乌兰布和沙漠两个沙冬青群落的水分来源差异

Difference of water source of two Ammopiptanthus mongolicus communities in Ulan Buh Desert,China

为了解植物群落水分利用过程对生境异质性的适应,2021年4—9月测定乌兰布和沙漠沙丘和戈壁沙冬青群落不同灌木的木质部水和潜在水源(各层土壤水或地下水)的δD和δ^(18)O值,通过MixSIAR模型量化不同潜在水源的贡献比例,明确各水分来源的季节动态。结果表明:早春大雨后4月和5月沙丘的沙冬青和旱蒿对10~25 cm土壤水利用较多,黑沙蒿主要利用10~200 cm土壤水;6—8月干旱时,沙冬青对100~200 cm土壤水和地下水的利用增加,旱蒿和黑沙蒿对50~200 cm土壤水的利用增加;9月中雨后沙冬青对各层土壤水和地下水的利用比例类似,旱蒿和黑沙蒿对10~50 cm土壤水的利用增加。戈壁的沙冬青和泡泡刺4月和5月对各层土壤水的利用比例类似,6—8月和9月它们分别主要利用50~150 cm和10~50 cm土壤水;刺旋花则分别主要利用10~50 cm(4—5月)、25~150 cm(6—8月)和10~25 cm土壤水(9月)。两个沙冬青群落不同灌木的水分利用过程存在季节差异。干旱时,沙丘的沙冬青能够利用深层土壤水和部分地下水,而戈壁的沙冬青仅依赖深层土壤水,对降雨更加敏感。

To understand the adaptation of water use strategy of plant community to habitat heterogeneity,we measured the δD and δ^(18)O values of xylem water of shrubs and potential water sources(soil water in different layers or groundwater)of Ammopiptanthus mongolicus communities on sand dune and Gobi from April to September in 2021 in the Ulan Buh Desert.Employing the MixSIAR model,we examined the seasonal dynamics of water source of each shrub by quantifying the contribution of different potential water sources.The results showed that A.mongolicus and Artemisia xerophytica on sand dune mainly used soil water of 10-25 cm in April and May after heavy rain in early spring,whereas Artemisia ordosica mainly used soil water of 10-200 cm.During the drought event within summer from June to August,A.mongolicus increasingly used soil water of 100-200 cm and groundwater,but A.xerophytica and A.ordosica increased the usage of 50-200 cm soil water.After the moderate rain in September,A.mongolicus evenly used soil water in all layers and groundwater,whereas two Artemisia shrubs preferred soil water of 10-50 cm.On Gobi,A.mongolicus and Nitraria sphaerocarpa evenly used soil water in all layers in April and May,mainly used 50-150 cm soil water from June to August and used 10-50 cm soil water in September.Convolvulus tragacanthoides mainly used soil water of 10-50 cm(from April to May),25-150 cm(from June to August),and 10-25 cm(in September),separately.There were seasonal differences in water use of three shrubs on sand dune and Gobi A.mongolicus communities.During drought,A.mongolicus on sand dune could use deep soil water and groundwater,and that on Gobi relied only on deep soil water,which was more sensitive to rainfall.