Role Of Typical Organisms And Their Carbonic Anhydrase In Karst Ecosystems

One of the important national object is to promote comprehensive treatment of rockydesertification in karst regions of Southwest China. However, studies on mechanisms ofrocky desertification formation and ecological rehabilitation are lagged behind the nationalobject. Four karst areas including Jinfu Mountain in Chongqing, Misuga in Liu Panshui,Nongla in Guangxi and the Guilin Yaji Karst Experimental Site in Guangxi, were selectedas representing different types of karst ecosystem in this thesis. Through analyzingcharacteristics of soil microorganisms and enzyme activities, their relationship with karstenvironment and their ecological effects would be discussed. At the same time, thedistribution and stability of carbonic anhydrase in karst environment wereinvestigated.The environmental factors in expressing extracellular activities of microbialcarbonic anhydrase, and its relationship with element migration in karst ecosystem wereexplored. The results in this thesis will provide scientific bases for opening out the roles ofsoil microorganism and enzymes in karst ecosystem, and the roles of carbonic anhydrasein natural weathering and its karst ecological effects. The results in this thesis will alsohelp to provide scientific support for comprehensive treatment of rocky desertification. The comparative study on the amount, distribution and composition of soilmicroorganisms in different types of karst ecosystem of Southwest China was conducted.The results showed that the amount, distribution and composition of soil microorganismscorrelated highly with characteristics of the karst ecosystems, including their differentgeochemical environments and vegetation. Of the four kinds of karst ecosystemsinvestigated, the amount of soil microorganism at Misuga in Liu Panshui representingenvironment of rock desertification was the lowest. Exemplified by the Yaji KarstExperimental Site, the distribution of soil microbial physiological community as well asthe seasonal and spatial characteristics of soil enzyme activities at different★ Jointly supported by the Major Research Plan of the National Natural Science Foundation(No.90202016), the General Program of the National Natural Science Foundation (No.40152002), theYouth Foundation Program of the National Natural Science Foundation (No.40302034), and the KarstDynamics Laboratory, Ministry of Land and Resources IIIgeomorphological locations and their relationship with soil fertility factors wereinvestigated. The results indicated that there were higher activities of soil hydrolase inDepression and Saddle, which were consistent with the result of more amount of soilmicrobial physiological community in these two geomorphological locations. Moreover,the amount of soil microorganisms and soil enzyme activities correlated highly with soilnutrients such as soil organic matter, total nitrogen, available nitrogen, and availablephosphorus in different geomorphological locations. These results illuminated that theamount of soil microorganisms and soil enzyme activities could not only be made as theimportant indicators in evaluating karst soil fertility level, but also provide a certaintheoretical base for land use in different geomorphological locations. The origin and distribution of carbonic anhydrase, which could accelerate limestonedissolution, were explored. It was found that carbonic anhydrase activity could be detectedwidespread not only in plants (including plant fresh leaves and litters) and microorganismsfrom karst ecosystems of Southwest China, but also in natural karst soil environments.Moreover, the variation of carbonic anhydrase activity in soils with season was almost inaccordance with seasonal changes in the quantities of soil microorganisms in karstecosystems, and that higher carbonic anhydrase activities could be detected in soils of plantrhizosphere. These facts implied that plant roots and soil microorganisms serve asimportant source...