Effects Of Different Vegetation Restoration Types On Soil Carbon, Nitrogen And Microbial Flora In Guandi Mountain

As the largest carbon and nitrogen pools of terrestrial ecosystem, there was tiny change that would bring about strong effect on global carbon and nitrogen cycle. The loess plateau which is one of the most widely distributed region of land degradation have a serious soil erosion, and vegetation restoration is counted as the most significant measure to ecological environment restoration. After vegetation restoration, the soil quality are improved, the soil fertility are increased. Therefore we studied the stability of carbon and nitrogen pools and microbial quantity in different vegetation restoration, and it would provide us consultative opinions for estimating soil quality and then plant composition and low-producing forest rebuilding.Soil labile organic matter which largely dominated carbon and nitrogen flux is subject to different land-use types. In this study, soil physiochemical characteristics were investigated under 5-year abandoned land, Hippophae rhamnoides shrub, Larix principis-rupprechtii plantation and mixed forest (mainly contain of Betula platyphylla, L. principis-rupprechtii and Populus davidiana). Soil labile and recalcitrant organic matter were measured by the two-step acid hydrolysis with 2.5 mol/L H2SO4 in the first step and 13 mol/L H2SO4 concentrations in the second step. Soil carbon mineralization was measured by incubating in the chamber for 54 days. We also studied the seasonal variations of soil NO3--N, NH4+-N and the quantities of soil microbes.1. Significant differences were found in soil bulk density, water holding capacity, pH, sand, silt, clay and dimension among four study sites. Soil water-holding capacity was low in deserted land and increased in soil under H. rhamnoides shrubs, L. principis-rupprechtii plantation and mixed forest. Soil bulk density was high in abandoned land and H. rhamnoides shrub and decreased significantly in soil under forests. Soils sampled from study sites were classified as sandy loam but the percent soil silt and clay markedly different between study sites, and the fractal dimension values also differed from each other.2. Compared to abandoned land, soil labile and recalcitrant carbon increased among three study sites, and mixed forest and Hippophae rhamnoides shrub had a higher contents. The season trends of soil labile carbon varied with restoration types. L. Principis-rupprechtii plantation possessed of the highest CO2 emission, mixed forest and abandoned land had the lowest when there are three to describe the per kilo soil, per organic carbon content, per soil volume.3. Vegetation restoration types significantly affect the labile and recalcitrant nitrogen, and the higher contents were in mixed forest and H. rhamnoides shrub. The similar season changes were in recalcitrant nitrogen, however, there were different seasonal variations under four restoration types. The significantly higher inorganic nitrogen were displayed in mixed forest and H. rhamnoides shrub than abandoned land. Season produced pronounced effects on inorganic nitrogen among all sites, and the highest and lowest ones respectively demonstrated in October and May.4. Restoration influenced significantly soil microbial population, and soil higher microbial density from mixed forest and H. rhamnoides shrub than abandoned land. Seasonal insignificant effects on soil fungi and nitrifying bacteria, however, soil bacteria, acitnomycetes, N-fixing and denitrifying bacteria population varied significantly with season.