Water-use strategies of temperate tree species

This dataset represents the data shown in the Figures 2 - 7 of Walthert et al. (2024): Coordination between degree of isohydricity and depth of root water uptake in temperate tree species. Science of the Total Environment (https://doi.org/10.1016/j.scitotenv.2024.174346). A detailed methodical description of the data can be found in the Methods section of the paper. Abstract In an increasingly dry environment, it is crucial to understand how tree species use soil water and cope with drought. However, there is still a knowledge gap regarding the relationships between species-specific stomatal behaviour, spatial root distribution, and root water uptake (RWU) dynamics. Our study aimed to investigate above- and below-ground aspects of water use during soil drying periods in four temperate tree species that differ in stomatal behaviour: two isohydric tracheid-bearing conifers, Scots pine and Norway spruce, and two more anisohydric deciduous species, the diffuse-porous European beech, and the ring-porous Downy oak. From 2015 to 2020, soil-tree-atmosphere-continuum parameters were measured for each species in monospecific forests where trees had no access to groundwater. The hourly time series included data on air temperature, vapour pressure deficit, soil water potential, soil hydraulic conductivity, and RWU to a depth of 2 m. Analysis of drought responses included data on stem radius, leaf water potential, estimated osmotically active compounds, and drought damage. Our study reveals an inherent coordination between stomatal regulation, fine root distribution and water uptake. Compared to conifers, the more anisohydric water use of oak and beech was associated with less strict stomatal closure, greater investment in deep roots, four times higher maximum RWU, a shift of RWU to deeper soil layers as the topsoil dried, and a more pronounced soil drying below 1 m depth. Soil hydraulic conductivity started to limit RWU when values fell below 10-3 to 10-5 cm/d, depending on the soil. As drought progressed, oak and beech may also have benefited from their leaf osmoregulatory capacity, but at the cost of xylem embolism with around 50% loss of hydraulic conductivity when soil water potential dropped below -1.25 MPa. Consideration of species-specific water use is crucial for forest management and vegetation modelling to improve forest resilience to drought.本数据集包含Walthert等人（2024）发表于《整体环境科学》（Science of the Total Environment，DOI: 10.1016/j.scitotenv.2024.174346）的论文《温带树种等渗性程度与根系吸水深度的协同关系》中的图2至图7所展示的数据。该数据集的详细方法学说明可参见该论文的方法部分。 摘要 在日益干旱的全球环境中，阐明树种如何利用土壤水分并应对干旱胁迫至关重要。然而，当前在树种特异性气孔行为、根系空间分布与根系吸水（root water uptake, RWU）动态之间的关联机制上仍存在认知空白。 本研究针对4种气孔行为存在差异的温带树种，探究了土壤干旱期内地上与地下的水分利用特征：2种具有管胞的等渗性针叶树种——欧洲赤松（Scots pine）与挪威云杉（Norway spruce），以及2种更偏向异渗性的落叶树种——散孔材的欧洲山毛榉与环孔材的夏栎（Downy oak）。2015年至2020年间，研究人员在无地下水补给的纯林样地中，针对每个树种测定了土壤-树木-大气连续体（soil-tree-atmosphere-continuum, STAC）相关参数。每小时时序数据集涵盖了气温、水汽压差、土壤水势、土壤导水率以及2米深度内的根系吸水数据。干旱响应分析所用数据则包括茎半径、叶片水势、渗透活性物质估算值以及干旱损伤程度数据。 本研究揭示了气孔调控、细根分布与水分吸收之间存在内在协同关系。相较于针叶树种，栎树与山毛榉更为显著的异渗性水分利用策略表现为：气孔关闭更为宽松、深根投入更多、最大根系吸水速率提升至4倍、随着表层土壤干涸根系吸水向深层土壤转移，以及1米以下土层的土壤干燥程度更为显著。土壤导水率在降至10⁻³至10⁻⁵ cm/d（依土壤类型而异）时，便开始对根系吸水形成限制。随着干旱加剧，栎树与山毛榉或可借助叶片的渗透调节能力获益，但这会以木质部栓塞为代价——当土壤水势降至-1.25 MPa以下时，其导水率损失可达约50%。考虑树种特异性的水分利用策略，对于提升森林应对干旱恢复力的森林管理与植被建模而言至关重要。