荒漠草原不同功能群优势植物的水分利用特征

Water utilization characteristics of dominant plant species from different functional groups of desert steppe

掌握植物的水分利用特征及植物间的水源关系对实现荒漠草原地区可持续的植被恢复至关重要。本研究以荒漠草原灰钙土生境(胡杨、中间锦鸡儿和短花针茅)和风沙土生境(胡杨、北沙柳和赖草)中的5种优势植物为对象,测定植物木质部水、土壤水、地下水和降雨中稳定同位素(δ^(2)H和δ^(18)O),并结合不同深度的土壤含水量和根系数据,使用MixSIAR模型对植物的水分利用特征进行定量分析。结果表明:生长季内5种植物主要利用土壤水,且在不同生长阶段会利用不同层次的土壤水。灰钙土生境中,胡杨的水源在整个生长季变化最大,生长季初期(5-6月)主要利用60~100cm土壤水,生长旺盛期(7-8月)水源下移至100~200cm土壤水,而在生长季末期(9月)水源又上移至0~20cm土壤水;中间锦鸡儿在生长季初期主要利用60~100cm土壤水,但在生长旺盛期和末期上移至0~20cm土壤水;短花针茅在生长季初期和末期主要利用20~60cm土壤水,而在生长旺盛期上移至0~20cm土壤水。在风沙土生境中,胡杨在生长季初期主要利用60~100cm土壤水,但在生长旺盛期和末期上移至0~20cm土壤水;北沙柳在生长季初期和生长旺盛期主要利用60~100cm土壤水,但在生长季末期下移至100~200cm土壤水;赖草整个生长季都主要利用20~60cm土壤水。土壤含水量、降雨的季节变化及植物的根系分布都会影响植物的水分利用特征。在整个生长季中,灰钙土生境中的乔木、灌木和草本3种优势植物间存在水文生态位分离,促进了其对水分的分配和利用;风沙土生境中对应的3种优势植物间存在水文生态位重叠,导致其对水分的激烈竞争(特别是乔木和灌木间)。因此,在进行植被恢复时必须同时考虑物种特征和土壤特性,引入具有互补性水分利用特征的物种组合,才能实现荒漠草原地区的物种多样性和植被恢复的可持续性。

Understanding water use characteristics of plants and their interrelations is essential for achieving sustainable vegetation restoration of desert steppe.This study focused on five dominant plant species inhabiting two habitats:sierozem(Populus euphratica,Caragana liouana,and Stipa breviflora)and aeolian sandy soil(P.euphratica,Salix psammophila,and Leymus secalinus).We analyzedδ^(2)H andδ^(18)O isotopes in xylem,soil water,groundwater,and precipitation.By integrating soil water content and root data at various depths,we employed the MixSIAR model to quantitatively assess water utilization characteristics.Results revealed that these plants primarily relied on soil water during the growing season,with variations in water uptake depths at different growth stages.In the sierozem habitat,Populus exhibited significant variations in water source throughout the growing season.Early in the growing season(May to June),P.euphratica primarily extracted soil water from depths of 60-100 cm.During the peak growth period(July to August),water source shifted to depths of 100-200 cm,and returned to the depth of 0-20 cm by the end of the season(September).C.liouana initially utilized soil water at 60-100 cm but shifted to 0-20 cm during and after peak growth.S.breviflora predominantly tapped into soil water at 20-60 cm early and late in the growing season,but shifted to 0-20 cm during peak growth.In the aeolian sandy soil habitat,P.euphratica initially utilized soil water at 60-100 cm but shifted to 0-20 cm during and after peak growth.S.psammophila primarily utilized soil water at 60-100 cm early and during peak growth,shifting to 100-200 cm by the end of the season.L.secalinus mainly relied on soil water at 20-60 cm throughout the growing season.Soil moisture,seasonal precipitation variation,and root distribution influenced vegetation water use patterns.Throughout the growing season,trees,shrubs,and herbs in the sierozem habitat exhibited hydrological niche partitioning,which facilitated their water distribution and utilization.Conversely,dominant plants in the aeolian sandy soil habitat showed hydrological niche overlap,which intensified water competition,particularly between trees and shrubs.Therefore,species traits and soil properties should be given full consideration when selecting species combinations for vegetation restoration.Introducing species combinations with complementary water use characteristics is essential for fostering species diversity and sustainable vegetation restoration in desert steppe.