祁连山高寒草原土壤水分与植被盖度的关系

Relationship between soil moisture and vegetation cover in Qilian Mountain alpine steppe

为了揭示高寒草原土壤水分与植被盖度的关系,提高植被盖度与土壤水分快测的精度,本研究在祁连山北麓中段高寒草原—甘肃马鹿冬季牧场,设置放牧率分别为1.00、1.45、2.45、3.45、4.85、6.90 AUM·hm-2的6个样地,通过逐月测定生长季植被盖度和土壤水分,结合Landsat5多光谱影像与SPOT2全色影像融合而成的SPOT-TM影像,分析土壤水分与植被盖度、归一化植被指数(NDVI)的关系,并在此基础上,确定植被盖度随土壤水分的变化阶段。除醉马草、银灰旋花、乳白黄耆外,其他种群盖度对表层土壤水分均响应敏感,在3%~7%至17%~26%的土壤水分范围内,种群盖度随土壤水分的增加呈反比例函数递增趋势,且增幅逐渐缩小;群落盖度对表层土壤水分的响应敏感,在1.1%~10.0%的土壤水分范围内,群落盖度随土壤水分的增加亦呈反比例函数递增趋势,并逐渐趋于饱和。研究结果对探讨干旱半干旱草原植被物种、种群、群落的抗旱性、水分利用效率具有一定意义,为草原植被和土壤水分管理提供科学依据。

This study investigated the relationship between soil moisture and vegetation cover in alpine steppe meadow in the Qilian Mountains with the aim of improving the precision of remote sensing estimates of soil moisture and vegetation cover.Six sample areas with different stocking rates of Cervus elaphus kansuensis(1.00,1.45,2.45,3.45,4.85,6.90 AUM·ha-1)in were set up,AUM means animal unit.Through comparing data from monthly field measurement of vegetation cover and soil moisture and SPOT-TM images combining Landsat5 multispectral images and SPOT2 panchromatic images,we analyzed the relationship between soil moisture,vegetation cover and normalized difference vegetation index(NDVI)and quantitatively explored the dynamics of seasonal change in vegetation cover and soil moisture in the sample areas in the Qilian Mountain alpine steppe.Except for Achnatherum inebrians,Convolvulus ammannii and Stragalus leucocephalus,the response of population cover to surface soil moisture was relatively sensitive,with the population cover of species inversely proportional to soil moisture in the range between c.5%and c.25%.The response of plant community cover to surface soil moisture was also relatively sensitive.In the soil moisture range from 10.0%to 1.1%,the community cover increased in the inverse proportional function.The results are highly relevant to remote sensing monitoring of the drought resistance and water use efficiency of plant species,populations and communities in arid and semi-arid steppe grassland,and provide scientific data for vegetation and soil moisture management in steppe grasslands.