Ecophysiology of riparian cottonwoods: stream flow dependency, water relations and restoration.
Ecophysiology of riparian cottonwoods: stream flow dependency, water relations and restoration.
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DOI：
10.1093/treephys/23.16.1113
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发表时间：
2003-11
期刊：
影响因子：
4
通讯作者：
S. Rood;J. Braatne;F. Hughes
中科院分区：
文献类型：
--
作者：
S. Rood;J. Braatne;F. Hughes
三叶杨（Populus spp.）适应整个北半球的河岸或洪泛区；它们也被用作快速生长的杂交杨树的亲本。我们回顾了最近对北美本土杨树杨小杨 (Populus angustifolia James)、香脂杨 (P. balsamifera L.)、三角杨 (P. deltoides Marsh.)、弗里蒙特杨 (P. fremontii S. Watson) 和毛果杨 (P. trichocarpa T. & G.) 以及欧洲杨 (P. nigra L.) 的生态生理学研究。物种和杂交品种内部和之间存在变异；然而，所有河岸杨树都依赖于与溪流水相关的浅层冲积地下水，特别是在半干旱地区。这一结论是基于对它们的自然发生、河流筑坝和脱水（除水）后的衰退、水关系、木质部水的同位素组成以及响应灌溉水的输送而增加流量后沿先前贫瘠的自然河道建立白杨的研究。当冲积地下水因河流脱水或抽取地下水而枯竭时，河岸三叶杨会表现出干旱胁迫反应，包括气孔关闭、蒸腾作用和光合作用减少、13C组成改变、黎明前和中午水势降低以及木质部空化。这些生理反应伴随着形态反应，包括芽生长减少、根生长改变、枝条牺牲和树冠枯死。严重时会导致死亡。例如，爱达荷州大失落河辫状河道严重脱水，导致窄叶杨 (P. angustifolia) 和邻近的沙洲柳 (Salix exigua Nutt.) 在 5 年内死亡，而附近的河道沿岸林地则蓬勃发展。三叶杨的保护和恢复将依赖于提供满足生存、生长和繁殖的生态生理要求的河流水流状况。
Cottonwoods (Populus spp.) are adapted to riparian or floodplain zones throughout the Northern Hemisphere; they are also used as parents for fast-growing hybrid poplars. We review recent ecophysiological studies of the native cottonwoods Populus angustifolia James, P. balsamifera L., P. deltoides Marsh., P. fremontii S. Watson and P. trichocarpa T. & G. in North America, and P. nigra L. in Europe. Variation exists within and across species and hybrids; however, all riparian cottonwoods are dependent on shallow alluvial groundwater that is linked to stream water, particularly in semi-arid regions. This conclusion is based on studies of their natural occurrence, decline following river damming and dewatering (water removal), water relations, isotopic composition of xylem water, and by the establishment of cottonwoods along formerly barren natural channels after flow augmentation in response to the conveyance of irrigation water. When alluvial groundwater is depleted as a result of river dewatering or groundwater pumping, riparian cottonwoods exhibit drought-stress responses including stomatal closure and reduced transpiration and photosynthesis, altered 13C composition, reduced predawn and midday water potentials, and xylem cavitation. These physiological responses are accompanied by morphological responses including reduced shoot growth, altered root growth, branch sacrifice and crown die-back. In severe cases, mortality occurs. For example, severe dewatering of channels of the braided Big Lost River in Idaho led to mortality of the narrowleaf cottonwood, P. angustifolia, and adjacent sandbar willows, Salix exigua Nutt., within 5 years, whereas riparian woodlands thrived along flowing channels nearby. The conservation and restoration of cottonwoods will rely on the provision of river flow regimes that satisfy these ecophysiological requirements for survival, growth and reproduction.