Soil Stoichiometry Under Conversion Of Grain To Green Program In Loess Hilly Region

Vegetation Restoration in combating soil erosion, restore the ecological environment and combating soil degradation has an extremely important role. However, different recovery modes are the major changes factor about the distribution of soil microbial biomass carbon(C), nitrogen(N) and phosphorus(P).In this study, we chose different degraded woodland vegetation recovery under typical erosion environment of Northern District for the study, using the way of space-time replace to analysis the C, N, P content distribution characteristics of different methods to restore degraded woodland vegetation and soil microbial life and C, N, P content distribution and different Effect of farmland vegetation and life on the soil and the measurement of microbial chemical characteristics. And illustrate the major effect factors of soil microbial C, N, P content and the stoichiometry’s ratio change of soil microbial C: main factors N, microbial C: main factors P, microbial N: main factors P; reveals the evolution discipline of C, N, P about soil characteristics of ecological stoichiometry and soil microorganisms; and further illustrated the relationship between soil C, N, P ecological stoichiometry and the response of microbial to soil about C, N, P. The following conclusions:(1)Abandoned after different forest vegetation restoration of soil C, N, P content and reserves increased significantly compared to the more arable land, and soil C: N, C: P and N: P stoichiometric ratio greatly influenced by the vegetation types and soil layer.Compared with cropland, different vegetation restoration years SOC, TN, TP, SOCD, STND, STPD all shows an increasing trend with the increase of age, and the surface has the highest content, with the increase of soil horizon show a decreasing trend, SOC, TN, TPchanges: RP45a> RP40a> RP15a> CL, CK40a> CK30a> CK20a> CL; SOCD, STND, STPD changes: RP45a> RP40a> RP15a> CL, Different types of vegetation soil C: N, C: P and N: P ratios the range of variation 7.79—14.31, 5.49—13.72 and 0.49—1.42, respectively. While the average of 10.57, 8.67, 0.86, respectively. And vegetation restoration and soil quality has been greatly improved.(2) Abandoned after different forest vegetation restoration of soil microbial C, N, P content was significantly improved, and with the increase of age shows an increasing trend, and soil microbial biomass C:N, C:P and N:P stoichiometric ratio greatly influenced by the depth of the soil profile and vegetation types.The study result of Loess Hilly Area different Soil microbial C, N and P content showed: Compared with cropland, the process of returning farmland to forest vegetation types in different microbial biomass C, N, P were significantly increased and has the highest content of topsoil, with the increase of soil layer showed a decreasing trend. The C, N, P of soil and soil microbial have a close relationship with vertical distribution of vegetation types and soil layers. With the increase of years, soil microbial biomass C, N, P showed an increasing trend, MBC, MBN, MBP changes : RP45a>RP40a>RP15a>CL, CK40a>CK30a>CK20a>CL. The soil MBC: MBN, MBC: MBP and MBN: MBP ratio the range of variation 5.04—21.21, 9.39—31.38 and 1.00—4.94, respectively. The average of 9.01, 18.60, 2.55, respectively. Because CK20 a low microbial biomass nitrogen content, exhibit a higher MBC: MBN ratio; RP15 a its low microbial biomass phosphorus content, exhibit higher MBC: MBP ratio. Different soil layer and vegetation types soil MBC: MBN, MBC: MBP and MBN: MBP stoichiometric ratio higher than crop land.(3)The relationship of soil and microbial biomass C, N, P with soil and microbial C:N, C:P, N:P stoichiometric feature, soil and microbial C:N, C:P, N:P ratio with soil microbial biomass C, N, P elements showed a significant correlation relationship.. Soil microbial biomass C is a significant role of mutual restraint between N and P. Soil microbial biomass C, N, P content and N : P and MBN : MBP was significantly associated with different vegetation N : P and MBN : MBP low, TP and MBP with previous similar studies: as the terrestrial ecosystem nutrient limitation index N : P was significantly lower than previous studies, but it is mainly from the soil TP soil phosphate mineral weathering decomposition and adequate phosphorus content, indicating the phenomenon of nitrogen nutrient limitation when vegetation growing in Loess Hilly Region.