Study On Dynamic Changes Of Soil Organic Carbon And Its Components In Purple Soil Of Different Sloping Farmland Under Tillage Erosion And Water Erosion

In the past,research on the effects of soil erosion on soil organic carbon focused on the independent effects of certain types of erosion,and seldom considered the interaction of different erosion processes.This study selects long-term natural farming slopes with different slopes and slope lengths,uses ¹³⁷Cs tracer technology to quantify the tillage erosion and water erosion rates of different slope positions(uphill,middle and downhill),and studies the different interactions of tillage erosion and water erosion Soil organic carbon,particulate organic carbon,easily oxidizable organic carbon and soil aggregate carbon distribution characteristics and organic carbon mineralization law;through analysis of different types of erosion slopes(sloping farmland and reclaimed farmland)soil erosion and soil organic carbon in 2020 and 2011 Differentiation characteristics,to study the change characteristics of soil organic carbon under different tillage and water erosion patterns around 10 years ago.The main results and conclusions are as follows:(1)Distribution pattern of tillage erosion and water erosion intensityIn the sloping farmland landscape,the soil ¹³⁷Cs area activity of the long gentle slope(slope length>40 m,slope<15°)showed a trend of middle slope>downslope>upslope,while the maximum value of other slope farmland appeared on the downslope,and the smallest The value appears on the uphill.Soil erosion intensity and tillage erosion intensity are proportional to slope and inversely proportional to slope length,further confirming that short slopes and steep slopes are dominated by tillage erosion,while long slopes and gentle slopes are dominated by water erosion;the intensity of tillage erosion and water erosion in different slope positions of sloping farmland The combination mode is different.The upslope is dominated by tillage erosion,the middle slope is dominated by water erosion,and the downslope depends on the relative intensity of tillage deposition and water erosion.Compared with 2011,the ¹³⁷Cs area activity of conventional cultivated slope land and converted slope land in 2020 was significantly greater than that of converted cultivated slope land,and the longer the conversion period,the greater the difference between the two.(2)Variation characteristics of soil organic carbon and its components under the effects of tillage and water erosionThe soil organic carbon,particulate organic carbon,and easily oxidizable organic carbon of slope farmland and reclaimed slope land decrease with the increase of soil depth.Among them,the difference in soil organic carbon concentration between 0-5 cm and 5-15 cm of the reclaimed slope land is significantly greater than that of the slope.Cultivated land,indicating that conversion of farmland leads to preferential storage of soil organic carbon in the surface layer 0-5 cm.The storage of organic carbon and its components of sloping farmland showed that the downslope was larger than the mid-slope and the upslope,and the variation coefficient of soil particulate organic carbon storage was generally greater than that of easily oxidizable organic carbon,indicating that particulate organic carbon was more affected by external conditions than the total soil carbon and Easily oxidized organic carbon is more sensitive.In 2020,the soil organic carbon in the surface layer(0-5 cm)of the converted sloping land was significantly higher than that in 2011,and the difference was small with the increase of soil depth,but the soil organic carbon storage did not increase unrestrictedly with the increase in the number of years of conversion.(3)Carbon distribution and mineralization characteristics of soil aggregates under the effects of tillage and water erosionThe aggregate content of>2 mm grain-size aggregates on the slope land withdrawn from farming was significantly greater than that of the slope with conventional farming,and showed an increasing trend with the increase of the number of years of returning farmland.The cumulative mineralization of soil organic carbon increased with the extension of the incubation time.On the 7th day of incubation,the mineralization rate of soil organic carbon reached the maximum,and then dropped sharply.The cumulative mineralization and potential mineralization of soil organic carbon on sloping farmland and de-cultivation sloping lands have a very significant positive correlation with the content of organic carbon and its components(P<0.01),indicating that the strength of soil organic carbon mineralization is not only affected by the The influence of external conditions such as cultivation temperature and moisture,and the level of nutrient content in the soil are also important limiting factors.The intensity of soil organic carbon mineralization in the middle slope is positively correlated with the slope,indicating that the steep slope dominated by tillage erosion,the transportation of tillage erosion in the middle slope position and the migration of water erosion have an important impact on the organic carbon mineralization.