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. 地下水位下降会显著改变植物物种的生理表现与存活状况。气候变化与人类地下水抽取导致的可利用水资源减少，对沿海沙丘生态系统的影响愈发受到学界关注，但目前仍无法确定植被在短期与长期内将如何响应此类变化。
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，并解析该过程在干旱程度各异的地中海沿海沙丘系统中对植物生理的影响。
3. 本研究通过构建地下水位埋深模型、利用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，并结合光谱与同位素数据表征植物生态生理学特征。研究发现，仅在旱季，地下水位埋深增加才会促使植物调整水分吸收策略，转向更深土层获取水分。此类水源利用策略调整仅见于针叶树（如Pinus pinea、P. pinaster）与湿生灌木（如Erica scoparia、Salix repens），旱生灌木Corema album并未进行此类调整。此外，研究发现在半干旱环境下，植物对地下水的利用程度更高。随着植物为响应地下水位埋深增加而更多利用深层土壤水分，半干旱环境下具有二态根系的针叶树Pinus pinea与湿生灌木Erica scoparia的水分含量（water content, WI）出现下降，但叶绿素含量（chlorophyll content, CHL）、光化学指数（photochemical index, PRI）及δ¹³C等光合参数并未受到显著影响。出乎意料的是，在半干旱环境下，浅根旱生灌木C. album（未进行水源利用策略调整）的水分含量、叶绿素含量及光化学指数均随地下水位埋深增加而出现下降。
4. 本研究揭示了隶属于不同功能型的各类物种，如何在遭受气候干旱且因人类开发导致地下水匮乏的区域中适应地下水位变化。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，会对植物的水源利用策略与生态生理特征产生显著影响。