Spruce-fir Stands Research Articles

Estimating nutritive, non-nutritive and defense foliar traits in spruce-fir stands using remote sensing and site data

The estimation of foliar traits has numerous potential applications, with the evaluation of ecosystem productivity generally regarded as one of the most widely used. In this study, we linked information regarding the concentration of various canopy traits to landscape-level forest health and pest susceptibility using remote sensing technology. Foliar traits that can affect insect herbivory, including nutritive elements such as nitrogen (N), phosphorous (P), potassium (K), and copper (Cu), non-nutritive elements such as iron (Fe) and calcium (Ca), and defensive parameters such as equivalent water thickness (EWT) and leaf mass per area (LMA), were estimated. We used Sentinel-2 and site data to develop trait estimation models in a forest dominated by spruce and fir. Several machine-learning algorithms, namely Random Forest (RF), Extreme Gradient Boosting (XGB), and Support Vector Machine (SVM) were tested. Based on the model performances, where normalized root mean square error (nRMSE) values were taken into account, XGB algorithm was selected to estimate Ca (nRMSE: 0.16), EWT (nRMSE: 0.12), Fe (nRMSE: 0.19), and K (nRMSE: 0.14). On the other hand, RF was used to model Cu (nRMSE: 0.18), LMA (nRMSE: 0.14), N (nRMSE: 0.16), and P (nRMSE: 0.22). Almost all best-performing models included Sentinel-2 red-edge indices and depth to water table (DWT) as the most important variables. We propose a novel framework to establish a connection between the concentration of foliar traits in SBW host foliage and tree susceptibility to the pest. This approach could allow for the assessment of host susceptibility on a landscape level based on the concentrations of foliar traits.

Tree-level responses to commercial thinning in spruce-fir forests across northern Maine, USA

Despite the widespread use of pre-commercial (PCT) and commercial thinning (CT) in spruce-fir (Picea-Abies) forests of North America, critical knowledge gaps exist on their long-term influences on individual tree growth and development. In this study, we used extensive repeated measurements from replicated experimental research sites across Maine (n = 96090 obs. from 7159 trees in 103 plots at 15 locations) to quantify the tree-level response of two shade-tolerant conifers: balsam fir (Abies balsamea (L.) Mill.; BF) and red spruce (Picea rubens Sarg.; RS) to contrasting thinning treatments in spruce-fir stands with and without a prior PCT (NoPCT). Treatments at the nine PCT sites included a combination of CT entry timings (immediate, 5-, and 10-year delay) and removal intensities (0, 33, and 50% relative density reduction). In contrast, at the six NoPCT sites, the CT treatments were a combination of thinning methods (dominant, crown, and low) and removal intensities (0, 33, and 50%). The results showed that compared to the unthinned control, BF in thinned NoPCT stands exhibited substantial increases in annual growth for basal area, merchantable volume, and aboveground carbon, ranging from 99 to 280%, 75 to 214%, and 104 to 312%, respectively. In comparison, RS showed more moderate increases of 36 to 121%, 6 to 81%, and 32 to 135%, respectively. Similarly, in thinned PCT stands, BF displayed annual growth increases of 11 to 139%, 28 to 87%, and 15 to 145% in basal area, merchantable volume, and aboveground carbon, respectively, while RS exhibited similar increases of 50 to 120%, 35 to 96%, and 51 to 122%, respectively. In addition, CT treatments in both PCT and NoPCT stands effectively reduced mean height-diameter ratios, while preserving live crown ratios and increasing tree-level growth efficiency. Overall, BF had a higher tree-level growth response than RS in NoPCT stands, while such differences were less pronounced in PCT stands. While stand-level growth and financial and operational factors should also be considered, our findings provide valuable insights into the long-term influences of both PCT and CT on individual tree growth, stability, vigor, and carbon sequestration potential in spruce-fir forests.

Differential impacts of spruce beetle outbreaks on snowshoe hares and red squirrels in the southern Rocky Mountains

Spruce beetles (Dendroctonus rufipennis) have impacted millions of acres of Engelmann spruce (Picea engelmannii) – subalpine fir (Abies lasiocarpa) forest in North America over the past decade, resulting in the most extensive outbreak in recorded history. This dramatic alteration of forest composition and structure has precipitated numerous changes to forest ecology and ecosystem services. Among the least studied of these changes are impacts to wild mammals, including snowshoe hares (Lepus americanus) and red squirrels (Tamiasciurus hudsonicus). We sampled a chronosequence of spruce-fir stands along a gradient of ‘years elapsed since spruce beetle outbreak’ (YSO) in order to estimate impacts to abundance of these two species in the southern Rocky Mountains. Snowshoe hare abundance was not related to YSO, at least in the first decade post-outbreak. Instead, hare abundance during this period was positively related to horizontal cover, especially that due to stem density of small diameter subalpine fir. Notably, snowshoe hare abundance was negatively related to stem density of small diameter Engelmann spruce, suggesting that elements of horizontal cover may not be uniformly beneficial to hares. Hare abundance was also negatively related to ground cover, which could help explain the lack of relationship to YSO, assuming reduction in overstory canopy would lead to increases in ground cover. Red squirrel abundance was negatively related to YSO and outbreak severity (i.e., basal area of large diameter dead trees). This was likely due to diminished cone crops in impacted areas, which red squirrels cache and rely on heavily to sustain them through the winter. Basal area of remaining large live fir trees was not related to squirrel abundance, suggesting that regeneration of spruce and associated cone crops may be necessary for recovery of red squirrels, which may take several decades.

Stand- and tree-level responses to a range of initial basal area densities following partial harvest of complex spruce–fir stands in central British Columbia: 25-year results of a long-term field experiment

As forest managers increasingly seek to implement partial-harvest silviculture systems in complex forests, more data are required on the potential development of the residual stand following treatment. In this study, we present 25-year data from a long-term silvicultural study of tree- and stand-level responses to differing levels of basal area following partial harvest in a complex spruce–fir forest in central British Columbia, Canada. Reducing stand basal area elicited stronger basal area increment response in fir than spruce; however, spruce productivity was overall higher than fir across all treatments. Smaller trees increased their size proportionally more than larger trees, and thinning resulted in increased recruitment of smaller trees into larger diameter classes. At the stand-level, basal area reductions to well below 20 m2/ha resulted in higher volume and basal area growth over the length of this study, and suggest that optimum stand-level growth may be achieved at lower basal areas than suggested in prior literature. We also found a positive relationship between stand-level residual basal area and mortality. In central British Columbia, stand structure, species composition, and growth rates in complex spruce–fir forests can be maintained through partial-harvest silviculture treatments.

Western Spruce Budworm Effects on Forest Resilience.

Western spruce budworm (Choristoneura freemani Razowski) is the most destructive defoliator of forests in the western US. Forests in northern New Mexico experienced high levels of WSBW-caused defoliation and subsequent mortality between the 1980s and 2010s. The effects of severe western spruce budworm outbreaks on stand dynamics in the US Southwest are still relatively unknown, but understanding the impacts is important to the management and resilience of these forests. To begin addressing this knowledge gap, we conducted a study along two gradients: an elevational gradient from mixed-conifer to spruce-fir forests and a gradient of WSBW-caused defoliation intensity. We recorded overstory and understory stand conditions (size structure, species composition, damaging agents). Western spruce budworm was the primary damaging agent of host trees in all stands andcaused host tree mortality across all size classes, particularly in spruce-fir stands. Results indicate an unsustainable level of mortality in spruce-fir stands and a transition towards non-host species in mixed-conifer stands. Low levels of regeneration coupled with high overstory mortality rates indicate a potential lack of resilience in spruce-fir stands, whereas resilience to future western spruce budworm defoliation events may have increased in mixed-conifer stands affected by these outbreaks.

Long-term influence of commercial thinning on stand structure and yield with/without pre-commercial thinning of spruce-fir in northern Maine, USA

Pre-commercial (PCT) and commercial thinning (CT) are important silvicultural tools applied to spruce-fir (Picea-Abies) forests, a key forest type in the northeastern portion of North America. However, the long-term influences of CT, particularly when combined with PCT, are relatively unknown, except for a few specific locations in the region. Utilizing the repeated measurements from replicated experimental research sites (n = 15) initiated in the early 2000s throughout Maine, we quantified the influence of contrasting thinning treatments on spruce-fir stands with prior PCT and without a prior PCT (NoPCT). Thinning treatments at the nine sites with a prior PCT were a combination of multiple entry timings (immediate, 5-, and 10-year delay) and removal intensities (0, 33, and 50 % relative density reduction). At the six NoPCT sites, the CT treatments were a combination of thinning methods (dominant, crown, and low) and removal intensities (0, 33, and 50 %). The most effective CT in terms of large tree response, sawlog volume, and stand value were immediate CT rather than delayed treatments after PCT, and low thinning in NoPCT stands. Dominant thinning in NoPCT showed detrimental effects on residual stand conditions leading to the lowest yield and generated product values. In general, the earlier CT entry in PCT stands led to greater long-term benefits of the treatment in terms of tree size, merchantable volume, and financial value of the stand. No thinning treatment significantly enhanced cumulative total volume or merchantable volume or financial value compared to unthinned controls because even though thinning enhanced sawlog production, unthinned stands produced more pulpwood and studwood. Although we did not find significant economic benefits of CT in stands with or without PCT, light low thinning in NoPCT, and light crown thinning without delay in PCT could be an optimal strategy to maximize the average merchantable stem size without compromising the total stand value, while providing additional benefits to stand composition and generating mid-rotation revenue. Overall, the findings highlight some complexities and challenges with effective thinning regimes in highly shade-tolerant conifer species.

Applicability evaluation of tree volume equation for Abies kawakamii (Hayata) Ito based on stem analysis data in Taiwan

ABSTRACT Abies kawakamii (Taiwan fir) typically constitutes pure forest distributed at 3,100–3,600 m above sea level in Taiwan. Its volume was first investigated in 1963 using aerial photography to identify the growing stock of the forest. In 1973, Taiwan Forestry Bureau established a fir volume estimation equation by considering Taiwan spruce and Taiwan fir stands. However, due to cutting natural forest is not permitted in Taiwan, it was difficult to reconstruct specific volume equation for Taiwan fir. We can only use and collect the uprooted trees as samples for this study by Typhoon Soudelor in 2015. We used these samples for estimation and used the remaining trees for verification and tested the suitability of six equations (models) for Taiwan fir volume estimation. We found that the Schumacher equation was suitable for juvenile trees, and the generalized combined-variable equation was suitable for semi-mature trees. The Schumacher equation (a logarithmic equation) and generalized combined-variable equation demonstrated the better suitability for volume estimation. However, when a juvenile was considered in the estimation, the generalized combined-variable equation provided underestimations. Thus, the Schumacher equation (V = aDbHc) was the better model for our test. The new tree volume estimation equation for Taiwan fir in the Mt. Xue region is presented as follows: .

Seed Rain and Seedling Establishment of Picea glauca and Abies balsamea after Partial Cutting in Plantations and Natural Stands

The conditions for natural regeneration of white spruce (Picea glauca) and balsam fir (Abies balsamea) in 12 natural stands and five plantations containing both species were investigated 9 to 30 years after partial cutting. We estimated seed input on the ground, measured light reaching the understory, and recorded the presence and age of seedlings smaller than 150 cm in height on six different substrates: mineral soil, moss, rotten wood, litterfall, herbaceous, and dead wood. Partial cutting generally prompted the establishment and growth of seedlings. The number of fir and spruce seedlings is always greater in natural stands than in plantations, a trend likely associated with the reduced abundance of suitable substrate for establishment in the latter. White spruce is significantly associated to rotten wood while fir settles on all types of substrates that cover at least 10% of the forest floor. There is a strong relationship between light intensity and the median height of spruce seedlings, but this relationship is non-significant for fir. Seedlings of both species can survive at incident light intensities as low as 3%, but an intensity of 15% or more seems to offer the best growth conditions. The results of this study provide guidelines for successful forest regeneration following partial cuts in spruce-fir stands.

Does the Practice of Silviculture Build Resilience to the Spruce Beetle? A Case Study of Treated and Untreated Spruce-Fir Stands in Northern Utah

Does the Practice of Silviculture Build Resilience to the Spruce Beetle? A Case Study of Treated and Untreated Spruce-Fir Stands in Northern Utah

Assessing Alternative Silvicultural Prescriptions for Mid-Rotation, Unthinned, Spruce-Fir Stands in Maine

Determining the optimal timing and type of entry in mid-rotation, unthinned stands can be complicated by a variety of economic and biological factors. In this analysis, long-term data from the Commercial Thinning Research Network was used to project spruce-fir (Picea spp.—Abies balsamea (L.) Mill.) stand growth on six different sites across Maine following six alternative thinning treatments (33% and 50% relative density removal paired with low, crown, and dominant thinning methods). Results showed that the low-thinning treatment performed best in terms of maximum net present value, stand age at time of maximum net present value, and average merchantable stem size. Although the low-thinning resulted in a 10% mean reduction in maximum net present value when compared to the control, the average merchantable stem size more than doubled. Overall, results of this analysis indicate that it may be financially responsible to commercially thin these stands using a low-thinning method and a light removal intensity, as the average merchantable stems size was increased and a mid-rotation financial return provided.

Straight from the caribou’s (Rangifer tarandus) mouth: detailed observations of tame caribou reveal new insights into summer–autumn diets

High-quality habitats for caribou (Rangifer tarandus (L., 1758)) are associated primarily with lichens, but lichens alone fail to satisfy summer nutritional requirements. To evaluate the summer forage value of plant communities across northeastern British Columbia (BC), where populations of northern and boreal ecotypes of caribou are declining, we observed foraging by tame, female caribou. We compared diet composition with forage abundance to determine forage selection and to quantify forage availability. Deciduous shrubs, not lichens, largely dominated summer diets. Caribou were highly selective foragers, with 28 species comprising 78% of diets. Caribou avoided ≥50% of understory vegetation in all communities, especially conifers, evergreen shrubs, mosses, and two genera of terrestrial lichens. Availability of accepted forage (species not avoided) was strongly heterogeneous across landscapes. Alpine shrub areas and mid-elevation spruce–fir stands in the mountains, as well as treed rich fens and white spruce communities in the boreal forests, provided the greatest quantities of accepted forage for caribou. Dry alpine sites and unproductive black spruce communities provided the least accepted forage. Our work has direct implications to caribou conservation by contributing to a greater understanding of the forage value of summer habitats, with implications to habitat selection, seasonal movements, and distribution ecology.

Does the Practice of Silviculture Build Resilience to the Spruce Beetle? A Case Study of Treated and Untreated Spruce-Fir Stands in Northern Utah

Does the Practice of Silviculture Build Resilience to the Spruce Beetle? A Case Study of Treated and Untreated Spruce-Fir Stands in Northern Utah

Development and evaluation of individual tree- and stand-level approaches for predicting spruce-fir response to commercial thinning in Maine, USA

Commercial thinning is a widely used silvicultural method in the spruce-fir (Picea-Abies) forests of the northeastern USA, but limited work has been done on predicting both short- and long-term individual tree- and stand-level responses to this treatment. Based on annual inventories of permanent plots from a replicated thinning experiment in Maine, USA, stand- and individual tree-level treatment response functions for spruce-fir stands were developed and evaluated. The developed thinning modifiers were shown to significantly improve predictions of annual stand-level basal area growth and mortality as well as species-specific, individual tree-level annual diameter increment, height to crown base increment, and mortality. For these response variables, duration and magnitude of the response functions were significantly influenced by thinning intensity and to a lesser extent by thinning method. In contrast, modifiers for stand-level dominant height increment as well as tree-level height increment did not show significant improvement when compared to the baseline model. When the developed modifiers were included in stand- and individual-tree growth models, a significant improvement in prediction over the baseline models was achieved, but the individual-tree approach was superior to predicting long-term response to various alternative thinning treatments. Overall, the study highlights the advantage of including thinning modifiers in growth and yield models, even for relatively shade-tolerant species, and the effectiveness of an individual-tree approach in structurally diverse and mixed-species stands.

Valuing albedo as an ecosystem service: implications for forest management

Surface albedo is a property of the Earth’s surface that provides an important climate regulating ecosystem service through the reflection of incoming solar radiation. In some regions, the cooling effect of higher albedo associated with snow-covered bare ground and young forests, compared to mature forests, can exceed the cooling effect of carbon sequestration from forest growth. Properly assigning an economic value to the net benefits of albedo-related shortwave radiative flux is therefore important in order to understand how these two ecosystem services may tradeoff under different scenarios and in different forests. Here we place an economic value on albedo-related shortwave radiation through the use of shadow prices derived from an integrated assessment model (DICE). We then examine the potential impact of this value on optimal forest rotation in the White Mountain National Forest (WMNF) in the state of New Hampshire, USA. Our results suggest that valuing albedo can shorten optimal rotation periods significantly compared to scenarios where only timber and carbon are considered. For instance, in spruce-fir stands, very short rotation periods of just 25 years become economically optimal when albedo is considered. We attribute this to the low productivity of the sites within the WMNF as well as the substantial snowfall that occurs in the area. Thus, in high latitude forests where snowfall is common and productivity is low, incorporating the valuation of albedo may lead to relatively short optimal rotation periods if the only ecosystem services considered are timber provisioning and climate regulation.

Commercial thinning stimulates natural regeneration in spruce–fir stands

Understanding the response of tree regeneration following commercial thinning treatments can improve planning in managed forests dependent on natural regeneration. We used long-term commercial thinning experiments in eastern spruce–fir stands of Maine, USA, to test two hypotheses: (1) commercial thinning increases the density of tree regeneration and (2) tree regeneration density increases with increasing thinning intensity. A decade after thinning, densities of softwood and hardwood regeneration were 10 times greater in thinned stands than unthinned stands. The abundance of small softwood (0.11–0.60 m tall) was highest in lower intensity thinning treatments, whereas medium (0.61–1.40 m tall) and large (≥1.41 m tall to 8.90 cm diameter at breast height) softwoods increased proportionally with thinning intensity, a pattern related to a higher rate of recruitment in more open stands created by heavier thinning. Hardwood density generally increased with thinning intensity and developed into a significant component of the large size class. Softwood regeneration density was higher in older spruce stands than younger fir stands, which may be due to greater abundance of advance regeneration, higher residual stand mortality, and greater harvest disturbance in older spruce stands. However, acceptable softwood stocking was achieved in all replicates of thinning treatments. Therefore, in addition to providing higher individual-tree growth and merchantable yield, commercial thinning in eastern spruce–fir stands also increases regeneration density. The rate of recruitment also increased as thinning intensity increased, thus stimulating understory regeneration similar to that of a shelterwood establishment cut.

Optimal uneven-aged stocking guides: an application to spruce-fir stands in New England

Management guides for uneven-aged forest stands periodically need to be revisited and updated based on new information and methods. The current silvicultural guide for uneven-aged spruce-fir management in Maine and the northeast (Frank, R.M. and Bjorkbom, J.C. 1973 A silvicultural guide for spruce-fir in the northeast. General Technical Report NE-6, Forest Service. U.S. Department of Agriculture) presents two options for each of three different cutting cycles, and all guides are based on a negative exponential distribution for the number of trees by diameter class. While this guide claims to be optimal, it will be demonstrated that it is not necessarily optimal in any commonly accepted sense and is overly restrictive in its adherence to the negative exponential model of stand structure.We review a methodology that allows the objective determination of optimal stocking guides for uneven-aged stands that can be tailored to the individual stand and provides consideration for a number of alternative objectives and cutting cycles. These guides do not necessarily conform to the strict negative exponential distribution. They also suggest residual basal areas somewhat lower than those recommended by the current spruce-fir silvicultural guide for the northeastern USA.

Midrotation response of ground vegetation to herbicide and precommercial thinning in the Acadian Forest of Maine, USA

Silvicultural practices can directly or indirectly influence the abundance and diversity of ground vegetation, and thereby influence a vital component of forest ecosystems. As silvicultural intensity increases, understanding the effects on ground vegetation become more critical. Long-term data on the response of ground vegetation to various intensities of forest management are limited. Therefore, we used a long-term experiment to quantify how individual and combined applications of herbicide and precommercial thinning (PCT) early in stand development influenced the cover, richness, and diversity of ground vegetation at midrotation (30–40years) in spruce–fir stands of the Acadian Region. Aerial application of different herbicides (including glyphosate, triclopyr, and phenoxys) had no long-term effect (23–33years after treatment) on cover, richness, and diversity of ground vegetation. In contrast, PCT had a positive and long-lasting effect (up to 24years post-treatment) on ground vegetation cover, richness, and diversity. Our results indicated that overstory structure had a larger influence on ground vegetation than overstory species composition. Thus, manipulation of stand structure and the maintenance of a variety of stand structures across the landscape are important strategies for managing the diversity of ground vegetation. We conclude that PCT, especially following herbicide application, is an effective silvicultural tool for the maintenance of ground vegetation diversity, as well as timber production.

Long-term response of spruce–fir stands to herbicide and precommercial thinning: observed and projected growth, yield, and financial returns in central Maine, USA

Herbicide application and precommercial thinning (PCT) are common silvicultural treatments used across North America and Europe. Despite this widespread use, long-term growth and yield responses from controlled experiments that include both of these treatments are relatively rare. We used 40-year growth and yield responses of spruce–fir stands to various combinations of early herbicide and PCT in a long-term silvicultural experiment in central Maine, USA, to calibrate the Forest Vegetation Simulator (Northeast Variant). Using the calibrated model, we projected rotation-length outcomes for stand development, merchantable wood volumes, and stumpage-based financial returns. Projections indicated gains in total yield (17%–31%) from herbicide treatments at the end of the rotation (∼60 years postharvest) relative to untreated stands. Substantial increases in merchantable wood volume also were achieved with PCT. Twenty-four years after PCT, stand stumpage value averaged $907 USD·ha−1 higher than that for unthinned stands. Total yield and stumpage gains from PCT were projected to continue through the end of rotation. Highest stumpage values resulted from combined herbicide and PCT treatments, followed by PCT-only and then herbicide-only. At end of rotation, highest net present value (NPV) resulted from PCT, whether alone or in combination with herbicides. PCT and herbicide investments substantially improved the NPV relative to untreated stands when using discount rates of 2% and 4%, but not when using a 6% rate. Our results documented that good financial returns are possible over the long-term from early investments in herbicide and PCT treatments in Maine spruce–fir stands.

Forest structure and regeneration following a mountain pine beetle epidemic in southeastern Wyoming

Rocky Mountain forests are currently experiencing a bark beetle epidemic of unprecedented severity and extent. Forest regeneration following bark beetle outbreaks is driven by the survival and density of understory trees (advance regeneration). The composition and density of the advance regeneration may differ substantially from the pre-outbreak overstory and across environmental gradients. We characterized and compared the density and species composition of advance regeneration, residual overstory, and pre-outbreak overstory in stands with varying lodgepole pine density and mortality following a massive mountain pine beetle outbreak in the Medicine Bow Range of Wyoming. Additionally, we examined the influence of moisture conditions, outbreak intensity, and stand characteristics on advance regeneration within these stands. While lodgepole pine experienced considerable mortality, it was still the dominant species in the overstory. Subalpine fir was the dominant species in the advance regeneration. Relative species density of the advance regeneration differed from the pre-outbreak overstory, demonstrating a significant shift towards subalpine fir dominance. Three different lodgepole pine forest types (pure lodgepole pine, aspen-influenced, and spruce-fir) were found prior to the outbreak in the Medicine Bow Range. In general, species composition of the advance regeneration was of the same forest type as the pre-outbreak overstory, indicating that there was very little shift between forest types within individual stands following the outbreak. However, the relative species density of the advance regeneration differed from the pre-outbreak overstory in the spruce-fir and the aspen-influenced forests types, with a much smaller proportion of lodgepole pine occurring in the advanced regeneration. Relative species densities of advance regeneration and residual overstory varied across local moisture conditions and pre-outbreak and lodgepole pine overstory density but not outbreak intensity. Subalpine fir and Engelmann spruce comprised a greater proportion of the overstory and understory in wetter stands while lodgepole pine was a greater proportion on the drier stands. Advance regeneration density was negatively correlated with pre-outbreak and lodgepole pine overstory density and basal area, except for lodgepole pine advance regeneration density which had a weak positive relationship. Succession trajectories are altered in both pure lodgepole pine stands and spruce-fir stands. Based on the density of advance regeneration compared to the pre-outbreak canopy, advance regeneration appears to be a suitable means for regenerating stands following mountain pine beetle outbreaks in the Medicine Bow Range. Relying on advance regeneration may increase heterogeneity in forest structure that may make these forests more resistant to mountain pine beetle attacks in the future.

Fine-scale heterogeneity in overstory composition contributes to heterogeneity of wildfire severity in southern boreal forest

Wildfire can create a mosaic of impacts of varying severity across the landscape. Although widely recognized, this feature and its causes are little understood or studied in ecology. We studied a 1,200-ha wildfire in the southern boreal forest of the Boundary Waters Canoe Area Wilderness (BWCAW) in northeastern Minnesota, USA, using 275 ground plots (stand-scale) and 1:7,000 scale aerial photographs for the entire burned area (landscape-scale). Fire severity was markedly heterogeneous. Overall, 50% of the burn extent was classified as high burn severity, but patches burned this severely were on average less than 70 m from patches of low severity. As expected, lowlands had lower average fire severity than uplands, but several lowland areas burned, and some upland areas remained unburned. At the landscape scale, pre-fire vegetation type—itself heterogeneous—and patch size of less flammable cover types influenced fire severity. Crown fire severity in upland areas was lowest in pure aspen–birch and red/white pine stands and highest in jack pine and spruce–fir stands. At the stand-scale, slope position and the density of certain tree species at adjacent plots influenced fire severity. Improved understanding of the severity patterns created by wildfire can help to guide the management of spatial patterns of forested systems. Based on our study, a larger range in disturbance severity at scales of 0.1 to several ha and increasing the average size, and range of sizes, of residual patches would in aggregate better mimic natural disturbance than typical harvests.