| These years, the research of global carbon cycle closely focuses on the source-sink of landecosystem to atmospheric CO2. Firstly, the dynamic of soil carbon pool is attended, theaccumulation, turnover and decomposition of soil carbon would bring magnitude influence toatmospheric CO2 change, because the soil carbon pool is huge and relative activity; Secondly, thekarst process is attended, karst area is occupied 12% the area of all land in the world and 1/3 landof China, karst area is an important part of the earth surface system. There is 99.55% carbon of theearth combined with carbonate rock. Moreover, recently research shows the modern karst processclosely connects with the global carbon cycle. In the earth surface system, the biosphere crossesthe other spheres through the matter exchanging and energy transferring. On the basis of the abovediscussion and in order to discover the regulation of the biological, and organic processes to thesystem of 'CaCO3-CO2-H2O'in karst soil system and in this paper, the biological action andcarbon cycle in karst soil was taken as the research objective, the data of field monitoring wascollected in Guilin karst experimental site, the technique approach of dynamic monitoring,simulation experiment and carbon stable isotope were used. The collected data from fieldmonitoring for one year and three simulation experiments could get some newly understandings:(1) Soil microorganism is the 'continuous renewed driver'for the change and transfer ofsoil carbon. During the metabolism, the soil microorganism decomposes soil organic matter andproduce different typical carbon while its assimilation. The different typical carbon can result inthe different effect to the system of'CaCO3-CO2-H2O'in soil. The dynamic of the microbialbiomass carbon(MBC), dissolved organic carbon(DOC), and CO2 of soil and their effect to thesystem 'CaCO3-CO2-H2O'are studied in this paper. The soil MBC is one of the most active carboncomponent. The soil MBC came out the minimum during the time with the warm and humidsummer and the maximum during the time with cold and a little rain winter. The result connectswith change of the structure of soil microbial community and its metabolism. The soilmicroorganism was in active metabolism, quick turnover in spring, summer with fitting suitablecondition. Furthermore, the speed of the cell of soil microorganism to die was faster than that toreproduce. And the microbial biomass carbon in soil was consumed. By contrary, in autumn,winter, the microbial biomass carbon in soil was accumulation. Both the soil DOC and soil CO2were the product of soil microorganism metabolism, however, their seasonal changes were indifferent way: the soil respiration keeps positive correlation with temperature,negative correlationwith soil MBC; The soil DOC went up during march to June with warm temperature and muchrain as the soil respiration; the minimum of soil DOC came into being during July to Septemberwith high temperature and a little rain; the growth and decline was kept between soil MBC andsoil DOC in autumn and winter with low temperature and a little rain. This is because the soil CO2is the ultimate product of soil organism metabolism, and the soil DOC is the perfect energy for thegrowth of soil microorganism. The turnover of soil microbial biomass carbon at Guilin karstexperimental site is 212 days. 2. DOC is one of most active organic carbon forms in water and soil environments. Theresults of small soil core leaching experiment show that the soil DOC is one of the drivers of karstdynamic system. Because the acidic component and chelate compound in soil DOC can result inthe carbonate rock eroded. Moreover, the amount of soil DOC losing from small soil coreoccupied 23.2-43.8% percent of the soil organic carbon decomposition during the experiment. Inthe meanwhile, the amount of carbonate rock erosion kept positive correlation with the amount ofsoil DOC losing. From the field monitoring, the change of the DOC concentration in karst springwas more complex than that of the HCO3 concentration, however, the annual average content ofDOC was slightly higher than that of HCO3. Furthermore, the content of soil DOC is decadaltimes as much as that of DOC in karst spring. This result indicates the DOC is important in soilcarbon cycle; 3. DOC is a group of complicated organic compound. The organic acid is an importantcomponent in DOC. The result of comparison dynamic experiment shows that the potentialerosion of citric acid with 50mg/l matches with that of the CO2-H2O system with 5×10-2atmCO2. 4.Compared with that in the soil-rock system, the feature of carbon cycle in the plant(woodentree Buxus sinia and herbage Liriope spicata)-soil-rock systems is of many differences in soil CO2content/soil respiration, the pH value/concentration of HCO3/Ca2+ in underground water andcarbonate rock erosion under soil, because the rich roots and radicels of plant. The results areshown in the following table:...
|
PDF Full Text Request