干旱区植物用水对水文条件的响应——以额济纳三角洲胡杨为例

植物用水对水文条件的响应是干旱区生态水文学的重点研究内容。本研究以额济纳三角洲为研究区,选取水文条件不同的典型河岸带植物胡杨(Populus euphratica)为研究对象,同步采集其根茎及可能为植物提供水分的土壤并真空抽提水分,同时采集河水和地下水水样,通过δ18 O分析潜在供水水源(河水、地下水)-土壤水-植物水之间的水分响应关系。研究发现,对于距离过水河道75m(地下水位埋深2.0m)的胡杨,其主要土壤供水层在1.0~2.0m,植物水分有93.7%来自河水;而距离过水主河道2km以外(地下水位埋深3.3m)的胡杨,主要吸收1.4~3.2m的土壤层水分,地下水(由河水补给,但在含水层停留时间较长的河水)对胡杨水分的贡献比例达到80.0%。可见,胡杨用水策略与模式受其距过水河道远近、地下水位深浅影响明显。

The response of plant water use strategy to hydrological conditions in arid areas: a case study of Populus euphratica in Ejina Delta

The response of plant water use strategy to hydrological conditions is important for eco-hydrological research in arid areas.In the present paper,we studied a typical riparian plant,Populus euphratica,under different hydrological conditions in Ejina delta.We simultaneously collected samples of the plants'xylem as well as the surrounding soil and extracted their water with a cryogenic vacuum extraction system.Meanwhile,we collected river water and groundwater samples.The δ18 O of these samples were tested to analyze the relationship between potential water sources (river water,groundwater),soil water,and plant water by the isotopic mass balance model.The results indicated that the Populus euphratica that stands 75 m away from riverbank with a 2 m-deep water table mainly consumes water from the 1.0～2.0 m deep soil layer and 93.7％ of the plant water is from the river.The Populus euphratica that stands 2 km away from riverbank with a 3.3 m-deep water table mainly absorbs soil water that is 1.4～3.2 m deep,and ultimately 80.0％ of the plant water comes from groundwater (river water that stays long in the aquifer).It can be seen that the water use strategy of Populus euphratica varies significantly with their distance from riverbank and groundwater table depth.