Soil Organic Carbon Sequestration Capacity And Mechanism In The Loess Hilly-gully Region

In order to reveal the ability of soil organic carbon sequestration and its influencing mechanism in the process of wasteland restoration in the Loess Hilly-Gully Region,the process of vegetation restoration and its carbon sequestration ecological function in wasteland were deeply recognized.In this study,the quantity distribution,retention form and mineralization characteristics of total organic carbon and its fraction in soil were studied and analyzed by combining soil environmental factor with the grassland of Wuliwan watershed in the Loess Hilly-Gully Region,which had been abandoned for 10,18,28 and 43 years,and the slope farmland as a control.Relevant analysis revealed the carbon sequestration process,capacity and key soil environmental impact factors of wasteland.The main results are as follows:?1?Soil organic carbon sequestration capacity of wasteland.The content of SOC,LC,RC and MOC increased with the increase of abandonment years,and decreased with the increase of depths,ranging from 1.36⁵.64 g·kg^-1.The content of POC increased significantly with the increase of years in 0²0 cm soil layer,the content of POC increased first and then slowed down with the increase of years in 20⁴0 cm soil layer.Soil organic carbon sequestration process and form in wasteland.The density and content of organic carbon and its components are similar.The soil organic carbon density ranged from 5.58 to 12.93 Mg·hm^-2 in 0²0 cm soil layer and 3.52⁶.70 Mg·hm^-2 in 20⁴0cm soil layer.?2?Soil carbon sequestration process and form of wastelandThe order of proportion of the four carbon components is POC<LC<RC<MOC.The proportion of MOC ranged from 62%to 84%,and the proportion of RC ranged from 53%to73%.Therefore,the main carbon components in the restoration process of abandoned grassland are inert carbon such as RC and MOC.The proportion of RC in grassland 43 a was effectively improved compared with sloping land,and the stability of organic carbon was significantly enhanced.SOC sources in 0²0 cm soil layer are not fixed in different periods,the early stage?0¹0 a?is POC and LC,the middle stage?10¹8 a?is POC,and the later stage?18⁴3 a?is RC and MOC.The increasing sources of organic carbon in 20⁴0 cm soil layer are RC and MOC.The soil organic carbon mineralization rate decreased with the increase of culture time.Under the condition of 25°C culture,the soil organic carbon mineralization ratios increased with the increase of the age of abandoned land,indicating that the soil carbon sequestration capacity was effectively improved during the vegetation restoration process.?3?Effect mechanism of soil environmental factors on carbon accumulation.With the increase of abandonment years,soil bulk density and total phosphorus content in 0¹0 cm soil layer decreased significantly,while soil water content,total nitrogen,microbial biomass carbon,biomass nitrogen and biomass phosphorus increased significantly.The results of correlation analysis showed that there was a significant correlation between soil physical,chemical and biological indicators and SOC and each carbon fraction?P<0.01?.RDA analysis showed that the interpretation rate of Axis I was 78.16%,indicating that soil physical,chemical and biological indicators had a high interpretation rate for the variation of SOC and its fraction.Negative correlation between soil bulk density,total phosphorus content,soil organic carbon content and carbon content,and there was a positive correlation between soil water content,total nitrogen content,microbial biomass carbon,microbial biomass nitrogen,microbial biomass phosphorus,soil organic carbon content and carbon content.Therefore,the recovery process of abandoned grassland in the loess hilly region helps to improve the organic carbon pool and its stability,and has a good ecological restoration effect.The research results can provide a theoretical basis for studying soil carbon sequestration process and mechanism during the restoration of abandoned grassland,and have certain reference significance for improving soil carbon sequestration.