Doctoral Dissertation Research: Environmental Heterogeneity and Insect Outbreaks in Patagonian Forests

森林昆虫的爆发可以使大量树木落叶，有时甚至死亡，从而导致森林结构、物种优势、生态系统生产力和生物多样性的重大变化。 昆虫暴发的动态是由气候变异性和其他环境因素之间复杂的相互作用控制的，这些因素在从区域到林分的一系列空间尺度上起作用。 这些环境因素包括与林分结构和物种组成有关的生物因素以及影响树木和昆虫生长条件的非生物立地因素。 在安第斯山脉南部的温带森林中，该地区的主要树种之一的Nothofagus pumilio定期经历由Ormiscodes属的毛虫引起的严重落叶。 这个博士论文项目将研究Ormiscodes爆发的空间和时间模式与区域尺度的气候变化和环境异质性的背景下，从立场通过景观和区域尺度。 该方法包括利用遥感和地理信息系统对过去疫情的年轮重建及其空间分析，以及关于环境对Ormiscodes种群增长影响的实验室实验。 将利用对暴发与所分析的环境因素之间的空间关系进行量化，开发逻辑回归模型，以生成暴发发生概率和严重程度的预测图，预计该项目将显示气候变化如何影响Ormiscodes毛虫引起的大范围森林落叶事件的概率。 此外，它将显示这些昆虫爆发的敏感性是如何受到环境因素的影响，如海拔，地形位置，土壤和林分条件（例如树木密度和年龄）。 这方面的知识将有助于森林资源管理人员评估过去和目前的管理对森林易发疾病的影响。 它还将提高对气候变化如何影响复杂生态过程的基本认识，其中包括食草昆虫对森林结构和生产力的影响。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。

Outbreaks of forest insects can defoliate and sometimes kill large numbers of trees, consequently causing major changes in forest structure, species dominance, ecosystem productivity, and biodiversity. The dynamics of insect outbreaks are controlled by complex interactions among climate variability and other environmental factors operating across a range of spatial scales from the regional to the stand scale. These environmental factors include both biotic factors associated with forest stand structures and species compositions as well as abiotic site factors that influence growing conditions for trees as well as insects. In the temperate forests of the southern Andes, Nothofagus pumilio, one of the dominant tree species of the region, periodically experiences severe defoliations caused by caterpillars of the Ormiscodes genus. This doctoral dissertation project will examine the spatial and temporal patterns of Ormiscodes outbreaks in relation to regional-scale climatic variability and in the context of environmental heterogeneity from stand through landscape and regional scales. The methodology includes tree-ring reconstructions of past outbreaks and their spatial analysis using remote sensing and geographic information systems as well as laboratory experiments on environmental influences on the growth of Ormiscodes populations. The quantification of the spatial relationships of outbreaks with respect to the analyzed environmental factors will be used to develop logistic regression models for generating predictive maps of probabilities of outbreak occurrence and severity.This project is expected to show how climatic variability affects the probability of widespread forest defoliation events caused by Ormiscodes caterpillars. Furthermore, it will show how the susceptibility of stands to these insect outbreaks is influenced by environmental factors like elevation, topographic position, soils, and stand conditions (for example tree densities and ages). This knowledge will assist forest resource managers in the assessment of past and current management influences on forest susceptibility to outbreaks. It will also improve basic understanding of how climate change affects complex ecological processes involving herbivorous insect impacts on forest structure and productivity. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.