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Forest structure classes used in the LADS model, classified based on stand age (AGE) and time since last fire (TFIRE). Developmental stages (small boxes) can be aggregated into broader structure classes (large boxes). Solid arrows illustrate succession following a high-severity fire. High-severity fires reset both AGE and TFIRE to 0, and the post-fire stand follows a pathway through open, young, mature, and old-growth stages. Broken arrows illustrate possible successional pathways following a moderate-severity fire. Moderate-severity fires reset only TFIRE to 0, leaving a remnant cohort of older trees. Depending on the value of AGE, the stand can transition into the mature or old-growth class 80 years after the moderate-severity fire.
Source publication
Concerns about the fragmentation of Pacific Northwest forests are based on the assumption that these land- scapes historically contained large, contiguous patches of old growth. However, this supposition appears to conflict with disturbance history research, which shows that wildfire was an important component of pre-settlement forest eco- systems....
Contexts in source publication
Context 1
... cell was assigned a forest structure class based on the number of years since the last high-severity, stand- replacing fire (AGE), and the number of years since the last moderate-or high-severity fire (TFIRE). Thus, high-severity fires reset both AGE and TFIRE to zero, whereas moderate- severity fires reset only TFIRE to zero (Fig. 2). Following a high-severity fire, forests passed though open, young single- story, mature, and old-growth stages. Following a moderate- severity fire, forests typically passed through semi-open and young multi-story stages. Then, if a remnant cohort of older trees was present (as represented by the AGE variable), the forests could move ...
Context 2
... of older trees was present (as represented by the AGE variable), the forests could move directly into the old-growth stage 80 years after the moderate-severity burn. For the purposes of this study, we combined open and semi-open classes into an "early successional" class, and young single-story and young multi-story classes into a "young" class (Fig. 2). Vegetation-related variability in fire susceptibility was mod- eled as a function of time since the last fire, following the U- shaped relationship described by Agee and Huff (1987). Fire susceptibility was assumed to be highest immediately after fire because of high fuel levels from the fire-killed trees. Developmental stages (small ...
Context 3
... young, and mature forest patches decreased with increasing MSIZE. Changes in SEV had a particularly strong influence on the area and spatial pattern of mature forests. As SEV de- creased, larger areas of moderate-severity fire occurred, and more forests moved directly from the young to old-growth classes without passing through the mature class (Fig. 2). The size of the largest early successional patch increased considerably when FEXT was raised 20% above its baseline value. Patch density and edge density also increased with FEXT, reflecting more complex patch perimeters and more unburned islands in the simulated fires. The effects of vary- ing the FEXT parameter were nonlinear; the ...
Similar publications
A major goal of managers in fire‐prone forests is restoring historical structure and composition to promote resilience to future drought and disturbance. To accomplish this goal, managers require information about reference conditions in different forest types, as well as tools to determine which individual trees to retain or remove to approximate...
Citations
... Flower et al. 2014;Halofsky et al. 2020;Johnston et al. 2017;Oliver and Ryker 1990;Waring and Franklin 1979;Wimberly 2002). Changes in regional climate have greatly influenced wildfire activity, as demonstrated by the frequency of large fires being over 140% of the annual average between 1973 and 2012 in the western United States compared with previous decades. ...
United States Pacific Northwest (PNW) forests are important ecological, cultural, and recreational landscapes. Direct seeding to aid forest regeneration in the PNW region was developed to reduce reforestation costs and timelines. These practices were largely discontinued in the 1970s due to poor establishment resulting from issues of seed predation, a lack of targeting favorable site conditions, seed distribution issues, and improvements to nursery seedling production. A recent renewed interest in direct seeding research has resulted from the growing geographic extent of postdisturbance areas requiring reforestation. This interest is also supported by the increasing recognition of the logistical impossibility of satisfying reforestation demand via planted seedlings. This historical review highlights the timeline of direct seeding research and practice in the PNW. It describes the main obstacles to its widespread use and opportunities for improvement. These opportunities include upscaling seed collection efforts, increasing distribution precision of seeding methods, upgrading seed quality evaluations, and mitigating seed predation and desiccation.
Study Implications: The availability of seedlings is increasingly limited due to the rising demand for reforestation as a result of more frequent and severe wildfires. Further research into direct seeding as an artificial regeneration strategy for trees is necessary to operationally increase reforestation abilities and thus supplement natural regeneration and seedling planting. This study summarizes findings from prior direct seeding studies in the Pacific Northwest region and identifies (1) improving seed collection efforts, (2) refining seed quality assessments, (3) standardizing seed dispersal methods, and (4) improving seedling establishment by targeting favorable site conditions and predation mitigation as key future research priorities.
... NRV refers to the fluctuation in ecosystem structure, composition, and processes over time and is often used to understand the influence of anthropogenic change in ecological systems [41]. We used estimates of NRV derived from the literature [42][43][44][45][46] to determine how the area of current habitat changed in each watershed compared to the NRV, and to estimate departure from the NRV [21,24]. Departure refers to changes in extents and configurations of habitat that may have important ecological implications in terms of effects to species viability and persistence [21,47]. ...
We evaluated ecosystem conditions known to influence the viability of a strictly arboreal species (the red tree vole, Arborimus longicaudus) endemic and historically distributed in the forests across the Coast Range, Cascades, and Klamath Mountains ecoregions in the Western United States of America. We found widespread reductions in ecosystem conditions needed to support the long-term viability of the red tree vole. This was particularly evident in the Coast Range where the weighted watershed index (WWI) was 26% of its historical value, and the current probability of maintaining viability departed the most from historical viability probabilities in ecoregions that were evaluated. In contrast, in the Cascades and Klamath Mountains, the WWI was 42% and 52% of their respective historical values, and the current probabilities of maintaining viability departed less from historical conditions than in the Coast Range. Habitat loss from timber harvest represented the most immediate threat in the Coast Range, while habitat loss from wildfires represented the most risk to the red tree vole in the Cascades and Klamath Mountains. Reducing the risks to the viability of the red tree vole will depend largely on the implementation of conservation practices designed to protect remaining habitat and restore degraded ecosystems in the Coast Range. However, the risk of large, high-severity wildfires will require the protection and increased resilience of existing ecosystems. Our results indicate that considerable adaptation to climate change will be required to conserve the red tree vole in the long term. Conservation may be accomplished by revising land and resource management plans to include standards and guidelines relevant to red tree vole management and persistence, the identification of priority areas for conservation and restoration, and in assessing how management alternatives influence ecosystem resiliency and red tree vole viability.
... Our results show the strong effect of local conditions (integrated in our models by stand age) on early seral songbird populations, but it is likely that landscape composition and configuration are also important (Betts et al., 2018;Cushman and McGarigal, 2004). Historically in the Oregon Coast Range, the infrequent (150-300 years) and high-severity fire regime would have created early seral patches that were larger, more homogenous, and longer-lasting than is available in modern Douglas-fir plantations (Spies et al., 2018;Wimberly, 2002;Wimberly et al., 2000). Today, because wildfires are actively suppressed, clearcut harvest for plantation management is the primary disturbance. ...
Tree plantations are integral for meeting society’s demand for wood products and are increasing in total area worldwide. It is therefore critical to understand how plantations affect native biodiversity. Our aim was to examine the degree to which plantations affect biodiversity by 1) quantifying songbird abundance across a gradient in forest stand age (stand initiation through canopy closure), 2) estimating the duration of early seral habitat, and 3) testing if forest structural and compositional elements prolong habitat availability. This approach is equivalent to the modeling of wood ‘yield curves’ common in forest management but applied to a biodiversity indicator.
We used a chronosequence sampling design to survey songbirds and vegetation in 283 plantations aged 0–30 years in the Oregon Coast Range, USA. Stands were randomly selected within age strata and surveys were temporally replicated in order to use N-mixture models to estimate abundance after accounting for imperfect detection. The Coast Range is considered one of the most productive forest regions in the world and plantations occur on over 50% of the forested land base. Our chronosequence encompasses the assumed age of canopy closure, which we anticipated to be the point at which early seral biodiversity declines.
We detected 5074 birds of 71 species during the 2018 and 2019 breeding seasons. Canopy closure occurred approximately 12 years following clearcut harvest and replanting. We found that bird abundance changed dynamically during this short early seral stage. Twenty species peaked in abundance either very early in stand development or with the approximate timing of canopy closure, and then subsequently declined to low levels by the end of the 30-year chronosequence. The estimated abundance of 3 species increased following canopy closure. We also found, contrary to our hypothesis, that the amount of broadleaf cover increased habitat longevity for only one species – Wilson’s warbler.
To our knowledge, our study provides the first quantitative estimates for how bird species abundances change throughout the entire early seral stage in tree plantations in western North America – information that can be used to assess tradeoffs between timber production and biodiversity. We found that the duration of early seral habitat in plantations is short and generally cannot be ameliorated by managing for higher levels of broadleaf cover. This finding has important implications for early seral species in the rapidly shifting mosaic of tree plantation landscapes.
... Box (1979) observed that no real-world system can be exactly represented by a model, suggesting that we ask not whether any model is "true, " but rather whether it is illuminating and useful. Landscape and ecosystem models range in complexity from simple conceptual models such as state-and-transition models that simulate vegetation dynamics using discrete successional pathways (Wimberly, 2002;Tipton et al., 2018) to complex biogeochemical models that explain vegetation processes and related energy and matter exchanges between vegetation, soil, and the atmosphere (Keane et al., 2011;Dong et al., 2019). Simple models are easier to use and interpret but have a limited set of output variables that are often highly dependent on input parameters (Jørgensen and Bendoricchio, 2001). ...
Complex, reciprocal interactions among climate, disturbance, and vegetation dramatically alter spatial landscape patterns and influence ecosystem dynamics. As climate and disturbance regimes shift, historical analogs and past empirical studies may not be entirely appropriate as templates for future management. The need for a better understanding of the potential impacts of climate changes on ecosystems is reaching a new level of urgency, especially in highly perturbed or vulnerable ecological systems. Simulation models are extremely useful tools for guiding management decisions in an era of rapid change, thus providing potential solutions for wicked problems in land management—those that are difficult to solve and inherently resistant to easily definable solutions. We identify three experimental approaches for landscape modeling that address management challenges in the context of uncertain climate futures and complex ecological interactions: (1) an historical comparative approach, (2) a future comparative approach, and (3) threshold detection. We provide examples of each approach from previously published studies of simulated climate, disturbance, and landscape dynamics in forested landscapes of the western United States, modeled with the FireBGCv2 ecosystem process model. Cumulatively, model outcomes indicate that typical land management strategies will likely not be sufficient to counteract the impacts of rapid climate change and altered disturbance regimes that threaten the stability of ecosystems. Without implementation of new, adaptive management strategies, future landscapes are very likely to be different than historical or contemporary ones, with significant and sometimes persistent changes triggered by interactions of climate and wildfire.
... Previous work examined static age distributions, including the landscape proportion of old-growth forest, arising from known stand-replacing fire rotations (Van Wagner 1978, Agee 1993, Spies and Turner 1999; but did not quantify dynamic ranges in the abundance of seral stages. More recent studies (Wimberly et al. 2000, Wimberly 2002, Nonaka and Spies 2005, DeMeo et al. 2018 used simulation models to develop ranges for late-seral forests in stand-replacing fire regimes; however, those studies assumed more frequent, regularly occurring (and thus generally smaller) fires, as opposed to a regime of rare, episodic, large fires. Many infrequent fire regimes are best characterized as driven mainly by the extremes: the temporally clustered (regionally synchronous) episodes of large fires that punctuate otherwise relatively quiet periods regionally, rather than semi-regularly occurring fires or fire-free periods (Romme 1982, Henderson et al. 1989, Agee et al. 1990, Morrison and Swanson 1990, Agee 1993, Weisberg and Swanson 2003. ...
... Even though our analysis incorporated extreme (lowprobability/high-impact) events, the ranges that emerged were surprisingly similar to previous estimates of NRV for moist forests of the Pacific Northwest. Wimberly et al. (2000) and Wimberly (2002) used an age-based landscape simulation and estimated historical late-seral Note: Rows do not necessarily add to 100%, as structurally simple early-seral conditions (i.e., young plantations with closed tree canopy and scarce deadwood) are not included. Such conditions range from 2% of National Park Service lands to 17% of private lands. ...
The natural range of variation (NRV) is an important reference for ecosystem management, but has been scarcely quantified for forest landscapes driven by infrequent, severe disturbances. Extreme events such as large, stand‐replacing wildfires at multi‐century intervals are typical for these regimes; however, data on their characteristics are inherently scarce, and, for land management, these events are commonly considered too large and unpredictable to integrate into planning efforts (the proverbial “Black Swan”). Here, we estimate the NRV of late‐seral (mature/old‐growth) and early‐seral (post‐disturbance, pre‐canopy‐closure) conditions in a forest landscape driven by episodic, large, stand‐replacing wildfires: the Western Cascade Range of Washington, USA (2.7 million ha). These two seral stages are focal points for conservation and restoration objectives in many regions. Using a state‐and‐transition simulation approach incorporating uncertainty, we assess the degree to which NRV estimates differ under a broad range of literature‐derived inputs regarding (1) overall fire rotations and (2) how fire area is distributed through time, as relatively frequent smaller events (less episodic), or fewer but larger events (more episodic). All combinations of literature‐derived fire rotations and temporal distributions (i.e., “scenarios”) indicate that the largest wildfire events (or episodes) burned up to 10⁵–10⁶ ha. Under most scenarios, wildfire dynamics produced 5th–95th percentile ranges for late‐seral forests of ~47–90% of the region (median 70%), with structurally complex early‐seral conditions composing ~1–30% (median 6%). Fire rotation was the main determinant of NRV, but temporal distribution was also important, with more episodic (temporally clustered) fire yielding wider NRV. In smaller landscapes (20,000 ha; typical of conservation reserves and management districts), ranges were 0–100% because fires commonly exceeded the landscape size. Current conditions are outside the estimated NRV, with the majority of the region instead covered by dense mid‐seral forests (i.e., a regional landscape with no historical analog). Broad consistency in NRV estimates among widely varied fire regime parameters suggests these ranges are likely relevant even under changing climatic conditions, both historical and future. These results indicate management‐relevant NRV estimates can be derived for seral stages of interest in extreme‐event landscapes, even when incorporating inherent uncertainties in disturbance regimes.
... Modelling approaches based only on physical habitat parameters can predict the vegetation at a location without the effect of direct anthropogenic land-use change (Kelly, Powell, & Riggs, 2005;Ricotta, Carranza, Avena, & Blasi, 2000) and have been applied to produce benchmarks for nature conservation (Arco Aguilar, González-González, Garzón-Machado, & Pizarro-Hernández, 2010;Rosati, Marignani, & Blasi, 2008) or to compare the outcomes of different types of management (Barnes, Pregitzer, Spies, & Spooner, 1982). Dynamic models also allow to simulate succession (Taylor, Chen, & VanDamme, 2009) and reconstruct historic developments (Keane et al., 2006;Li, 2000;Wimberly, 2002). In the past, many different models have been developed to predict the vegetation distribution in floodplains based on environmental factors (Aggenbach & Pelsma, 2005;Franz & Bazzaz, 1977;Friedman & Auble, 1999;Jungwirth, Muhar, & Schmutz, 2002;Lenders, Leuven, Nienhuis, De Nooij, & Van Rooij, 2001;Runhaar, 2003) or, more recently, to simulate their development over time (Benjankar, Egger, Jorde, Goodwin, & Glenn, 2011;Camporeale & Ridolfi, 2006;García-Arias & Francés, 2016;Van Oorschot, Kleinhans, Geerling, & Middelkoop, 2016). ...
Most large rivers in Europe and North America suffered flow regulations and channelization in the 19th and 20th century. To study the effects of the altered site conditions on the development of floodplain vegetation and create a benchmark map for their restoration, we calibrated and applied a dynamic floodplain vegetation model that accounts for the processes recruitment as well as morphodynamic disturbance and physiologic stress on vegetation to reconstruct the succession dynamics of the floodplain vegetation of a segment of the Rhine River from shortly after it was channelized (1872) until today (2016). The model calibration was based on historical maps and hydrologic data.
Our simulation demonstrated a steady, one‐way progression of the vegetation communities towards mature phases without regression to younger stages. It was possible to attribute this development to a lack of morphodynamic disturbances strong enough to reset succession and to identify physiological stress caused by long inundations periods as the most relevant controlling factor of succession. The resulting vegetation distribution (2016) can be considered an estimation of the potential natural vegetation (PNV) under altered site conditions.
The good agreement of the model results with an expert‐based PNV map showed that our approach is a good alternative to create benchmark maps for floodplain conservation and restoration projects. From a research and practitioners' viewpoint, it has the big advantage over the traditional approach that it allows to analyse different points in time as well as to be comprehensive and reproducible.
... Landscape and ecosystem models range in complexity from simple conceptual models such as state-and-transition models that simulate vegetation dynamics using discrete successional pathways [39][40][41][42][43] to complex biogeochemical models that explain vegetation processes and related energy and matter exchanges between vegetation, soil, and the atmosphere [44][45][46]. Other models of intermediate complexity include Fig. 1 A summary of the ways models can be used in natural resource decision making across temporal and spatial scales. ...
Purpose of Review
Climate change and associated ecological impacts have challenged many conventional, observation-based approaches for predicting ecosystem and landscape responses to natural resource management. Complex spatial ecological models provide powerful, flexible tools which managers and others can use to make inferences about management impacts on future, no-analog landscape conditions. However, land managers who wish to use ecosystem and landscape models for natural resource applications are faced with the difficult task of deciding among many models that differ in important ways. Here, we summarize a process to aid managers in the selection of an appropriate model for natural resource management.
Recent Findings
To guide management planning, scientifically credible information on how landscapes will respond to management actions under changing climate is required. Landscape models are increasingly used in a management context to evaluate of impacts of changing climate and interacting stressors on ecosystems and to test effects of alternative management options on desired conditions. However, the wide range of available models makes selection of appropriate and viable models a complex process.
Summary
We present a series of preliminary steps to define critical scales of time, space, and ecological organization to guide an experimental design for a modeling project and then list a set of criteria for selecting a landscape or ecological model. Material presented includes the preliminary steps (crafting modeling objective, designing modeling project), organizational concerns (resources available, expertise on hand, timelines), and modeling details (complexity, design, documentation) of model selection.
... They were constrained by calibration to the available data record, which was short in duration (44 years), contained relatively few ignitions per year due to the high rainfall in the region, and contained only one fire >2000 ha in size. Other studies have provided a longer-term perspective of pre-settlement wildfire in the Coast Range (Long et al. 1998, Wimberly et al. 2000, Wimberly 2002, Thompson et al. 2006), but our model calibration was limited to the recent time period with a continuous record of wildfire events, incorporating the effects of suppression. The potential for large fires in our simulations was also limited by the small number of ignitions that occur in the Coast Range, providing few opportunities to start a fire that could potentially grow to a large size. ...
Balancing economic, ecological and social values has long been a challenge in the forests of the Pacific Northwest, where conflict over timber harvest and old-growth habitat on public lands has been contentious for the past several decades. The Northwest Forest Plan, adopted two decades ago to guide management on federal lands, is currently being revised as the region searches for a balance between sustainable timber yields and habitat for sensitive species. In addition, climate change imposes a high degree of uncertainty on future forest productivity, sustainability of timber harvest, wildfire risk, and species habitat. We evaluated the long-term, landscape-scale tradeoffs among carbon
... particular allocations of resources, making it important to understand the optimum arrangement of heterogeneity for co-habiting fire dependent species (Bradstock et al., 2005). The specific formation of spatial and temporal heterogeneity is particularly important in maintaining biodiversity and is thus at the heart of the "pyrodiversity begets biodiversity" paradigm with spatial age pattern mosaics being documented in many historic fire regimes worldwide Faivre et al., 2011;Fernandez-Manso et al., 2009;Minnich, 1983;Wimberly, 2002). ...
... Fire regimes are globally variable and driven by many complex interactions. Not all natural fire regimes displayed and shared similar spatial heterogeneity characteristics but a MAFM pattern may have been present at some scale relative to ecosystem extent in most, if not all fire regimes (Heinselman, 1973;Pickett and Thompson, 1978;Wimberly, 2002). The potential for heterogeneity in most fire regimes is high as research indicates small fires are often most frequent (Moritz et al., 2005), creating the opportunity for spatial heterogeneity to occur. ...
... The potential for heterogeneity in most fire regimes is high as research indicates small fires are often most frequent (Moritz et al., 2005), creating the opportunity for spatial heterogeneity to occur. Research specifically investigating natural fire regimes indicates they were highly variable, and many were dominated by frequent small fires in a mosaic pattern (Beaty and Taylor, 2001;Bergeron et al., 2002;Duncan et al., 2010Duncan et al., , 2011Weir et al., 2000;Wimberly, 2002). Not all systems are driven by frequent, small fires however (Keeley and Fotheringham, 2001;Romme, 1982), and fire management in each system needs to be tailored specifically for the needs of that system and the native species inhabiting it. ...
Reduction of fire hazard is becoming increasingly important in managed landscapes globally. Fuels reduction prescribed burn treatments are the most common form of reducing fire hazard on landscapes around the world but often result in homogenized fuel age structures and habitats. Alternatively, the size of unplanned fires, and hence fire hazard, can be reduced by controlling the size and patterning of fuels treatments in a patch mosaic arrangement on landscapes. Patch mosaic burning is being implemented globally as a means to increase heterogeneity to mimic natural fire regime results. Funding for prescribed fire programs is often justified primarily on hazardous fuels reduction with secondary consideration given for ecological effectiveness, which can be increased by particular fire mosaic patterns in some systems. The question we address is: Which of two prescribed fire treatment regimes, fuels reduction or patch mosaic burning, reduces fire hazard most effectively? We address the question using computer simulation modeling on synthetic landscapes representing both fire regime treatments. Treatment scale was important. Among fuel reduction treatments, large blocks burned less area than small blocks. For the mosaic treatments, small blocks reduced fire size the most (out of all treatments) and had the least variance in area burned. It is possible to reduce fire hazard and to provide heterogeneous age fuels structure on the landscape, simultaneously benefiting humans and many native fire-dependent species requiring mosaic habitat patterns.
... Another coupled FLM and LCM simulation application has been developed by integrating the demand-allocation land cover and land use change algorithms from the FORE-SCE model ( Sohl and Sayler 2008 ;Sohl et al. 2012 ) into the Landscape Dynamics Simulator (LADS) model of natural disturbance and forest succession ( Wimberly 2002 ;Wimberly and Kennedy 2008 ). The new model, entitled the Coupled Human and Natural Geospatial Environments (CHANGE) simulator, uses the FORE-SCE algorithms to control transitions among a set of land cover and land use classes, and then applies the LADS algorithms to simulate natural vegetation dynamics within the land cover classes that are dominated by natural vegetation ). ...
