PARENT SESSION
Contributed Oral Session 130: Forest Infestations and Mortality
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 514 A, Level 5, Palais des congrès de Montréal

Multi-scale analysis of spatial patterns of spruce budworm defoliation.

James, Patrick¹, Fortin, Marie-Josee¹, Kneeshaw, Daniel², ¹ University of Toronto, Toronto, ON, Canada² Universite du Quebec a Montreal, Montreal, QC, Canada

ABSTRACT- Ecology aims to understand spatial processes that drive heterogeneous spatial patterns. These efforts are often complicated by the fact that different processes may contribute to the character of any given pattern. Moreover, spatial heterogeneity often influences the very processes we wish to examine. Forest spatial dynamics are complex and influenced by many processes operating at multiple spatial and temporal scales. One method recently proposed to identify these spatial scales in ecological data is that of wavelet transformations. Here, we use wavelet transformations to identify key scales of spatial structure in patterns of forest insect defoliation. Wavelet transformations find multiple scales in ecological pattern through local hierarchical decomposition of spatial variability to constituent waveforms. In this way, both local and global patterns are characterized. Relevant scales of pattern are identified through correlation with dependent variables of interest through regression. Using this method, we ask the following questions: at what scales are patterns of defoliation most evident? And, what can we then infer about defoliation processes from observed spatial patterns? We tested the method using two dimensional simulated data (e.g., categorical maps) with known characteristics and assessed model sensitivity to differences in spatial attributes (i.e., scale and heterogeneity). We then analyzed actual spatio-temporal data (maps) of spruce budworm (SBW) defoliation for the boreal forest of central Quebec, Canada. We found support for our hypothesis that the relevant scales of forest defoliation are extractable from overall spatial heterogeneity using wavelet transforms in a two-dimensional case. Multiple relevant scales of defoliation dynamics were identified and discussed with regards to local and broad scale processes thought to determine synchrony among outbreak locations. Identifying spatial scales of influence is important to develop a further mechanistic understanding of complex ecosystem processes and can inform further investigative approaches to multi-scale ecological phenomena.

Key words: multi-scale, spatial pattern, spruce budworm, wavelets