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The majority of National Forests in the southwestern United States need fuels-reduction treatments that have not kept pace with tree growth and fuels accumulation. The harvested small-sized trees are commonly disposed of through pile burning on the site due to their low market values. We assessed the environmental and health benefits of using small diameter wood from the fuels-reduction treatments as a renewable energy source for electricity production to increase forest health and environmental quality. Our study area was located in northern Arizona within the Four Forest Restoration Initiative project area. We investigated eight air pollutants, projected stand conditions, calculated pollutant emissions from power generators and assessed damage costs from power production. We further used life cycle assessments to investigate emissions from feedstock production, transportation and power generation. Our life cycle assessment results indicate that the annual total damage costs of three treatment-energy scenarios, 1) no thin-coal, 2) thin & pile burning-coal, and 3) thin-bioenergy, are $978,157, $1,732,300 and $43,216, respectively. We determined that in comparison with the no-action (no thin-coal) scenario, the total environmental and health damage cost avoided by utilizing removed woody biomass for the yearly output of a 1 MW (megawatt) power plant was $934,941 annually.

Pareto efficiency frontiers are ideal analytical tools for evaluating likely shifts in the production of forest ecosystem services under climate change. In the context of multi-objective forest management, these frontiers, or the set of non-dominated solutions for a set of objectives at varying levels of output, provide quantitative measures of trade-offs between competing ecosystem services and changes in the best-possible management outcomes for different climate change scenarios. We used outputs from a forest growth-and-yield model that simulated wildfire and management to examine three types of Pareto frontier analyses: 1) carbon storage maximization under changing budgetary constraints with and without wildfire effects, 2) minimization of undesirable wildfire effects under changing budgetary constraints, and 3) minimization of undesirable wildfire effects at varying constrained carbon storage levels. We found that over 45 years climate change reduced the average amount of carbon stored, whether or not we simulated a wildfire on the 23,204 ha study area despite our best management efforts. Climate change also adversely affected the trade-off rate, or slope of the frontiers, between carbon storage and wildfire effects. We illustrate how the application of a methodology typically used in economics can reveal insights in forest ecosystem management otherwise hidden to decision-makers.

Forest managers are faced with the difficulty of promoting multiple ecosystem services (ES) with an incomplete understanding of the complex ways these ES interact. We developed a quantitative model to help managers better understand the effect of different management options on eight ES over time. These ES were (1) Mexican spotted owl (Strix occidentalis lucida) habitat, (2) the harvest of merchantable timber, (3) the harvest of woody biomass for potential conversion to bioenergy, (4) northern goshawk (Accipiter gentilis) habitat, (5) scenic beauty, (6) fire hazard reduction, (7) carbon storage, and (8) restoration of pre-European settlement forest structure represented through larger quadratic mean diameters (QMD). We integrated production functions for these eight ES with a forest growth-and-yield model to simulate the effects of three management actions over a 45-year period in northern Arizona, USA. We scaled ES values based on their observed maximum and minimum values as a means to compare achievement levels between ES. These scaled ES values were input into a goal-programming model to identify the optimal management regimes given a corresponding set of five different management objectives. The combination of simulation modeling with goal-programming is a novel approach for evaluating ES responses to management and for optimizing ES attainment objectives. To illustrate the value of this novel approach, we designed management objectives to reflect the likely goals a forest manager may choose for each ES in this region. ES goals were distinguished at the forest- and stand-level spatial extents. Results demonstrate the flexibility of the ES optimization model to plan for a variety of situations and preferences. For instance, two ES management goals viewed as conflicting are the protection of Mexican Spotted Owl habitat and the reduction of fire hazard risk. One ES optimization scenario (Scenario 5) produces a plan that reduces area considered as having a high fire hazard from 56% to 7% of the study area in 2015 without any reduction in owl habitat quality throughout the time horizon. We recommend that our methodology be applied and developed further by those in both the research and applied fields of ecosystem sciences.

The Forest Vegetation Simulator (FVS) growth and yield model is widely used throughout the United States, but recent studies have reported unexpectedly large bias for some regional model variants. Here we propose a general framework for model evaluation, designed to highlight model strengths and weaknesses and inform calibration efforts. We apply the framework to evaluate the Lodgepole Pine (LP) model of the FVS Central Rockies Variant (FVS-CR), which has rarely been evaluated in the literature despite its widespread use in the western US. We started with a qualitative verification of the structure and logic of the FVS-CR LP model against a modified Bakuzis matrix, determining that it adequately reproduces known patterns of stand dynamics. We then compared stand-level growth simulations to a chronosequence developed from 554 Forest Inventory and Analysis (FIA) plots measured in Colorado and Wyoming lodgepole pine forests. This quantitative validation exercise revealed that the default model settings substantially over-predict basal area and total stand carbon after 50 years for both pure lodgepole pine stands and mixed lodgepole pine stands containing a minor proportion of Engelmann spruce, subalpine fir, and quaking aspen. Using equivalence testing to validate the large-tree diameter increment model against a separate dataset of 3,790 remeasured trees on 124 lodgepole pine FIA plots, we found that the default FVS–CR LP model adequately predicts lodgepole diameter growth, though we observed large variation in model errors. Equivalence tests also revealed systematic under-estimation of spruce–fir and over-estimation of aspen productivity. Finally, we conducted a sensitivity analysis to identify the most important model parameters and data inputs driving simulated stand structure and carbon accumulation in both the short- (50 years) and long-term (200 years). The model shows the greatest sensitivity to initial species composition; a small proportion of aspen, spruce, or fir seedlings led to long-term stand re-structuring and greatly increased carbon accumulation. Other sensitive parameters included site index, the fixed large-tree diameter increment adjustment factor, and the parameter controlling the point at which density-dependent self-thinning begins (maximum stand density index). This evaluation leads us to conclude that the FVS-CR LP model tends to under-estimate tree mortality (particularly in young stands) and the default site index represents relatively high productivity stands, such that re-calibration may often be necessary to capture realistic long-term stand behaviors. Our sensitivity analysis provides guidance for future efforts to re-calibrate the FVS-CR LP model and highlights the importance of collecting site index and seedling species composition data wherever possible to produce the most realistic simulations.

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.