Soil Fertility Status under Different Utilization Types in Mountain Area of the Upper Lancang River

The mountain ecosystem of upper Lancang River is faced with the menace of excessive exploitation of resources and changes in environmental conditions caused by the activities of an expanding human population. Human disturbances and forests destroying have largely affected soil properties. Eight normal soil utilization types in the area were selected to study their soil characteristics. The results showed that there were significantly differences among soil utilization types within soil organic matter, total N, available N, P, K, and NH4-N and NO3-N but no such differences in vertical spatial variation within 0～40 cm soil layer for each type. The soil nutrients of all soil utilization types were declined for secondary forests, planted economic forests,cropland,and even abandoned land. The soil organic matter and total N were mostly declined for the types of eucalyptus forest, pine forest and slop cropland. Comparison with nature broadleaved forest, the soil organic matter reduced 70.89% in slop cropland, 76.80% in eucalyptus forest and 73.14% in pine coniferous forest, and total N reduced 76.40%, 88.76% and 85.39% for slop cropland, eucalyptus forest and pine coniferous forest respectively. Soil available nutrients have same declining trends, especially available P and N declined to 2～10 times. The soil deterioration index was applied to explanation of the degree of soil degradation and soil quality improving, also soil nutrients declining caused by human disturbances. In our study the deterioration index of slop cropland, pine coniferous forest and abandoned land was higher than -0.6%, indicating that the soils are seriously degraded. The deterioration index of mixed forest was the highest among all soil utilization types, which indicatedthat the type might be a model for restoration degraded soil ecosystem in mountainous area.