Drought response and changing mean sensitivity of European beech close to the dry distribution limit
Drought response and changing mean sensitivity of European beech close to the dry distribution limit
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DOI：
10.1007/s00468-012-0786-4
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发表时间：
2013-02
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影响因子：
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通讯作者：
P. Weber;H. Bugmann;A. R. Pluess;L. Walthert;A. Rigling
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作者：
P. Weber;H. Bugmann;A. R. Pluess;L. Walthert;A. Rigling
欧洲山毛榉(Fagus sylvaticaL.)覆盖了大片区域，主要分布在欧洲的科林山脉和山地山脉，预计在未来几十年里，更干燥、更温暖的气候可能会改变其分布。到目前为止，已经使用各种建模方法预测了海拔高度的变化。然而，我们缺乏关于气候和土壤因素的知识，这些因素控制着山毛榉在其干燥分布极限下的生长和竞争行为。我们应用并进一步发展了树生态学方法来研究不同水分条件下山毛榉的干旱响应和敏感模式。我们比较了来自瑞士山毛榉干燥分布界限附近不同地理区域的三对地点，每对地点包括一个干燥地点和一个中等地点。径向生长在中生地和旱地之间存在差异，中生地的平均年轮宽度是干地的两倍左右。在整个研究期间(1930-2006年)，土壤有效水容量(AWC)最低的地点对干旱的反应最敏感。然而，近年来，AWC较高的地点表现出越来越强的干旱敏感性，即它们对干旱的反应甚至比干旱地点更强烈。敏感度的这种变化与中期站点干旱反应的季节性变化相对应，与过去相比，这三个研究地区的干旱反应在月份中都发生了变化。尽管干旱地区通常比中部地区表现出更多的负指示年，但在中部地区，指标年的频率似乎增加了，也就是说，它们变得更加敏感，特别是在二十世纪的最后四分之一。然而，干旱地区的指示年频率保持相当稳定。这些结果表明，接近其干燥分布极限的山毛榉已经适应了极端条件，而在中等条件下，山毛榉的生长模式必须发生变化。
European beech (Fagus sylvaticaL.) covers a large area mainly in the colline and montane ranges in Europe, and a drier and warmer climate, as expected for the coming decades, is likely to alter its distribution. So far, an altitudinal shift has been projected using a variety of modelling approaches. However, we lack knowledge about the climatic and edaphic factors that control the growth and competitive behaviour of beech at its dry distribution limit. We applied and further developed dendroecological methods to study the drought response and sensitivity pattern of beech at sites with different moisture regimes. We compared three pairs of sites from different geographical regions near the dry distribution limit of beech in Switzerland, consisting of a dry and mesic site each. Radial growth differed between mesic and dry sites, in that average ring-width at mesic sites was around double the width at dry sites. For the whole study period (1930–2006), the sites with the lowest available soil water capacity (AWC) were found to respond most sensitively to drought. However, in recent years, sites with higher AWC have shown increasing drought sensitivity, i.e. they have responded even more strongly to drought than the dry sites. This change in sensitivity corresponds to a seasonal shift in drought response at mesic sites, with a change in the months showing significant drought response in all three studied regions compared with the past. Even though dry sites generally displayed a larger number of negative pointer years than mesic sites, it appears that the frequency of pointer years has increased at mesic sites, i.e. they have become more sensitive particularly in the last quarter of the twentieth century. Yet, the frequency of pointer years at the dry sites has remained fairly constant. These results indicate that beech trees near their dry distribution limit are adapted to extreme conditions already, while changes in the growth patterns of beech under mesic conditions have to be expected.