地下水埋深和季节性干旱对古尔班通古特沙漠南缘梭梭生理和生长的影响

干旱区因降水稀少，地下水成为荒漠植被重要且稳定的水源。选取古尔班通古特沙漠南缘建群种植物梭梭（Haloxylon ammodendron）为研究对象，通过测量不同地下水埋深（3.45、9.08、10.47、13.27 m和15.91 m）下生长季前期和后期同化枝生理生化指标（黎明水势、正午水势、含水量、氯离子、钠离子、脯氨酸和非结构性碳水化合物）和生长与形态特征（生长速率和胡伯尔值），旨在认识荒漠植物对地下水埋深增加和季节性干旱的响应特征和调节适应机制。结果表明：（1）梭梭应对地下水埋深变化的生理调节对策，是采取先降低后升高黎明前同化枝水势、降低新枝形成期同化枝生长速率、增大胡伯尔值和积累非结构性碳水化合物的策略；（2）梭梭应对生长季大气干旱的生理调节对策，是通过降低黎明前同化枝水势、维持较高胡伯尔值、积累钠离子和消耗淀粉抵御季节性干旱；（3）在大气干旱与地下水水文干旱交互作用下，梭梭是采取降低正午同化枝水势、维持较高的同化枝含水量和积累可溶性糖的生态策略。综上所述，梭梭在响应地下水水文干旱和季节性大气干旱的生理特征间存在差异。研究结果丰富了水文和大气干旱对梭梭生理和生长影响的认知，可以为基于地下水资源管理的干旱区荒漠植被保育提供参考。

Effects of groundwater depth and seasonal drought on the physiology and growth of Haloxylon ammodendron at the southern edge of Gurbantonggut Desert

Groundwater is an important and stable water source for desert vegetation due to the scarcity of precipitation in arid areas. Currently, anthropogenic withdraw of groundwater and climatic drought further limits the water availability for phreatophytic vegetation in arid regions and results in the decline of native vegetation. However, how phreatophytic plant response and adaptation to reduced water availability along the groundwater depth gradient are not clear. Haloxylon ammodendron was widely distributed in northwest arid zone of China and played an important role in desertification control. Groundwater was an important water resource for H. ammodendron. The declining groundwater depth has caused the partially decline even death of H. ammodendron in their native distribution area. In this study, we selected H. ammodendron, one of the main constructive species, at the southern edge of Gurbantonggut Desert as the taget species. In order to understand the response characteristics and regulatory adaptation mechanisms of desert plants to increasing groundwater depth and seasonal drought, we measured physiological and biochemical traits (including predawn water potential, midday water potential, water content, sodium ion, chloride ion, proline and non-structural carbohydrates), growth and morphological characteristics (including growth rate and Huber value) of assimilation branches in the early and late growing season under different groundwater depths (3.45, 9.08, 10.47, 13.27 and 15.91 m). The results showed that:(1) H. ammodendron adopted the strategy of first decreasing and then increasing predawn assimilation branch water potential, decreasing assimilation branch growth rate during new branch formation, increasing the Huber value and accumulating non-structural carbohydrates in response to increase in groundwater depth. (2) With the prolonged drought, H. ammodendron reduced predawn assimilation branch water potential, maintained high Huber values, accumulated sodium ions and consumed starch to resist seasonal drought during the growing season. (3) Reducing midday assimilation branch water potential, maintaining high assimilation branch water content and accumulating soluble sugars are ecological strategies in H. ammodendron to acclimate atmospheric and hydrological drought. In summary, there are differences in the physiological characteristics of H. ammodendron in response to groundwater hydrological drought and seasonally atmospheric drought. The results of the study enriched the knowledge of the effects of hydrological and atmospheric drought on the physiology and growth of H. ammodendron, and provided a reference for the conservation of desert vegetation based on groundwater resource management in arid areas.