| Abstract |
- 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.
|
|---|
