Key message

Effect of drought during 2017 and 2018 resulted in radial stem increment reduction to 78% and 61%, respectively, of the levels occurring in normal year 2016 in Central Europe.

Abstract

Norway spruce (Picea abies (L.) Karst.) is currently the most threatened commercial tree species in Central Europe. This is due to increased drought stress from advancing climate change as well as the species’ distribution outside its natural range. Tree water status and water movement through a tree are key parameters influencing tree growth and vitality. This study is focused on the growth and stress reaction of spruce to climatic conditions, analysing stem diameter variation along an elevation gradient (381–995 m a.s.l.) in the Czech Republic. Tree water deficit based on the zero-growth concept (TWD), calculated from high-frequency dendrometer records and the temporal dynamics of radial growth, was studied for 3 years (2016–2018). Two of these 3 years were affected by severe drought during the growing season. Contrary to our expectations, the observed TWD showed no clear linear decline with rising elevation. The most severe tree desiccation was observed in experimental sites at middle elevations of about 600 m a.s.l. Here, we show that both the timing and level of tree water deficit had an impact on annual stem radial increment (SRI_annual). Severe drought had a substantial negative impact on SRI_annual of Norway spruce in both 2017 and 2018. Drought conditions in 2017 and 2018 resulted in reduction of SRI_annual relative to measurements for the wetter year in 2016 to 78% and 61%, respectively. We report the evidence that the current climatic conditions in the Central European region are not suitable for growing Norway spruce at lower and middle elevations and that forest management needs to react immediately to this situation.

中文翻译：

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挪威云杉在中欧当前消亡之前沿海拔梯度的云杉云杉应力证据

关键信息

2017年和2018年的干旱影响使radial茎的增幅分别降低到中欧2016年正常年份的78％和61％。

抽象

挪威云杉（云杉云杉（L.）Karst。）目前是中欧受威胁最大的商业树种。这是由于气候变化带来的干旱压力增加以及该物种在自然范围之外的分布。树木的水状态和通过树木的水运动是影响树木生长和活力的关键参数。这项研究的重点是云杉对气候条件的生长和应力反应，分析了捷克共和国沿海拔梯度（381-995 m asl）的茎直径变化。对基于高频树状记录和径向生长的时间动态计算的零增长概念（TWD）的树木缺水进行了3年（2016-2018年）研究。这3年中有2年在生长期受到严重干旱的影响。与我们的期望相反，观测到的TWD随高度升高没有明显的线性下降。在海拔约600 m的中等海拔的实验点观察到最严重的树木干燥现象​​。在这里，我们表明树木水分亏缺的时间和水平都对年度茎径增加（SRI）有影响。_年度）。严重干旱对挪威云杉的SRI_年度在2017年和2018_年均造成重大负面影响。相对于2016年较湿润的年份，2017年和2018年的干旱条件使SRI_年度分别降低至78％和61％。我们报告的证据表明，中欧地区当前的气候条件不适合在中低海拔的挪威云杉生长，森林管理需要对此情况立即作出反应。