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81.
Plant water use plays a crucial part in the soil–plant-atmosphere continuum. However, in karst regions, plants frequently suffer from water shortages due to low soil water storage capacity. Therefore, it is necessary to understand plant water consumption (as determined by sap flow) and seasonal variation of water sources to improve water management in karst catchments. In this study, thermal dissipation probes (TDP), calibrated using empirical equations, were used to measure the sap flow of three typical woody vegetations, including Coriaria nepalensis (sparse-shrub), Toona sinensis (secondary forest) and Populus adenopoda (shrub-grass). Oxygen and hydrogen stable isotopes were used to analyze seasonal variation of plant water sources. The results showed that: (1) T. Sinensis (3.89 ± 3.87 L·day−1) had significantly higher daily sap flow than C. nepalensis (0.33 ± 0.37 L·day−1) and P. adenopoda (0.09 ± 0.12 L·day−1); (2) daily sap flow was closely correlated to photosynthetically active radiation (PAR) and vapour pressure deficit (VPD); (3) over the entire study period, plants mainly used water from the surface soil horizons; and (4) a greater proportion of epikarst water was used for C. nepalensis than by T. sinensis and P. adenopoda over the whole growth stage, and more epikarst water was used in early and mid-growth stages compared to the late stage for the three species. This study contributes to a deeper understanding of the plant water use strategies in karst regions, and is helpful for ecosystem management. 相似文献
82.
土壤水分动态随机模型研究进展 总被引：6，自引：0，他引：6
土壤水是地球表层系统的重要组成,是水文循环的核心,控制着最基本的陆地生态系统格局与过程,是陆地生态系统健康运行的关键。土壤水分动态是研究水文过程和陆地生态系统过程相互作用及反馈必不可少的一环,是一系列水文、气候和生态过程非线性动态作用的结果。因此,土壤水分动态表现为脉动、无规律和随机的过程,对其研究需要随机方法。本文综述了基于土壤水分平衡的土壤水分动态随机模拟的研究进展,主要关注土壤水分动态随机模型的分类比较和适用性。希望能为国内生态水文学的定量研究提供一些参考,促进对水文循环与陆地生态系统之间相互作用更好的理解,最终有助于水资源和生态系统的可持续管理。 相似文献
83.
气候变暖背景下,冰雪、冻土剧烈消融引起的寒区径流成分改变对流域径流演变规律及水循环机制产生了深刻影响。对长江源区各水体水化学特征及其生态水文学研究进行归纳总结,主要进展包括：长江源区的大气降水的水汽来源主要受西风环流和季风环流的控制。冰雪融水的水化学特征受到消融强度、消融持续时间和新雪融水的影响,同时在冰雪融水、积雪以及冰川融水之间可能存在化学离子的交换。冻土层上水受到降水、冰雪融水、地下冰融水等的混合补给,造成水化学特征变化的随机波动。海拔在4 500 m的地区是冻土层上水水化学特征对研究区离子控制源较为敏感的区域。随着海拔高度的增加,降雨直接补给对河水中化学离子的稀释作用逐渐减弱,同时,海拔从4 500 m到5 000 m的降水对河水中离子浓度的稀释效果最大,而在海拔5 000 m以上河水主要受冰雪融水的补给,降水和消融期的变化对河水水化学的影响很小。研究结果为更系统地认知寒区下垫面变化所引起的水文效应提供科学依据,为流域水资源的合理开发利用提供决策依据。 相似文献
84.
Transpiration in Quercus suber trees under shallow water table conditions: the role of soil and groundwater 
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下载免费PDF全文 Clara A. Pinto Nadezhda Nadezhdina Jorge S. David Cathy Kurz‐Besson Maria C. Caldeira Manuel O. Henriques Fernando G. Monteiro João S. Pereira Teresa S. David 《水文研究》2014,28(25):6067-6079
Water is one of the major environmental factors limiting plant growth and survival in the Mediterranean region. Quercus suber L. woodlands occupy vast areas in the Iberian Peninsula, frequently under shallow water table conditions. The relative magnitude of soil and groundwater uptake to supply transpiration is not easy to evaluate under these circumstances. We recently developed a conceptual framework for the functioning of the root system in Q. suber that simulates well tree transpiration, based on two types of root behaviour: shallow connected and deep connected. Although this significantly improved knowledge on the functional traits of Mediterranean Q. suber, the approach has the limitation of requiring root sap flow data, which are seldom available. In this work, we present alternative methodologies to assess if trees are connected to groundwater and to estimate the soil and groundwater contributions to tree transpiration. We provide evidence on the tree unrestricted access to groundwater solely based on meteorological, stem sap flow and leaf water potential data. Using a soil mass balance approach, we estimated the yearly soil and groundwater contributions to tree transpiration: 69.7% and 30.3%, respectively. Groundwater uptake became dominant in the dry summer: 73.2% of tree transpiration. Results reproduce extremely well those derived from root modelling. Because of its simplicity both in formulation and data requirements, our approach is potentially liable to be adapted to other groundwater‐dependent Mediterranean oak sites, where interactions between land use and water resources may be relevant. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
85.
Large urban areas are typically characterized by a mosaic of different land uses, with contrasting mixes of impermeable and permeable surfaces that alter “green” and “blue” water flux partitioning. Understanding water partitioning in such heterogeneous environments is challenging but crucial for maintaining a sustainable water management during future challenges of increasing urbanization and climate warming. Stable isotopes in water have outstanding potential to trace the partitioning of rainfall along different flow paths and identify surface water sources. While isotope studies are an established method in many experimental catchments, surprisingly few studies have been conducted in urban environments. Here, we performed synoptic sampling of isotopes in precipitation, surface water and groundwater across the complex city landscape of Berlin, Germany, for a large -scale overview of the spatio-temporal dynamics of urban water cycling. By integrating stable isotopes of water with other hydrogeochemical tracers we were able to identify contributions of groundwater, surface runoff during storm events and effluent discharge on streams with variable degrees of urbanization. We could also assess the influence of summer evaporation on the larger Spree and Havel rivers and local wetlands during the exceptionally warm and dry summers of 2018 and 2019. Our results demonstrate that using stable isotopes and hydrogeochemical data in urban areas has great potential to improve our understanding of water partitioning in complex, anthropogenically-affected landscapes. This can help to address research priorities needed to tackle future challenges in cities, including the deterioration of water quality and increasing water scarcity driven by climate warming, by improving the understanding of time-variant rainfall-runoff behaviour of urban streams, incorporating field data into ecohydrological models, and better quantifying urban evapotranspiration and groundwater recharge. 相似文献
86.
生态水文学——揭示生态格局和生态过程水文学机制的科学 总被引：19，自引：11，他引：19
水文过程和生态过程的时空耦合机制，是管理水资源和维持生态系统健康运行的关键机理，将成为未来研究的前沿领域，生态水文学是描述生态格局和生态过程的水文学机制的一门科学，文中简要介绍了生态水文学的内涵、基础理论、主要研究内容和研究现状，展望了生态水文学的发展趋势和应用前景，最后结合西部开发和生态环境建设的有关问题，探讨了加强我国生态水文学，特别是干旱区和高寒地区生态水文学研究的必要性和迫切性。 相似文献