Forest Vegetation Simulator Research Articles

Performance of the Forest Vegetation Simulator in Managed White Spruce Plantations Influenced by Eastern Spruce Budworm in Northern Minnesota

Silvicultural strategies such as thinning may minimize productivity losses from a variety of forest disturbances, including forest insects. This study analyzed the 10-year postthinning response of stands and individual trees in thinned white spruce (Picea glauca [Moench] Voss) plantations in northern Minnesota, USA, with light to moderate defoliation from eastern spruce budworm (Choristoneura fumiferana Clemens). Using the Forest Vegetation Simulator, model results suggested overprediction of stand basal area growth and tree diameter increment in these stands. Growth modifiers indicated that trees growing in unthinned stands and with greater defoliation levels (i.e., 20‐32%) would need the largest adjustment for diameter increment. Modifiers for height were similarly specified to compensate for the underprediction of height increment in these stands. Thinned stands continued to maintain target live crown ratios in excess of 0.40, suggesting long-term productivity. Results highlight the need for simulation models that represent appropriate responses to stands and trees affected by forest insects and diseases. Ultimately, accurate representations of growth and development in these models that account for influences of biotic disturbance agents are essential under future global change scenarios, particularly as silvicultural strategies are implemented to reduce the impacts of forest health threats and other stressors.

Implications of Diameter Caps on Multiple Forest Resource Responses in the Context of the Four Forests Restoration Initiative: Results from the Forest Vegetation Simulator

Meeting multiple resource objectives, such as increasing resilience to climate change, while simultaneously increasing watershed health, conserving biodiversity, protecting old-growth, reducing the risk of catastrophic wildfire, and promoting ecosystem health, is paramount to landscape restoration. Central to public land management efforts in the West is the widespread adoption of size-prohibited cutting of “large” trees, a limitation referred to as a “diameter cap.” In this study, we used the most commonly proposed prescription for the Four Forest Restoration Initiative in northern Arizona to explore the implications of diameter caps for multiple resource responses through the use of model simulations. We found that implementing progressively smaller caps in southwestern ponderosa pine may result in relatively similar live tree densities, canopy cover, and large snag densities but higher basal areas, mean tree size, torching indices, and scenic beauty with lower water yield and herbaceous production. When diameter cap scenarios are compared, tradeoffs exist, and no single metric is suited for overall scenario evaluation.

Evaluating short term simulations of a forest stand invaded by emerald ash borer

The invasive emerald ash borer (Agrilus planipennis - EAB) is causing rapid and widespread ash (Fraxinus spp.) mortality in eastern North America, has established populations near Moscow, Russia, and is threatening ash resources in Europe. Given the prevalence of susceptible hosts these post-invasion forests will clearly differ from their pre-invasion counterparts. Understanding these changes is key to mitigating the impacts of invasion and developing sound management strategies. We evaluated short term changes in a forest stand invaded by EAB, and examined if the southern variant of the Forest Vegetation Simulator (FVS) could accurately predict those changes. Through simulation, managers can gain a clearer understanding of how pest invasions impact and alter future forest dynamics. However, many simulators are designed to achieve long-term predictions and thus do not align with the short term changes associated with rapid EAB-induced ash mortality. Woody vegetation was surveyed in 2010 and used to project impacts of EAB invasion into 2012 by simulating a 50% ash mortality rate. The same plots were then re-surveyed in 2012, allowing us to evaluate: (1) changes in actual forest composition and structure; and (2) simulation accuracy. Within our forest stand, FVS accurately estimated short term changes in stem density and basal area parameters, thus demonstrating its value as a short-term simulator for EAB-induced changes within the southern region of the United States. EAB-induced ash mortality is quickly changing these forests and will ultimately alter how stakeholders manage their lands. We discuss the potential usefulness of FVS as a tool for aiding management decisions in response to EAB invasion.

Simulation of Quaking Aspen Potential Fire Behavior in Northern Utah, USA

Current understanding of aspen fire ecology in western North America includes the paradoxical characterization that aspen-dominated stands, although often regenerated following fire, are “fire-proof”. We tested this idea by predicting potential fire behavior across a gradient of aspen dominance in northern Utah using the Forest Vegetation Simulator and the Fire and Fuels Extension. The wind speeds necessary for crowning (crown-to-crown fire spread) and torching (surface to crown fire spread) were evaluated to test the hypothesis that predicted fire behavior is influenced by the proportion of aspen in the stand. Results showed a strong effect of species composition on crowning, but only under moderate fire weather, where aspen-dominated stands were unlikely to crown or torch. Although rarely observed in actual fires, conifer-dominated stands were likely to crown but not to torch, an example of “hysteresis” in crown fire behavior. Results support the hypothesis that potential crown fire behavior varies across a gradient of aspen dominance and fire weather, where it was likely under extreme and severe fire weather, and unlikely under moderate and high fire weather. Furthermore, the “fire-proof” nature of aspen stands broke down across the gradient of aspen dominance and fire weather.

Representative regional models of post-disturbance forest carbon accumulation: Integrating inventory data and a growth and yield model

Disturbance is a key driver of carbon (C) dynamics in forests. Insect epidemics, wildfires, and timber harvest have greatly affected North American C budgets in the last century. Research is needed to understand how forest C dynamics (source duration and recovery time) following disturbance vary as a function of disturbance type, severity, forest type, and initial C stocks. We used the Forest Vegetation Simulator (FVS) to simulate total C stocks (excluding soil) for 100years following three types of disturbance (fire, harvest, and insects) with four levels of severity. We initiated the model using empirical data from a large representative sample of forest conditions on the national forest ownership in the Rocky Mountain region (Forest Inventory and Analysis data). Unlike analyses based on stand age, an ambiguous quantity with respect to disturbance history, our approach enables explicit consideration of disturbance type and severity, as well as pre-disturbance forest C. On average, stands became a C sink after fire in 5, 6, 14, and 23years for low to high-severity fire. Pre-fire C stocks were reached 25–55years later. Following bark beetle epidemics, on average stands continued to be a C source for 10years longer than fire and up to 40years longer in some cases, but pre-disturbance C stocks were reached in a similar amount of time. C stocks following harvest showed the largest initial decline, but on average stands became a sink sooner at 1, 5, 15, and 12years post-harvest for low to high-severity harvests. Differences in C dynamics based on disturbance type and severity, initial conditions, and forest type demonstrate the importance of considering this variability when modeling forest C dynamics. The regionally averaged models of C response quantified in this study can be combined with remotely sensed data on disturbance type and severity and used with C accounting approaches that rely on growth and yield or state and transition models.

Converting Even-Aged Plantations to Uneven-Aged Stand Conditions: A Simulation Analysis of Silvicultural Regimes with Slash Pine (Pinus elliottii Engelm.)

There has been increasing interest in managing forest stands as uneven-aged structures to promote sustainable harvests as well as maintain ecosystem services. This study provides a framework for simulating conversion of mature even-aged stands to uneven-aged slash pine (Pinus elliottii Engelm.) stands using the USDA Forest Vegetation Simulator (FVS) model. A total of 73 scenarios, representing combinations of two harvest methods (based on either “BDq” and/or “low thinning”), two harvesting cycles (10 or 20 years), three harvest intensities (4.6 or 8.0 or 11.5 m 2 ha 1 residual basal areas), and six levels of regeneration (0 –2,224 seedlings ha 1 ) were evaluated for structural diversity, timber production, and carbon (C) stocks over a 100-year period. The BDq harvest approach, which applied selection cutting based on diameter regulation from the first cutting cycle onwards, resulted in higher structural diversity. Scenarios based on low thinning in the first cutting cycle and BDq method from the third cutting cycle onwards tended to result in higher total merchantable timber and C stocks over the entire simulation period, particularly at higher residual basal areas and longer cutting cycles. None of the scenarios maximized all of the three variables simultaneously. Based on the desired objectives, land managers can choose among scenarios presented. The study revealed that regeneration and establishment of as low as 247 seedlings ha 1 can lead to successful conversion and multiple benefits from uneven-aged slash pine stands.

California's regulatory forest carbon market: Viability for northeast landowners

Carbon markets have the potential to reward landowners for improved forest management and forest conservation. To date, the Over the Counter (OTC) voluntary market represents the greatest opportunity for forest landowners to participate in carbon transactions. However, lack of a consistent carbon price signal and sporadic demand coupled by high transaction costs has prevented widespread participation from family forest landowners. Adoption of a U.S. based cap-and-trade program reduces price risk and may provide incentives for sustainable forest management across large areas. Yet few studies have examined the supply side of carbon offsets and factors affecting project financial viability. To address this gap, we assessed how (1) property characteristics (i.e. stocking level, forest type, size etc.); (2) silvicultural treatments; and (3) protocol and legislative requirements affect the financial viability of compliance forest offset projects, focusing on California's Air Resource Board (ARB) program due to its significance as the world's second largest carbon market. We used forest inventory data from 25 properties in the northeastern United States to examine the viability of the sites as ARB offset projects. We utilized the U.S. Forest Service Forest Vegetation Simulator for our growth and yield simulations. To examine the factors that influence project viability, we used a classification and regression tree analysis performed in S-Plus software. Results indicate C stocking and property size are the most important property characteristics driving return on investment. However, protocol requirements and legislative assumptions impacting long-term monitoring costs are also important factors. While reduced price risk in a compliance carbon market has the potential to improve forest management in North America; high initial project development costs, long-term monitoring obligations, and legislative uncertainty are significant barriers that will limit family forest landowner market participation. The model developed here can be used by U.S. landowners to assess the financial viability of their property as a compliance offset project and can be utilized by policymakers to develop cost-effective climate change policy.

Rehabilitation forestry and carbon market access onhigh-graded northern hardwood forests

Decades of heavy-cutting and high-grading in the northeastern United States provide an opportunity for rehabilitation and increased carbon stores, yet few studies have examined the feasibility of using carbon markets to restore high-graded forests. We evaluated the effectiveness of rehabilitation on 391 ha of high-graded forest in Vermont, USA. Thirteen silvicultural scenarios were modeled over 100 years using the Forest Vegetation Simulator. Carbon offsets were quantified with the Climate Action Reserve (CAR) and American Carbon Registry (ACR) protocols and evaluated under voluntary and regulatory carbon price assumptions. Results indicate that management scenarios involving no harvest or low-intensity harvest yield the greatest incentives, yet these scenarios include a range of short-term rehabilitation options that provide flexibility for landowners. The choice of protocol also significantly influences results. Although ACR consistently generated more offsets than CAR for the same scenarios (p < 0.05), the protocols yielded similar net present values of US$121–US$256·ha−1 under high offset price assumptions. These returns are comparable to those generated from timber harvest alone under more intensive management scenarios. While timber will continue to be a primary source of revenue for many landowners, carbon markets may increasingly appeal as a new incentive for restoring high-graded forests.

A Comparison of Carbon Stock Estimates and Projections for the Northeastern United States

We conducted a comparison of carbon stock estimates produced by three different methods using regional data from the USDA Forest Service Forest Inventory and Analysis (FIA). Two methods incorporated by the Forest Vegetation Simulator (FVS) were compared to each other and to the current FIA component ratio method. We also examined the uncalibrated performance of FVS growth simulations for predicting net carbon accumulation in live trees. In general, the three carbon stock estimation approaches do not produce estimates that are either equivalent or are simply convertible. A strong spatial pattern of relationships between estimates was associated with regional variation in stand top height. Uncalibrated growth projections gave downwardly biased results that were also poorly correlated with observed carbon accumulation rates, yielding little improvement in root mean square error over the use of a simple regional average. These results reinforce the need for managers and scientists to be careful in choosing methods and reporting carbon stock estimates and to use appropriate model calibration methods in projecting future carbon accumulation.

Calibrating and Testing the Forest Vegetation Simulator to Simulate Tree Encroachment and Control Measures for Heathland Restoration in Southern Europe

Calibrating and Testing the Forest Vegetation Simulator to Simulate Tree Encroachment and Control Measures for Heathland Restoration in Southern Europe

Modeling Population Dynamics and Woody Biomass in Alaska Coastal Forest

Alaska coastal forest, 6.2 million ha in size, has been managed in the past mainly through clearcutting. Declining harvest and dwindling commercial forest resources over the past 2 decades have led to increased interest in management of young-growth stands and utilization of woody biomass for bioenergy. However, existing models to support these new management systems are very limited in number and value. This study presents a density-dependent, size-specific, and species-specific matrix growth model for forest in coastal Alaska. This model enables short- and long-term predictions of stand basal area, volume, and biomass in a simple and accurate way and facilitates understanding of the ecological and economic effects of forest management alternatives. Components of forest growth were estimated from tree- and stand-level attributes from repeated measurements of 544 Forest Inventory and Analysis permanent sample plots located throughout coastal Alaska with a wide range of stand conditions. The model was tested on 293 postsample validation plots and found to have significantly higher accuracy than the Forest Vegetation Simulator, the only growth model available for the region. Analysis of residuals revealed no spatial autocorrelation, which indicates that this model is able to adequately account for the effects of physiographic factors and other differences between southeast and southcentral Alaska.

The Effectiveness and Limitations of Fuel Modeling Using the Fire and Fuels Extension to the Forest Vegetation Simulator

Fuel treatment effectiveness is often evaluated with fire behavior modeling systems that use fuel models to generate fire behavior outputs. How surface fuels are assigned, either using one of the 53 stylized fuel models or developing custom fuel models, can affect predicted fire behavior. We collected surface and canopy fuels data before and 1, 2, 5, and 8 years after prescribed fire treatments across 10 National Forests in California. Two new methods of assigning fuel models within the Fire and Fuels Extension to the Forest Vegetation Simulator were evaluated. Field-based values for dead and downed fuel loading were used to create custom fuel models or to assign stylized fuel models. Fire was simulated with two wind scenarios (maximum 1-minute speed and maximum momentary gust speed) to assess the effect of the fuel model method on potential fire behavior. Surface flame lengths and fire type produced from custom fuel models followed the fluctuations and variability of fine fuel loading more closely than stylized fuel models. However, results of 7 out of 10 statistical tests comparing surface flame length between custom and stylized fuel models were not significant (P 0.05), suggesting that both methods used to assign surface fuel loads will predict fairly similar trends in fire behavior. FOR .S CI. ❚❚(❚):000-000.

Evaluating Forest Vegetation Simulator Performance for Trees in Multiaged Ponderosa Pine Stands, Black Hills, USA

Evaluating Forest Vegetation Simulator Performance for Trees in Multiaged Ponderosa Pine Stands, Black Hills, USA

Carbon Stocks and Climate Change: Management Implications in Northern Arizona Ponderosa Pine Forests

Researchers have observed climate-driven shifts of forest types to higher elevations in the Southwestern US and predict further migration coupled with large-scale mortality events proportional to increases in radiative forcing. Range contractions of forests are likely to impact the total carbon stored within a stand. This study examines the dynamics of Pinus ponderosa stands under three climate change scenarios in Northern Arizona using the Climate Forest Vegetation Simulator (Climate-FVS) model to project changes in carbon pools. A sample of 90 stands were grouped according to three elevational ranges; low- (1951 to 2194 m), mid- (2194 to 2499 m), and high- (2499 to 2682 m.) elevation stands. Growth, mortality, and carbon stores were simulated in the Climate-FVS over a 100 year timespan. We further simulated three management scenarios for each elevational gradient and climate scenario. Management included (1) a no-management scenario, (2) an intensive-management scenario characterized by thinning from below to a residual basal area (BA) of 18 m2/ha in conjunction with a prescribed burn every 10 years, and (3) a moderate-management scenario characterized by a thin-from-below treatment to a residual BA of 28 m2/ha coupled with a prescribed burn every 20 years. Results indicate that any increase in aridity due to climate change will produce substantial mortality throughout the elevational range of ponderosa pine stands, with lower elevation stands projected to experience the most devastating effects. Management was only effective for the intensive-management scenario; stands receiving this treatment schedule maintained moderately consistent levels of basal area and demonstrated a higher level of resilience to climate change relative to the two other management scenarios. The results of this study indicate that management can improve resiliency to climate change, however, resource managers may need to employ more intensive thinning treatments than currently proposed to achieve the best results.

Introduction to the Special Section on the Fourth Forest Vegetation Simulator (FVS) Conference

Introduction to the Special Section on the Fourth Forest Vegetation Simulator (FVS) Conference

Net carbon fluxes at stand and landscape scales from wood bioenergy harvests in the US Northeast

AbstractThe long‐term greenhouse gas emissions implications of wood biomass (‘bioenergy’) harvests are highly uncertain yet of great significance for climate change mitigation and renewable energy policies. Particularly uncertain are the net carbon (C) effects of multiple harvests staggered spatially and temporally across landscapes where bioenergy is only one of many products. We used field data to formulate bioenergy harvest scenarios, applied them to 362 sites from the Forest Inventory and Analysis database, and projected growth and harvests over 160 years using the Forest Vegetation Simulator. We compared the net cumulative C fluxes, relative to a non‐bioenergy baseline, between scenarios when various proportions of the landscape are harvested for bioenergy: 0% (non‐bioenergy); 25% (BIO25); 50% (BIO50); or 100% (BIO100), with three levels of intensification. We accounted for C stored in aboveground forest pools and wood products, direct and indirect emissions from wood products and bioenergy, and avoided direct and indirect emissions from fossil fuels. At the end of the simulation period, although 82% of stands were projected to maintain net positive C benefit, net flux remained negative (i.e., net emissions) compared to non‐bioenergy harvests for the entire 160‐year simulation period. BIO25, BIO50, and BIO100 scenarios resulted in average annual emissions of 2.47, 5.02, and 9.83 Mg C ha−1, respectively. Using bioenergy for heating decreased the emissions relative to electricity generation as did removing additional slash from thinnings between regeneration harvests. However, all bioenergy scenarios resulted in increased net emissions compared to the non‐bioenergy harvests. Stands with high initial aboveground live biomass may have higher net emissions from bioenergy harvest. Silvicultural practices such as increasing rotation length and structural retention may result in lower C fluxes from bioenergy harvests. Finally, since passive management resulted in the greatest net C storage, we recommend designation of unharvested reserves to offset emissions from harvested stands.

Using climate-FVS to project landscape-level forest carbon stores for 100 years from field and LiDAR measures of initial conditions

BackgroundForest resources supply a wide range of environmental services like mitigation of increasing levels of atmospheric carbon dioxide (CO2). As climate is changing, forest managers have added pressure to obtain forest resources by following stand management alternatives that are biologically sustainable and economically profitable. The goal of this study is to project the effect of typical forest management actions on forest C levels, given a changing climate, in the Moscow Mountain area of north-central Idaho, USA. Harvest and prescribed fire management treatments followed by plantings of one of four regionally important commercial tree species were simulated, using the climate-sensitive version of the Forest Vegetation Simulator, to estimate the biomass of four different planted species and their C sequestration response to three climate change scenarios.ResultsResults show that anticipated climate change induces a substantial decrease in C sequestration potential regardless of which of the four tree species tested are planted. It was also found that Pinus monticola has the highest capacity to sequester C by 2110, followed by Pinus ponderosa, then Pseudotsuga menziesii, and lastly Larix occidentalis.ConclusionsVariability in the growth responses to climate change exhibited by the four planted species considered in this study points to the importance to forest managers of considering how well adapted seedlings may be to predicted climate change, before the seedlings are planted, and particularly if maximizing C sequestration is the management goal.

Managing burned landscapes: evaluating future management strategies for resilient forests under a warming climate

Climate change effects on forested ecosystems worldwide include increases in drought-related mortality, changes to disturbance regimes and shifts in species distributions. Such climate-induced changes will alter the outcomes of current management strategies, complicating the selection of appropriate strategies to promote forest resilience. We modelled forest growth in ponderosa pine forests that burned in Arizona’s 2002 Rodeo–Chediski Fire using the Forest Vegetation Simulator Climate Extension, where initial stand structures were defined by pre-fire treatment and fire severity. Under extreme climate change, existing forests persisted for several decades, but shifted towards pinyon–juniper woodlands by 2104. Under milder scenarios, pine persisted with reduced growth. Prescribed burning at 10- and 20-year intervals resulted in basal areas within the historical range of variability (HRV) in low-severity sites that were initially dominated by smaller diameter trees; but in sites initially dominated by larger trees, the range was consistently exceeded. For high-severity sites, prescribed fire was too frequent to reach the HRV’s minimum basal area. Alternatively, for all stands under milder scenarios, uneven-aged management resulted in basal areas within the HRV because of its inherent flexibility to manipulate forest structures. These results emphasise the importance of flexible approaches to management in a changing climate.

Simulated impacts of mountain pine beetle and wildfire disturbances on forest vegetation composition and carbon stocks in the Southern Rocky Mountains

Abstract. Forests play an important role in sequestering carbon and offsetting anthropogenic greenhouse gas emissions, but changing disturbance regimes may compromise the capability of forests to store carbon. In the Southern Rocky Mountains, a recent outbreak of mountain pine beetle (\\textit{Dendroctonus ponderosae}; MPB) has caused remarkable levels of tree mortality. To evaluate the long-term impacts of both this insect outbreak and another characteristic disturbance in these forests, high-severity wildfire, we simulated potential changes in species composition and carbon stocks using the Forest Vegetation Simulator (FVS). Simulations were completed for 3 scenarios (no disturbance, actual MPB infestation, and modeled wildfire) using field data collected in 2010 at 97 plots in the lodgepole-pine-dominated forests of eastern Grand County, Colorado, which were heavily impacted by MPB after 2002. Results of the simulations showed that (1) lodgepole pine remained dominant over time in all scenarios, with basal area recovering to pre-disturbance levels 70–80 yr after disturbance; (2) wildfire caused a greater magnitude of change than did MPB in both patterns of succession and distribution of carbon among biomass pools; (3) levels of standing-live carbon returned to pre-disturbance conditions after 40 vs. 50 yr following MPB vs. wildfire disturbance, respectively, but took 120 vs. 150 yr to converge with conditions in the undisturbed scenario. Lodgepole pine forests appear to be relatively resilient to both of the disturbances we modeled, although changes in climate, future disturbance regimes, and other factors may significantly affect future rates of regeneration and ecosystem response.

Late-successional and old-growth forest carbon temporal dynamics in the Northern Forest (Northeastern USA)

Comprehensive data on the capacity and rates of change for carbon pools in managed and unmanaged forests is essential for evaluating climate change mitigation options being considered by policy makers at regional and national levels. We currently lack real and long-term data on forest carbon dynamics covering a wide range of forest management practices and conditions. Because of this, selecting the best policies for conserving forest carbon must rely on forest growth and yield models such as US Forest Service (USFS) Forest Vegetation Simulator (FVS) to predict the future forest carbon impacts of management actions. FVS may underestimate the capacity of older stands to accumulate carbon because the model relies on USFS Forest Inventory and Analysis data that lack data from late-successional and old-growth (LSOG) stands. Improving these models will increase the likelihood of selecting policies that successfully use forests to reduce atmospheric carbon. From 1995 to 2002, Manomet Center for Conservation Sciences conducted research on 65 10m by 50m permanent plots to evaluate forest structure (standing live and dead trees, and down coarse woody material) in LSOG stands across northern Maine. We re-measured these plots in 2011 to assess long-term carbon sequestration trends in LSOG stands of common forest types in the Northern Forest region for above ground alive, standing dead, and coarse woody material carbon pools. Late-successional (LS) and Old-growth (OG) aboveground live carbon (C) stocks were very high relative to regional mean C stocks (2.0–2.5 times the mean), LS plots were accumulating aboveground live C at a positive rate (0.61Mgha−1 year−1), while C stocks on OG plots are declining (−0.54Mgha−1 year−1). This change is driven by the presence of beech bark fungus (Nectria sp.) that is leading to mortality in larger diameter American beech (Fagus grandifolia) trees. We also found that the Northeast Variant of the Forest Vegetation Simulator is not a reliable predictor of aboveground live carbon accumulation rates in Northeastern LS and OG stands. This work provides important baselines for understanding the role of older forests and forest management within climate change mitigation strategies in the northeastern US. Late-successional and old-growth forests can play an important role in mitigating climate change, but understanding and quantifying natural disturbance risk to forest carbon stocks is critical for successful implementation of mitigation strategies. Further, regional forest carbon models will need calibration to accurately predict carbon accumulation rates in older forests.