| Affected by geological disasters and human interference,the ecological environment in Gansu's Longnan area has been deteriorating.Under this background,a series of ecological restoration projects have been carried out.Soil organic carbon is an indicator of soil structure and soil environmental quality in the process of ecological restoration.Higher soil organic carbon levels often represent good soil structure and quality.Therefore,in the process of ecological restoration,it is of great significance to study soil organic carbon.In this study,field observations,indoor experiments,and model simulations were conducted to study soil organic carbon density and soil carbon sequestration potential of typical artificial vegetation types of cultivated land,artificial grassland,and artificial forest land in the region,In order to provide scientific basis for geological disaster prevention,climate change and ecological sustainable development in the study area.The following conclusions are follows.(1)The soil organic carbon content and total soil nitrogen content in artificial forest land,cultivated land,artificial grassland,and barel land ranged from 1.62 to 45.91 g/kg and 0.53 to 3.88g/kg,respectively,The order of their contents is as follows:artificial forest>artificial grassland>cultivated land>bare land?The changes of soil organic carbon content and soil total nitrogen content were consistent along the soil vertical profile.Soil organic carbon content and total soil nitrogen content decreased along the soil vertical profile.There was no significant difference in soil total phosphorus content,and its content ranged from 0.405 g/kg to 0.645 g/kg.(2 Soil in the study area is dominated by silty loam and with the same mechanical composition.There was a significant difference in the content of macroaggregates.The content of macroaggregates of artificial forests was the highest,reaching a maximum of 69.73%.In different soil depths and different d vegetation,the particle size characteristics of large aggregates are different.The soil bulk density in the study area was between 1.20 g/cm~3 and 1.41 g/cm~3.The bulk density of soil in bare land was the largest while the artificial forest land was the smallest,and there was no significant difference of soil bulk density between artificial grassland and cultivated land.The soil in the study area isweakly alkaline,and soil pH is between 7.53 and 8.03.The total soil porosity in the study area is between 46.2%and 53.8%.Along the vertical soil profile,the total soil porosity shows a decreasing trend.The total soil porosity of the artificial forest land is the largest,while the bareland is the smallest.(3)The results of studies on the correlation between soil organic carbon and environmental factors show that soil organic carbon content is negatively correlated with bulk density and p H and positive correlated with soil moisture content,total soil porosity,litter,aboveground biomass.Redundancy analysis results showed that there was a high correlation between soil organic carbon and soil pH,soil water content,aboveground biomass,underground biomass,litter and large aggregates.(4)Currently,the organic carbon densities of cultivated land,artificial grassland and artificial forest land were 23917,25713 and 139724 kgC/ha,respectively.Under the existing cultivation methods and land management,the potential carbon sequestration potential of cultivated land,artificial grassland,and artificial forest land is 9195,12946,and 16796 kgC/ha,respectively.The increase of temperature will promote the release of carbon from the soil into the atmosphere,and the low temperature will be more conducive to the fixation of carbon in from atmosphere to soil.Currently,the cultivated land,artificial grassland and artificial forest land in the study area all play the role of"carbon sink",and the soil organic carbon pool in the study area shows an increasing trend. |
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