Comparative study of diurnal and nocturnal sap flow of Quercus ilex and Phillyrea latifolia in a Mediterranean holm oak forest in Prades (Catalonia, NE Spain)
Comparative study of diurnal and nocturnal sap flow of Quercus ilex and Phillyrea latifolia in a Mediterranean holm oak forest in Prades (Catalonia, NE Spain)
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DOI：
10.1007/s00468-012-0741-4
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发表时间：
2012-10-01
影响因子：
2.3
通讯作者：
Penuelas, Josep
中科院分区：
文献类型：
--
作者：
Barbeta, Adria;Ogaya, Roma;Penuelas, Josep
干旱是地中海生态系统的周期性干扰，气候变化模型预测干旱的频率和严重程度将会增加。一些实验和观察研究表明，共生物种可能会以不同的策略应对干旱条件并表现出不同的反应。在这里，我们研究了树液流对干旱的反应，以解释在普拉德斯霍尔姆橡树林（西班牙东北部）观察到的栎属冬青和大叶麻栎的生长和死亡率差异。我们测量了这些物种的液流，并比较了它们的昼间、夜间和季节模式及其与环境变量的关系。这两个物种都描述了性质相似的日常模式，无论是白天还是夜间。除秋季和春季外，宽叶松的汁液流速显着较高。宽叶松对土壤湿度较为敏感。在这两个物种中都检测到了夜间液流，没有显着差异，并且在大多数采样的夜晚，从凌晨 3 点到黎明，每小时的液流逐渐增加。我们的结果表明，P. latifolia 更好地适应了该地点，因为它可以更好地利用湿润期，同时在干旱期保持较高的树液流速。结合之前在同一地点进行的生态生理学研究，可以推断，在其较干燥的分布限制下，冬青树相对于其他物种（如大叶冬青树）处于不利地位，因为后者能够更好地应对已经出现的日益增加的干旱条件，并进一步预测地中海生态系统的干旱条件。我们的结果还表明，夜间液流与这两个物种的个体水损失有关，因为它们可能高达每日液流的 35-40%。需要对这种夜间液流的潜在机制进行进一步研究，因为它还可能增强清晨二氧化碳的固定或对叶子的养分供应。
Droughts are a cyclical disturbance in Mediterranean ecosystems and climate change models forecast an increase of their frequency and severity. Some experimental and observational studies have shown that co-occurring species may cope with drier conditions with different strategies and present different responses. Here, we investigate sap flow response to drought in order to explain the observed differential growth and mortality of Quercus ilex and Phillyrea latifolia at Prades Holm oak forest (NE Spain). We measured sap flow of these species and compared their diurnal, nocturnal and seasonal patterns and their relationship with environmental variables. Both species described qualitatively similar daily patterns, either during daylight or night. Sap flow rates were significantly higher in P. latifolia except in autumn and spring. P. latifolia was more sensitive to soil moisture. Nocturnal sap flow was detected in both species with no significant differences and hourly rates suffered a progressive increase from 3 a.m. to dawn in most sampled nights. Our results indicate a better adaptation of P. latifolia to this site as it can take better advantage of wet periods while maintaining higher sap flow rates during dry periods. Along with previous ecophysiological studies at the same location it may be inferred that at its drier distributional limit Q. ilex would be at disadvantage with respect to other species like P. latifolia, as the latter would cope better with increasing xeric conditions already occurring and further predicted for Mediterranean ecosystems. Our results also show nocturnal sap flow to be relevant in individual water losses in these two species as they can be up to 35-40 % of daily sap flow. Further research on the underlying mechanisms of this nocturnal sap flow is required since it may also enhance early morning CO2 fixation or nutrient supply to leaves.