Complex climate constraints of upper treeline formation in the Pyrenees
Complex climate constraints of upper treeline formation in the Pyrenees
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DOI：
10.1007/s00468-015-1176-5
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发表时间：
2015-06-01
影响因子：
2.3
通讯作者：
Buentgen, Ulf
中科院分区：
文献类型：
--
作者：
Gonzalez de Andres, Ester;Julio Camarero, J.;Buentgen, Ulf
在比利牛斯山脉，低温和降水稀少限制了树线的径向生长。在中纬度山区，树线形成的气候驱动因素是温度和湿度的变化。高山树线通常是由最低温度阈值引起的，高于该阈值，树木通常不再可能生长。然而，这种全球模式可能无法解释更多的干旱倾向，在那里，降水量的变化也可能影响到山区的生态系统功能和生产力。在这里，我们的目标是确定树木年轮的形成在交错带沿着比利牛斯山脉确实主要取决于温度的手段，也反映了水文气候的变化。比利牛斯山脉树木生长季节的平均持续时间为177天，从5月中旬持续到11月初，相当于平均根区温度为8.2摄氏度。在生长季节的早期和晚期的温度是最关键的山松生长在最高海拔，高于平均春季温度也有助于径向扩大管胞。显示更相似的土壤温度的网站也提出了更相似的长期增长趋势，表明当地条件跟踪区域的影响增长。然而，在夏季更潮湿的条件下，加强生长在树木受到更多的地中海的影响，因此有一个较高的夏季水分亏缺。一个更广泛的角度来看，土壤水分供应在春季和夏季，但是，也影响年轮宽度形成在其他位于中纬度山区分离温带和半干旱生物群落。我们的研究结果建议重新评估纯粹的温度限制的树木线的想法，特别是在中纬度山区，经历水分季节性或降水量随海拔升高而减少。
Key Message In the Pyrenees low temperature and scarce precipitation limit radial growth at treeline. The climatic drivers of treeline formation in mid-latitude mountains are temperature and also moisture variability.Alpine treelines are often induced by a threshold of minimum temperatures above which tree growth is generally not possible anymore. However, this worldwide pattern may not account for more drought-prone tains, where changes in precipitation can also ecosystem functioning and productivity at moun-affect higher elevations. Here, we aim to determine if tree-ring formation in ecotones along the Pyrenees indeed primarily depends on temperature means or also reflects hydroclimatic changes. The mean duration of the growing season at Pyrenean treelines was 177 days, lasting from mid-May to early November, which corresponds to a mean root-zone temperature of 8.2 degrees C. Temperatures during the early and late growing season were most critical for mountain pine growth at highest elevations, and above average spring temperatures also contributed to radial enlargement of tracheids. Sites showing more similar soil temperatures also presented more similar long-term growth trends indicating that local conditions trace regional influences on growth. Nevertheless, more wet conditions in summer enhanced growth at treelines subjected to more Mediterranean influence and therefore having a higher summer water deficit. A broader perspective reveals that soil moisture availability during spring and summer, however, also influence ring width formation at other treelines located in mid-latitude mountains separating temperate and semi-arid biomes. Our results suggest re-evaluating the idea of purely temperature-limited treelines, especially in mid-latitude mountains that experience moisture seasonality or where precipitation decreases with increasing elevation.