Late-season extreme climatic events induced variations in wood density and extended growth for more than a month in 2016 in Juniperus przewalskii Kom. growing on the Northeastern Tibetan Plateau, suggesting extraordinary growth resilience of the species in response to short extreme events over the cold and arid region. Monitoring xylem formation (xylogenesis) during extreme meteorological events helps assessing climate change impacts on tree growth. For better insight into tree-growth responses, here we compare the intra-annual formation of annual ring with and without intra-annual density fluctuation in J. przewalskii in a cold and arid environment on the Northeastern Tibetan Plateau. Cambial phenology and xylogenesis observations of five mature trees during the 2016 intra-annual density fluctuation growth ring and the five-preceding year (2011–2015) were used for comparison. The frequency of population level occurrence of intra-annual density fluctuation in 2016 was examined on additional 50 randomly selected trees. The return of precipitation in conjunction with warm temperatures after summer drought promoted the growth resumption in 64% of our study trees, resulting in the observed intra-annual density fluctuation. These trees experienced a growing season 1 month longer than trees without intra-annual density fluctuation. The extended growth period resulted in a 17% increase in stem biomass in trees that experienced intra-annual density fluctuation. Our results highlight the extraordinary resilience of J. przewalskii trees in response to extreme climatic events in the cold and dry conditions of the Tibetan Plateau.

中文翻译：

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Juniperus przewalskii Kom 中延长的木糖发生和茎生物质生产。在极端的晚季气候事件期间

2016 年，晚季极端气候事件导致杜松的木材密度发生变化，并延长了一个多月的生长时间。生长在青藏高原东北部，表明该物种在应对寒冷和干旱地区的短期极端事件时具有非凡的生长恢复能力。在极端气象事件期间监测木质部形成（木原形成）有助于评估气候变化对树木生长的影响。为了更好地了解树木生长的响应，我们在这里比较了青藏高原东北部寒冷干旱环境中普氏原虫在有和没有年内密度波动的情况下年轮的年内形成。使用2016年年内密度波动生长轮和前五年（2011-2015）期间五棵成熟树木的形成层物候和木发生观察进行比较。在另外 50 棵随机选择的树木上检查了 2016 年种群水平发生年内密度波动的频率。夏季干旱后降水的恢复以及温暖的气温促进了我们研究的 64% 树木的生长恢复，导致观察到的年内密度波动。这些树木的生长季节比没有年内密度波动的树木长 1 个月。延长的生长期导致经历年内密度波动的树木的茎生物量增加了 17%。我们的结果突出了 J.