Studies On The Effects Of Fertilization And Grazing On Soil Enzyme Activity In Eastern Qinghai-Tibet Plateau

Soil enzyme is a general term for a kind of protein with catalytic function in the ecological system.lt is involved in all the biochemical processes in soil.The active can be characterized the metabolic status of substance in soil. It is an important indicator of soil quality evaluation. We conducted a series of observation and control experiment in Gannan territory in2012and2013:Choose the swamp meadow as the study object.The effect of different grazing processing mode and seasonal change on soil enzyme activity and soil nutrients.Choose classic alpine meadow as the study object. We studied the response of soil enzyme activity under different fertilization gradient patterns.The response of soil enzyme activity under different fertilization gradient and seasonal change.The response of soil enzyme activity under continuous fertilization. We tried to explore the function of soil ecosystem and potential program by the response of soil enzyme activity to environmental changes.To explore the program of soil degradation and provide a theoretical basis for the sustainable development of grassland ecosystems in Gannan territory.Our main objectives are as follows:1. In the swamp meadow,we found β-glucosidase activity, acid phosphatase activity and urease activity had an obvious vertical distribution characteristics in swamp meadow soil. Under non-grazing pattern and winter grazing pattern,β-glucosidase activity showed a high-low-high trend as the growing season goes.lt means soil carbon cycle rate showed a high-low-high trend as the growing season goes. Urease activity decreased as the growing season goes.It means soil organic N intensity gradually weakened as the growing season goes. Different grazing patterns influence on P-glucosidase enzymes was winter grazing highest, annual grazing was the lowest. Proper grazing play a positive role in soil carbon cycle.Acid phosphatase activity was the winter grazing highest, annual grazing lowest, the potential ability of phosphorus was the winter grazing highest, annual grazing lowest. Urease activity increased as the increased grazing intensity. It may due to livestock manure increased the organic N rate.β-glucosidase activity showed significantly correlated relationship with the soil nutrient,which we could prove β-glucosidase activity was a ideal biological indicator to evaluating soil quality in the area, β-glucosidase and acid phosphatase activity had a very significant positive correlation with water content.which showed that the soil moisture were the main factors to promote β-glucosidase and acid phosphatase to hydrolysis of organic matter.2. At the beginning of the growing season, β-glucosidase activity increased with the increase of fertilizer rate alpine meadow.By the end of the growing season β-glucosidase activity appeared unimodal curve changes.Acid phosphatase activity decreased with growing season goes on under over-fertilization measures.The mineralization rate would slow down the effective phosphorus fertilization.Soil urease activity reached its peak at30g/m2fertilizer rate in three seasons.The proper application of fertilizer played a positive role in decomposition of organic N.β-glucosidase activity reached its peak at60g/m2fertilizer rate. Three kinds of enzyme activities (urease activity especially) showed significantly or very significant correlated relationship with the soil nutrient. They all can be used to evaluate the soil fertility. Especially the urease activity can play a perfect characterize to evaluate soil fertility conditions.3. Compared with2012, β-glucosidase activity increased in2013for two consecutive years fertilization.lt turned out soil C cycle has been strengthened under continuous fertilization disturbance. Acid phosphatase activity generally appeared the following year was lower than the first year. This can infer nitrogen and phosphorus mixed in fertilizer can make acid phosphatase activity been suppressed. Compared with first year,urease activity was higher in the following year.The possible reasons maybe fertilization practice increased the substrate of urease enzyme reaction,but too much nitrogen can inhibit urease activity.