Distribution Of Soil Organic Carbon And Its Affecting Factors Under Different Land Utilization Patterns

Soil is the core carbon pool of terrestrial ecosystem.Its tiny changes will cause large fluctuations of CO2 concentration in the atmosphere,which will have an important impact on the terrestrial ecosystems and even the global carbon cycle.Different land-use patterns will lead to changes in the quality and quantity of soil organic matter input,soil quality and nutrients,and the decomposition rate of soil organic carbon,thus controlling the organic carbon content and transformation process in terrestrial ecosystems.Therefore,under the background of global climate change,researching the distribution characteristics and influencing factors of soil organic carbon in different land use has great significance for the regulation of soil nutrients,maintaining soil fertility and sustainable utilization of soil resources,improving soil carbon and fixing on the mitigation of global climate change.However,it is necessary to point out that the current research on the spatial distribution characteristics of soil organic carbon mainly focus on the distribution in soil organic carbon levels,and less on the vertical distribution characteristics of soil organic carbon research,especially the vertical distribution of soil organic carbon andreadily oxidizable organic carbon under different land use patterns in Hainan Island is rarely reported.Therefore,in this study,8representative administrative villages was selected as the sampling area,through data collection,using field sampling and laboratory analysis method,combined the characteristics of each kind of land use,analysis and clarify the level distribution and vertical distribution characteristics of soil organic carbon and readily oxidizable organic carbon lunder different land use patterns and its influencing factors,to provide the theory basis for the rational utilization of land resources in Hainan Island.The main results of the study are as follows:(1)The content of soil organic carbon in the study area was 0.79 ~ 29.97g/kg,the average value was 10.09 ±1.02 g/kg,and the coefficient of variation was 0.81.In the soil layer of 0~30cm,there were some differences in soil organic carbon content under different land use patterns,which were paddy field > abandoned land > orchard land > rubber forest land.The variation of soil organic carbon content in vertical space under different land use patterns showed the same law,that is,with the deepening of soil layer,the soil organic carbon content decreased gradually.The content of organic carbon in 0~10cm soil layer was muchhigher than that in 10~20cm and 20~30cm soil layer under different land use patterns,which indicated that the soil organic carbon in the study area had "apparent accumulation".(2)In 0~30cm soil layers,the average value of readily oxidizable organic carbon content was 4.85±0.27g/kg,and the variation was 1.82~10.92g/kg.In the soil layer of 0~30cm,the content of readily oxidizable carbon in the study area decreased with the deepening of soil depth,which is consistent with the vertical variation characteristics of organic carbon in the study area.The content of readily oxidizable carbon in soils under different land use patterns was different.The content of readily oxidizable carbon of rubber forest land was the lowest,and that in abandoned land,paddy field and orchard land was higher than that in rubber forest land.On the soil profile of 0~30cm,the content of readily oxidizable organic carbon in paddy field,orchard land and rubber forest soil decreased gradually with the deepening of soil depth,but the wasteland showed a tendency of decreasing first and then increasing.(3)Under different land use patterns,the soil organic carbon content of paddy field,abandoned land and rubber forest land was significantly positively correlated with the content of readily oxidizable carbon,and that of orchard land was significantly positive correlation.Therefore,it can be inferred that the content of soil organic carbon is an important factor affecting the change of the content of readily oxidizable organic,and with the increase of total organic carbon content,the content of readily oxidizable organic is also increasing.(4)The distribution ratio of readily oxidizable organic carbon in the soil of the study area is 41%~94%.The distribution ratio of readily oxidizable organic carbon in paddy field,abandoned land,orchard land and rubber forest land was 41%~47%,47%~62%,65%~94%and 49%~61%,which indicated that land use mode had a significant effect on the distribution ratio of readily oxidizable organic carbon in soil.The results of correlation analysis showed that,except for orchard land,there was a significant linear correlation between the distribution ratio of easily oxidized organic carbon and organic carbon in paddy field,abandoned land and rubber forest land they all showed a decreasing trend with the increase of organic carbon.(5)In 0~30cm soil layer,the soil clay and silt content of paddy field,wasteland and orchard land were relatively high,sand content was relatively low,but the proportion of clay and sand in rubber woodland was not very different.Correlation analysis showed that there was a positive correlation between soil organic carbon content and soil clay content in fourland use patterns in the study area,and a negative correlation between sand content and sand content(P<0.05),but the correlation coefficient was different under different land use patterns.The soil clay and silt content in paddy field and wasteland are higher,the soil organic carbon content is controlled by clay and silt content obviously,so the correlation coefficient between them is also higher,and the soil organic carbon content is also higher.(6)The average pH of 0~30cm soil layer under four land use patterns shows abandoned land(5.65±0.14)>rubber forest land(5.62±0.47)>paddy field(5.51±0.09)>orchard land(5.34±0.12).The correlation coefficient between soil organic carbon content and pH value in paddy field and abandoned land was-0.851* and-0.728*(P < 0.01),which indicated that the soil organic carbon content was affected by pH value in paddy field and abandoned land,and in orchard land and rubber forest land.For orchard land and rubber forest land,there was no significant correlation between them,which indicated that the soil organic carbon content in them was less affected by pH value,and other factors should be considered comprehensively.