Sparks J P, Ehleringer J R
Stable Isotope Ratio Facility for Environmental Research, Department of Biology, University of Utah, Salt Lake City, UT 84112, USA, , , , , , US.
Oecologia. 1997 Feb;109(3):362-367. doi: 10.1007/s004420050094.
Leaf carbon isotope discrimination (Δ), seasonal estimates of the leaf-to-air water vapor gradient on a molar basis (ω), and leaf nitrogen contents were examined in three riparian tree species (Populus fremontii, P. angustifolia, and Salix exigua) along elevational transects in northern and southern Utah USA (1500-2670 m and 600-1820 m elevational gradients, respectively). The ω values decreased with elevation for all species along transects. Plants growing at higher elevations exhibited lower Δ values than plants at lower elevations (P. fremontii, 22.9‰ and 19.5‰, respectively; P. angustifolia, 23.2‰ and 19.2‰, respectively; and S.␣exigua, 21.1‰ and 19.1‰, respectively). Leaf nitrogen content increased with elevation for all species, suggesting that photosynthetic capacity at a given intercellular carbon dioxide concentration was greater at higher elevations. Leaf Δ and nitrogen content values were highly correlated, implying that leaves with higher photosynthetic capacities also had lower intercellular carbon dioxide concentrations. No significant interannual differences were detected in carbon isotope discrimination.
在美国犹他州北部和南部沿海拔梯度（分别为1500 - 2670米和600 - 1820米海拔梯度）对三种河岸树种（弗里蒙特杨、窄叶杨和矮柳）的叶片碳同位素分辨率（Δ）、基于摩尔的叶片与大气水汽梯度的季节性估计值（ω）以及叶片氮含量进行了研究。沿样带所有物种的ω值均随海拔降低。生长在较高海拔的植物比生长在较低海拔的植物表现出更低的Δ值（弗里蒙特杨分别为22.9‰和19.5‰；窄叶杨分别为23.2‰和19.2‰；矮柳分别为21.1‰和19.1‰）。所有物种的叶片氮含量均随海拔升高而增加，这表明在给定的细胞间二氧化碳浓度下，较高海拔处的光合能力更强。叶片Δ值和氮含量值高度相关，这意味着具有较高光合能力的叶片其细胞间二氧化碳浓度也较低。在碳同位素分辨率方面未检测到显著的年际差异。
