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Drought and cold spells trigger dieback of temperate oak and beech forests in northern Spain
Dendrochronologia ( IF 3 ) Pub Date : 2021-01-20 , DOI: 10.1016/j.dendro.2021.125812
J. Julio Camarero , Michele Colangelo , Antonio Gazol , Cesar Azorín-Molina

Dieback in temperate forests is understudied, despite this biome is predicted to be increasingly affected by more extreme climate events in a warmer world. To evaluate the potential drivers of dieback we reconstructed changes in radial growth and intrinsic water-use efficiency (iWUE) from stable isotopes in tree rings. Particularly, we compared tree size, radial-growth trends, growth responses to climate (temperature, precipitation, cloudiness, number of foggy days) and drought, and changes in iWUE of declining and non-declining trees showing contrasting canopy dieback and defoliation. This comparison was done in six temperate forests located in northern Spain and based on three broadleaved tree species (Quercus robur, Quercus humilis, Fagus sylvatica). Declining trees presented lower radial-growth rates than their non-declining counterparts and tended to show lower growth variability, but not in all sites. The growth divergence between declining and non-declining trees was significant and lasted more in Q. robur (15–30 years) than in F. sylvatica (5–10 years) sites. Dieback was linked to summer drought and associated atmospheric patterns, but in the wettest Q. robur sites cold spells contributed to the growth decline. In contrast, F. sylvatica was the species most responsive to summer drought in terms of growth reduction followed by Q. humilis which showed coupled changes in growth and iWUE as a function of tree vigour. Low growth rates and higher iWUE characterized declining Q. robur and F. sylvatica trees. However, declining F. sylvatica trees became less water-use efficient close to the dieback onset, which could indicate impending tree death. In temperate forests, dieback and growth decline can be triggered by climate extremes such as dry and cold spells, and amplified by climate warming and rising drought stress.



中文翻译:

干旱和寒冷的天气引发西班牙北部温带橡树和山毛榉森林的灭绝

尽管在温和的世界中,这种生物群落受到越来越严重的极端气候事件的影响,但对温带森林中的死亡的研究却很少。为了评估死亡的潜在驱动力,我们从树木年轮中的稳定同位素重建了径向生长和内在水分利用效率(iWUE)的变化。特别是,我们比较了树木的大小,径向生长趋势,对气候(温度,降水,阴天,有雾天数)和干旱的生长响应,以及下降和不下降的树木的iWUE的变化,显示出不同的树冠枯萎和落叶。这项比较是在西班牙北部的六个温带森林中进行的,并且基于三种阔叶树种(栎木栎木淡水青冈)。下降的树木比没有下降的树木具有更低的径向生长率,并且往往显示出较低的生长变异性,但并非在所有地点都如此。下降,非下滑树间的经济增长差异是显著更在持续Q.栎(15-30岁)比F. sylvatica(5-10岁)的网站。死背与夏季干旱和相关的大气模式有关,但在最湿的罗伯(Q. robur)地区,寒冷季节导致了生长下降。相比之下,F。sylvatica是降低增长方面最敏感的夏季干旱的品种,然后问:蒿草它显示出生长和iWUE随树木活力变化的变化。低增长率和较高的灌溉水利用效率,其特征下降Q.栎F. sylvatica树木。然而,下降的西番莲树木在接近枯萎开始之前的节水效率降低,这可能预示着即将死亡的树木。在温带森林中,干旱和寒冷季节等极端气候事件可能导致枯死和生长下降,而气候变暖和干旱压力上升则加剧了枯死和生长下降。

更新日期:2021-01-29
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