Study On Degradation Characterisitics And Evaluation Of Ecosystem Service Value Of Alipine Meadow In Tianzhu Of Gansu Province

In order to provide theoretical support for the rational utilization, restoration and protection of degraded alpine meadow, 4 sampling sites according to the grazing intensity(non-grazing, light grazing, moderate grazing and heavy grazing) in Tianzhu Tibetan Autonomous County of Gansu province were selected to study the vegetation characteristic, soil properties and the grassland health index. And the ecosystem survice values of 4 sampling sites were assessed. The main research results are as follows:1. Along with the increase of grazing intensity, the vegetation community showed a degraded succession and the dominant species including Kobresia humilis, K. capillifolia and Elymus nutans were replaced by Polygonum viviparum. The poisonous species including Oxytropis kansuensis and Stellera chamaejasme gradually invaded in community. The vegetation richness decreased and the number of plant species decreased from 19 to 7. The biomass percentage of high quality forage decreased from 90.14% to 37 % and that of poisonous plants and low quality grasses increased from 9.77% to 62.93%.2. The above-ground biomass, vegetation coverage and vegetation height showed an obvious decreasing trend along with the increase of the grazing intensity. From the non-grazing to heavy grazing, the vegetation coverage decreased from 95.54% to 52% and the above-ground biomass decreased from 1136.51 g·m-2 to 65.20 g·m-2.The differences of vegetation coverage and above-ground biomass were significant among 4 sites(P<0.05). The average vegetation height decreased from 20 cm to 3.2cm and the difference of the average vegetation height between heavy grazing site and other sites was significant(P<0.05), while the difference of vegetation height were not significant among non-grazing, light grazing and heavy grazing sites(P>0.05).3. The health indexes of 4 sites were 91, 84, 66 and 34 respectively, which showed an obvious decreasing trend along with the grazing intensity. The health statuses of 4 sites were ranked as good, healthy, sub-healthy and unhealthy.4. The contents of soil organic carbon, soil total phosphorus and soil moisture showed a decreasing trend along with the increase of grazing intensity. Soil total nitrogen content increased in light grazing site and showed a decreasing trend in moderate grazing and heavy grazing sites while the soil bulk density showed an increasing trend. Soil organic carbon decreased from 70.49 g·kg-1 to 42.51 g·kg-1, total nitrogen decreased from 0.79 g·kg-1 to 0.68 g·kg-1, total phosphorus decreased from 0.84 g·kg-1 to 0.66 g·kg-1, and soil water content decreased from 26.04% to 11.83%, while soil bulk density increased from 1.34 g·cm-3 to 1.39 g·cm-3.5. Along with the increase of grazing intensity, the ecosystem service value of alipine meadow decreased gradually. From non-grazing, light grazing, moderate grazing to heavy grazing sites, the ecosystem service values were 18713.51 yuan/hm2·a-1, 12214.98 yuan/hm2·a-1, 8586.37 yuan/hm2·a-1 and 4598.79 yuan/hm2·a-1 respectively. The losses of ecosystem services value caused by grazing in light grazing, moderate grazing and heavy grazing sites were 6498.53 yuan/hm2·a-1, 10127.13 yuan/hm2·a-1 and 14114.72 yuan/hm2·a-1 respectively. The estimated total value of ecosystem services of alpine meadow in Tianzhu was 559 million yuan in 2014.