Graduate Thesis Or Dissertation
 

Historical disturbance regimes as a reference for forest policy

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  • Using the historical range of forest conditions as a reference for managing landscapes has been proposed as a "coarse-filter" approach to biodiversity conservation. By emulating historical disturbance processes, it is thought that forest management can produce forest composition and structure similar to the conditions that once supported the native biota. Although several examples of disturbance-based management exist, only recently has this concept been incorporated into policy. This thesis explored hypotheses related to disturbance-based forest policy through a literature review, policy analyses, and simulation experiments. The primary objective of chapter 2 was to examine several examples disturbance-based forest management and evaluate their potential to transition into policy within North America. The review highlighted two Canadian provinces British Columbia and Ontario--that have codified disturbance-based management but used distinct methodologies. Nearly all of the forests in these provinces are government owned, which assisted policy development. In addition, both policy-structures focused on emulating stand-replacing fires that are characteristic in boreal forests; this minimized the costs and the degree of departure from conventional forest management. In much of the U.S., land tenure is complex and disturbance regimes vary widely; this presents difficult challenges for disturbance-based policy development. In the third chapter, disturbance-based policies were developed that attempted to address these challenges. Using datasets from the Coastal Landscape Analysis and Modeling Study (CLAMS) and the Landscape Management and Policy Simulation model (LAMPS), the economic costs and ecological benefits of several policy structures were explored. The policies included two variants of the current policy structure and three policies reflecting various aspects of the natural disturbance regime. The study area was the 3-million hectare Oregon Coast Range. Four owner groups were recognized--forest industry, nonindustrial private, state, and federal. The management intentions of each group guided the application of policies. Disturbance-based policies were primarily addressed to clearcutting on private lands because it constituted the preponderance of harvesting in the region. Information on the Coast Range's historical fire regime was used as a reference to develop disturbance-based policies. Fire severity was emulated with green-tree retention standards; fire frequency was emulated with annual harvestable area restrictions; and fire extent was emulated with harvest-unit size regulations. LAMPS projected landscape conditions, forest dynamics, management activities (clearcutting, thinning), and harvest volumes over the next century. Simulated disturbance-based policies produced age-class distributions more similar to the historical range than those created by the current policy structure. The proportions of early seral and young forest were within the historical range within 100 yrs; within this timeframe, older forests moved closer to but were still below historical conditions. In contrast, patch size distributions were less similar to historical conditions. This was because, even after a ten-fold increase in the average harvest size, the clearcut size limit remained well below the average historical fire size. Also, this was due to the scale of the analysis, which treated multiple proximate harvest-units as individual disturbance events. Therefore, regions with a high density of clearcuts, which were ubiquitous in the current policy scenarios, more closely resembled the large historical fire size. In the near term, annual revenue produced by the disturbance-based policies was estimated to be 20 to 60 percent lower than the current policy. However, relative costs were reduced significantly through time. This reflected the degree of departure between the modem and historical disturbance regimes. This simulation experiment suggested that policies attempting to reproduce historical conditions in the Coast Range would require federal forests to provide large patches of old forest that were conmon in the historical landscape. Employing public lands for this purpose would dampen costs to private landowners who would continue harvesting and provide young and early seral forest structure, which were also historically abundant. In addition, this experiment illustrated the difficultly of meeting regional-scale conservation goals across multiple private landowners and suggested that distributing costs and benefits equitably across large landscapes could be a significant challenge.
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Déclaration de droits
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  • Master files scanned at 600 ppi (24-bit Color and 256 greyscale) using Capture Perfect 3.0 on a Canon DR-9080C in TIF format. PDF derivative scanned at 300 ppi (24-bit Color and 256 greyscale), using Capture Perfect 3.0, on a Canon DR-9080C. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
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