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）是一个重要的落叶阔叶林遍布加拿大。目前，在魁北克，有两个疫源地的爆发似乎是独立循环的：一个在南部的糖枫上，一个在北部的颤白杨上。在这些森林类型中，严重的爆发大约每隔10年发生一次，造成森林生产力下降。从历史上看，爆发的种群在一年或两年的落叶后崩溃，但近年来观察到更长和更严重的爆发。因此，在预测的气候变化的背景下，人们认为，FTC的爆发可能会变得更加严重，并导致森林生产力的更大损失。FTC疫情的特点是人口极端波动和死亡率高度可变。最近的研究表明，捕食在种群控制中起着重要的作用。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，在暴发期间，FTC可以增加土壤中的有机质含量，增加食草动物的可用资源。这些改变对土壤无脊椎动物群落结构、有机质分解、养分有效性以及苗木的存活和生长都有重要影响。从长远来看，这些影响可以对森林的组成产生重要的控制作用。该项目的目标是更好地了解1）捕食者在抑制和结束FTC爆发中的作用，2）FTC爆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，并有助于制定创新的造林方法。例如，我们的项目将允许确定最有可能受到未来FTC爆发影响的林分类型。这项研究还将有助于更好地预测未来的FTC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林业的木材供应。

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.**********