Critical minimum temperature limits xylogenesis and maintains treelines on the Tibetan Plateau
Critical minimum temperature limits xylogenesis and maintains treelines on the Tibetan Plateau
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DOI：
10.1101/093781
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发表时间：
2016-12
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影响因子：
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通讯作者：
Xiaoxia Li;Eryuan Liang;J. Gričar;S. Rossi;K. Čufar;A. Ellison
中科院分区：
文献类型：
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作者：
Xiaoxia Li;Eryuan Liang;J. Gričar;S. Rossi;K. Čufar;A. Ellison
定义树线的生理和生态机制仍然存在争议。有人认为，树线以上没有树木是由于低温限制了生长。因此，我们提出的假设，有一个临界最低温度（CTmin）阻止在树线的木质化。我们测试了这一假设，通过检查每周在三个和四个生长季节在两个天然史密斯冷杉（冷杉georgei变种。smithii）的树木线网站的东南青藏高原。尽管细胞分化的时间在不同年份之间存在差异，但最低气温是与木质部生长相关的主要气候变量;木质部发生开始和结束的临界最低温度（CTmin）发生在0.7 ± 0.4 ° C。一个基于过程建模的年轮形成年表使用此CTmin是与实际的年轮数据相一致。这种极低的CTmin允许史密斯冷杉生长在树线完成年度木质部生产和成熟，并提供支持和树线形成的机制。
Physiological and ecological mechanisms that define treelines are still debated. It is suggested that the absence of trees above the treeline is caused by the low temperature that limits growth. Thus, we raise the hypothesis that there is a critical minimum temperature (CTmin) preventing xylogenesis at treeline. We tested this hypothesis by examining weekly xylogenesis across three and four growing seasons in two natural Smith fir (Abies georgei var. smithii) treeline sites on the south-eastern Tibetan Plateau. Despite differences in the timing of cell differentiation among years, minimum air temperature was the dominant climatic variable associated with xylem growth; the critical minimum temperature (CTmin) for the onset and end of xylogenesis occurred at 0.7±0.4 °C. A process-based-modeled chronology of tree-ring formation using this CTmin was consistent with actual tree-ring data. This extremely low CTmin permits Smith fir growing at treeline to complete annual xylem production and maturation and provides both support and a mechanism for treeline formation.