Study On Soil Physical And Chemical Properties And Niche Characteristics Of Undergrowth Vegetation Under Land Of Conversion Cropland To Forestland In Hilly Loess Region

This study based on different vegetation restoration for ten years in Hilly Loess Region. Soil physical and chemical properties, niche characteristics of undergrowth vegetation were studied by using field survey, soil samples taken and experimental analysis in Ansai country, which consider typical regional as land of conversion cropland to forestland. The results explain the relationship among vegetation restoration; soil Soil physical and chemical properties; niche characteristics of undergrowth vegetation. It provides scientific and rational evaluation of artificial vegetation effectcts in the Hilly Loess Region. The main research results were summarized as follows:(1) Arbor soil water contents higher56%than slope farmland, Shrubs soil water contents higher6.06%than slope farmland, but Herbaceous soil water content decreased6.6%in2010. In2011, Arbor soil water contents and Shrubs soil water contents increased17%,13.7%compared with solpe farmland, but herbaceous soil water contents decreased7.3%. The change soil bulk densities were not obvious, but they were affected obviously with different cover types. The peak of the content of soil aggregate had emerged in0.25-0.053mm in0-60cm, occupied44.35-77.9%, it means this level is very important for soil structure.(2) Soil organic matter content(10.43g/kg); total nitrogen(0.82g/kg) and available nitrogen(52.5mg/kg) is4.23,5.13,7.5times compared with solpe farmland in Populus simonii(40a). The total phosphorus content is lagest in pseudoacacia(40&), the available phosphorus is lagest in Prunus davidiana-Caragana korshinskii(40a). It is1.52times compared with solpe farmland (0.87mg/kg).(3) The soil nutrient inceased while the soil depth decreased in different vegetation restoration. In0-20cm the soil orangic matter higher57%than40-60cm in pseudoacacia (40a), and in0-20cm, available nitrogen is16%compared with40-60cm. Total nitrogen and available phosphorus, in0-20cm, higher42.2%,18.8%respectively than40-60cm. Total phosphorus, in0-20cm, is1.56times than40-60cm. distribution of organic C concentrate in0.25mm and0.053mm, there is nothing in some of them.(4) Shannon-Wiener Niche breadth of Lespedezadavurica Schindl(0.89) and Heteropappus altaicus(0.84) were larger than other species. The lowest Niche breadth is Artemisia capillaries and Artemisia scoparia. But lowest Shannon-Wiener index is Artemisia scoparia; lowest Levins index is Artemisia capillaries. All of overlap, there are23kinds on the niche overlap value of0, representing all kinds of12.1%, reflecting the populations of long-term competitive and adaptation, niche obviously tends to specialization.174sets of species had niche similarity values greater than0.5, accounting for91.6%. Therefore, species had different requirements to environment, representing stable communities. And species can harmonious exist in communities.