Kolb T E, Hart S C, Amundson R
School of Forestry, College of Ecosystem Science and Management, Northern Arizona University, Flagstaff, AZ 86011-5018, USA.
Tree Physiol. 1997 Mar;17(3):151-60. doi: 10.1093/treephys/17.3.151.
To assess the influence of stream water on leaf gas exchange and water potential in different sized boxelder trees (Acer negundo L.), we compared these characteristics in trees growing beside a perennial stream and a nearby ephemeral stream in a montane-riparian forest in northern Arizona. Patterns of tree water use were quantified by stable isotope analysis (delta(18)O). Physiological characteristics were similar for large and small trees. Similarity between sites in predawn and daytime water potentials and xylem delta(18)O indicated that stream water was not a physiologically important water source. Seasonal and site variations in light-saturated net photosynthetic rate were significantly related to leaf-to-air vapor pressure deficit (r = -0.691) and foliar nitrogen concentration (r = 0.388). Although deep water was the dominant water source, surface soil water was utilized following precipitation, especially by small trees. We conclude that net carbon gain and severity of water stress are only weakly coupled to stream water availability.
为评估溪水对不同大小的梣叶槭树（Acer negundo L.）叶片气体交换和水势的影响，我们比较了生长在亚利桑那州北部山地河岸森林中一条常年溪流和附近一条季节性溪流旁的树木的这些特征。通过稳定同位素分析（δ¹⁸O）对树木的水分利用模式进行了量化。大树和小树的生理特征相似。黎明前和白天水势以及木质部δ¹⁸O在不同地点之间的相似性表明，溪水不是生理上重要的水源。光饱和净光合速率的季节和地点变化与叶 - 气蒸气压亏缺（r = -0.691）和叶片氮浓度（r = 0.388）显著相关。尽管深层水是主要水源，但降雨后表层土壤水也被利用，尤其是小树。我们得出结论，净碳增益和水分胁迫的严重程度与溪水可利用性的关联较弱。
