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

在世界范围内，树皮甲虫及其真菌伙伴正在破坏许多森林生态系统。全球变暖增加了小蠹的地理范围，影响了小蠹和病原体的生命周期和生存，以及树木对害虫的生理反应。在加拿大，山地松甲虫和云杉甲虫的爆发是影响木材纤维供应、生物多样性和以林为生的社区的主要森林健康风险的主要例子。在不列颠哥伦比亚省，MPB通常攻击成熟的黑松。最近MPB攻击不同的主机和年轻的树木威胁到新的地理区域，天然林再生和计划重新造林。在这方面，对大规模森林健康风险的现实评估涉及确定以昆虫为媒介的真菌流行病动态中的关键因素，例如甲虫携带的微生物多样性、真菌致病性的变异性和真菌在新宿主中的定植。由于这些因素的信息非常少，我们建议a）使用MP B的最致病性真菌伴生物的分离物来评估真菌致病性对火炬松的传统和新指标，B）确定MPB真菌病原体是否可以定殖并对非宿主树木致病（例如云杉），c）评价可在流行群体中区分毒性与非毒性真菌分离株的遗传标记，d）确定哪些树木防御机制在宿主树木中被有毒和无毒真菌病原体激活和灭活，以及为了评估MPB流行可能蔓延到其他树种和地理区域的风险，解决这些问题并向政府和森林产品行业提供工具和信息至关重要。这些信息将支持森林管理组织的决策，以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/真菌爆发做好准备。加拿大林务局作为一个支助组织的积极参与将使该项目的新知识和工具能够立即转让给最终用户。

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.