Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; University of Chinese Academy of Sciences, No.19A, Yuquan Road, Shijingshan District, Beijing 10049, China.
Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China.
Sci Total Environ. 2018 Sep 1;634:341-354. doi: 10.1016/j.scitotenv.2018.03.307. Epub 2018 Apr 6.
In water-limited ecosystems, spatial and temporal partitioning of water sources is an important mechanism that facilitates plant survival and lessens the competition intensity of co-existing plants. Insights into species-specific root functional plasticity and differences in the water sources of co-existing plants under changing water conditions can aid in accurate prediction of the response of desert ecosystems to future climate change. We used stable isotopes of soil water, groundwater and xylem water to determine the seasonal and inter- and intraspecific differences variations in the water sources of six C and C shrubs in the Gurbantonggut desert. We also measured the stem water potentials to determine the water stress levels of each species under varying water conditions. The studied shrubs exhibited similar seasonal water uptake patterns, i.e., all shrubs extracted shallow soil water recharged by snowmelt water during early spring and reverted to deeper water sources during dry summer periods, indicating that all of the studied shrubs have dimorphic root systems that enable them to obtain water sources that differ in space and time. Species in the C shrub community exhibited differences in seasonal water absorption and water status due to differences in topography and rooting depth, demonstrating divergent adaptations to water availability and water stress. Haloxylon ammodendron and T. ramosissima in the C/C mixed community were similar in terms of seasonal water extraction but differed with respect to water potential, which indicated that plant water status is controlled by both root functioning and shoot eco-physiological traits. The two Tamarix species in the C shrub community were similar in terms of water uptake and water status, which suggests functional convergence of the root system and physiological performance under same soil water conditions. In different communities, Haloxylon ammodendron differed in terms of summer water extraction, which suggests that this species exhibits plasticity with respect to rooting depth under different soil water conditions. Shrubs in the Gurbantonggut desert displayed varying adaptations across species and communities through divergent root functioning and shoot eco-physiological traits.
在水资源有限的生态系统中，水分来源的时空分离是一种重要的机制，它促进了植物的生存，并减轻了共存植物之间的竞争强度。深入了解物种特定的根系功能可塑性以及在变化的水分条件下共存植物的水分来源差异，有助于准确预测沙漠生态系统对未来气候变化的响应。我们使用土壤水、地下水和木质部水的稳定同位素，确定了古尔班通古特沙漠六种 C 和 C 灌木在季节性和种间及种内水分来源的差异变化。我们还测量了茎水势，以确定在不同水分条件下每种植物的水分胁迫水平。研究的灌木表现出相似的季节性水分吸收模式，即在早春期间，所有灌木都从融雪水补给的浅层土壤水中吸收水分，而在干旱的夏季期间则返回到更深的水源，这表明所有研究的灌木都具有二态根系，使它们能够获得时空上不同的水分来源。由于地形和根系深度的差异，C 灌木群落中的物种在季节性水分吸收和水分状况方面存在差异，表现出对水分供应和水分胁迫的不同适应。C/C 混合群落中的 H. ammodendron 和 T. ramosissima 在季节性水分提取方面相似，但在水势方面存在差异，这表明植物水分状况既受根系功能的控制，也受地上部分生态生理特征的控制。C 灌木群落中的两个柽柳物种在水分吸收和水分状况方面相似，这表明在相同土壤水分条件下，根系系统和生理表现具有功能趋同。在不同的群落中，H. ammodendron 在夏季水分提取方面存在差异，这表明该物种在不同的土壤水分条件下，其根系深度具有可塑性。古尔班通古特沙漠的灌木通过不同的根系功能和地上部分生态生理特征，在不同的物种和群落中表现出不同的适应能力。
