Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark.
Nat Ecol Evol. 2018 Sep;2(9):1428-1435. doi: 10.1038/s41559-018-0630-3. Epub 2018 Aug 13.
Plant water storage is fundamental to the functioning of terrestrial ecosystems by participating in plant metabolism, nutrient and sugar transport, and maintenance of the integrity of the hydraulic system of the plant. However, a global view of the size and dynamics of the water pools stored in plant tissues is still lacking. Here, we report global patterns of seasonal variations in ecosystem-scale plant water storage and their relationship with leaf phenology, based on space-borne measurements of L-band vegetation optical depth. We find that seasonal variations in plant water storage are highly synchronous with leaf phenology for the boreal and temperate forests, but asynchronous for the tropical woodlands, where the seasonal development of plant water storage lags behind leaf area by up to 180 days. Contrasting patterns of the time lag between plant water storage and terrestrial groundwater storage are also evident in these ecosystems. A comparison of the water cycle components in seasonally dry tropical woodlands highlights the buffering effect of plant water storage on the seasonal dynamics of water supply and demand. Our results offer insights into ecosystem-scale plant water relations globally and provide a basis for an improved parameterization of eco-hydrological and Earth system models.
植物蓄水通过参与植物代谢、养分和糖分运输以及维持植物水力系统的完整性，对陆地生态系统的功能至关重要。然而，我们仍然缺乏对植物组织中储存的水储量的大小和动态的全球观点。在这里，我们基于 L 波段植被光学深度的卫星测量，报告了生态系统尺度植物蓄水的季节性变化及其与叶物候关系的全球模式。我们发现，对于北方森林和温带森林，植物蓄水的季节性变化与叶物候高度同步，但对于热带林地则不同步，植物蓄水的季节性发展滞后于叶面积长达 180 天。在这些生态系统中，植物蓄水与陆地地下水蓄水之间的时间滞后模式也存在明显差异。对季节性干旱热带林地水循环组成部分的比较突出了植物蓄水对供水和需水季节性动态的缓冲作用。我们的结果提供了对全球生态系统尺度植物水分关系的深入了解，并为改进生态水文学和地球系统模型的参数化提供了基础。
