Effective post-fire management – including flood mitigation, revegetation, and salvage logging – depends on timely and reliable burn-severity assessments that characterize impacts to vegetation and soils. These assessments are typically derived from satellite-based change detection but can be delayed or degraded by aerosols (i.e., dust or smoke), clouds, and snow. Across 9,129 large fires (≥404 ha) in Canada and the United States from 2016–2024, we quantified sources of post-fire data obstruction and evaluated observational latency – the time to acquire the first usable scene – for four freely available, moderate-resolution datasets: Landsat, Sentinel‑1, Sentinel‑2, and the Harmonized Landsat Sentinel-2 (HLS) product. For 77 fires with field-derived burn-severity indicators, we also assessed mapping accuracy in forested ecosystems and quantified variation over time. Cloud cover was the dominant cause of data obstruction, especially in mesic and coastal regions. Sentinel‑1 exhibited the shortest observational latency (median = 4 days), followed by HLS (7 days), Sentinel‑2 (10 days), and Landsat (17 days). Composite imagery from Sentinel‑1 (89.6%) and HLS (82.8%) achieved near‑complete coverage of most fires within one month, substantially better than Sentinel‑2 (70.5%) and Landsat (56.1%). HLS, Landsat, and Sentinel‑2 produced maps of stand-replacing disturbance that exceeded 80% accuracy within one month of fire, only slightly lower than maps generated after the following growing season. Sentinel‑1 had lower initial accuracy (<70%), but outperformed other sensors in winter and improved over time. High‑frequency multispectral datasets such as HLS facilitate timely, accurate post‑fire assessments, informing critical management activities that can prevent the loss of human life and minimize economic losses following fire.

The spatial patterns of fire effects and tree mortality have profound consequences for forest resilience. Cost-effective, medium-resolution, and spatiotemporally extensive fire severity measurements are essential for informing post-fire restoration and improving our understanding of wildfires—from forest stands to continents and from days to decades. Remote sensing advancements have improved burn severity mapping, but methods vary in interpretability, scalability, generalizability, and alignment with field measurements. One meaningful metric of fire effects on forests is proportion basal area loss, but existing methods are limited by a lack of region-specific field reference data and a scalable mapping framework. To address these issues, we compiled 3280 field reference plots from 123 fires in forests across the Western US to calculate the proportion of fire-induced basal area loss. We then used spatially cross-validated machine learning models with concurrent hyperparameter tuning to select a skillful, parsimonious model from a large candidate set of remotely-sensed, climatic, and topographic predictors. Spectral-only measures of severity over- or underestimated basal area loss in dry versus wet years and across aspects, demonstrating the value of incorporating climatic and topographic context. We also tested model performance on a separate holdout dataset in the Southwest US as a demonstration of reproducibility and transparency. We provide a Google Earth Engine tool for estimating proportional basal area loss for any fire perimeter in the Western US, enabling rapid map creation for land management and ecological modeling. All code, model parameters, and training data are released to support reproducibility, community adoption, regional refinement, and adaptation to new regions.

Large, severe fires are increasing throughout frequent-fire forests of the western United States due to warming climatic conditions, as well as legacies of early twentieth century land-use practices and anthropogenic fire exclusion. Resource objective (RO) wildfires—where naturally ignited wildfires are allowed to burn to accomplish management objectives—are increasingly accepted due to relatively low cost and flexibility on lands where mechanical treatments are not allowed (e.g., designated wilderness) or economically feasible. We previously implemented a field study across a portion of the Mount Trumbull Wilderness to identify differences between historical (ca. 1870) and contemporary (1999) forest structural conditions following 100 + years of fire exclusion. The study area subsequently experienced two RO wildfires (2012 and 2019), which presented an opportunity to (1) assess how closely post-wildfire (2023) conditions approximated historical forest conditions and (2) evaluate how RO fires influenced patterns of tree mortality and regeneration. Reconstructed forest structure was made up of open stand conditions (density: 62 trees ha−1; basal area: 9 m2 ha−1) with large ponderosa pines (quadratic mean diameter: 42 cm). By 1999, the site was dominated by closed-canopy stands with many small-diameter trees. In 2023, following the two RO wildfires, tree density, basal area, and canopy cover were significantly reduced (20–50

The extent and severity of tree mortality events are increasing in pinyon-juniper ecosystems of the American Southwest, mirroring trends observed in forested systems globally. Although disturbances may alter habitat suitability for numerous species, and indices of structural complexity may serve as useful, easily measured proxies for biodiversity and ecological resilience, few studies have examined relationships between structural complexity and disturbance severity in pinyon-juniper systems. In this study, we surveyed woodland structure across gradients of tree mortality and environmental conditions at 12 pinyon-juniper sites in northern Arizona, USA, and estimated recent tree mortality using stand reconstructions. Results indicated that 58% of sites showed overall tree density declines between 1996 and 2022. Mortality of pinyon pine (Pinus edulis) reached as high as 99.8% at one site. We found significant linear relationships among nine individual indicators of structural complexity, while our aggregate structural complexity index showed a significant (p < 0.001), positive linear relationship with actual evapotranspiration and tree loss (trees ha−1). We found limited support for a non-linear model that predicted maximum structural complexity at intermediate values of tree mortality. Our findings indicated that woodland structure is rapidly changing due to drought and insect outbreaks, and structural complexity is increasing under moderate levels of tree mortality, particularly on highly productive sites. Understanding these patterns may help managers in planning climate adaptation strategies and conserving biodiversity.

Reforestation activities such as tree planting are important management tools to offset carbon emissions and restore forest ecosystem integrity. Severe wildfire activity, a key driver of forest loss, is increasing throughout the western United States (US) and creating an immense backlog of areas needing reforestation. Major financial investments and recent policy changes are expected to accelerate rates of tree planting, yet the broad-scale impact and efficacy of post-fire planting activities remain poorly understood. We quantified the outcomes of recent (1987-2022) post-fire plantings in the US Interior West using remotely sensed estimates of forest cover change and in-situ survival records (69,245 seedlings) spanning 297 unique fire events. Overall, planted areas gained forest cover 25.7 % more rapidly than environmentally similar, unplanted sites in the same fires, and planted seedling survival averaged 79.5 % (SD = 23.2 %) after one growing season. However, the effects of planting were highly variable over time and across environmental gradients. Forest cover gain and planted seedling survival were typically highest in cold, wet areas and when planting was followed by wetter-than- average years. Planting season also shaped outcomes, with late summer or fall plantings performing best on warm, dry sites, and spring plantings performing best in cold, wet areas. Forest cover gain was fastest in planting units that burned at low to moderate severity and had > 20 % post-fire forest cover in the surrounding area. Nearly half of all plantings were completed in such areas, where natural regeneration processes are most likely to promote forest recovery even without intervention. Here, we demonstrate that tree planting can enhance post- fire forest recovery rates at broad scales, though its effects are dependent on a range of environmental and operational factors. Our results help inform realistic expectations of planting outcomes, an issue of global relevance as such projects expand to achieve restoration and climate mitigation goals.

Tree thinning and the application of prescribed surface fire are widespread forest restoration strategies used to regain ecological structure and function throughout dry forests of the western United States. Though such treatments are increasingly applied to broad extents, their effects on forest ecosystems are commonly evaluated at individual experimental sites or treatment units rather than large, operational landscapes. We evaluated the responses of forest structure, regeneration, old‐tree mortality, and tree growth to forest restoration for 21 years in a landscape‐scale (2114 ha) experiment in a Ponderosa pine ( Pinus ponderosa )‐Gambel oak ( Quercus gambelii ) forest in northern Arizona, United States. Relative to the start of the experiment in 1996, tree density and basal area (BA) in the treated area were reduced by 56 and 38%, respectively, at the end of the study period compared to the untreated control. Conifer seedling densities generally declined and sprouting hardwoods increased following treatment. Mortality of old oak trees was significantly higher in the treated area compared to the control, likely due to fire‐caused injury during the prescribed burning. Mean annual BA increment of individual trees was 93% higher in the treated area than in the control. Our study provides new information on Ponderosa pine forest responses to restoration treatments at broad spatial scales and under realistic operational conditions. Results from this study can help inform landscape‐scale restoration projects in dry, fire‐dependent forests.

Background Steep elevational gradients bring multiple forest types and fire regimes together in close proximity. The San Francisco Peaks/Dook’o’oosłííd in northern Arizona rise to 3851 m elevation with slopes that span many of the major forest types of the southwestern US mountains. To reconstruct past fire regimes across this broad elevational gradient, we sampled fire-scarred trees across the south face of the Peaks, complementing previous research on forest structure, composition, and origin of aspen stands. Results At the highest elevations, Rocky Mountain bristlecone pine forests had a mean fire interval (MFI) of 19.7 years prior to a modern fire exclusion period beginning after 1879. Other high-elevation (> 2800 m) mixed conifer forests had MFI = 5.7 years and low-elevation (< 2,800 m) pine forests had MFI = 4.0 years. After 1879, there were no large fires through the end of the twentieth century. Before 1879, fires occurred in the early to middle growing season, and fire event years were linked to climate across all elevations, with a stronger association to drought (i.e., the Palmer Drought Severity Index) than to El Niño-Southern Oscillation phase. Pulses of forest regeneration were associated with the fire regime, with the largest pulse occurring shortly after fire exclusion. In addition to fire exclusion, other factors such as post-fire sprouting and regeneration after tree harvesting likely contributed to the current dense forest structure on the Peaks. Conclusions Following over a century of fire exclusion, fire activity has increased on the Peaks over the past two decades, with large recent fires of uncharacteristic severity raising concerns about tree mortality, erosion, flooding, and infrastructure damage in surrounding human communities. Past fire regimes provide useful insight into fire-climate-forest interactions and the conditions under which existing forest communities were well adapted, but adaption to future conditions is likely to be challenging due to the rapid pace of projected environmental changes.

Climate change is altering the distribution of woody plants by influencing demographic processes and modifying disturbance regimes. Trailing-edge forests may be particularly vulnerable to these effects because they exist at warm, dry margins of tree distributions. To better understand recent climate-driven changes in trailing-edge forests, we used Landsat time series and 1558 field reference plots to develop annual land cover maps from 1985 to 2020 in two large, biodiverse landscapes in central Arizona, USA. We then combined annual land cover maps with tree ring records and spatial data describing interannual climate, terrain, bark beetle (Curculionidae: Scolytinae) activity, wildfire, and harvest to quantify drivers of forest change. Throughout the two landscapes, forest extent declined by 0.3 % and 0.8 % from 1985 to 2020. However, considerable variation occurred within the study period, with abrupt (ca. 1-2 years) declines in forest extent followed by gradual (ca. 10 years) recovery on each landscape. Pinyon-juniper (Pinus edulis, Pinus monophylla, and/or Juniperus spp.) cover increased from 1985 to ca. 2000 but declined after 2000, a period of extreme drought and regional tree die-off. In contrast, pineoak (Pinus ponderosa and Quercus spp.) cover increased from 2000 to 2020, primarily due to declines in ponderosa pine and mixed conifer cover over the same period. Wildfire was a key driver of transitions from forest to non-forest cover in our study area, with the occurrence of multiple compounded drought years playing an important role in unburned areas. By driving transitions to alternative forest types or non-forest cover, disturbance and drought will increasingly shape forest dynamics and ecosystem transformations throughout the southwestern US.

Understanding naturally occurring pine regeneration dynamics in response to thinning and burning treatments is necessary not only to measure the longevity of the restoration or fuels treatment, but also to assess how well regeneration meets forest sustainability guidelines and whether natural regeneration is sufficient for maintaining a sustainable forest structure and composition. A synthesis review was carried out on the effects of mechanical thinning and prescribed burn treatments on natural pine regeneration response in frequent-fire ponderosa pine forests across the western United States. The focus was on site-specific variability in pine regeneration dynamics, temporal trends in regeneration presence and abundance, and response to treatment as described in the current literature using 29 studies that met our evidence-based review protocols. Data showed that the effects of thinning and burning treatments on regeneration depended on time since treatment. Mechanical thinning, prescribed burning, and thinning plus burn treatments all increased seedling density, but there was high variability among sites and studies. There were mixed results in the short-term (< 10 years) with both increasing and decreasing regeneration, and a general increase in regeneration 11 − 20 years post-treatment. Some long-term studies (> 20 years) concluded that stands can return to pre-treatment densities in terms of total trees per hectare and forest floor duff levels when there are no maintenance treatments applied. Several studies showed the average ponderosa pine seedling presence, survival and growth found in today’s forests to be at a high density; this combined with missed fire cycles could contribute to future fire risk and reduce the efficacy of maintaining fuel reduction goals.

Wildland fires have a multitude of ecological effects in forests, woodlands, and savannas across the globe. A major focus of past research has been on tree mortality from fire, as trees provide a vast range of biological services. We assembled a database of individual-tree records from prescribed fires and wildfires in the United States. The Fire and Tree Mortality (FTM) database includes records from 164,293 individual trees with records of fire injury (crown scorch, bole char, etc.), tree diameter, and either mortality or top-kill up to ten years post-fire. Data span 142 species and 62 genera, from 409 fires occurring from 1981-2016. Additional variables such as insect attack are included when available. The FTM database can be used to evaluate individual fire-caused mortality models for pre-fire planning and post-fire decision support, to develop improved models, and to explore general patterns of individual fire-induced tree death. The database can also be used to identify knowledge gaps that could be addressed in future research.

Background Frequent-fire forests of the western United States have undergone remarkable changes in structure, composition, and function due to historical exclusion of naturally occurring fire. Mechanized tree thinning to reduce forest density and fuel loads tends to be expensive and cannot be effectively implemented across all lands, and there is increasing interest in managing naturally ignited wildfires for meeting forest restoration objectives. To investigate general effectiveness of resource objective (RO) wildfires for restoring frequent-fire and associated forests of the western United States, we conducted a review of the related peer-reviewed literature. Results Formal analysis of ecological responses to RO fires is relatively recent, and 21 of the 37 papers (57%) we reviewed were published between the years 2010 and 2018. We found 17 studies that investigated RO fire outcomes in Sierra Nevada forests, while other ecoregions that were represented in the literature included Arizona–New Mexico Mountains, Middle Rockies–Blue Mountains, and the Colorado Plateau. Yosemite National Park was utilized in 14 of the studies we reviewed. We noted several ecoregions where frequent-fire forests occur, but for which published studies on RO fires are lacking. The main focus of research (14 studies) was related to RO fire effects on forest structure, and next in importance was research (12 studies) related to fire severity, extent, and type, with studies of understory vegetation responses and landscape-scale patterns or dynamics also prevalent. Research findings indicated that RO fires were effective for reducing tree density and fire behavior; however, densities often remained above known historical ranges of variation in several studies. Understory responses reported in the literature were mixed with respect to effects on abundance and species richness. Increases in invasive species abundance in areas of high burn severity were consistently reported. Research on landscape patterns indicated that RO fires can increase heterogeneity with respect to vegetation distribution. Conclusion RO fires can be generally effective for restoration of frequent-fire forests, particularly on landscapes with long histories of fire use and in areas of moderate burn severity. More research is needed to test fire outcomes against specific restoration targets, and additional studies are needed concerning important ecological processes and functions.

Ponderosa pine (Pines ponderosa) forests occur at their warmer, drier environmental limits in the Mogollon Highlands ecoregion (MHE) of the Southwestern United States, and are commonly found in stringers or discrete stands that form ecotones with interior chaparral. These "rear edge" forests are likely to be highly vulnerable to rapid changes in structure and composition with climate warming, drought, and wildfire. There is increasing interest in understanding historical conditions, ecosystem changes, and restoration needs for MHE forests. However, comprehensive reconstruction analysis of fire regimes and stand structure has not been done for these systems, which differ from many montane ponderosa pine forests by having an abundance of understory shrubs. In this study we used demographic data from field plots, fire scar samples, and dendroecology to reconstruct historical fire regimes and landscape structure at ponderosa pine-dominated sites that spanned a range of environmental conditions on the Prescott and Tonto National Forests. We found strong evidence of historical surface fire regimes with mean fire intervals ranging 1.3-15.6 years across the five MHE sites during the period 1700-1879. We found very little evidence of historical high-severity fire at any study site. Historical forest structure was open with tree densities ranging 84.7-136.4 trees ha(-1) and stand basal area (BA) ranging 4.5-8.4 m(2) ha(-1). Historical composition showed codominance of ponderosa pine, Arizona white oak (Quercus arizonica), Emory oak (Q. emoryi), and Gambel oak (Q. gambelii). Thus, oak species and likely other hardwoods were important historical components of these ecosystems. Contemporary forests are greater in stand density and BA by 359-703% and 285-502%, respectively, compared to historical estimates. In addition, we observed contemporary shifts in species composition. Changes related to disruption of historical fire regimes have increased susceptibility of ponderosa pine forests in the MHE to rapid shifts in structure and composition that may come about with climate change and high-intensity wildfire. Meeting fuels reduction and ecological restoration goals will be challenging for land managers due to vigorous regeneration responses of shrubs to tree thinning, prescribed burning, or other management activities. Managers will be required to balance attention to historical reference conditions, conservation of biological diversity, and needs for fuels management.

Pinyon-juniper ecosystems occur extensively across western North America, and at the landscape scale, variation in structure and composition is influenced by topographic position, soils, disturbance history, and local climate. The persistent pinyon-juniper woodland is a common structural form, and though they are known to be infrequent-fire systems, there is increasing interest in implementation of hazardous fuels reduction treatments in woodlands, especially in the wildland-urban interface. Few studies have quantified stand dynamics following fuels reduction treatments in persistent woodlands or compared treatment outcomes to conditions that develop under natural disturbance and successional processes. In 2004, we established a randomized, replicated study in woodlands of northern Arizona, and monitored stand dynamics and understory responses to determine how stand-level changes differed between common fuels reduction approaches. We compared the resulting structure with a conceptual state-and-transition model. Results showed that, over the 11 yr after treatment, juniper tree densities decreased by 8.4% and 0.9% but increased by 14.0% and 27.3% in Control, Burn, Thin, and Thin + Burn treatments, respectively. Pinyon tree densities decreased by 1.1% and 3.3%, increased by 12.2%, and decreased 7.9% in Control, Burn, Thin, and Thin + Burn treatments, respectively. All treatments showed fuel load reductions throughout the 11-yr study period and minimal rebound of tree recruitment toward pretreatment conditions. Prescribed fire alone (Burn) maintained persistent woodland conditions. Thinning treatments substantially reduced small tree densities and, with the addition of prescribed fire, produced losses of large trees. Thinning with prescribed fire (Thin + Burn) tended to produce conditions qualitatively unlike those described by our state-and-transition model. Evaluation of these commonly used fuels treatments against our state-and-transition model suggested that concerns regarding loss of ecological integrity may be warranted.

Accelerated vegetation changes are predicted for Southwestern forests due to changing disturbance regimes and climate. The 2001 Leroux Fire burned across a landscape with pre-existing permanent plots during one of the most extreme drought periods over the last few decades, providing a rare opportunity to assess wildfire−drought interactions. The wildfire burned with variable severity across a mountainous transition zone. We took advantage of this opportunity to re-measure plots originally established in 2000, and extend the temporal scale of response data to 15 years post-fire.

Prescriptions for ecological restoration of ponderosa pine (Pinus ponderosa) forests of the American Southwest are generally aimed at approximating pre-fire-exclusion conditions by reducing tree densities and hazardous fuels, and reintroducing surface fire. Increasingly, land managers are utilizing natural fire ignitions to achieve restoration and hazardous fuels reduction objectives, but to minimize risk of escape and reduce potential for undesirable outcomes fires are commonly managed under weather and fuel moisture conditions that produce lower burn severities. Few studies have examined effectiveness of incremental approaches that attempt to restore these ecosystems by allowing repeated, low-severity wildfires to reburn sites. We analyzed a 12,035-ha landscape on the Kaibab National Forest in northern Arizona and compared forest structure, hazardous fuel loading, and potential fire behavior in areas that had burned once (single fire) to others that had burned twice (re-entry) over the preceding 13 years. Forest structure and hazardous fuels characteristics in re-entry areas tended to be closer to historical ranges of variability (HRV) than in single fire areas; however, we found few statistically significant differences and tree densities in both single and re-entry fires remained higher than HRV by up to 3.5-fold. Similarly, potential fire behavior variables were statistically similar between single and re-entry fire areas. Analysis of burn severity effects suggested that trends toward reduced tree density and canopy fuels in re-entry areas were consistently driven by "cleanup effects", whereby re-entry fires produced low-severity effects in areas showing unburned/low severity after first-entry fires. Evidence of "additive effects", whereby restoration and hazardous fuels reduction objectives were being met incrementally by repeated low-severity fire, was difficult to detect on the re-entry fire landscape. Thus, with similar management, several additional fire entries will be required to restore tree densities to within the historical range. Further, our findings suggest that managing resource objective wildfires to allow for more moderate-severity burning, even with a single entry, may be more effective for restoring these forests than repeated low-severity entries.

Current conditions in dry forests of the western United State have given rise to policy mandates for accelerated ecological restoration on U.S. National Forest System and other public lands. In southwestern ponderosa pine (Pinus ponderosa Laws.) forests, mechanized tree thinning and prescribed fire are common restoration treatments but are not acceptable for all sites. Currently there is much interest in managing naturally ignited fires to accomplish restoration objectives but few studies have systematically examined the efficacy of such "resource objective" wildfires for restoring historical ranges of variability (HRV). In this study we used field plots to retrospectively sample 10 resource objective fires on two national forests in northern Arizona. We used four burn severity classes identified on Monitoring Trends in Burn Severity (MTBS) maps to stratify field sampling and compared post-fire means for 12 structure and hazardous fuels attributes to HRV and guidelines for ecosystem management. Results indicated significant differences among burn severity classes in tree density, basal area, coarse wood loads, canopy cover, and canopy fuel loads. Furthermore, areas classified as moderate (M) burn severity met HRV ranges for more attributes (67%) than did other areas in other severity classes. High (H) severity areas were within HRV for the fewest (17%) of the 12 attributes. Restoration ranges for large snag density, tree patch density and maximum patch size, and tree diameter distribution were not met within any burn severity class. Resource objective fire landscapes were comprised mainly (85%) of areas classified as unburned/low (U/L) and low (L) burn severity, whereas the M severity class made up just 12% of fire landscapes on average. Overall effectiveness of resource objective fires for meeting restoration objectives was 42%. Results suggested that effectiveness may be increased by managing for proportionally more moderate burn severity on these landscapes. For this, managers will be required to accept greater risk in terms of escaped fires and high-severity fire, which, in turn, will necessitate increasing public awareness of the potential benefits and limitations of managing wildfires for restoring ponderosa pine forest ecosystems. (C) 2017 Elsevier B.V. All rights reserved.

We investigated general effects of ecological restoration treatments on soil function in frequent-fire forests of the western United States using a systematic review methodology. We searched numerous publication databases for original research papers and used well-defined criteria developed a priori to select papers for review. We used meta-analysis and qualitative summaries to compare reported responses of macronutrients, nitrogen cycling, and soil respiration among tree thinning (thin), prescribed fire (burn), and thinning plus prescribed fire treatments (composite). Results of meta-analysis showed that mean differences in macronutrients were consistently higher in composite treatments (standardized using controls) when compared to thin-only and burn-only treatments. Mean responses related to nitrogen cycling showed similar patterns, with significant increases detected in composite treatments for all nitrogen cycling variables (mineralization, ammonification, and nitrification) and insignificant responses for the majority of the burn-only and thin-only treatments. Mean difference in response for soil respiration following composite treatments showed increases as compared to the controls, and no significant differences were detected in response to burn- and thin-only treatments. While soil function, nutrient cycling, and soil respiration differed among treatments, the most significant effects were observed for nitrogen and carbon responses, net mineralization and nitrification, ammonium availability, and soil respiration rate, which experienced the greatest increase following treatments that were both thinned and burned.

Depauperate understory plant communities resulting from intensive livestock grazing in pinyon-juniper woodlands of the western United States may represent degraded stable states, resistant to ecological restoration treatments. In this study, we analyzed 10-yr understory plant community responses to restoration treatments that included tree thinning to approximate historical densities of pinyon pine (Pinus edulis) and juniper (Juniperus osteosperma), scattering of thinning slash to improve soil conditions, and seeding at two woodland sites (Craig Ranch and Goose Pond) in northwestern Arizona. Results showed that thinning resulted in significant reductions in tree density at both sites, as well as reductions in tree basal area at the Goose Pond site. Boles, branches, and tops of the thinned trees scattered across the study sites resulted in few changes to woody surface fuel loading. Thinning and addition of woody material, along with seeding, resulted in only minor changes in understory cover and species richness at both sites. However, plant cover and species richness were both negatively correlated with tree density. Degraded conditions at the sites appeared to be stable, and we suggest that treatments implemented in our studies may have not been intensive enough to produce significant understory responses and meet restoration objectives. Managers aiming to restore understory diversity at similar sites may be required to use heavier thinning prescriptions and repeated seeding. More work is needed to test new restoration approaches that are designed to drive degraded pinyon-juniper woodlands over resilience thresholds toward more diverse understory communities.