The Effects Of Land Use Change On The Soil Organic Carbon And The Soil Respiration

The soil organic carbon pool is about 1550Pg, which is 3 times of vegetation's carbon storage, 2 times of atmosphere. The soil let 60⁸0Pg C to atmosphere with the soil respiration annually, which is 12¹6 times of the burn of fossil energy. Due to the growth of population and the human's active, the land use and land cover have been changed greatly. So more carbon was released to atmosphere and people has attached importance to the release of CO₂ lead by the change of land use. It was reported that the CO₂ released by land use change was about 25% of the globe.The mountains are high and steep in the red soil region of sub-tropic in China. The rainfall is great and concentrates. As a result of high population's density and the quickly development of economy, human' s action have greatly changed the mode of land use. Many natural forests which were clean-cut ,slash burned and land prepared, were changed to plantation forests, secondary forests, orchards and steep farmlands. The storage of organic carbon in red soil region is low, so the content of soil organic matter is important symbolization of the soil quality and sustainability. People have attended to the change of land use. Therefore we chose different land uses mode including :the Altingia gracilipes natural forest, the Schima superba and Cunninghamia lanceolata plantation forest, secondary forest,Castanea henryi and Citrus aurantium orchards and steep farmland in Jianou City of Fujian Province. We researched the effect of land use changes on the soil carbon pool, dissoveled organic carbon,light fraction organic carbon,microbial biomass carbon and soil respiration.The major results were summarized as follows:(1) Soil organic carbon contents decreased with soil depth increasing in different land utilization types, in which the drop extent of natural forest, plantation forest and secondary forest was bigger than orchard and steep farmland. The effect of land use change on the surface layer soil was more significant than on the substrate soil, in which the influence to soil organic content and storage in 0⁵cm soil layer is most great. Soil organic carbon storage in 0²0cm was 30.43%⁴0.86% of that in 0 100cm soil layer, so the soil layer of 0²0cm is main. The influence to SOC content and storage in 0⁴0cm soil layer was few.(2) The order of soil organic storage in 0 100cm soil layer : Altingia gracilipes natural forest> Cunninghamia lanceolata plantation forest > Citrus aurantium orchard > Castanea henryi orchard > Schima superba plantation forest > the closing land for reforestation>steep farmland. The SOC storage of Altingia gracilipes is 55.17%, 36.53%, 75.44%, 45.91 %, 44.07% and 86.10% higher respectively than Schima superba, Cunninghamia lanceolata forest plantation, the land closing for...