The pine looper Bupalus piniaria is one of the most widespread phyllophagous insect species across Northern Eurasia, defoliating Scots pine forests over vast territories. Since there are not enough long-term documented observations on a series of outbreaks, there is a need for methods allowing them to be reconstructed to study their dynamics patterns. Previously, dendrochronological methods were successfully used to solve such issues. However, the most common approach is not applicable for the Western Siberian forest-steppe since it requires comparison with a non-damaged tree species close to pine in terms of longevity and resistance to rot. In the pine forests of the steppe and forest-steppe zones of Western Siberia, there are no species that are not damaged by the pine looper that meets these requirements. Methods allowing not using control species are also not free from disadvantages (e.g., weak specificity). Therefore, we have developed a new method based on the analysis, not of the tree-ring width but the early- and latewood width to reconstruct past defoliation events. The past defoliation by the pine looper is indicated by the presence of a negative pointer year for latewood, followed by a negative pointer year for earlywood in a subsequent year among the majority of individuals. Linear modeling showed a difference between the climate impact on radial growth and the defoliation one. The obtained reconstruction was compared with the results of other methods (mowing window, OUTBREAK, independent component analysis), literature, and Forest Service data. The developed new method (pointer year method; PYM) showed high efficiency confirmed by results of the tree-ring series analysis (11 revealed outbreaks in the past). Compared with other reconstruction techniques under the given conditions (a favorable combination of heat and humidity; probably low-intense and short defoliation), the proposed method provided more precise results than those proposed earlier. Due to high accuracy, the PYM can be useful for detecting late-summer and autumn past defoliations of tree species with clear difference between early- and latewood even though the damage was weak.

中文翻译：

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松弯尺Bupalus piniaria（L.）爆发重建：一个西伯利亚南部的案例研究

松木弯管Bupalus piniaria是整个北欧亚大陆最广泛的食叶昆虫种类之一，使广阔领土上的苏格兰松树森林落叶。由于对一系列暴发没有足够的长期记录的观察结果，因此需要一种允许对其进行重构以研究其动力学模式的方法。以前，树轮年代学方法已成功用于解决此类问题。但是，最常见的方法不适用于西伯利亚西部草原，因为就寿命和抗腐性而言，它需要与接近松树的未受损树种进行比较。在西西伯利亚的草原和森林草原区的松树林中，没有任何满足这些要求的不受松树弯damaged损害的物种。不允许使用对照物种的方法也存在缺点（例如，特异性弱）。因此，我们在分析的基础上开发了一种新的方法来重建过去的落叶事件，而不是树轮宽度，而是早木和晚木宽度。在大多数人中，对于阔叶木，过去的落叶是由负木指针年份表示的，而随后的年份则是负木指针年份。线性模型显示气候对径向生长的影响与落叶的影响之间的差异。将获得的重建结果与其他方法（修剪窗口，OUTBREAK，独立成分分析），文献和森林服务数据的结果进行比较。开发新方法（指针年法；树木年轮系列分析的结果证实了PYM（高效率）（过去有11次暴发）。与在给定条件下（热和湿度的良好组合；可能是低强度和短脱叶）的其他重建技术相比，所提出的方法提供了比早先提出的更为精确的结果。由于精度高，即使损坏程度较弱，PYM仍可用于检测树木的夏末和秋天落叶，而早木和晚木之间的区别明显。与先前提出的方法相比，提出的方法提供了更精确的结果。由于精度高，即使损坏程度较弱，PYM仍可用于检测树木的夏末和秋天落叶，而早木和晚木之间的区别明显。与先前提出的方法相比，提出的方法提供了更精确的结果。由于精度高，即使损坏程度较弱，PYM仍可用于检测树木的夏末和秋天落叶，而早木和晚木之间的区别明显。