艾比湖流域典型荒漠植被水分利用来源研究

在以风沙和干旱为基本特征的干旱、半干旱生态环境中,荒漠植被在防风固沙及维持荒漠和绿洲生态系统的稳定性方面有重要作用。选取艾比湖流域不同生境（河岸、沙丘、荒漠、盐沼）典型荒漠植被胡杨（Populus euphratica）、梭梭（Haloxylon ammodendron）、白刺（Nitraria sibirica）和盐穗木（Halostachys caspica）为研究对象,运用稳定同位素方法分析降水、土壤水、植株水和地下水同位素组成变化特征,量化4种植被在整个生长期内吸水来源及比例。结果表明：① 艾比湖流域降水δ²H和δ¹⁸O值变化范围为-142.5‰~-0.6‰和-20.16‰~1.20‰,表现为夏季最大,冬季最小,春秋季居中的态势。② 4类生境条件下的土壤水δ²H和δ¹⁸O值沿剖面总体表现为随着深度增加逐渐减小;不同植株茎水δ²H和δ¹⁸O值时间变化趋势基本一致,春季最大,夏季最小,秋季又逐渐增加;不同植株间比较,盐穗木茎水稳定同位素值最大,其余依次为白刺、梭梭和胡杨。③ 荒漠植被在不同生长期吸水来源及利用比例不同,梭梭在整个生长期主要利用地下水;白刺利用水源比例在整个生长季内变化较大,春季主要利用表层土壤水,贡献率为80%~94%,夏季利用深层土壤水的比例为31%~36%,秋季利用中层土壤水的比例达到33%~36%;盐穗木春季和秋季主要利用表层土壤水,夏季中间层土壤水比例略有提升,为20%~36%;胡杨春季主要利用中间层土壤水,利用比例为53%~54%,夏季主要利用地下水,比例达到72%~88%,河水利用比例仅为2%~5%,秋季河水利用比例升高为11%~21%。研究结果显示,干旱区荒漠植被生长季内水分利用来源差异明显。本文为了解干旱区荒漠植被的水分利用机理、水分适应策略,以及植被恢复和管理提供理论依据。

Water sources of the typical desert vegetation in Ebinur Lake basin

In arid and semi-arid environments, desert vegetation plays an important role in preventing soil erosion by wind and maintaining the stability of the desert and oasis ecosystem. Four types of typical desert vegetation, namely, Populus euphratica, Haloxylon ammodendron, Nitraria sibirica and Halostachs caspica, in different habitats (i.e., banks, sand dunes, desert, and salt marshes) were chosen as the model vegetation in this research. The δ²H and δ¹⁸O of rain water, soil water and plant water were applied to identify the water sources and quantify the proportions of water used during the whole growth period (from March to October). The results showed that the precipitation δ²H and δ¹⁸O in the Ebinur Lake basin varied from -142.5‰ to -0.6‰ and from -20.16‰ to 1.20‰, respectively. The largest values of δ²H and δ¹⁸O were found in summer and the smallest ones in winter. The soil water δ²H and δ¹⁸O of the four habitats decreased gradually with the increase of the depth. The δ²H and δ¹⁸O values of water extracted from the four plant stems had similar variation trend, i.e., the maximum was observed in spring, and the minimum was in summer. Among the four plants, Halostachs caspica had the highest stable isotopic values in the stem water, followed by Nitraria sibirica, Haloxylon ammodendron and Populus euphratica. The water sources and utilization ratios of desert vegetation varied in different growth stages. In the whole growing period, Haloxylon ammodendron mainly used groundwater. The proportion of water used by Nitraria sibirica varied greatly throughout the growing season. In spring, plants mainly relied on surface soil water, with a contribution rate of 80%-94%; in summer, the proportion of deep soil water use was 31%-36%; and in autumn, the proportion of middle soil water use was 33%-36%. Halostachs caspica mainly relied on topsoil water in spring and autumn, and the proportion of soil water in the middle layer slightly increased in summer, which was 20%-36%. Populus euphratica mainly used the intermediate soil water in spring, with a utilization rate of 53%-54%; in summer, groundwater was the main source, with a utilization rate of 72%-88%, and only 2%-5% from river water; in autumn, the utilization rate of river water rose to 11%-21%. The results indicated that there were significant differences in water use sources during the growing season of desert vegetation in arid areas. This research provides a theoretical basis for understanding the water use mechanism, water adaptation strategies, and vegetation restoration and management of desert vegetation in arid areas.