Effects Of Land Management And Utilization Modes On Soil Organic Carbon Fractions And Nutrients In Sloping Land Of Karst Region

To provide scientific basis in determining reasonable land management and utilization mode under different slope conditions of Karst region, the differences in soil organic carbon fractions and nutrients under different land management and utilization modes were investigated in this region. This study chose typical slope in Karst area and had six treatments, including enclosure (E), maize planting (M), pasture planting (P), burning (B), cutting (C) and cutting plus root removal (CR), and then soil organic carbon, labile organic carbon fraction, enzyme activity, nutrient content and carbon pool management index were measured. The main results are shown as follows.(1) Compared to E treatment, M, P and CR treatments reduced the soil organic carbon content significantly, and M treatment reduced the organic carbon content by 38.75%.(2) If compared to E treatment, M, P, B and CR treatments significantly reduced the soil dissolved organic carbon (DOC) content, and the other five treatments reduced the contents of microbial biomass carbon (MBC) and readily organic carbon (ROC) in soil significantly, and M treatment decreased the contents of DOC, MBC and ROC by 75.62%,79.40% and 41.14%. Compared to E treatment, the other five treatments reduced soil carbon pool management index significantly, and M and B treatments had the lowest carbon pool management index.(3) When compared to E treatment, the other five treatments decreased soil urease activity significantly, but the differences in urease activity between these five treatments were not obvious, and M, P, B and CR treatments reduced soil invertase activity significantly. However, the soil catalase activity under M, P, B, C and CR treatments was similar to that of E treatment except the catalase activity on upper slope in 2015.(4) Compared with E treatment, the other five treatments significantly reduced the contents of total nitrogen and phosphorus and slowly available potassium in soil, and M treatment had the lowest content of soil total nitrogen and phosphorus and slowly available potassium. The contents of soil available nitrogen under M, P, C and CR treatments were significantly lower than that of E and B treatments, and the contents of soil available potassium under M, P, C and CR treatments were significantly lower than that of E treatment. The available phosphorus content was ranked as M> B> E> P, CR> C sequence, the total potassium content was ranked as M> E, P> CR> B> C sequence.In summary, soil carbon pool management index, enzyme activity, the contents of soil organic carbon, labile organic carbon fraction and soil nutrient were reduced with the increase of human disturbance in Karst region. In the fragile ecological land, human disturbance on the slope should be reduced, measures on returning farmland to forest and grassland should be implemented, and a reasonable land management and utilization mode should be adopted, so as to promote the accumulation of organic carbon in soil and increase soil fertility, and then recover ecological function.