Indicators of conifer forest health in bark bettle-vectored fungal epidemics

在世界范围内，树皮甲虫和它们的真菌正在摧毁许多森林生态系统。全球变暖扩大了树皮甲虫的地理范围，影响了甲虫和病原体的生活史和生存，以及树木对害虫的生理反应。在加拿大，山松甲虫(MPB)和云杉甲虫的暴发是影响木材纤维供应、生物多样性和依赖林业的社区的重大森林健康风险的主要例子。在不列颠哥伦比亚省，MPB通常会攻击成熟的松树。最近MPB对不同宿主和幼树的攻击威胁到新的地理区域、天然森林再生和计划中的重新造林。在这方面，对大规模森林健康风险的现实评估涉及确定虫媒真菌流行动态的关键因素，例如甲虫携带的微生物多样性、真菌致病能力的变异性和新宿主的真菌定居。由于这些因素的信息非常少，我们建议a)使用MPB最致病的真菌伴生菌株来评估传统的和新的寄主松致病力指标，b)确定MPB真菌病原体是否可以在非寄主树木(如云杉)中定居并对其致病，c)评估可以区分流行种群中致病和非致病真菌分离物的遗传标记，d)确定哪些树木防御机制被致病和非致病真菌激活，以及e)建立允许真菌病原体克服树木防御的机制。要评估MPB疫情可能蔓延到其他树种和地理区域的风险，关键是要解决这些问题，并向政府和林产品行业提供工具和信息。这些信息将支持森林管理组织的决策，旨在防止当前和未来的流行病蔓延到新的地区，并为未来的树皮甲虫/真菌暴发做好准备。加拿大林业局作为支助组织的积极参与将使该项目能够立即向最终用户转让新的知识和工具。

Worldwide, bark beetles and their fungal associates are devastating many forest ecosystems. Global warming increases the geographic range of bark beetles and affects the life cycle and survival of beetles and pathogens as well as tree physiological responses to pests. In Canada, outbreaks of mountain pine beetles (MPB) and spruce beetles are prime examples of major forest health risks impacting wood fibre supplies, biodiversity and forestry dependent communities. In British Columbia, MPB typically attacks mature lodgepole pine trees. Recent MPB attacks on different hosts and younger trees threaten new geographic areas, natural forest regeneration and planned reforestation. In this context, realistic assessments of large-scale forest health risks involve characterizing key factors in the dynamics of insect-vectored fungal epidemics, e.g. microbial diversity carried by the beetle, variability in fungal pathogenicity and fungal colonization of new hosts. Because very little information is available for such factors, we propose to a) assess traditional and new indicators of fungal pathogenicity on lodgepole pine using isolates of the most pathogenic fungal associate of MPB, b) determine whether MPB-fungal pathogens can colonize and be pathogenic to non-host trees (e.g. spruce), c) evaluate genetic markers that can differentiate virulent from non-virulent fungal isolates in an epidemic population, d) establish which tree defence mechanisms are activated and inactivated in host trees by virulent and non-virulent fungal pathogens, and e) establish which mechanisms allow fungal pathogens to overcome tree defences. To assess risks that the MPB epidemic could spread to other tree species and geographic regions, it is critical to address these issues and provide tools and information to government and forest products industries. The information will support decision-making in forest stewardship organizations aimed at preventing current and future epidemics from spreading to new regions and preparing for future bark beetle/fungal outbreaks. The active participation of the Canadian Forest Service as a supporting organization will allow for immediate transfer of new knowledge and tools from this project to the enduser.