Study On The Influence Of The Rocky Desertification On Soil Carbon Pool And Soil Carbon Emissions

The soil play a key role in the global carbon balance, while the soil carbon is sensitive tothe land use change. The paper addresses the scientific question that how the land degradationand the decreasing of the quality of soil will influence the soil carbon emissions, which wascaused by the rocky desertification in the Karst region of southwest China. We selectedmonitoring plots include Not rocky desertification land(Non-rocky desertification land andpotential rocky desertification land) and desertification land(slight, middle,serious,significantslight) in the typical rocky desertification management area Huajiang karst gorge in Guanlingcounty of Guizhou province. We measured the soil organic carbon and soil inorganic carbon inthe not rocky desertification land and rocky desertification land and used the Li-8100automated soil CO2flux system to monitor the seasonal variations of soil respiration from2012-2013in the fields, We used test specimens made from lithology rocky to monitor thecorrosive rate,to study the influence of Karst process on the soil carbon pool and soil carbonemissions. Through the monitor data analysis of the area and degrees of rocky desertificationland of Guanling County before and after the rocky desertification management. The influenceon the soil carbon pool and soil carbon emissions by rocky desertification management wasevaluated quantitatively. The main results are as follows:(1)Soil organic carbon content: the soil organic carbon content of Non-rockydesertification land is higher than that of potential rocky desertification land, among rockydesertification land, the soil organic carbon content of serious and significant serious rockydesertification land are higher than that of the slight rocky desertification land; the soil organiccarbon content of Not rocky desertification land is higher than that of rocky desertificationland.In non-Rocky desertification land, the soil inorganic carbon density of grass land was thelargest, which was two times of shrub land and five times of bare land. It indicate that the soilinorganic carbon density had a great relevance with the surface vegetation types. In the potential-Rocky desertification land, the soil inorganic carbon density was lower than that ofnon-Rocky desertification land. In the Rocky-desertification land, the soil inorganic carbondensity was the lowest.The average soil carbon density of Non-rocky desertification land and potential rockydesertification land are respectively14320.15t/km~2and6331.16t/km~2, and in rockydesertification land the average soil carbon density of different degree land arerespectively2251.25t/km~2,1012.14t/km~2,333.67t/km~2,278.47t/km~2; the carbon density ofdifferent lands follow the changing rule that non-rocky desertification land＞potential＞slight＞middle＞serious＞significant serious rocky desertification land, which is mainly determinedby the soil coverage and soil depth.(2) The soil respiration rate in Rocky region had a very high concordance with thedegree of Rocky desertification, and also had obvious seasonal variation. The soil respirationrate of non-rocky desertification land had obvious seasonal variation, the change rule wasbroken while the land become Rocky desertification land as the rule of soil respiration rate nolonger follow the plant growth season order to change, the soil respiration rate in summerseason is the highest,the second is autumn season, and that in spring is a little higher than thatin winter,which are basically flat, the average soil respiration rate of the four seasons is lowerthan that in Non rocky desertification land obviously, the rule of non-Rocky desertification ofsoil respiration is follow the four seasons, and this abnormal change law is uncertain, further toget data for validation is needed; However, the change rule was broken while the not rockydesertification land degrade into rocky desertification land, the soil respiration rate in autumn isthe highest, and followed by summer, spring, winter of different rocky desertification lands.The annual average soil respiration rate of Non-rocky desertification land and potentialrocky desertification land are respectively850.21t/km~2and445.88t/km~2, and in rockydesertification land the annual average soil carbon density of different degree land arerespectively515.83t/km~2，287.38t/km~2，72.59t/km~2and44.39t/km~2; The annual soilcarbon emissions has correlation with the soil respiration rate and the soil coverage. (3)The Karst process increase the capacity of soil carbon sinks, the annual carbon sinks ofNon-rocky desertification land and potential rocky desertification land in Not-rockydesertification land type are respectively0.35t/km~2and0.50t/km~2；the annual carbon sinks ofdifferent degree rocky desertification land type are respectively0.89t/km~2,1.28t/km~2,1.31t/km~2, and1.45t/km~2；the influence of Karst process on soil carbon pool and soil carbonemissions depend on the degree of rocky desertification land, which has little influence on Notrocky desertification land, but as the degree increased,the influence also increased; the result isdifferent from other research in Karst region, the reason is that this area is dry and less ofrainfall, the lower soil water depressed the Karst process.(4)The rocky desertification comprehensive management impeneted in Guanling Countyimproved the eco-environment, which reflected in the change of degree and area of the land.Among them, the area of non-rocky desertification land increased69.06km~2and potentialrocky desertification land increased2.07km~2, slight rocky desertification land increased12.21km~2, middle rocky desertification land decreased78.14km~2, serious rocky desertificationland decreased55.72km~2,significant serious rocky desertification land increased55.72km~2.Through rocky desertification contral managment from2005to2010, the total soil carbonemissions increased47.7thousand t, the soil carbon pool increased881.8thousand t, thecarbon storage increased834.1thousand t, which was equal to637.67t C every squarekilometers in the Karst region of this County. The research has provided quantitative evaluationof the influence of the rocky desertification management on soil carbon storage function.