Data from: Contrasting plant water-use responses to groundwater depth in coastal dune ecosystems

1.Groundwater lowering can produce dramatic changes in the physiological performance and survival of plant species. The impact of decreasing water availability due to climate change and anthropogenic groundwater extraction on coastal dune ecosystems has become of increasing concern, with uncertainties about how vegetation will respond in both the short and long terms. 2.We aimed to evaluate the water‐use responses of different plant functional types to increasing groundwater table depth and how this would affect their physiology in Mediterranean coastal dune systems differing in aridity. 3.We modeled water table depth, quantified the contribution of different soil layers to plant water through Bayesian isotope mixing models, and used a combination of spectral and isotope data to characterize plant ecophysiology. We found that increasing depth to groundwater triggered water uptake adjustments towards deeper soil layers only in the dry season. These adjustments in water sources use were made by conifer trees (Pinus pinea, P. pinaster) and hygrophytic shrubs (Erica scoparia, Salix repens) but not by the xerophytic shrub Corema album. Moreover, we observed a greater use of groundwater under semi‐arid conditions. Accompanying the greater use of water from deep soil layers as a response to increasing groundwater depth, the semi‐arid dimorphic‐rooted conifer tree P. pinea and hygrophytic shrub E. scoparia declined their water content (WI), without implications on photosynthetic parameters, such as chlorophyll content (CHL), photochemical index (PRI) and δ13C. Unexpectedly, under semi‐arid conditions, the shallow‐rooted xerophytic shrub C. album, associated with an absence of water‐sources‐use adjustments, showed a decline in WI, CHL, and PRI with groundwater table lowering. 4.We provide insight into how different species, belonging to different functional types, are acclimating to groundwater changes in a region experiencing climatic drought and a scarcity in groundwater due to anthropogenic exploitation. Greater depth to groundwater combined with limited precipitation can have a significant effect on plants’ water‐sources use and ecophysiology in semi‐arid coastal dune ecosystems.1. 地下水位下降可对植物物种的生理表现与存活产生显著影响。由气候变化与人为地下水开采引发的可利用水资源缩减，对沿海沙丘生态系统的影响日益受到学界关注，当前学界对植被在短期与长期尺度上的响应机制仍存在诸多不确定性。 2. 本研究旨在评估不同植物功能型（plant functional types）对地下水位埋深增加的水分利用响应，以及在干旱程度各异的地中海沿海沙丘生态系统中，该响应如何作用于植物的生理状态。 3. 本研究通过建模模拟地下水位埋深，借助贝叶斯同位素混合模型（Bayesian isotope mixing models）量化不同土层对植物水分的贡献比例，并结合光谱数据与同位素数据表征植物的生态生理特征。研究发现，仅在旱季，地下水位埋深增加会促使植物调整水分吸收策略，转向更深土层获取水分。此类水源利用调整仅发生在针叶树（如Pinus pinea、P. pinaster）与湿生灌木（如Erica scoparia、Salix repens）中，旱生灌木Corema album并未出现该类调整。此外，研究观察到半干旱环境下植物对地下水的利用程度更高。伴随地下水位埋深增加、植物转向深层土层取水的过程，半干旱地区的双型根系针叶树P. pinea与湿生灌木E. scoparia的水分含量（water content, WI）出现下降，但并未对光合参数产生显著影响，包括叶绿素含量（chlorophyll content, CHL）、光化学指数（photochemical index, PRI）以及碳同位素比值δ¹³C。出乎意料的是，在半干旱环境下，浅根系旱生灌木C. album未进行水源利用调整，但其水分含量、叶绿素含量与光化学指数均随地下水位埋深下降出现降低。 4. 本研究为解析不同功能型物种如何适应气候干旱与人为开采导致的地下水短缺所引发的地下水位变化提供了新的认知视角。在半干旱沿海沙丘生态系统中，地下水位埋深增加叠加降水不足，可对植物的水源利用策略与生态生理特征产生显著影响。