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

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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.