Variations Of Soil CO₂ Emission On Remediated Land And Their Driving Factors Of Tang County

China is a country largely rely on traditional agriculture,however,its cultivated land resources are relatively scarce.With the rapid development of the economy and the gradual expansion of agricultural demand,the contradiction between increasing demand of human being and limited land resource is becoming severe.The lack of cultivated land is an important issue that cannot be ignored on our land to an all-round well-to-do society.In order to effectively increase the amount of cultivated land and ensure food security,the state attaches great importance to land remediation projects.The implementation of irrigation and drainage,field roads and other projects in land remediation projects,especially land formation,has caused serious disturbances to the soil environment and ecosystems,and has been rectified.The soil carbon pool of the remediated land has undergone great changes.The loss of soil carbon caused by land remediation has brought about a decline in soil quality and an increase in atmospheric greenhouse gases.With the expansion of the scale of land remediation in China,CO₂emissions from land remediation have been increasingly valued by relevant departments and experts and scholars,and CO₂ emission studies of land remediation projects are of great significance to optimizing land-use patterns and responding to climate change.This research took the land renovation project area in Tang County as the research object,and studied the seasonal and annual changes of soil CO₂ emissions in different land use types and different years after remediation.We further aimed to figure out the driving factors of variations of soil CO₂ emission,in terms of soil physical,chemical,microbiological and other indicators.The comparative analysis of the impacts and the main research results obtained are as follows:?1?Effects of different land use types on soil CO₂ emissions:The average values of soil CO₂ emission were generally highest in abandoned grassland(787.53 gC·m^-2·a^-1),followed by orchard(735.20 gC·m^-2·a^-1),and lowest in cultivated land(692.53 gC·m^-2·a^-1).On annual scale,the soil CO₂ emission in orchard ranged from 8.36 gC·m^-2·month^-1to 186.98 gC·m^-2·month^-1throughout the year,and the average monthly amount was 64.40 gC·m^-2·month^-1.Soil CO₂ emission from cultivated land ranged from 7.61 gC·m^-2·month^-1to 251.66 gC·m^-2·month^-1annually,and the average monthly amount was 57.71 gC·m^-2·month^-1.The annual soil CO₂emission in abandoned grassland ranged from 9.32 gC·m^-2·month^-1to 208.49gC·m^-2·month^-1,and the average monthly amount was 65.63 gC·m^-2·month^-1.?2?Impacts of different years after land remediation on soil CO₂ emission:Compared with soil CO₂ emission from abandoned grassland,the amount from land remediated into arable use showed decreasing trend.After two years of land remediation,the soil CO₂ emission from cultivated land was significantly lower than that from other soils?p<0.05?.Concerning the different years after land remediation,total amounts of soil CO₂ emission followed a sequence of land without remediation?abandoned grassland?(827.38 gC·m^-2·a^-1),8 years(825.62 gC·m^-2·a^-1),20 years(628.58 gC·m^-2·a^-1)and 2 years(569.39 gC·m^-2·a^-1).With the remediating year increased,the total amount of soil CO₂ emission from cultivated land showed firstly an increasing trend and then a decreasing trend.After eight years of cultivation,the maximum amount of CO₂ emission from cultivated land was achieved.However,after two years of land remediation,the amount of arable soil CO₂ emission was the smallest.Compared with soil CO₂ emission from abandoned grassland,the amount from land remediated into orchard use showed increasing trend.After two years of land remediation,the soil CO₂ emission from orchard was significantly lower than that from other soils?p<0.05?.Concerning the different years after land remediation,total amounts of soil CO₂ emission followed a sequence of 8 years(891.51 gC·m^-2·a^-1),20years(813.94 gC·m^-2·a^-1),land without remediation?abandoned grassland?(747.67gC·m^-2·a^-1),and 2 years(564.45 gC·m^-2·a^-1).With the remediating year increased,the total amount of soil CO₂ emission from orchard showed firstly an increasing trend and then a decreasing trend.After eight years of cultivation,the maximum amount of CO₂emission from orchard was achieved.However,after two years of land remediation,the amount of orchard soil CO₂ emission was the smallest.?3?Impacts of soil environmental factors on soil CO₂ emission on remediated land:The principal component analysis of the influencing factors of soil CO₂ emission from different land use types showed that the key drivers were soil organic carbon content and soil temperature.In addition,the other main driving factors for soil CO₂emission on land remediated into arable use were soil pH,soil bulk density,soil total nitrogen content,and soil microbial biomass nitrogen content.While the other main driving factors for soil CO₂ emission on land remediated into orchard use were available soil phosphorus content,soil microbial carbon-nitrogen ratio,soil microbial entropy,and soil microbial carbon.In summary,this study monitored the changes in soil CO₂ emission from land remediation project area in the Tang County concerning different land use types and different years after remediation.Land remediation affected soil CO₂ emissions through changing soil physiochemical and microbiological factors.This research was aimed providing a theoretical basis for the implementation of land remediation projects in the hilly zones.It could also provide an optimize plan on land-use practices,and strategies to mitigate climate change by increasing soil CO₂ emissions.