Soil Nitrogen Content and Enzyme Activity in Different Utilization Types of Land in the Upper Reaches of Lancang River

Nitrogen content and enzyme activity under six different kinds of soil utilization types in Eryuan County in Northwest Yunnan mountainous area of the upper reaches of Lancang River were studied,the changes in soil nitrogen and enzyme activities and the interrelationship between these two parameters in these lands were examined in order to restore the deteriorated soils in the mountainous region and provide the theory basis on sustainable land uses.The results showed that:(1) Soil nitrogen content and enzyme activities were different in different land utilization types,which reflected the different degree of soil degradation.Rich nutrients were accumulated in Alnus nepalensis forest land,and the soil ecological environment were good,namely soil nitrogen content and enzyme activity were greater than other land utilization types;(2) Under all kinds of land utilization types,the higher is the soil nitrogen content,the greater is the enzyme activity.In the process of nitrogen cycling,the soil enzyme activity decreased with the nitrogen decayed and soil also degraded in various degrees;(3) From the vertical profile of the soil,the land utilization and human activities affected surface layers in these lands since the soil nitrogen content and enzyme activity decreased with the depth of soil profile;(4) Soil nitrogen content had certain correlation with soil enzyme activity.The degree of soil degradation became serious along with decrease in soil nitrogen content and the soil enzyme activity.