Quantifying change in the spatial pattern of forests: assessing impacts of mountain pine beetle infestation and harvest




Long, Jed

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British Columbia’s current mountain pine beetle epidemic has led to salvage and mitigation harvesting strategies intended to slow the dispersal of beetles, and recover economic value from infested timber stands. These resulting harvesting strategies will alter the spatial pattern of forest landscapes in impacted regions, often resulting in forest fragmentation. As a result, wildlife habitat, hydrologic regimes, local carbon budgets, and soil dynamics, amoung other ecological properties, are expected to be negatively impacted. Monitoring of forest fragmentation in Canada is now required for the Montreal Process, an international forest monitoring policy. Effective methods that quantify changes in forest fragmentation, the breaking up of forest land cover into smaller, and more numerous parts, are required to meet forest monitoring objectives. This research provides two new methods that build upon existing approaches widely used for quantifying the spatial patterns of landscape features (i.e., landscape pattern indices). The first approach I demonstrate aids the quantification of forest pattern change over two time periods, by accounting for the impact of composition on spatial configuration. The value of this method is demonstrated using a case study that highlights the impacts of forest harvesting, associated with insect salvage and mitigation activities. This method allows landscapes that have changed primarily in composition to be distinguished from those that have experienced large configurational change. In the second approach I use multivariate cluster analysis for regionalization (the grouping of objects in space), and identify regions within a study area where increased fragmentation is observed. Regions delineated based on forest spatial pattern can be linked to underlying processes. Ancillary information (e.g., elevation) can be used to identify areas where observed forest pattern is due to underlying physiological features. Pattern indices (e.g., patch perimeter-area ratio) can be used to distinguish between patterns arising from forest disturbance that is likely natural (e.g., fire) or anthropogenic (e.g., harvest activity) in origin. The methods presented in this thesis may be most appropriate when observed changes in landscape pattern can be attributed to substantial changes in landscape composition.



Geography, Spatial Pattern, Mountain Pine Beetle, Forest Disturbance