The Effects Of Carbon Sinks In Karst Rocky Desertification Restoration

Since the 21st Century,the karst rocky desertification?KRD?has been an environmental problem in Southwest China?SWC?,which destroyed the forests and eroded the topsoil,resulting in a great quantity of carbon stocks losing.The State and Local government had conducted lots of projects on ecosystem restoration,environmental management,and KRD restoration in the recent decades,so that the vegetation coverage rate had been significantly increased.The news that the KRD restoration projects can increase the total of carbon sink will be a powerful measurement to the global climate change in SWC.The KRD restoration measurements can not only increase the rate of vegetation,but also affect the total carbon sink in soil and karstification.However,most researchers paid more attention on the single process of carbon sink,the interacting and mechanism of carbon sink among vegetation,soil and karstification are not clearly.This paper carried out a lots of work on different processes of carbon cycle in the peak cluster depression landform,a typical karst landform in SWC,where the KRD level is sever and the climate is prone to vegetation growing.To discriminate the relationship among the processes of carbon sink in vegetation,soil and karstification,a database on carbon stock was developed with GIS/RS technique.The data was collected by filed sample survey.The karstification and soil carbon emission were monitored by the hydro-chemical method and dissolute carbonate rock test method,respectively.The coupling mechanism carbon cycle among vegetation,soil,and karstification was presented based on the database.Finally,we estimated the total carbon sink in the study area by remote sensing technology.The RS technology can not only overcome the shortcomings of many single study,but also be facilitate to compare the results with other regions.At the same time,the RS can overcome the difficulty of field investigation in karst areas and improving the method on quantitative estimation of carbon sinks in KRD.The related researches presented as followed:?1?The KRD restoration,such as forest reservation and trees planting,increased the rate of vegetation cover and improved the structure of the forest so that the distribution of carbon stocks varied in different land use types.The carbon density of vegetation in different land use types ranked as:shrub land>abandoned farmland>farming land>grass land,the average value is 1.94t/hm²,1.61t/hm²,1.48t/hm²,and 1.37t/hm²,respectively.The land use changing?abandoned cultivated land?is an important factor to the carbon sink in karst.The carbon sink in different land use types was in the order of artificial forage land>abandoned cultivated land>crop cultivated land.The annual vegetation carbon sink in ecological agriculture was higher than that of the traditional agricultural model and the abandoned land model.Therefore,developing ecological agriculture is an effective way to increase vegetation carbon stocks.?2?There was greater heterogeneity of soil stocks in karst than that in non-karst regions.Hence,the estimation of soil carbon storage based on a 100 cm depth of soil layer may overestimate the soil stocks.This paper improved the method to predicate the soil stocks.The affection of soil loss cannot be ignored and the control measurements on soil loss will be an important way to increase carbon sink in the process of KRD restoration.?3?In addition,the soil carbon emissions varied in seasons,the concentration of soilin summer was significantly higher than that in winter.Theemission flux in soil in different land use types in the range of depression land>woodland>slope farmland>grassland>bare rock.In different soil thickness layer,the total of soilemissions ranged as D5>D40>D20,the annual carbon emission flux was 2.45 t·km^-2·a^-1,2.06 t·km^-2·a^-1 and 1.71 t·km^-2·a^-1,respectively.?4?Combined with remote sensing technology and the database,the total carbon stocks were predicated in a region scale,including vegetation carbon stock,soil carbon stock and karst carbon sink,.The results showed that the total of carbon stock in soil and vegetation was 3979.1 t and 677.2 t in 2012,respectively.From 2003 to 2012,the carbon stock in vegetation increased 165%,indicated increasing vegetation cover rate in KRD area is an effective measurement.Comparing with the terms of different RS images,we found that the ratio of rocky desertification land area decreased from 23%in 2003 to 9%in 2012;The ratio of vegetation area the area increased from 42%in 2003 to 60%in2012;the bare land area also decreased from 35%in 2003 to 31%in 2012.In a word,the KRD restoration has a positive effecting on the process of carbon sink in the study area.There are a couple relationships among the vegetation carbon cycle,soil carbon cycle and karstification,so a comprehensive study for the coupling mechanism of the three carbon sink models is needed.As the KRD restoration measurement works well for the carbon sink,it is suggested that the second phase of rocky desertification project should pay more attention to the land use change?abandoned cultivated land?on carbon sink and the on remote sensing models.