Lengyel Tegan E, Karavan-Jahromi Iman, Driscoll Avery W, Ehleringer James R
School of Biological Sciences University of Utah Salt Lake City Utah USA.
Department of Soil and Crop Sciences Colorado State University Fort Collins Colorado USA.
Plant Environ Interact. 2025 Aug 28;6(4):e70080. doi: 10.1002/pei3.70080. eCollection 2025 Aug.
This study assessed variations in leaf intrinsic water use efficiency (iWUE) and δN values among , a genus of drought-deciduous shrubs distributed across arid regions of southwestern North America between 1972 and 1980 when climates were cooler than today. We hypothesized that geographical variations in climate would significantly influence iWUE, a response to water-related climate constraints, and δN values, a proxy for the balance between N fixation and denitrification. Leaf samples were collected from six species of across 78 sites representing the genus range. The δN and δC values of these samples were measured and analyzed to identify drivers of spatial variability. Significant variations among iWUE and δN values were observed as a function of climate, along a spring-summer precipitation gradient. Precipitation and vapor pressure deficit (VPD) were significant drivers of variations in iWUE values, with iWUE increasing with VPD and/or decreasing precipitation, as would be predicted based on water-related constraints on leaf gas exchange. Climate values were significant drivers of variations in δN values, with lower δN values occurring in cooler temperature, spring-growing plants (northern latitudes) than in warmer summer-growing plants (southern latitudes). leaf iWUE and δN observations suggest few, if any, species-specific differences; but more likely that there is high plasticity in these values driven by variations in climate.
本研究评估了1972年至1980年期间，一种分布于北美西南部干旱地区的旱落叶灌木属植物叶片内在水分利用效率（iWUE）和δN值的变化情况，当时的气候比现在更凉爽。我们假设气候的地理差异会显著影响iWUE（对与水相关的气候限制的一种响应）和δN值（固氮与反硝化平衡的一个指标）。从代表该属分布范围的78个地点的六种植物中采集了叶片样本。对这些样本的δN和δC值进行了测量和分析，以确定空间变异性的驱动因素。沿着春夏降水梯度观察到，iWUE和δN值随气候存在显著变化。降水和水汽压亏缺（VPD）是iWUE值变化的重要驱动因素，正如基于叶片气体交换的与水相关的限制所预测的那样，iWUE随VPD增加和/或降水减少而增加。气候值是δN值变化的重要驱动因素，较凉爽温度下春季生长的植物（北纬地区）的δN值低于较温暖夏季生长的植物（南纬地区）。该属植物叶片iWUE和δN的观测结果表明，即使有物种特异性差异也很少；但更有可能的是，这些值存在高度可塑性，由气候差异驱动。
