Abstract Water availability is the most important factor for the vitality of forest ecosystems, especially in dry environments. The Mediterranean region is one of the hotspots of future climate change; therefore, data on the water cycle are urgently needed. We measured oxygen isotope compositions in creek water, precipitation, stem water, needle water, and tree-ring cellulose over one growing season to establish the relationship between isotope compositions in different compartments along a fractionation pathway. We analyzed plant material from pine trees (Pinus nigra J.F. Arn subsp. laricio (Poiret) Maire var. Corsicana Hyl. and Pinus pinaster Aiton) at five locations along an elevation gradient from sea level to 1600 m asl. We traced back the oxygen isotope composition from source to sink in tree-ring cellulose in order to identify the water sources used by the trees, and to quantify the extent of isotope fractionation processes. Our results showed that the trees used different water sources over the course of the growing season, ranging from winter snow meltwater to summer precipitation at higher sites and deep soil water reservoirs at coastal sites. Needle water enrichment was higher at higher elevation sites than at coastal locations, highlighting the importance of site-specific climate conditions on the isotopic composition values in tree material. Water availability seems to be most restricted at the highest site, making these trees most vulnerable to climate change.

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来自δ18O的地中海生态系统中沿海拔梯度的松树水源季节和空间变化的初步迹象

摘要 水资源可用性是森林生态系统活力的最重要因素，尤其是在干旱环境中。地中海地区是未来气候变化的热点之一；因此，迫切需要有关水循环的数据。我们在一个生长季节测量了溪水、降水、茎水、针状水和树轮纤维素中的氧同位素组成，以确定沿分馏路径不同隔室中同位素组成之间的关系。我们分析了沿海拔梯度从海平面到 1600 m asl 的五个位置的松树（Pinus nigra JF Arn subsp. laricio (Poiret) Maire var. Corsicana Hyl. 和 Pinus pinaster Aiton）的植物材料。我们追溯了树轮纤维素中从源到汇的氧同位素组成，以确定树木使用的水源，并量化同位素分馏过程的程度。我们的结果表明，树木在整个生长季节使用不同的水源，从冬季雪融水到较高地点的夏季降水和沿海地点的深层土壤水库。高海拔地点的针状水富集度高于沿海地点，突出了地点特定气候条件对树木材料同位素组成值的重要性。最高点的可用水量似乎最受限制，使这些树木最容易受到气候变化的影响。我们的结果表明，树木在整个生长季节使用不同的水源，从冬季雪融水到较高地点的夏季降水和沿海地点的深层土壤水库。高海拔地点的针状水富集度高于沿海地点，突出了地点特定气候条件对树木材料同位素组成值的重要性。最高点的可用水量似乎最受限制，使这些树木最容易受到气候变化的影响。我们的结果表明，树木在整个生长季节使用不同的水源，从冬季雪融水到较高地点的夏季降水和沿海地点的深层土壤水库。高海拔地点的针状水富集度高于沿海地点，突出了地点特定气候条件对树木材料同位素组成值的重要性。最高点的可用水量似乎最受限制，使这些树木最容易受到气候变化的影响。强调特定地点的气候条件对树木材料中同位素组成值的重要性。最高点的可用水量似乎最受限制，使这些树木最容易受到气候变化的影响。强调特定地点的气候条件对树木材料中同位素组成值的重要性。最高点的可用水量似乎最受限制，使这些树木最容易受到气候变化的影响。