Smith Stanley D, Wellington A Bruce, Nachlinger Janet L, Fox Carl A
Ecol Appl. 1991 Feb;1(1):89-97. doi: 10.2307/1941850.
Partial streamflow diversion due to the siting of hydroelectric generating plants may increase the incidence and degree of water stress in riparian vegetation. This study, conducted on Bishop Creek in the eastern Sierra Nevada (California), compared the water relations of riparian vegetation on paired undiverted (natural flow) and diverted (low flow) reaches. Riparian plants on diverted reaches had reduced stomatal conductance and water potential compared to plants on undiverted reaches in a dry year, but not in a high-runoff year. Juvenile plants on diverted reaches had reduced stomatal conductance and lower midday water potentials relative to surrounding mature trees, a trend that was not observed on undiverted reaches. Predawn water potentials were uniformly high in all species and sites, but low midday water potentials (-1.2 to -1.5 MPa) were observed for most species on diverted reaches. Plants on diverted reaches possessed significantly smaller, thicker leaves and a reduced total leaf area relative to trees on streamside reaches. Reduced community leaf area and effective stomatal control of water loss may allow riparian corridors on diverted reaches to retain their canopies in low-runoff years. However, a long-term consequence of streamflow diversion may be selective mortality of juvenile plants because of the elimination of floods and high flows.
由于水力发电厂的选址导致部分水流改道，可能会增加河岸植被水分胁迫的发生率和程度。本研究在加利福尼亚州内华达山脉东部的毕晓普溪进行，比较了成对的未改道（自然水流）河段和改道（低水流）河段上河岸植被的水分关系。在干旱年份，与未改道河段的植物相比，改道河段的河岸植物气孔导度和水势降低，但在高径流年份则没有这种情况。与周围成熟树木相比，改道河段的幼树气孔导度降低，午间水势更低，而在未改道河段未观察到这种趋势。所有物种和地点的黎明前水势均普遍较高，但改道河段的大多数物种午间水势较低（-1.2至-1.5兆帕）。与溪边河段的树木相比，改道河段的植物叶片明显更小、更厚，总叶面积减小。群落叶面积减少以及对水分损失的有效气孔控制，可能使改道河段的河岸走廊在低径流年份保持树冠。然而，水流改道的一个长期后果可能是幼树因洪水和高流量的消失而出现选择性死亡。
