青藏高原多稳态高寒草甸生态系统蒸散特征对比研究

Comparative study on evapotranspiration characteristics of Multi-stable alpine meadow ecosystem on the Tibetan Plateau

在青海海北高寒草地生态系统国家野外科学观测研究站,以禾草-矮嵩草群落、矮嵩草群落、小嵩草群落、杂类草-黑土滩次生裸地4种演替稳态高寒草甸为研究对象,利用小型蒸渗仪法和烘干法等,研究多稳态高寒草甸的蒸散量、土壤含水率、贮水量变化特征。结果表明:随放牧强度增加,生长季盛期,4种演替稳态高寒草甸生态系统每日平均蒸散量出现下降趋势;4种稳态高寒草甸总蒸散量分别是禾本-矮嵩草群落235.2 mm,矮嵩草群落209.1 mm,小嵩草群落203.1 mm,杂类草-黑土滩次生裸地150.3 mm,均低于同期降水量。多稳态高寒草甸表层0~10 cm土壤含水率呈逐渐减小的趋势,且8月含水率降低速度较快,9月含水率下降不明显。禾本-矮嵩草群落10~20 cm土壤含水率变化不明显,其余3种草甸10~20 cm土层含水率均呈减小的趋势,但变化幅度低于表层土壤;高寒草甸0~10、10~20 cm土层贮水量均呈先降低后增加的趋势,生长季4种演替稳态高寒草甸生态系统各土层贮水量均逐渐减小。

This study aims to clarify the response of alpine meadow evapotranspiration to different grazing intensities.It is helpful to deepen the study of water cycle process in degraded ecosystems of alpine meadows,and to reveal the grassland degradation mechanism from the perspective of ecological hydrology.In this study,we taken 4 successional stable alpine meadows(Gramineae-Kobresia humilis community;K.humilis community;K.pygmaca community;forb-black soil type secondary bare land)as research objects,and the evapotranspiration,soil moisture content and water storage of the multi-stable alpine meadow were studied by using the mini lysimeter method and the drying method.The results showed that with the increase of grazing intensity,the average daily evapotranspiration of the four successional stable alpine meadow ecosystems decreased during the peak season of growth;the total evapotranspiration of the four stable alpine meadows was respectively 235.2 mm for Gramineae-Kobresia humilis community,209.1 mm for K.humilis community,203.1 mm for K.pygmaca community,and 150.3 mm for forb-black soil type secondary bare land,all of which were lower than the precipitation;the moisture content of 0~10 cm soil layer showed the trend of gradual reduction,and the rate of reduction in August is faster,and the decrease in water content in September is not obvious.The soil moisture content of 10~20 cm in Gramineae-K.humilis community was not obvious,and that of other 3 alpine meadows decreased,but the change range was lower than that of the 0~10 cm soil layer;the water storage capacity of 0~10 cm and10~20 cm soil layer showed an increasing trend after decreasing in alpine meadow.In the growing season,the water storage capacity of each soil layer in the 4 successional stable alpine meadow ecosystems decreased gradually.By reducing the grazing intensity to restore the degraded alpine meadow ecosystem,the water storage capacity of the ecosystem will be significantly increased,and the grassland production function will be improved.