民勤绿洲边缘不同演替阶段白刺灌丛水分利用动态

Water utilization dynamics of Nitraria tangutorum nebkhas in different succession stages at the edge of Minqin oasis

白刺(Nitraria tangutorum)灌丛是民勤绿洲边缘的建群种,也是绿洲风沙灾害防治的重要天然屏障。水分是干旱区植物生存发展的限制性因子,研究不同演替阶段白刺灌丛水分利用动态对民勤绿洲边缘生态恢复与重建具有重要的理论和实践意义。通过测定白刺灌丛不同季节降水、土壤水、地下水、植物木质部水的稳定氢氧同位素变化特征,结合IsoSource模型,定量分析了不同演替阶段白刺灌丛生长季的水分利用策略。结果表明:不同演替阶段白刺灌丛土壤水分0-200cm垂直分布的季节变化差异明显,土壤水分排序表现为衰退阶段>发育阶段>稳定阶段。5月-9月民勤绿洲大气降水线性方程LMWL为δD=6.59δ18O-4.38,R2=0.90,n=114。土壤水、地下水、植物水、降水δ18O随季节和演替阶段的变化规律各异。白刺灌丛发育阶段,春季主要利用中层土壤水,夏季和秋季利用地下水。稳定阶段,春季主要利用浅层土壤水分,夏季主要利用降水,秋季主要利用地下水。衰退阶段,春季主要利用深层土壤水,夏季和秋季主要利用地下水。地下水埋深、结皮覆盖度、灌丛与农田之间距离等环境因子以及植株枯枝程度共同影响着不同演替阶段白刺灌丛的水分利用策略。

Nitraria tangutorum nebkhas is the dominant species on the edge of Minqin oasis and an important natural barrier for the prevention and control of wind-sand disaster in oasis.Water is a limiting factor for the survival and development of plants in arid areas.It is of great theoretical and practical significance to study the water use dynamics of N.tangutorum nebkhas in different succession stages for the ecological restoration and reconstruction of Minqin oasis edge.Through measuring the characteristics of stable hydrogen and oxygen isotope changes of precipitation,soil water,ground water and plant xylem water in different seasons,and combining IsoSource model,we quantitatively analyzed the water utilization strategies in the growth seasons of N.tangutorum nebkhas in different succession stages.The results showed that there were significant seasonal differences in the vertical distribution of soil moisture 0-200 cm in N.tangutorum nebkhas at different succession stages.The order of soil moisture in 0-200 cm soil layer was as followed:deterioration stage>early development stage>stable stage.The meteoric water line equation in Minqin oasis from May to September wasδD=6.59δ18O-4.38,R2=0.90,n=114.Theδ18O of soil water,groundwater,plant water and precipitation varied with seasons and succession stages.During the development stage,soil water in middle layer was mainly used in spring,and groundwater was used in summer and autumn.In the stable stage,the soil moisture of shallow 0-60 cm was mainly used in spring,precipitation was mainly used in summer and groundwater was mainly used in autumn.In the recession stage,deep soil water was mainly used in spring,and groundwater was mainly used in summer and autumn.Environmental factors such as groundwater depth,crust coverage,distance between shrubs and farmland,and the degree of deadwood affected the water use strategy of N.tangutorum shrubs in different succession stages.