黑河流域不同生境植物水分来源及环境指示意义

Plant Water Sources of Different Habitats and Its Environmental Indication in Heihe River Basin

选择黑河流域三种典型生境类型(绿洲、绿洲-荒漠过渡带、荒漠),通过分析其不同植物木质部水分与其土壤潜在水源稳定氢(δD)和氧(δ18 O)同位素组成,研究了不同生境中植物的水分来源情况.结果表明:荒漠生境中植物倾向于利用深层土壤水(>160cm);绿洲-荒漠过渡带中沙蒿和沙拐枣主要利用20～40cm层位的土壤水,梭梭可能的利用层位是60～80cm,花棒可能利用100cm左右的水分,柽柳则利用120cm以下的土壤水;绿洲植物吸水层位多集中在0～100cm,其中,假苇拂子茅可能水源是20cm左右的土壤水,玉米则为20～40cm,柽柳和杨树的吸水层位为60cm左右,棉花则是利用80cm左右的水分.稳定性同位素估测各生境植物水分来源的结果与其土壤含水量的结果一致,同一生境中吸水层位相似的植物间存在水分来源竞争.不同生境中植物水分来源的深浅存在递变,从深到浅表现为荒漠>过渡带>绿洲,不同生境同种植物也存在同样变化,说明植物稳定氢氧同位素组成可以用来指示干旱区绿洲化、荒漠化过程.

Stable hydrogen and oxygen isotopes(δD and δ18O) of plant stem water and potential water sources were analyzed to investigate the water sources of different plant species in three typical habitats(oasis,oasis-desert transitional zone and desert) in the Heihe River basin.It is found that plants in the desert habitat absorb water mostly from deeper soil(>160 cm).In the oasis-desert transitional zone,Artemisia arenaria and Calligonum mongolicum are likely absorb water mainly from the soil about 20~40 cm in depth,Haloxylon ammodendron absorbs water primarily from 60~80 cm in depth,Hedysarum scoparium may absorb water from soil about 100 cm in depth and Tamarix ramosissima obtain water from deeper soil(>120 cm).Plants in the oasis habitat absorb soil water mainly from 0 to 100 cm deep.Calamagrostis pseudophragmites absorbs water about 20 cm in depth,Zea mays extracts soil water from the depth of 20~40 cm,Tamarix ramosissima and Populus simonii absorb soil water about 60 cm deep and Gossypium hirsutum absorbs water from soil about 80 cm in depth.Plant water sources in the three studied habitats are coincidence with soil water content.It is believed that water competition may exist among plant species which absorb water from similar soil depth.The depth of plant water sources of different habitats is gradually changed in the order from deep to shallow: desert,oasis-desert transitional zone and oasis.This order also exists in different habitats for the same plant species.It is illustrated that plant stable hydrogen and oxygen isotope composition can be used to indicate the processes of oasisization and desertification in arid regions.