Data from: Quantifying in situ phenotypic variability in the hydraulic properties of four tree species across their distribution range in Europe

Many studies have reported that hydraulic properties vary considerably between tree species, but little is known about their intraspecific variation and, therefore, their capacity to adapt to a warmer and drier climate. Here, we quantify phenotypic divergence and clinal variation for embolism resistance, hydraulic conductivity and branch growth, in four tree species, two angiosperms (Betula pendula, Populus tremula) and two conifers (Picea abies, Pinus sylvestris), across their latitudinal distribution in Europe. Growth and hydraulic efficiency varied widely within species and between populations. The variability of embolism resistance was in general weaker than that of growth and hydraulic efficiency, and very low for all species but Populus tremula. In addition, no and weak support for a safety vs. efficiency trade-off was observed for the angiosperm and conifer species, respectively. The limited variability of embolism resistance observed here for all species except Populus tremula, suggests that forest populations will unlikely be able to adapt hydraulically to drier conditions through the evolution of embolism resistance.

诸多研究已证实，不同树种间的水力特性（hydraulic properties）差异显著，但目前学界对其种内变异以及适应暖旱气候的能力仍知之甚少。本研究针对欧洲范围内四种树种的纬度分布梯度，量化了其抗栓塞性（embolism resistance）、导水率（hydraulic conductivity）与枝条生长的表型分化（phenotypic divergence）和渐变变异（clinal variation）。供试树种包含2种被子植物（angiosperms）：白桦（Betula pendula）、欧洲山杨（Populus tremula），以及2种裸子植物（conifers）：挪威云杉（Picea abies）、欧洲赤松（Pinus sylvestris）。研究结果显示，枝条生长与水力效率在种内及种群间均存在较大变异；抗栓塞性的变异程度总体弱于生长与水力效率，除欧洲山杨外，其余三个物种的抗栓塞性变异均极低。此外，被子植物与裸子植物分别未观测到、仅观测到微弱的安全-效率权衡（trade-off）关系。本研究中除欧洲山杨外，其余物种的抗栓塞性变异均较为有限，这表明森林种群难以通过演化提升抗栓塞性，进而在水力生理层面适应更为干旱的环境条件。