不同地下水位处梭梭(Haloxylon ammodendron)水分来源特征

Water sources of Haloxylon ammodendron under different groundwater depths

梭梭(Haloxylon ammodendron)是中亚荒漠区分布最广泛的植物,长期被作为防风固沙的优良树种。在降水严重匮乏的荒漠区,地下水埋深对梭梭的正常生长具有关键作用。选择黑河中游临泽绿洲边缘人工梭梭林为研究区域,选择生长沙丘和丘间低地相同林龄的梭梭,对植物茎水及其他潜在水源(降水、土壤水、地下水)的氢氧同位素值进行了测定,并结合IsoSource模型计算了梭梭在沙丘和丘间低地不同微地形条件下的水分来源比例。结果显示:分布于沙丘顶部和丘间低地的梭梭茎木质部水δ18O值存在显著的差异,且沙丘顶部梭梭对降水变化的响应程度显著大于丘间低地的梭梭。沙丘和丘间低地地下水埋深条件的差异对梭梭主要水分来源以及对水分变化的响应程度的影响较为显著,分布于沙丘顶部的梭梭利用地下水的比例为60.6%;而丘间低地梭梭对地下水的利用比例为86.4%。沙丘和丘间低地分布的梭梭的水分利用策略发生变化,沙丘梭梭在降水事件发生时能够及时响应,而丘间低地梭梭对降水的利用不显著,夏季的严重干旱胁迫致使沙丘和丘间低地梭梭都增加了对地下水的利用,说明梭梭对地下水具有很强的依赖性,但是可以根据环境条件调节自身水分利用模式以适应荒漠环境。

Haloxylon ammodendron is the most widely distributed vegetation type in the desert areas of Central Asia,and has long been used as an excellent tree species for windbreak and sand fixation.In desert areas where precipitation is severely scarce,the depth of groundwater level plays a key role in the normal growth of H.ammodendron.In this study,the artificial H.ammodendron forest at the edge of the Linze Oasis in the middle reaches of the Heihe River was selected as the research area,and H.ammodendron of the same age growing in the sand dunes and inter-dune lowland was selected as the research object.The hydrogen and oxygen isotope values of H.ammodendron plant stem water and other potential water sources(precipitation,soil water,groundwater)were measured,and the ratio of water sources of H.ammodendron under different micro-topography conditions in the sand dunes and inter-dune lowland was calculated based on the IsoSource model.The results showed that there were significant differences in theδ18O values of the xylem water of H.ammodendron stalks distributed on the top of the sand dunes and inter-dune lowland,and the impact of precipitation changes on the sand dunes is more significant.The difference in groundwater depth between sand dunes and inter-dune lowland has a significant impact on the main water source of H.ammodendron and its response to water changes.The percentage of groundwater used by H.ammodendron distributed on the top of sand dunes was 60.6%;while the utilization ratio of groundwater by H.ammodendron was 86.4%.Therefore,the water use strategy of H.ammodendron distributed in sand dunes and inter-dune lowland has changed.H.ammodendron can respond in time when precipitation events occur,while H.ammodendron in the inter-dune lowland makes no significant use of precipitation.The severe drought stress in summer increased the utilization of groundwater by H.ammodendron on sand dunes and inter-dune lowland,indicating that H.ammodendron has a strong dependence on groundwater,but it can adjust its own water use mode according to environmental conditions to adapt to the desert environment.