Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland.
Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki, Finland.
Plant Cell Environ. 2020 Jul;43(7):1751-1765. doi: 10.1111/pce.13778. Epub 2020 May 28.
Tree stems are an overlooked source of volatile organic compounds (VOCs). Their contribution to ecosystem processes and total VOC fluxes is not well studied, and assessing it requires better understanding of stem emission dynamics and their driving processes. To gain more mechanistic insight into stem emission patterns, we measured monoterpene, methanol and acetaldehyde emissions from the stems of mature Scots pines (Pinus sylvestris L.) in a boreal forest over three summers. We analysed the effects of temperature, soil water content, tree water status, transpiration and growth on the VOC emissions and used generalized linear models to test their relative importance in explaining the emissions. We show that Scots pine stems are considerable sources of monoterpenes, methanol and acetaldehyde, and their emissions are strongly regulated by temperature. However, even small changes in water availability affected the emission potentials: increased soil water content increased the monoterpene emissions within a day, whereas acetaldehyde and methanol emissions responded within 2-4 days. This lag corresponded to their transport time in the xylem sap from the roots to the stem. Moreover, the emissions of monoterpenes, methanol and acetaldehyde were influenced by the cambial growth rate of the stem with 6-10-day lags.
树木茎干是挥发性有机化合物（VOCs）的一个被忽视的来源。它们对生态系统过程和总 VOC 通量的贡献尚未得到很好的研究，评估这一贡献需要更好地了解茎干排放动态及其驱动过程。为了更深入地了解茎干排放模式的机制，我们在三个夏季测量了成熟的欧洲赤松（Pinus sylvestris L.）茎干的单萜、甲醇和乙醛排放。我们分析了温度、土壤含水量、树木水分状况、蒸腾和生长对 VOC 排放的影响，并使用广义线性模型来测试它们在解释排放方面的相对重要性。我们表明，欧洲赤松茎干是单萜、甲醇和乙醛的重要来源，其排放受到温度的强烈调节。然而，即使是水分可用性的微小变化也会影响排放潜力：土壤含水量的增加会在一天内增加单萜的排放，而乙醛和甲醇的排放则会在 2-4 天内响应。这一时间差与它们从根部到茎干的木质部汁液中的运输时间相对应。此外，茎干的形成层生长速度也会影响单萜、甲醇和乙醛的排放，时间滞后为 6-10 天。
