克里雅河尾闾河岸不同生长阶段胡杨的水分利用

Water use of Populus euphratica in different development stages growing near the riverbank at the tail of the Keriya River

胡杨(Populus euphratica)是荒漠河岸林的重要组成树种,在调节气候、防风固沙、稳定河道、维持绿洲群落稳定性等方面具有重要生态作用。本研究以生长在塔克拉玛干沙漠腹地克里雅河尾闾河岸旁的主要建群种胡杨为对象,依据胸径(DBH)变化,将胡杨划分为幼苗(地径≤4 cm)、幼树(4 cm40 cm)4个生长阶段。利用氧稳定同位素技术,测定了不同生长阶段胡杨小枝木质部水、0~300 cm土层的土壤水、地下水和河水的δ^(18)O值。水源依据深度划分为浅层土壤水(0~140 cm)、深层土壤水(140~300 cm)、地下水和河水。应用IsoSource模型计算了胡杨对潜在水源的利用比例,利用碳稳定同位素技术分析了不同生长阶段胡杨叶片的水分利用效率。结果表明:胡杨木质部水的δ^(18)O值随径级的增加而减小,变化范围在-6.10‰~-5.67‰;胡杨幼苗、幼树、成熟木和过熟木的主要水源为河水,利用比例分别为0~74%、0~77%、7%~80%和17%~82%。胡杨叶片的δ13C值随径级的增加波动较小,变化范围为-29.96‰~-29.02‰。研究表明,克里雅河尾闾生长在河岸旁不同生长阶段的胡杨水分状况良好,没有受到显著的干旱胁迫。

Populus euphratica is the main tree species in desert riparian forests,with an important role in regulating climate,fixing sand,stabilizing river channel,and maintaining the stability of oasis community.In this study,we investigated P.euphratica near the riverbank at the tail of the Keriya River in the hinterland of Taklimakan Desert in northwestern China.Based on diameter at breast height(DBH),P.euphratica individuals were classified into four development stages,i.e.,seedling(Basal diameter≤4 cm),sapling(4 cm 40 cm).We measured oxygen stable isotope ratios(δ^(18)O)in xylem water,soil water in different soil layers(0-300 cm depth),groundwater,and river water.Four potential water sources were classified:shallow soil water(0-140 cm),deep soil water(140-300 cm),groundwater,and river water.The ratios of different potential water sources used by P.euphratica were determined using the IsoSource model.Stable carbon isotope technology was used to examine the water use efficiency of P.euphratica in different development stages.The result showed thatδ^(18)O value of xylem water of P.euphratica decreased with DBH,with a range of-6.10‰to-5.67‰.Seedling,sapling,mature tree,and overmature tree of P.euphratica mainly used river water,with corresponding water use ranges of 0-74%,0-77%,7%-80%,and 17%-82%,respectively.Foliarδ13C of P.euphratica changed slightly with increasing DBH,ranging between-29.96‰and-29.02‰.Our findings suggested that P.euphratica growing near the riverbank at the tail of the Keriya River have good water conditions and suffer little drought stress.