Inter-specific transpiration differences between aspen, spruce, and pine in a sky-island ecosystem of the North American Great Basin
Inter-specific transpiration differences between aspen, spruce, and pine in a sky-island ecosystem of the North American Great Basin
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DOI：
10.1016/j.foreco.2021.119157
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发表时间：
2021-07
影响因子：
3.7
通讯作者：
Xinsheng Liu;F. Biondi
中科院分区：
文献类型：
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作者：
Xinsheng Liu;F. Biondi
由于气候变化加剧了土壤干旱，半干旱森林今后可能面临挑战。由于土壤干燥导致的树木死亡率和风险在共存物种之间可能存在很大差异，因此需要评估树木反应的种间差异，以设计专门针对标志性天岛生态系统的科学驱动的最佳管理策略。我们连续五年（2014-2018年）在北美大盆地的一个偏远的高海拔地区分析了颤白杨（Populus tremuloides），Engelmann云杉（Picea engelmannii）和软松（Pinus flexilis）的液流。我们的研究结果揭示了物种特异性的树干液流下降的土壤水分的反应。对于震颤的白杨，多年的树液流轨迹模仿生长季节土壤水分的枯竭。2017年充足的冷季降水减少了夏季干旱对Engelmann云杉和软松液流的影响，表明这两种针叶树可以比落叶树种利用更深的土壤水库。由于种特异性蒸腾响应土壤干旱是由移动降水制度，我们的研究结果表明生态位分区共存树种之间的根际。此外，云杉和松树迅速下调冠层电导与土壤水分有效性的降低，而白杨冠层电导是不敏感的土壤干燥。这种生理特性允许颤白杨在生长条件有利时最大限度地获取资源，但在土壤干燥下造成水力失效和随后死亡的风险。总的来说，我们发现对比水文生态位和生理策略共存树种在半干旱，高海拔生态系统。我们还强调长期、实地观察的价值，以确定偏远山区物种对环境变化的敏感性。
Semiarid forests may face future challenges because of climate change-exacerbated soil droughts. Because the risk and rate of tree mortality from soil drying can vary widely between co-occurring species, inter-specific differences in tree response need to be evaluated for designing science-driven best-management strategies specifically tailored to iconic sky-island ecosystems. We analyzed sap flow of quaking aspen (Populus tremuloides), Engelmann spruce (Picea engelmannii), and limber pine (Pinus flexilis) for five consecutive years (2014–2018) at a remote, high-elevation site in the North American Great Basin. Our results revealed species-specific responses of sap flow to declining soil moisture. For quaking aspen, multi-year sap-flow trajectories mimicked growing-season depletion of soil moisture. Ample cool-season precipitation in 2017 diminished the summer drought impact on sap flow of Engelmann spruce and limber pine, indicating that the two conifers could tap a deeper soil water reservoir than the deciduous species. Since species-specific transpiration response to soil droughts was driven by shifting precipitation regimes, our findings suggest niche partitioning in the rhizosphere among coexisting tree species. In addition, spruce and pine rapidly downregulated canopy conductance with decreasing soil water availability, whereas aspen canopy conductance was insensitive to soil drying. This physiological characteristic allows quaking aspen to maximize resource acquisition when growing conditions are favorable, but poses a risk of hydraulic failure and subsequent mortality under soil drying. Overall, we found contrasting hydrological niches and physiological strategies between co-occurring tree species in semiarid, high-elevation ecosystems. We also emphasize the value of long-term, in-situ observations to determine species-specific susceptibility to environmental changes in remote mountain areas.