Interaction between forest tent caterpillar and forest composition: Role of predation in outbreak dynamics and effects on litter, soils and tree regeneration

森林帐篷毛虫（FTC）是加拿大各地硬木林的重要落叶者。目前，在魁北克有两个爆发似乎独立循环的疫源地：一个在南方的糖枫，一个在北方的颤杨。在这些森林类型中，大约每10年发生一次严重的疫情，造成森林生产力下降。从历史上看，在一到两年的落叶后，爆发的种群数量就会减少，但近年来观察到更长时间和更严重的爆发。因此，在预测气候变化的背景下，人们认为联邦贸易委员会的爆发可能会变得更加严重，并造成更严重的森林生产力损失。联邦贸易委员会爆发的特点是人口极端波动和死亡率变化很大。最近的研究表明，捕食在种群控制中起着重要作用。然而，我们对捕食率和不同捕食者对FTC的相对重要性的理解仍然是高度假设的。此外，在疫情期间，联邦贸易委员会可以增加土壤中的有机质数量，增加营养动物可利用的资源。这些改良可能对土壤无脊椎动物群落结构、有机质分解、养分有效性以及树苗的生存和生长产生重要影响。从长期来看，这些影响可能对林分组成产生重要的控制作用。该项目的目的是更好地了解1)捕食者在控制和结束FTC暴发中的作用；2)FTC暴发对土壤节肢动物群落、土壤过程和树木再生的影响。该项目将使人们更好地了解森林生态系统的功能，并有助于发展创新的造林方法。例如，我们的项目将允许识别最有可能受到未来FTC疫情影响的林分类型。这项研究还将有助于更好地预测未来FTC的爆发，并对脆弱的树种和林分类型进行先发制人的采伐。这些干预措施将有助于维持加拿大森林工业的木材供应。

The forest tent caterpillar (FTC) is a significant defoliator of hardwood stands throughout Canada. Currently, in Quebec there are two foci in which outbreaks appear to cycle independently: one in the south on sugar maple and one in the north on trembling aspen. In these forest types, severe outbreaks occur at approximately 10-year intervals and are responsible for decreases in forest productivity. Historically, outbreaking populations collapsed after one or two years of defoliation, but longer and more severe outbreaks have been observed in the recent years. For this reason, in the context of the projected climate change it is thought that FTC outbreaks may become more severe and result in more significant losses of forest productivity. FTC outbreaks are characterized by extreme population fluctuations and highly variable mortality rates. Recent studies suggest that predation plays an important role in population control. However, our understanding of predation rates and the relative importance of different predators on FTC remain highly hypothetical. Furthermore, during outbreaks FTC could increase the amount of organic matter to the soil and increase resources available to detritivores. These modification could have important effects on the structure of soil invertebrate communities and influence decomposition of organic matter, nutrient availability, and tree seedlings survival and growth. On the long term, these effects could exert important controls on forest stand composition. The objectives of this project are to better understand 1) the role of predators in keeping down and ending FTC outbreaks and 2) the effects of FTC outbreaks on soil arthropod communities, soil processes, and tree regeneration. This project will provide a better understanding of forest ecosystem functioning and contribute to the development of innovative silvicultural approaches. For instance, our project will allow for the identification of stand types most likely to be affected by future FTC outbreaks. This study will also contribute to better anticipate future FTC outbreaks and conduct pre-emptive harvesting of vulnerable tree species and stand types. These interventions will help maintain the timber supply for the Canadian forest industry.