| The rainy area in west China was located in a special geographical position, where rainy was heavy and soil loss was severe. In this place there was a significant difference in soil anti-erodibility under different land-use types which resulted in soil nutrient loss and spatial variation. In this study we chose the typical river basin in rainy area of west China as object and studied the differences of soil anti-erodibility and soil nutrition spatial variability under different land-use types which could offer some suggestions on river basin management. The main results were as follows:(1)By analyzing soil aggregate, we found that in all three land-use types the amounts of >0.25mm dry-sieved aggregates and the amounts of >0.25mm water-stable aggregates from high to low were all forest soil>paddy soil>arid land, respectively, while the destruction rates of soil aggregates structure were arid land>paddy soil>forest soil.(2)By analyzing soil dispersibility, we found that in different land-use types structural grain index and the degree of aggregation from high to low was forest soil>paddy soil>arid land, while dispersion rate, erosion efficient and eroded index were arid land>paddy soil>forest soil.(3)In all three land-use types, soil anti-erodibility comprehensive index from high to low was forest soil (69.052)>paddy soil (53.943)>arid land(27.047) which indicated that forest soil had the strongest soil erosion resistance, paddy soil was medium and arid land was the weakest.(4) The descriptive statistics of soil nutrient showed that the average value of soil nutrient were all in high nutrient contents. The coefficient of variation of all nutrients belonged to 13.21%～70.23% which has all reached moderate variability.(5) The semi-variance analysis of soil nutrition showed that the spatial pattern ranging of all indexes were in 204～2232 m. The analysis of ratio of nugget/sill showed that soil organic matter, total nitrogen, alkali hydrolysable nitrogen and total potassium had a strong spatial correlation, while total phosphorus, available phosphorus and available potassium had a moderate spatial correlation.(6) The spatial analysis of soil nutrient in river basin showed that the area where soil organic matter in middle level or above was 73.5% of the total. In different land-use types, the content of soil organic matter was highest in the south of forest and paddy soil took the second place. The organic matter was lowest in arid land and the north of forest. There was a significant difference in total nitrogen distribution. The content of total nitrogen in south of forest was highest and paddy soil took the second places. The content in major area of arid land was in the middle or the middle and low level. There was a significant difference of distribution in alkali hydrolysable nitrogen which was lowest in arid land and highest in forest soil. The content in major paddy soil was in the middle or the middle and high level. The distribution of total phosphorus showed a tendency of low in middle and high in both sides. The distribution of total phosphorus in paddy soil and arid land were all in the middle and high level, while forest showed the middle level, the middle and high level and the high level from the north to south respectively. The distribution of available phosphorus was lower in middle and either side of the river basin and higher in other areas. There was a significant difference in the distribution of total potassium and available potassium. Total potassium in all land-use types were in the middle level except in the north of forest, and the available potassium in paddy soil and arid land were significantly higher than that in forest soil. The paddy soil and arid land were mainly in the middle and high level,while the available potassium in forest soil increased from low level to the middle and high level from north to south of the forest respectively. |
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