andtotal nitrogen storages for differentland-use types in Central Yunnan Plateau

Two-factor analysis of variance and redundancy analysis were used to analyze the characte-ristics of soil organic carbon total nitrogen storage in garden land,forestland,grassland,farmland,and bare land in the Dachunhe watershed of Jinning District,Kunming City,Yunnan Province,China.The effects of the soil organic carbon,total nitrogen stratification ratio,soil physical and chemical factors on the storage characteristics of organic carbon and total nitrogen of different land-use types were analyzed.The results show that the rates of carbon and nitrogen stratification in soil from 0-20 cm and 40-60 cm of the same land-use types differed are statistically significant(P<0.05).The organic carbon and total nitrogen stratification ratio SR1 of garden land soil are 38.5%and 25.3%,respectively,which are higher than SR^(2).The soil organic carbon and total nitrogen stratification ratio SR^(2) of different land-use types are greater than SR1.There are statistically significant differences in the SR^(2) soil organic carbon and total nitrogen stratification ratios(P<0.05).Soil organic carbon and total nitrogen storage of diffe-rent land-use types gradually decrease with increasing soil depth,with the maximum soil organic carbon and total nitrogen storage in the 0-20 cm soil layer.Soil organic carbon and total nitrogen sto-rage at the same soil depth are significantly different(P<0.05).Soil organic carbon and total nitrogen storage in the garden land are greater than those in the other land-use types.Soil organic carbon and total nitrogen storage in 0-20 cm garden land are 4.96 and 3.19 times than those in bare land,respectively;soil organic carbon and total nitrogen storage are explained by 93.66%and 1.53%in redundancy analysis RDA1 and RDA2,respectively.All physicochemical factors except Available Phosphorus and pH are statistically significance with carbon and nitrogen storage(P<0.05).Soil cationic exchange capacity,Available Phosphorus,C/N ratio,and Moisture Content are positively correlated with organic carbon and total nitrogen storage.In contrast,soil Bulk Density is negatively correlated with organic carbon storage and total nitrogen storage.Available Phosphorus,C/N ratio,and Moisture Content are the main factors promoting soil organic carbon and total nitrogen accumulation.

Research Status, Problems and Direction of Soil Organic Carbon in Zoige Peat Wetland

Peatlands,as a special type of wetland,occupy only 3%of the Earth’s surface,but bear about one-third of the world’s soil carbon storage and play an important role in the global carbon cycle.The Zoige Wetland is located on the eastern edge of the Qinghai-Tibet Plateau,and its peat reserves are up to 1.9 billion tons,accounting for more than 40%of the country’s peat resources,which is an important support for China to achieve the“double carbon”goal.This paper reviews the research status and storage estimation of soil organic carbon in Zoige Wetland.The statistical results show that there is a large difference in the estimation of carbon storage in the peatland of Zoige(0.43-1.42 Pg).The reasons are mainly related to marked differences in values reported for soil densities,organic carbon levels,and accu­mulation rates.There are still great uncertainties in the estimation of wetland carbon stocks,and future studies should focus on reducing soil carbon sink uncertainties,climate change,the impact of permafrost melting on carbon sink functions,the impact of degraded ecosystem restoration and sink enhancement pathways,and other greenhouse gas functions.In order to accurately reveal the current situation and future trend of carbon sink in peat wetlands,a model-multi-source observation data fusion system was constructed to complement the observation shortcomings in key ar­eas,and provide reference and support for the construction of carbon neutral ecological civilization.

Tillage Effect on Organic Carbon in a Purple Paddy Soil

The distribution and storage of soil organic carbon (SOC) based on a long-term experiment with various tillage systems were studied in a paddy soil derived from purple soil in Chongqing, China. Organic carbon storage in the 0-20 and 0-40 cm soil layers under different tillage systems were in an order: ridge tillage with rice-rape rotation (RT-rr) > conventional tillage with rice only (CT-r) > ridge tillage with rice only (RT-r) > conventional tillage with rice-rape rotation (CT-rr). The RT-rr system had significantly higher levels of soil organic carbon in the 0-40 cm topsoil, while the proportion of the total remaining organic carbon in the total soil organic carbon in the 0-10 cm layer was greatest in the RT-rr system. This was the reason why the RT-rr system enhanced soil organic carbon storage. These showed that tillage system type was crucial for carbon storage. Carbon levels in soil humus and crop-yield results showed that the RT-rr system enhanced soil fertility and crop productivity. Adoption of this tillage system would be beneficial both for environmental protection and economic development.

SOC storage and potential of grasslands from 2000 to 2012 in central and eastern Inner Mongolia, China

Grassland ecosystem is an important component of the terrestrial carbon cycle system. Clear comprehension of soil organic carbon（SOC） storage and potential of grasslands is very important for the effective management of grassland ecosystems. Grasslands in Inner Mongolia have undergone evident impacts from human activities and natural factors in recent decades. To explore the changes of carbon sequestration capacity of grasslands from 2000 to 2012, we carried out studies on the estimation of SOC storage and potential of grasslands in central and eastern Inner Mongolia, China based on field investigations and MODIS image data. First, we calculated vegetation cover using the dimidiate pixel model based on MODIS-EVI images. Following field investigations of aboveground biomass and plant height, we used a grassland quality evaluation model to get the grassland evaluation index, which is typically used to represent grassland quality. Second, a correlation regression model was established between grassland evaluation index and SOC density. Finally, by this regression model, we calculated the SOC storage and potential of the studied grasslands. Results indicated that SOC storage increased with fluctuations in the study area, and the annual changes varied among different sub-regions. The SOC storage of grasslands in 2012 increased by 0.51×1012 kg C compared to that in 2000. The average carbon sequestration rate was 0.04×1012 kg C/a. The slope of the values of SOC storage showed that SOC storage exhibited an overall increase since 2000, particularly for the grasslands of Hulun Buir city and Xilin Gol League, where the typical grassland type was mainly distributed. Taking the SOC storage under the best grassland quality between 2000 and 2012 as a reference, this study predicted that the SOC potential of grasslands in central and eastern Inner Mongolia in 2012 is 1.38×1012 kg C. This study will contribute to researches on related methods and fundamental database, as well as provide a reference for the protection of grassland ecosystems and the formulation of local policies on sustainable grassland development.

Gulong shale oil enrichment mechanism and orderly distribution of conventional–unconventional oils in the Cretaceous Qingshankou Formation,Songliao Basin,NE China

Through the study of organic matter enrichment,hydrocarbon generation and accumulation process of black shale of the Cretaceous Qingshankou Formation in the Songliao Basin,the enrichment mechanism of Gulong shale oil and the distribution of conventional–unconventional oil are revealed.The Songliao Basin is a huge interior lake basin formed in the Early Cretaceous under the control of the subduction and retreat of the western Pacific plate and the massive horizontal displacement of the Tanlu Fault Zone in Northeast China.During the deposition of the Qingshankou Formation,strong terrestrial hydrological cycle led to the lake level rise of the ancient Songliao Basin and the input of a large amount of nutrients,resulting in planktonic bacteria and algae flourish.Intermittent seawater intrusion events promoted the formation of salinization stratification and anoxic environment in the lake,which were beneficial to the enrichment of organic matters.Biomarkers analysis confirms that the biogenic organic matter of planktonic bacteria and algae modified by microorganisms plays an important role in the formation of high-quality source rocks with high oil generation capability.There are four favorable conditions for the enrichment of light shale oil in the Qingshankou Formation of the Gulong Sag,Songliao Basin:the moderate organic matter abundance and high oil potential provide sufficient material basis for oil enrichment;high degree of thermal evolution makes shale oil have high GOR and good mobility;low hydrocarbon expulsion efficiency leads to a high content of retained hydrocarbons in the source rock;and the confinement effect of intra-layer cement in the high maturity stage induces the efficient accumulation of light shale oil.The restoration of hydrocarbon accumulation process suggests that liquid hydrocarbons generated in the early(low–medium maturity)stage of the Qingshankou Formation source rocks accumulated in placanticline and slope after long-distance secondary migration,forming high-quality conventional and tight oil reservoirs.Light oil generated in the late(medium–high maturity)stage accumulated in situ,forming about 15 billion tons of Gulong shale oil resources,which finally enabled the orderly distribution of conventional–unconventional oils that are contiguous horizontally and superposed vertically within the basin,showing a complete pattern of“whole petroleum system”with conventional oil,tight oil and shale oil in sequence.

Detecting the storage and change on topsoil organic carbon in grasslands of Inner Mongolia from 1980s to 2010s

Soil carbon sequestration and potential has been a focal issue in global carbon research. Under the background of global change, the estimation of the size as well as its change of soil organic carbon（SOC） storage is of great importance. Based on soil data from the second national soil survey and field survey during 2011–2012, by using the regression method between sampling soil data and remote sensing data, this paper aimed to investigate spatial distribution and changes of topsoil（0–20 cm） organic carbon storage in grasslands of Inner Mongolia between the 1980 s and 2010 s. The results showed that：（1） the SOC storage in grasslands of Inner Mongolia between the 1980 s and 2010 s was estimated to be 2.05 and 2.17 Pg C, with an average density of 3.48 and 3.69 kg C·m–2, respectively. The SOC storage was mainly distributed in the typical steppe and meadow steppe, which accounted for over 98% of the total SOC storage. The spatial distribution showed a decreased trend from the meadow steppe, typical steppe to the desert steppe, corresponding to the temperature and precipitation gradient.（2） SOC changes during 1982–2012 were estimated to be 0.12 Pg C, at 7.00 g C·m–2·yr–1, which didn＇t show a significant change, indicating that SOC storage in grasslands of Inner Mongolia remained relatively stable over this period. However, topsoil organic carbon showed different trends of carbon source/sink during the past three decades. Meadow steppe and typical steppe had sequestered 0.15 and 0.03 Pg C, respectively, served as a carbon sink; while desert steppe lost 0.06 Pg C, served as a carbon source. It appears that SOC storage in grassland ecosystem may respond differently to climate change, related to vegetation type, regional climate type and grazing intensity. These results might give advice to decision makers on adopting suitable countermeasures for sustainable grassland utilization and protection.

Variation in glomalin in soil profiles and its association with climatic conditions,shelterbelt characteristics,and soil properties in poplar shelterbelts of Northeast China

Glomalin-related soil protein(GRSP)sequesters large amounts of carbon and plays important roles in maintaining terrestrial soil ecosystem functions and ecological restoration;however,little is known about GRSP variation in 1-m soil profiles and its association with stand characteristics,soil properties,and climatic conditions,hindering GRSP-related degraded soil improvement and GRSP evaluation.In this study,we sampled soils from 1-m profiles from poplar(Populus spp.)shelterbelts in Northeast China.GRSP contents were 1.8–2.0 times higher in the upper 40 cm soil layers than at 40–100 cm.GRSP-related soil organic carbon(SOC)sequestration in deeper soil layers was*1.2 times higher than in surface layers.The amounts of GRSP-related nutrients were similar throughout the soil profile.A redundancy analysis showed that in both surface and deeper layers,soil properties(pH,electrical conductivity,water,SOC,and soil nutrients)explained the majority of the GRSP variation(59.5–84.2%);the second-most-important factor in GRSP regulation was climatic conditions(temperature,precipitation,and altitude),while specific shelterbelt characteristics had negligible effects(<5%).Soil depth and climate indirectly affected GRSP features via soil properties,as manifested by structural equation model analysis.Our findings demonstrate that GRSP is important for carbon storage in deep soils,regardless of shelterbelt characteristics.Future glomalin assessments should consider these vertical patterns and possible regulating mechanisms that are related to soil properties and climatic changes.

Three-dimensional modelling of soil organic carbon density and carbon sequestration potential estimation in a dryland farming region of China

Soil organic carbon density(SOCD)and soil organic carbon sequestration potential(SOCP)play an important role in carbon cycle and mitigation of greenhouse gas emissions.However,the majority of studies focused on a two-dimensional scale,especially lacking of field measured data.We employed the interpolation method with gradient plane nodal function(GPNF)and Shepard(SPD)across a range of parameters to simulate SOCD with a 40 cm soil layer depth in a dryland farming region(DFR)of China.The SOCP was estimated using a carbon saturation model.Results demonstrated the GPNF method was proved to be more effective in simulating the spatial distribution of SOCD at the vertical magnification multiple and search point values of 3.0×106 and 25,respectively.The soil organic carbon storage(SOCS)of 40 cm and 20 cm soil layers were estimated as 22.28×10^(11)kg and 13.12×10^(11)kg simulated by GPNF method in DFR.The SOCP was estimated as 0.95×10^(11)kg considered as a carbon sink at the 20–40 cm soil layer.Furthermore,the SOCP was estimated as–2.49×10^(11)kg considered as a carbon source at the 0–20 cm soil layer.This research has important values for the scientific use of soil resources and the mitigation of greenhouse gas emissions.