Impact Of Alpine Meadow Degradation On Soil Water Conservation Function In Sanjiangyuan Region

The Sanjiangyuan region is the source area of Yellow, Yangtze and Lantsang river. Its ecological strategic position is of great importance. Because of global climate change and human activity, alpine meadow in Sanjiangyuan region has become severely damaged in recent years. Study on the impact of alpine meadow degradation on regional water conservation in Sanjiangyuan region can offer some references for improving rangeland resources management, helping find restoration measures, and providing vital theoretical and scientific basis in precisely evaluating and dynamicly monitoring regional ecosystem water conservation.By largely field sampling, investigation, and statistical analysis, this study focused on the change of vegetation and soil during the alpine meadow degradation. Impact of alpine meadow degradation on soil water conservation capacity and its relevant factors have been analyzed. Via ecological economic meathod, the study evaluated economic loss of soil water conservation caused by alpine meadow degradation. Main conclusions obtained are as follows:(1) Compared with above-ground biomass, under-ground biomass has a delayed reaction to alpine meadow degradation. Above-ground biomass and under-ground biomass were significantly moderately positive correlation with soil water conservation capcacity(the correlation coefficient is between0.4-0.6, p<0.05).(2) Soil bulk density, soil total porosity, and soil capillary porosity significantly changed with the increasing degreee of degradation, and were significantly highly correlation with soil water conservation capacity(p<0.01). Soil bulk densiy was negative correlation with soil water conservation capacity, while soil total porosity and soil capillary porosity were positive correlation with it. By multi-stepwise regression analysis, an equation has been established used soil bulk density(X4) and water soil conservation capacity(Y):Y=2721.280-1061.988×X4. Ajusted R2=0.94623, which meant that the model was fitting good.(3) Soil natural water-holding capacity at each depth and the sum was decreasing with the increasing degree of meadow degradation, and the total natural water-holding capacity decreased significantly (p<0.05). The change of soil capillary and minimum water-holding capacity at each depth and total capacity was different among diverse soil types. Soil water conservation was significantly positive correlation with water-holding capacity(p<0.01). The correlation coefficient between soil water conservation capacity and water-holding capacity of natural, capillary and minimum at0-30cm was between0.6-0.8.(4) The variation tendency of soil pH and soil nutrients was different among diverse soil types. Soil water conservation capacity was significantly negative correlation with soil pH(the correlation coefficient was0.745, p<0.01), and was significantly positive correlation with soil humus content, soil hydrolyzable nitrogen and soil exchangeable base concentration(the correlation coefficient was larger than0.8, p<0.01).(5) Alpine meadow soil water conservation was decreasing with the increasing degree of degradation. Soi water conservation capacity in severely degraded meadow significantly was lower than others(p<0.05). Because of diverse soil types, variation of soil water conservation capacity among different degraded meadow come difference. Outcomes of mean comparation showed that soil water conservation capacity significantly differ among diverse soil types. While evaluating impact of rangeland degradation on soil water conservation, the type of soil should be considered.(6) The impact of meadow degradation on soil water conservation capacity and its value depended on soil type. Compared with not degraded meadow at alpine meadow soil, soil water conservation and its value lost was the largest. Loss of soil water conservation capacity at moderately and severely degraded meadow were45.30X107t and121.28X107t, and the value were31.80×109yuan and85.14X109yuan. Compared with moderately degraded meadow at alpine meadow steppe soil, the loss of soil water conservation capacity and value were17.00×107t and11.93X109yuan. The loss soil water conservation capacity and value in alpine meadow degradation of three soil type at this study were187.45×107t and131.59×109yuan.