Changes Of Soil Erosion Properties In Different Land-use Types In The Three Gorges Reservoir Region

Land use and land cover (LULC) change is one of the global environment changes. There are a lot of eco-environment problems such as soil quality degradation and soil erosion as the results of LULC change. The LULC have great change in the three gorges reservoir because of economy and population pressure. The ecosystem in the three gorges reservoir region is very vulnerable. So understanding the influence of the LULC change on soil properties is very important to make an effective protection plans.Ruxi river watershed in three gorges reservoir region was selected to research the soil erosion properties caused by LULC change. Four land use types was chosen in the area of elevation from 175m to the top of the fist mountain near the river (barrier zone). They are massion pine forests forest converted from farmland、grassland converted from farmland and cultivated land. Four parts was divided in the water-level-fluctuating zone according to the elevation (145m-156m,156m-172m,172m-175m and 175m-180m). The soil erosion properties included soil permeable characteristics, soil erodibility and soil nutrient. Soil permeable characteristics included soil bulk density, soil water content, soil porosity, soil capillary porosity and soil non-capillary porosity. The soil particle size distribution was still measured in order to understand the reason of controlling soil porosity. The soil erodibility K value was calculated by the EPIC model, the inerrill erodibility (Ki), rill erodibility(Kr) and critical hydraulic shear (Tc) were calculated by WEPP model. Soil nutrient included pH, organic matter (OM), total N(TN), total P(TP), total K(TK), hydrolysoble N(HN), available P(AP) and available K(AK).The results showed that the bulk density in farmland was significant lower than those in other three land use types. And the soil porosity was also much higher. The farmland and nature forest land had much non-capillary porosity than the forest land and grass land converted from farmland which meant that farmland and nature forest land had better permeability. The soil erodibility K value in four land use types were significant different (p<0.05), farmland>grass land>forest land (convert from Farmland)> nature forest land. The soil organic matter content in farmland was significant lower than that in other three types, and the organic matter content in these three land use types did not have significant difference. The correlation between OM and TN was significant(r=0.69, p<0.05)In the water-level-fluctuating zone, the soil bulk density and porosity in four parts had no significant difference, the water content was highest in the partⅠ, and lowest in the partⅣ, which meant the longer influenced by water, the soil had higher water content. The soil capillary porosity in four parts had the same trend just as soil water content. The non-capillary porosity was much lower with the flooding time. The soil erodibility K value, Ki and Kr in the uncultivated farmland had no significant differences in the four parts. In the grassland, K value in the partⅠwas significant lower than that in other three parts. Ki in the partⅣwas lower, and the Kr between 20-40cm soil in partⅣwas much lower. The soil organic matter in the four parts of cultivated land was:Ⅰ<Ⅱ<Ⅲ<Ⅳ. In the grass land, the organic matter content of part IV was lowest.