Community Structure And Output Of Non-point Pollution Of Different Land Use Atterns At Samachans Of Mid-Yunnan, China

Land use changes have a significant effect on land cover and ecological processes. Large areas of mountainous lands at Samachang small watershe which is represented as Central Yunnan are becoming sloped cropland to cultivate economic crops, such as Eucalyptus, tea, and pear. Human-land relations are led to a threatening situation and the ecological equilibrium is destroyed seriously in this region. Forest hydrological effects can be influenced by land use changes. The study of the eco-environmental effects in different land use patterns has an important significance for environmental management.In this paper, by use of field investigation and laboratory analysis the characteristics about community structures, soil physicochemical properties and non-point pollution had been studied in seven land use types, including shrubland, pinus forest, semi-natural forest, natural secondary forest, Eucalyptus forest, pear plantation and tea plantation in the study site. The main conclusions are as follows:(1) Community structures were significantly different between natural forests and economic forests. As the natural forest communities tended to be more complex, the parameters of tree layer indicators were gradually increased, and the parameters of shrub layer were gradually reduced. But the trends about the economic forests were significantly different. Compared with natural forest, economic forests had higher land use intensity. And the forest density in economic forests was higher than that in the natural forest, but economic forests had a more simple community. Thus its tree height, species richness and the thickness of litter layer were lower than that in the natural forests.(2) Land use patterns had significant effects on soil physical properties. Soil physical properties had been analysed by perturbation analysis. The natural secondary forest had the highest synthetic evaluation, and the perturbation value was only0.04. The pinus forst had the lowest synthetic evaluation with the highest perturbation value0.45. The perturbation value of soil physical properties was in the order of natural secondary forest> tea plantation> semi-natural forest> pear plantation> eucalyptus forest>shrubland> pinus forest.(3) Land use patterns had significant effects on soil chemical properties. Soil chemical properties hadbeen analysed by perturbation analysis.The tea plantation had the highest synthetic evaluation, and the perturbation value was only0.20. The eucalyptus forest had the lowest synthetic evaluation with the highest perturbation value0.41. The perturbation value of soil physical properties was in the order of tea plantation> natural secondary forest>shrubland>semi-natural forest>pear plantation>Pinus forest>Eucalyptus forest.(4) Land use patterns had significant effects on non-point pollution.In five land-use types, the runoff of micro-plots ranged38.89-667.22m3/ha. The output of SS ranged85.10-403.34g/ha. The output of TN ranged98.35-1058.82g/ha. The output of TP ranged20.32-103.69g/ha. The output of TK ranged146.43-4858.81g/ha. The output of COD ranged1308.87-41621.37g/ha. Compared slope scales with micro-plot, the concentration and the amount of pollutants had decreased significantly.(5) The output of non-point pollutions in Samachang watershed was influenced by community structure, soil physical and chemical properties. And the runoff was the power of the output of non-point pollutions. Community structure and soil phy-chemical properties were all correlated with the runoff. The indicators about the output of non-point pollutions were significantly correlated with soil source but TN was significantly correlated with soil physical properties.