Changes Of Soil Organic Carbon Pool In The Loess Plateau Following The "Grain For Green"

The Loess Plateau is located in arid and semi-arid regions of China,In the late 1980s,environmental degradation and soil erosion became more and more serious,posing a huge challenge to the sustainable development of the region.To this end,the Chinese government initiated the project of "Grain for Green" project in 1999 to reforest and restore vegetation in the area.Based on the background of "Grain for Green",this paper studies the changes of soil organic carbon pool and carbon sequestration rate after farmland conversion to different vegetation types in the Loess Plateau.At present,relevant studies have reported the carbon sequestration rate in the Loess Plateau,but the effects of tree species and vegetation types have been ignored,Studying these issues can provide a scientific basis for the development of reasonable vegetation restoration plans and strategies for the Loess Plateau,and can provide reference for planning similar projects in other parts of the world.At the same time,understanding the mechanisms of soil organic carbon change can help prdict future changes in regional carbon pools.In this paper,the Loess Plateau was used as the research area,and 335 sample data of soil organic carbon change since the implementation of the project of "Grain for Green" was collected by meta-analysis.Through stepwise multiple linear regression analysis,the effects of restoration age,vegetation types,tree species and other potential\variables on soil organic carbon density were studied,and the effects of different vegetation types and tree species on carbon sequestration rate were emphasized.The main research contents and conclusions are as follows:(1)Using stepwise multiple linear regression to analyze the carbon sequestration rate of different vegetation types and tree species,thhe results show that the difference in carbon sequestration between different vegetation types and tree species is significant.Artificial grassland(41 g C m-2 yr-1)had the highest carbon sequestration rate,the middle of the shrubland(25 g C m-2 yr-1),and the carbon sequestration rate of the artificial forest(19 g C m-2 yr-1).The lowest natural grassland(0.09 g C m-2 yr-1);analysis of different tree species in plantations showed that the carbon sequestration rate of evergreen coniferous forests(Platycladus orientalis and Pinus tabulaeformis)was higher than that of deciduous broad-leaved species(Robinia pseudoacacia and orchard).The analysis of different tree species in shrubland did not reveal the effect of tree species on carbon sequestration rate.(2)Analysis of the potential influencing factors of soil carbon sequestration dynamics,the results show that soil texture(clay and silt)and initial soil organic carbon have a positive effect on carbon sequestration rate,but the initial soil organic carbon impact is not Significant.At the same time,the spatial distribution pattern of soil texture in the Loess Plateau was studied.The results showed that the soil clay and silt content in this area showed a reasonable gradient from southeast to northwest,reflecting the gradient of precipitation and vegetation from forest to shrub and grassland.Then transfer to the desert system.(3)The current reserves of soil organic carbon are the integration of the continuous decomposition of primary organic carbon and the input of new organic carbon.The decomposition constants of different vegetation types and tree species are different.The relationship between the decomposition constant of soil organic carbon and the potential variables was analyzed.The results showed that with the increase of temperature and precipitation,the decomposition constant showed a weak increase trend,and it was negatively correlated with soil clay and silt,and initial soil organic carbon.In addition,the decomposition constants(k values)of four different reforestation vegetations(natural grassland,artificial grassland,artificial forest land and shrub)were studied.The results showed that natural grassland and artificial grassland were much larger than artificial forest land and shrub.