| In the research of global carbon cycle, people pay more attention to the effect of source-sink of terrestrial ecosystem to atmospheric CO2. In epikarst system, soil as the important media of karstification occurred, the changes of the physicochemical properties and biological activities products of soil have a significant impact on the intensity of karst. Ecological environment in Southwest China Karst Region is fragile,land carrying capacity is low, the obvious contradiction between people and land, the distribution of a wide area of low-yielding fields, agricultural production is severely limited. The rocky desertification and soil carbon sequestration of organic combination, has become a hot research topic. In the long-term of the rocky desertification process, has explored a series of feasible soil improvement technology, on the basis of drawing on quality improvement technology of soil, in-depth research on the soil improvement effect of karst carbon sinks, and provide scientific basis for the exploration of karst carbon sequestration increased sinks.This research based on the karst dynamics theory, combined with the earth system science thinking mode, based using sugar mill mud organic fertilizer on lime soil improvement, according to the mechanism of occurrence of karst, from the soil properties, field corrosion tests, seepage water chemistry indicators of soil,soil biomass, dynamic monitoring of soil environmental factors and other aspects, comprehensive in-depth analysis of the effect of soil improvement, to explore the impact of soil improvement in karst area of carbonate dissolution, and calculate the amount of carbon sinks that may arise.First, using an organic fertilizer to improve soil have greatly improved to physical and chemical properties of soil, after improvement, soil gas phase, liquid phase, solid phase ratio has been adjusted, so that the soil regulate water, fertilizer, gas, heat capacity has been improved. Secondly, after improvement, soil organic matter and soil available trace elements were improved,before the improvement soil organic carbon storage increased from 36534.53 t to 37335.44 t, increased by 800.90 t. The increase of soil nutrients, promote the photosynthesis of crops, conducive to the absorption of CO2 in the atmosphere,and enhance soil biological activity, is conducive to the formation of high concentration of CO2 in soil, to promote the occurrence of Karst.In addition,the organic from the decomposition of organic matter and plant root exudates produced,in the promotion of carbonate dissolution,at the same time, combined with the Ca2+ ions in soil to form a stable organic components,increase the stability of soil organic carbon.Using principal component analysis, we can see that,in the study area, the main factors affecting the role of soil in karst soil depth and soil CO2 concentration, Soil depth affected the rate of carbonate rock into the soil, the soil ripening and the formation process, soil biological role can not be ignored. The concentration of CO2 in soil mainly from the respiration of plants and animals and the release from microbial decomposition of organic carbon.In addition, organic acids from secreted by plant roots and produced when organic matter is decomposed,can promote the positive movement of karst. Therefore, the role of soil organisms have an important impact on the dissolution of carbonate rocks, after improvement of soil,nutrient in soil 10-20 cm is increased, the root is more developed, soil biological activity increased, the soil CO2 concentration increased greatly, a maximum of 20 cm of soil in spring, as 28875.24mg/m3.The specimens of limestone dissolution in different soil, different plots of dissolution rate difference, the maximum erosion rate in soil at 40 cm, as 3.1796 mg/(cm2?a), the peak in the depth of 20 cm, as 2.9166 mg/(cm2?a),which indicated that the soil biological activity and soil thickness have an impact on karst.Use the data obtained,Estimate the amount of carbon sequestration may increase of soil improvement, if the Guohua demonstration area of 66.41hm2 cultivated soil was improved, compared with the unimproved land increasing carbon sink is 2.75 tCO2/a.The aboveground biomass was improved greatly by soil improvement, the test area biomass was 973.80g/m2, is 1.85 times the control area of the biomass, and crop yield are improved, the test area than the control area of pitaya fruit yield by 27.64%, peanut yield by 37.73%, net of investment costs and labor lost income, farmers’ income is 30000yuan/(year· hm2) at least. Therefore, soil improvement measures used in this study can be extended and easy to be accepted, can become the karst carbon sink approach application. |
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