Irrigated urban trees exhibit greater functional trait plasticity compared to natural stand analogs

           Urbanization creates novel ecosystems comprised of species assemblages and environments with no natural analog. Moreover, irrigation can alter plant function compared to non-irrigated systems. However, the irrigations capacity to alter functional trait patterns across multiple species is unknown but may be important for the dynamics of urban ecosystems. We evaluated the hypothesis that urban irrigation influences plasticity in functional traits by measuring carbon-gain and water-use traits of 30 tree species planted in southern California, USA spanning a coastal-to-desert gradient. Tree species respond to irrigation through increasing the carbon-gain trait relationship of leaf nitrogen per specific leaf area compared to their native habitat. Moreover, most species shift to a water-use strategy of greater water loss through stomata when planted in irrigated desert-like environments compared to coastal environments, implying that irrigated species capitalize on increased water...城市化会催生由物种组合与无自然类似物的环境构成的新型生态系统。此外，与非灌溉生态系统相比，灌溉措施会改变植物的功能表现。然而，目前尚不明确灌溉能否改变多物种间的功能性状（functional trait）格局，但该过程或许对城市生态系统的动态变化至关重要。我们针对"城市灌溉会影响功能性状（functional trait）可塑性"这一假说开展了验证实验：对美国加利福尼亚州南部沿海至沙漠梯度下种植的30个树种，测量了其碳增益性状与水分利用性状。研究发现，与各树种的原生栖息地相比，灌溉会使树种的"单位比叶面积（specific leaf area）的叶片氮含量"这一碳增益性状关系显著增强，以此响应灌溉环境。此外，与种植在沿海环境中的树种相比，多数树种在类沙漠的灌溉环境中会转向通过气孔（stomata）散失更多水分的水分利用策略，这表明灌溉条件下的物种会利用增加的水分……