Key message

Higher solar radiation leads to higher crown temperatures, sap flow, and airborne volatile concentrations as well as altered bark chemical composition in trees at fresh forest edge.

Abstract

Spruce bark beetles are likely to attack trees that are at newly opened forest edges after wind disturbance due to higher temperatures and higher emission of primary attractants. The mechanisms behind these phenomena are still not fully known. We investigated how sudden gap creation affects tree physiology parameters related to induced defence processes in Norway spruce trees 2 months after the disturbance driven gap formation. We hypothesized that the sudden sun exposure of mature spruce trees would increase: (1) bark and crown temperatures, (2) sap flow rates, and (3) the phloem and airborne concentration of terpenes. Using a terrestrial and airborne thermal camera, sap flow sensors, and chromatography, we confirmed that trees at the forest edge had significantly higher (1) mean tree crown temperature, (2) mean sap flow rates (2-fold higher) and (3) airborne concentration of α-pinene (αP, 12.2-fold higher) and β-pinene (βP, 7.9-fold higher) close to the bark. We observed a significant positive correlation (R² = 0.77) between the measured sap flow rates and terpene concentrations in airborne samples. Bark temperatures were not significant. In the phloem samples, analyzed by GC–MS, αP and βP predominated over monoterpenes 3-carene, myrcene, limonene, 1.8-cineole, and bornyl acetate. GC × GC–TOF–MS analysis of phloem showed a higher relative abundance of resin acid methyl esters in the forest interior trees and higher relative abundances of dehydro-p-cymene in the trees at the forest edge. Our findings are discussed in the context of the enhanced predisposition of trees at the newly formed forest edge to bark beetles attack.

中文翻译：

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挪威云杉林中突然形成缺口对树木温度和挥发性成分分布的短期影响

关键信息

较高的太阳辐射会导致较高的树冠温度，树液流量和空气中的挥发物浓度以及新鲜森林边缘树木的树皮化学成分发生变化。

抽象

由于较高的温度和主要引诱剂的排放，在风扰后，新近开放的森林边缘的云杉树皮甲虫可能会袭击树木。这些现象背后的机制仍不完全清楚。我们调查了干扰驱动间隙形成后2个月，突然间隙的产生如何影响与挪威云杉树木诱导诱导防御过程有关的树木生理参数。我们假设成熟的云杉树木突然暴露在阳光下会增加：（1）树皮和树冠温度，（2）汁液流速，以及（3）萜类的韧皮部和空气传播浓度。使用地面和机载热像仪，树液流量传感器和色谱法，我们确认了森林边缘的树木具有明显更高的（1）平均树冠温度，（2）平均树液流速（高2倍）和（3）接近树皮的空气中α-pine烯（αP，高12.2倍）和β-pine烯（βP，高7.9倍）的空气浓度。我们观察到显着正相关（R ²  = 0.77），介于所测得的汁液流速和空气中样品中的萜烯浓度之间。树皮温度不显着。在韧皮部样品中，通过GC-MS分析，αP和βP优先于单萜3烯，月桂烯，柠檬烯，1.8桉树脑和乙酸冰片酯。韧皮部的GC×GC–TOF–MS分析表明，森林内陆树木的树脂酸甲酯相对丰度较高，而森林边缘树木中的脱氢对苯丙氨酸的相对丰度较高。我们在新形成的森林边缘树皮对树皮甲虫的侵袭有所增强的情况下讨论了我们的发现。