仅在2007-2016年间,全世界就建造了约8000座大型水坝,增加了超过50,000个以前建造的水坝。这些结构扰乱了河流的非生物和生物成分,但迄今为止,对其影响的了解主要来自下游河流的观测。从水坝上游,然而,回水波动引起沉积物沉积,导致更频繁和更高的谷底淹没,提高地下水位,并改变河道形态和河岸植被。关于这些干扰对河流生物地貌过程的影响知之甚少。在这篇综述中,我将有关回水对河流影响的知识综合为河流系统中回水诱导的非生物-生物相互作用的模型。接下来,该模型用于提出有关温带气候区砾石床河流生物地貌的新假设和研究任务。根据最新的生物地貌见解和方法学方法,在河流横截面中概念化了对水流-沉积物-形态-植被相互作用和反馈的影响,从而可以在未来的研究中进行探索。该模型突出表明,回水引起的河流系统非生物和生物成分的变化会触发它们之间的进一步反馈,即使没有直接的回水影响,也会影响这些成分。回水引起的水动力和泥沙运移变化有利于种子发芽和植物生长,并降低其在洪水期间的死亡率,而且还消除了对长期淹没和密集的细沉积物沉积不耐受的植物。这些影响可能会通过修改生物地貌演替周期的轨迹以及河流走廊中植被-水文形态相互作用的相关区域来改变河流系统的生物地貌结构。具体来说,回水效应可能会促进更稳定的河道形态和河岸植被和动物栖息地的多样化马赛克的发展,与温带地区自由流动的河流形成鲜明对比。
Only in the years 2007-2016 about 8000 large dams were constructed all over the world, adding to >50,000 previously built dams. These structures disturb abiotic and biotic components of rivers, but to date the knowledge of their impacts has been mainly derived from observations of downstream river reaches. Upstream from dams, however, backwater fluctuations induce sediment deposition, cause more frequent and higher valley-floor inundation, increase groundwater level, and change channel morphology and riparian vegetation. Little is known on the effects of these disturbances on the river biogeomorphological processes. In this
review I synthesized knowledge on backwater effects on rivers into a model of backwater-induced abiotic-biotic interactions in the fluvial system. This model is next used to propose new hypotheses and research tasks concerning the
biogeomorphology of gravel-bed rivers in the temperate climatic zone. Implications for flow-sediment-morphology-vegetation interactions and feedbacks are conceptualized in a river cross-section based on recent biogeomorphological insights and methodological approaches allowing to explore them in future studies. The model highlights that backwater-induced changes in abiotic and biotic components of river system trigger further feedbacks between them that additionally influence these components even without a direct backwater influence. Backwater-induced changes in hydrodynamics and sediment transport favour seed germination and growth of plants and decrease their mortality during floods, but also eliminate plants intolerant to prolonged inundation and intensive fine sediment deposition. These impacts may change the biogeomorphical structure of river system by modifying trajectories of biogeomorphic succession cycles and related zones of vegetation-hydromorphology interactions in the river corridor. Specifically, backwater effects may promote the development of more stable channel morphology and a less diverse mosaic of riparian vegetation and animals habitats, contrasting with those occurring in free-flowing rivers of the temperate zone.