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Using Criteria Based on the Natural Fire Regime to Evaluate Forest Management in the Oregon Coast Range of the United States: Concepts and Applications

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Using Criteria Based on the Natural Fire Regime to Evaluate Forest Management in the Oregon Coast Range of the United States: Concepts and Applications

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... In boreal forests, these older forests have attributes such as large diameter trees and coarse woody debris, which can be impor-tant for many kinds of specialized organisms. For a given region, the area covered by older forests is directly and negatively related to the frequency of severe natural disturbances, and particularly standreplacing fires (Johnson, 1992;Wimberly et al., 2004;Bergeron et al., 2006). In regions where frequency of stand-replacing fires is high, the amount of old forests is low, and it is thus realistic to assume that forest management can maintain a forest age-class structure that is relatively close to what occurs in nature, particularly if fire suppression is efficient (Bergeron et al., 2006). ...
... In regions where frequency of stand-replacing fires is high, the amount of old forests is low, and it is thus realistic to assume that forest management can maintain a forest age-class structure that is relatively close to what occurs in nature, particularly if fire suppression is efficient (Bergeron et al., 2006). However, in regions where severe fire return intervals are relatively long, for instance in humid coastal areas, it will be harder to implement forest management policies based on the use of even-aged silvicultural systems, while at the same time maintaining a relatively natural forest age class structure (Cissel et al., 1999;Wimberly et al., 2004;Nonaka and Spies, 2005). This difficulty can be compounded by the fact that, in many regions, natural disturbances are not efficiently suppressed, and continue to occur in juxtaposition with forest management practices such as clearcutting (Kurz and Apps, 1999;Armstrong, 1999;Bergeron et al., 2006;Girard et al., 2009). ...
... Maintaining forests within the RNV can be much more difficult to achieve in regions where natural disturbance return intervals are long, a fact that has already been underlined for forest ecosystems of the Pacific Northwest (Cissel et al., 1999;Wimberly et al., 2004;Nonaka and Spies, 2005). In this context, the tools usually proposed for the maintenance or restoration of forests with pre-industrial characteristics, such as the modification of silvicultural practices (Franklin et al., 2002;Harvey et al., 2002), or the emulation of the spatial pattern of disturbance patches (Mladenoff et al., 1993;Delong and Tanner, 1996) may be insufficient, unless they are accompanied by a decrease in the annual rates of severe disturbance (i.e., clearcutting) compared with the levels currently determined using standard annual allowable cut calculations (Didion et al., 2007). ...
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In boreal forests, historical variations in the area disturbed by natural disturbances or harvesting have rarely been compared. We measured temporal and spatial variations in areas affected by severe fires and clearcutting throughout the 20th century in a 57, 332km2 section of the eastern Canadian boreal forest. We examined the effects of these disturbances on spatio-temporal variations in the abundance of forests >60 years. Natural variability for the abundance of forests >60 years was estimated from simulations of natural disturbance regimes. We also measured compositional and structural differences between three categories of stands originating from relatively recent disturbances (∼50 years; clearcutting, fires, and clearcutting followed by fires), and one category of stands that were undisturbed for at least 200 years. At the regional level, we observed that forests >60 years gradually became scarcer throughout the 20th century due to a gradual expansion of harvested areas, an effect most pronounced in the southern part of the region, where mature and old forest abundance was clearly outside the range of natural variability at the end of the studied period. At the stand level, forest composition and structure differed between stand-origin categories: clearcutting-origin stands contained more balsam fir (Abies balsamea), fire-origin stands more black spruce (Picea mariana), and fire/clearcutting-origin stands more hardwoods (Betula papyrifera and Populus tremuloides). Overall, we estimate that strict forest management targets based on natural disturbance regimes will be difficult to achieve in eastern North-American boreal forests, most notably because contemporary disturbance rates, including both clearcutting and fire, have gradually become higher than the fire rates observed during the preindustrial period.
... The historical range of variability (HRV) in forest landscape structure created by natural disturbances has been proposed as a guide for biodiversity conservation in the past decade (e.g., Morgan et al. 1994, Montreal Process Working Group 1998, Aplet and Keeton 1999, Landres et al. 1999 ). Despite the attention and theoretical appeal, studies that rigorously quantify HRV are limited (but see Cissel et al. 1999, Tinker et al. 2003, Wimberly et al. 2004). Much has been learned about the application of HRV in forest management from studies in the Pacific Northwest (Cissel et al. 1999, Wimberly et al. 2000, Agee 2003). ...
... Much has been learned about the application of HRV in forest management from studies in the Pacific Northwest (Cissel et al. 1999, Wimberly et al. 2000, Agee 2003). Wimberly (2002) and Wimberly et al. (2004) investigated the HRV in landscape structure for the 2 million ha Oregon Coast Range province and concluded that old-growth forest (200 years) was the dominant forest type prior to Euro-American settlement, occupying at least 40% of the landscape on average. Wimberly et al. (2004) found that the current landscape is outside the HRV for major seral stages ranging from young to old growth, and for basic spatial patterns such as mean patch size and edge density. ...
... el et al. 1999, Wimberly et al. 2000, Agee 2003). Wimberly (2002) and Wimberly et al. (2004) investigated the HRV in landscape structure for the 2 million ha Oregon Coast Range province and concluded that old-growth forest (200 years) was the dominant forest type prior to Euro-American settlement, occupying at least 40% of the landscape on average. Wimberly et al. (2004) found that the current landscape is outside the HRV for major seral stages ranging from young to old growth, and for basic spatial patterns such as mean patch size and edge density. The amount of old-growth forest has been considerably reduced and fragmented, while the area of young forest has strongly increased and now comprises the ma ...
Article
We estimated the historical range of variability (HRV) of forest landscape structure under natural disturbance regimes at the scale of a physiographic province (Oregon Coast Range, 2 million ha) and evaluated the similarity to HRV of current and future landscapes under alternative management scenarios. We used a stochastic fire simulation model to simulate presettlement landscapes and quantified the HRV of landscape structure using multivariate analysis of landscape metrics. We examined two alternative policy scenarios simulated by two spatially explicit simulation models: (1) current management policies for 100 years into the future and (2) the wildfire scenario with no active management until it reached the HRV. The simulation results indicated that historical landscapes of the province were dynamic, composed of patches of various sizes and age classes ranging from 0 to >800 years including numerous, small, unburned forest islands. The current landscape was outside the HRV. The landscape did not return to the HRV in the 100 years under either scenario, largely because of lack of old-growth forests and the abundance of young forests. Under the current policy scenario, development of landscape structure was limited by the spatial arrangement of different ownerships and the highly contrasting management regimes among ownerships. As a result, the vegetation pattern after 100 years reflected the ownership pattern. Surprisingly, the wildfire scenario initially moved the landscape away from the HRV during the first 100 years, after which it moved toward the HRV, but it required many more centuries to reach it. Extensive forest management and human-caused fires in the 20th century have left legacies on the landscape that could take centuries to be obliterated by wildfire. Departure from the HRV can serve as an indicator of landscape conditions, but results depend on scale and quantification of landscape heterogeneity. The direct application of the concept of HRV to forest policy and management in large landscapes is often limited since not all ownerships may have ecological goals and future climate change is anticipated. Natural disturbance-based management at large scales would not show the projected effects on landscape structure within a typical policy time frame in highly managed landscapes.
... For example, high fuel loading and ladder fuels can reduce foraging or nesting habitat quality for California spotted owls in Sierra Nevada forests (Roberts andNorth 2012, Keane 2013). A vegetation treatment may accelerate the development of NSO nesting habitat (Wimberly et al. 2004) or reduce the risk of highseverity fire for forest birds ( White et al. 2013b), even if it temporarily degrades existing habitat and "takes" owls in the near term ( Franklin et al. 2006). Forest management projects may adversely affect and take NSOs, but these projects might still be compatible with NSO recovery and CH if the overall magnitude of the impacts is limited in scope temporally and geographically, especially where the primary intent of the project is long-term restoration ( Gaines et al. 2010a). ...
... Under these conditions, harvesting as a form of disturbance could be used to reduce strong competition for resources, facilitating rapid growth and colonization of recently disturbed sites by early-seral plant communities and generalist and early-seral associated bird species. Historically, natural disturbances maintaining earl-seral habitats were commonly large, infrequent events (Wimberly et al. 2004;Whitlock et al. 2003;Wimberly 2002). Thus, earlyseral species would have had to disperse or migrate over large distances to find suitable habitat and persist between disturbance events. ...
... For example, high fuel loading and ladder fuels can reduce foraging or nesting habitat quality for California spotted owls in Sierra Nevada forests (Roberts andNorth 2012, Keane 2013). A vegetation treatment may accelerate the development of NSO nesting habitat (Wimberly et al. 2004) or reduce the risk of highseverity fire for forest birds (White et al. 2013b), even if it temporarily degrades existing habitat and "takes" owls in the near term (Franklin et al. 2006). Forest management projects may adversely affect and take NSOs, but these projects might still be compatible with NSO recovery and CH if the overall magnitude of the impacts is limited in scope temporally and geographically, especially where the primary intent of the project is long-term restoration (Gaines et al. 2010a). ...
... For example, high fuel loading and ladder fuels can reduce foraging or nesting habitat quality for California spotted owls in Sierra Nevada forests (Roberts andNorth 2012, Keane 2013). A vegetation treatment may accelerate the development of NSO nesting habitat (Wimberly et al. 2004) or reduce the risk of highseverity fire for forest birds (White et al. 2013b), even if it temporarily degrades existing habitat and "takes" owls in the near term . Forest management projects may adversely affect and take NSOs, but these projects might still be compatible with NSO recovery and CH if the overall magnitude of the impacts is limited in scope temporally and geographically, especially where the primary intent of the project is long-term restoration (Gaines et al. 2010a). ...
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Franklin and Johnson (2012) state that stakeholders have created polar opposites for federal lands: either managing them for intensive wood production or for spotted owls. However, the NWFP was designed to meet the viability requirements of >1,000 late-successional species, not just owls, and is a compromise between these two competing views. Many scientists and conservation groups have offered ways to restore forests beyond thinning, have proposed thinning measures with less impact, and other active management approaches that constitute more comprehensive restoration measures. Ecological forestry as currently conceived will create more tension over management of federal forests than it resolves, initiating questions about its adequacy as an ecologically credible framework.
... Under these conditions, harvesting as a form of disturbance could be used to reduce strong competition for resources, facilitating rapid growth and colonization of recently disturbed sites by early-seral plant communities and generalist and early-seral associated bird species. Historically, natural disturbances maintaining earl-seral habitats were commonly large, infrequent events (Wimberly et al. 2004; Whitlock et al. 2003; Wimberly 2002 ). Thus, earlyseral species would have had to disperse or migrate over large distances to find suitable habitat and persist between disturbance events. ...
Article
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Huston’s Dynamic Equilibrium Hypothesis predicts that the response of biodiversity to disturbance varies with productivity. Because disturbance is thought to break competitive advantage of dominant species in productive ecosystems, species richness is predicted to increase with disturbance frequency in productive systems. Recovery of plant biomass following disturbance is also predicted to be faster in productive systems. Here we provide the first test of Huston’s hypothesis in the context of setting harvest rates in managed forests for achieving biodiversity objectives. We examined predictions relating to vegetation and bird response to disturbance and succession in productive and less productive forests in western Oregon and Washington, USA. We found that measurements of understory cover and shrub diversity were higher in young, productive stands than less productive stands of similar age. Later-seral forests in productive environments (mean age=67years) had less variable and more complete canopy closure than similar-age forests in less favorable settings. At the stand scale, bird abundance and richness decreased with canopy closure in highly productive forests whereas bird abundance and richness increased with canopy closure in less productive forests. At the landscape scale, bird abundance and richness within stands increased with increasing levels of disturbance in the surrounding landscape within highly productive forests, whereas bird abundance and richness decreased with increasing disturbance in the surrounding landscape within less productive forests. Our results indicate that bird response to disturbance varies across levels of productivity and suggest that bird species abundance and associated species richness will be maximized through relatively more frequent disturbance in highly productive systems. KeywordsDisturbance-Productivity-Dynamic equilibrium-Intermediate disturbance hypothesis-Competition-Forest ecology-Forest management-Birds-Diversity
... 2004; Gauthier et al., 2004;Wimberly et al., 2004) and policies (OMNR, 2001;ASRD, 2006;Jetté , 2007). A crucial need for the pursuit of emulating natural forest disturbances as a management goal, whether at stand-or landscape-scale, is adequate knowledge of natural disturbances at appropriate scales (Perera et al., 2004a). ...
Article
Emulating natural forest disturbance is an increasingly popular forest management paradigm that is considered a means of achieving forest sustainability. Adopting this goal requires a sound understanding of natural disturbances at scales that correspond to management policies and strategies. In boreal forest landscapes driven by periodic stand-replacing fires this requires knowledge of fire regime characteristics, especially their spatial and temporal variability as well as stochasticity. The major goal of this study was to demonstrate the utility of fire regime simulation modeling to explore the variability of fire regime characteristics, with respect to formulating and assessing forest management strategies. We conducted a modeling experiment in a boreal forest landscape of northwestern Ontario, Canada, to examine its long-term fire regime in relation to forest policies on harvest size distribution. We used BFOLDS, a spatially explicit fire regime model that simulates individual fire events mechanistically in response to fire weather, fuel patterns, and terrain. The fire regimes in four large eco-regions were modeled for a 200-year period under three fire-weather (cold, normal, and warm) scenarios, with replications. We found that fire size distribution in all eco-regions followed power law under all weather scenarios, but their slopes and intercepts varied among eco-regions and fire weather scenarios. Warming fire weather increased burn rates and fire numbers in all eco-regions, albeit to different degrees. Overall, the variability among eco-regions was higher than the variability among fire weather scenarios, and among replicates. Comparisons of simulated fire size classes with those from an 86-year long fire history showed that empirical data cannot capture the variability that could be revealed by simulation modeling. We also show that fire size distribution is spatially heterogeneous within eco-regions, and provide several suggestions for forest policy directions with respect to forest harvest size distributions and harvest rates, based on the variability of fire regime characteristics. An assessment of present forest policies of emulating natural disturbances that guide forest harvest sizes showed that these are incongruent with simulated fire size distributions under all scenarios with one exception. Overall, this study illustrates the value of scenario simulation modeling to explore and quantify the variability of forest fire regime, for use in forest policies and strategies that attempt to emulate natural disturbance.
... The model used in this research was the landscape dynamics simulator (LADS), a spatially explicit grid-based model originally developed to study historical variability of old-growth forests in the coastal Pacific Northwest ( Wimberly et al., 2000Wimberly et al., , 2004Wimberly, 2002). The current version of LADS has been updated to reflect forest dynamics in mixed-severity fire regimes of the interior Pacific Northwest. ...
Article
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Simulation models of disturbance and succession are being increasingly applied to characterize landscape composition and dynamics under natural fire regimes, and to evaluate alternative management strategies for ecological restoration and fire hazard reduction. However, we have a limited understanding of how landscapes respond to changes in fire frequency, and about the sensitivity of model predictions to assumptions about successional pathways and fire behavior. We updated an existing landscape dynamics model (LADS) to simulate the complex interactions between forest dynamics, fire spread, and fire effects in dry forests of the interior Pacific Northwest. Experimental model runs were conducted on a hypothetical landscape at fire rotations ranging from 5 to 50 years. Three sensitivity analyses were carried out to explore the responses of landscape composition to (1) parameters characterizing succession and fire effects on vegetation, (2) the probability of fire spread into different successional stages, and (3) the size and spatial pattern of static fire refugia. The area of old open-canopy forests was highest at the shortest fire rotations, and was particularly sensitive to the probability of stand-replacement fire in open-canopy forests and to the fire-free period required for ingrowth to occur in open-canopy forests. The area of old closed-canopy forests increased with lengthening fire rotation, but always comprised a relatively small portion of the landscape (<10%). The area of old closed-canopy forests increased when fire spread was more rapid in open-canopy forests than in closed-canopy forests, and when the physical landscape incorporated large “fire refugia” with low fire spread rates. Old closed-canopy forests appear to comprise a relatively minor landscape component in mixed-severity fire regimes with fire rotations of 50 years or less. However, these results are sensitive to assumptions about the spatial interactions between fire spread, landscape vegetation patterns, and the underlying physical landscape.
Article
United States National Forests encompass 77.7 million ha (192 million acres) of grasslands and forests, which comprise 7% of the nation's total land base and 20% of the nation's forested lands. Increasing demand for wood has raised concerns about producing forest products without impeding the land's ability to provide a variety of other renewable goods and ecosystem services (Aber et al. 2000). Land-use conflicts often arise that result in challenges to forest plans and, in many cases, costly and time-consuming litigation. A more comprehensive planning and management approach is needed that allows public lands to generate multiple values and benefits. Landscape ecologists are among those contributing concepts, perspectives, and information to help meet this need (e.g., Forman 1995; Lindenmayer and Franklin 2002; Liu and Taylor 2002; Wiens and Moss 2005). © 2006 Springer Science+Business Media, LLC. All rights reserved.
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This chapter outlines how landscape simulation models can be used to support forest landscape restoration. In the first type of application, landscape models of disturbance and forest succession were used to estimate historical variability in landscape composition and configuration. An example is given based on a study in the Oregon Coast Range of USA which showed the present day forest patterns are outside the range of historical variability. Problems with this approach lie in deciding the landscape metrics to use and, in this particular case, in assembling reliable data on historical fire regimes. A second common application of landscape simulation models is to project future landscapes under alternative landscape restoration scenarios. These types of simulation experiments with landscape models focus less on making predictions of historical or future landscape conditions but, rather, place more emphasis on exploring general hypotheses about pattern-process relationships. One important insight is that changes in landscape composition and configuration often lag behind shifts in disturbance regimes, and that temporal as well as spatial landscape heterogeneity is important to consider when assessing ecological responses to changing disturbance regimes.
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The historical range of variability (HRV) in landscape structure and composition created by natural disturbance can serve as a general guide for evaluating ecological conditions of managed landscapes. HRV approaches to evaluating landscapes have been based on age-classes or developmental stages, which may obscure variation in live and dead stand structure. Developing the HRV of stand structural characteristics would improve the ecological resolution of this coarse-filter approach to ecosystem assessment. We investigated HRV in live and dead wood biomass in the regional landscape of the Oregon Coast Range by integrating stand-level biomass models and a spatially explicit fire simulation model. We simulated historical landscapes of the region for 1000 years under pre-Euro-American settlement fire regimes and calculated biomass as a function of disturbance history. The simulation showed that live and dead wood biomass historically varied widely in time and space. The majority of the forests historically contained 500-700 Mg·ha-1 (50-70 kg·m-2) of live wood and 50-200 Mg·ha-1 (5-20 kg·m-2) of dead wood. The current distributions are more concentrated in much smaller amounts for both biomass types. Although restoring the HRV of forest structure is not necessarily a management goal for most landowners and managing agencies, departure from the reference condition can provide relative measure to evaluate habitat conditions for managers seeking to use forest structure as a means to maintain or restore ecosystem and species diversity.
Article
Using a landscape simulation model, we examined ecological and economic implications of forest policies designed to emulate the historical fire regime across the 2 x 10⁶ ha Oregon Coast Range. Simulated policies included two variants of the current policy and three policies reflecting aspects of the historical fire regime. Policy development was guided by the management intentions of four owner groups: forest industry, nonindustrial private, state, and federal. 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. Simulated disturbance-based policies produced age-class distributions closer to the estimated historical range than those created by the current policy. Within 100 years, proportions of younger forests were within the historical range, while older forests moved closer to, but remained below, historical conditions. In the near term, disturbance-based policies produced annual harvest volumes 20%-60% lower than those produced by the current policy. However, relative costs of disturbance-based policies diminished over time. Our results suggest that if expediting a return to historical age-class distributions at a provincial-scale was a goal, then public lands would be needed to provide large patches of old forest. In addition, this experiment illustrated that distributing costs and benefits of conservation policies equitably across multiple private landowners is a significant challenge.
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