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土壤-根系统水分再分配：土壤-植物-大气连续体中的一个小通路

期刊名称：植物生态学报, 31(5),794-803
时间：0
分类：S152.7[农业科学—土壤学;农业科学—农业基础科学]
作者机构：[1]北京师范大学资源学院,环境演变与自然灾害教育部重点实验室,北京100875, [2]中国科学院地理科学与资源研究所,北京100101, [3]中国科学院研究生院,北京100049
相关基金：国家自然科学基金重大项目（30590384）感谢郭大立博士和张林博士对本文提出的有益建议
相关项目：我国主要陆地生态系统对全球变化的响应和适应性样带研究

关键词：水分提升, 水分下传, 土壤水势, 土壤水分含量, 木质部液流, 水流导度, 植物生理生态, 生态水文, hydraulic lift, hydraulic descent, soil water potential, soil water content, sap flow, hydraulic conductance, plant physiological ecology, ecohydrology

中文摘要：

吸收和传导水分一直被视为植物根系最主要的功能之一，而人们对根系在某些情况下还可以向土壤释放水分的事实及其对植物生长和生态系统功能的影响了解得还很不充分，尽管这样的证据由来已久。土壤一根系统水分再分配（Hydraulic redistribution，HR）是近加年间被发现和证实的，指水分从土壤中较湿的部分经由植物的根系传导而运动到土壤中较干的部分，通常发生在蒸腾减弱的夜间，可以沿水势梯度下降的方向而在不同土层间向上向下或侧向运动。HR研究揭示了土壤．植物一大气连续体中有时会存在土壤一根一土壤的水流小通路，细化了土壤．根系统中水分储存和运输的时空动态和机制。土壤水分状况的连续监测、根木质部液流测量、稳定性同位素技术的使用构成了HR实验研究的三大手段。当土壤中深层水分充足的时候，HR可以提高根系吸收和传导水分的效率，有利于植物充分利用资源，延长了浅层土壤的水分可利用期，有利于维持植物组织的生理活性和水流传导；旱季后降水来临的时候，HR可以将一部分降水转移到深层土壤，增加了可利用性水分的总量。对于干旱半干旱的沙地和草原、季节性干旱的森林等类型，HR过程可能对生态系统水分循环产生重要影响。有必要在国内针对这些生态系统展开深入的实验研究，同时探索将HR过程适当结合到生态系统模型和水文模型中，从而更准确地研究和预测群落内植物水分关系和生态系统水分动态。此外，结合农林设计、植被恢复、生态需水量估算和农业节水等方面进行的HR研究也值得深入探索。

英文摘要：

Water uptake is generally accepted as the most important function of plant roots, while the fact that roots can also release water to soil and its ecological consequences and significance to ecosystem function are not well understood. Studies in the past 20 years confirmed the existence of hydraulic redistribution （HR）, which describes the passive movement of water from moist soil to dry soil via roots when transpiration ceases （ usually at night）. The direction of HR can be upward, downward or lateral in soil along water potential gradients. Because this newly recognized small cycle of soil-root-soil exists within the Soil-Plant-Atmosphere Continuum （SPAC）, the mechanism of dynamic movement and storage in the soil-root system has interested many functional ecologists. Continuous measurement of soil water potentials or contents and root sap flow and the use of stable isotopes techniques have been extensively used in HR research. HR acts as a good feedback mechanism between plant water status and soil water dynamics. When deep soil water is plentiful, HR could enhance the efficiency of water uptake via roots, helping plants to make full use of water to improve transpiration and photosynthesis rates and hence maintain physiological function and hydraulic conductivity of the SPAC system. When rainfall comes after the dry season, more precipitation could be transferred to deep soil as an effective storage because of HR, thus increasing availability of rainfall to plant growth. HR was significant for water flux in some ecosystems, for example arid-semiarid sandlands and grasslands, as well as seasonal dry forests. Experiments on HR in Chinese ecosystems are expected or are already underway. On the other hand, integrating HR into ecosystem and hydrology models to study the water relationships between neighboring plants and predict the dynamics of ecosystems with HR is also important. The implications of HR to designing agro-forestry, vegetation recovery, calculating ecological water demand and water conserv

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