高寒沙地典型固沙植物在沙丘不同地貌部位的水分利用特征

Water use patterns for a typical afforested shrub among topographic positions in an alpine desert of Qinghai⁃Tibet Plateau using stable isotopes tracers

乌柳是高寒半干旱沙地植被恢复中常用的灌木树种,对乌柳水分利用来源的研究有助于理解沙地人工生态系统的稳定性维持及可持续发展。在青海湖湖东沙地,以沙丘不同地貌部位(迎风坡、丘顶和背风坡)生长的乌柳为研究对象,利用IsoSource模型分析植物生长季内的水分利用来源。研究结果表明:在生长季内,乌柳主要利用3个层次的土壤水,但不同地貌部位的乌柳在不同生长季利用不同层次的土壤水。生长季初期,迎风坡的乌柳以深层(60—150cm)土壤水为主要水源(50.28±18.11)%,而丘顶和背风坡的乌柳主要利用表层20cm的土壤水,利用比例分别为(79.96±7.59)%和(53.47±6.47)%。生长季中期,迎风坡的乌柳更多地利用中层20—60cm土壤水(45.52±26.91)%,丘顶的乌柳主要利用表层土壤水(45.17±20.14)%,而背风坡的乌柳以深层土壤水为主要水源(39.26±23.28)%。生长季末期,迎风坡的乌柳仍以(46.07±27.17)%的比例利用中层土壤水,丘顶的乌柳转而利用深层土壤水(44.25±26.23)%,而背风坡的乌柳却以表层土壤水作为主要水源(42.57±18.78)%。不同沙丘地貌部位乌柳对土壤水分的利用模式与其根系分布特征及其下方的土壤含水量具有相关性。

Salix cheilophila is a typical afforested shrub species that is widely used as the sand-binding shrub in alpine and semi-arid sandy land.Research on water use source of S.cheilophila helps to understand the stability and maintenance of the artificial ecosystem of desert sustainable development.In the sandy land at east shore of the Qinghai Lake,we took S.cheilophila growing on different geomorphology of the dunes(windward slope,dune top,and leeward slope)as objects to analyze water use source during the plant growth season by IsoSource isotope mixing model.The results showed that S.cheilophila mainly absorbed three layers of soil water during growing season in 2018,and individuals among different topographic positions used different layers of soil water in different growing seasons.At the beginning of the growing season,S.cheilophila on the windward slope primarily depended on deep soil water in 60—120 cm depth and the proportion was(50.28±18.11)%,while individuals on the top of the dune and the leeward slope used(79.96±7.59)%and(53.47±6.47)%surface soil water of 20 cm depth.In the middle of the growing season,S.cheilophila on the windward slope absorbed(45.52±26.91)%the middle layer of 20—60cm soil water,however,S.cheilophila on the top of the dune and leeward slope took up(45.17±20.14)%shallow 20 cm soil water and(39.26±23.28)%deep soil water under 60 cm soil depth,respectively.At the end of the growing season,S.cheilophila on the windward slope still used(46.07±27.17)%middle layer of soil water,and individuals on the top of dune transferred to rely on(44.25±26.23)%deep soil water,while S.cheilophila on the leeward slope switched to take up(42.57±18.78)%surface soil water as main water source.The differences in water use patterns are closely linked with the range of the active root zones and soil water content along different micro⁃topography conditions.This study can provide insight into plant⁃water relations to facilitate the selection of woody species for afforestation and desert restoration management in the semiarid desert region.