As the largest terrestrial biome, boreal forests play a critical role in the global carbon cycle, support diverse wildlife habitats, and sustain timber production, while wildfires represent a major natural disturbance shaping their function. Understanding post-fire aboveground biomass (AGB) recovery is essential for predicting long-term ecosystem functions. In this study, we tracked post-fire AGB trajectories over a 71-year period for 332 fire events in Wood Buffalo National Park, Canada. We evaluated AGB recovery across four pre-fire forest types dominated by black spruce, jack pine, white spruce, and deciduous tree species. Our results suggest substantial variation in post-fire AGB recovery rates, with the fastest AGB accumulation observed in forests dominated by deciduous species (57 gC/m2/yr), followed by white spruce (39 gC/m2/yr) and jack pine (36 gC/m2/yr), and the slowest recovery occurring in forests dominated by black spruce (21 gC/m2/yr). These differences primarily reflect the site-productivity gradient, with pre-fire forest type serving as an integrated indicator of species composition, fire behavior, and regeneration strategy. Recognizing the distinct recovery trajectories among forest types is important for understanding long-term ecosystem functions and for assessing boreal forest resilience under increasingly frequent and severe fire regimes. Moreover, our findings suggest that pre-fire forest type serves as a practical, integrated indicator of post-fire biomass recovery rates, providing valuable insights for boreal forest fire management and ecosystem modeling.
Stem surface area plays a key role in stem respiration, methane exchange, tree growth, and rainfall interception, and as a habitat for diverse organisms. However, methods for estimating stem surface area remain limited compared with well-established stem volume equations. In this study, a compatible equation for predicting stem surface area that shares coefficients with existing volume equations was developed. The equation was derived based on the square root law of form-factors and requires diameter at breast height, tree height, and a taper index based on form-factors (TIFF). Its validity was tested using empirical data from Pinus banksiana. No significant difference was found between the predicted and observed stem surface areas, with a relative mean bias of −0.063% and a relative root mean square error of 5.493%. TIFF variability is expected to have a limited effect on surface area estimates. This insensitivity enables extensive forest inventory data, including diameter at breast height and tree height from continuous and national forest inventories, to be applied immediately without the need for supplementary field measurements. The equation provides a practical pathway to shift from volume-based forest mensuration to a surface-area-based quantification of land–atmosphere exchange processes.
Western Canada hosts two endangered trees: whitebark pine (Pinus albicaulis) and limber pine (Pinus flexilis), subalpine and montane keystone species. Populations have declined sharply, primarily due to a virulent introduced pathogen (Cronartium ribicola) causing white pine blister rust. Other threats include mountain pine beetle (Dendroctonus ponderosae), human impacts, changes to historical fire regimes, and climate change. Restoring ecological function in degraded high-elevation pine ecosystems requires decades of targeted actions at multiple scales: from genes associated with disease resistance, to individual tree seed collection, to stand-level assessment and planting, to landscape connectivity planning, to establishing seed orchards for climatically adapted seed zones. Successful recovery across the species’ Canadian ranges requires partners to share resources and data, tailoring treatments to ecological and demographic conditions, and consistent tracking. Applying the Conservation Standards framework, the Whitebark Pine Ecosystem Foundation of Canada coordinates partners across jurisdictions, focusing limited resources for maximum recovery impact. Progress is tracked towards targets, goals, and objectives. Jurisdictional achievements and national progress are reported annually. Indicators and objectives are adjusted to reflect emerging knowledge and adaptive management results. We present an overview of the Conservation Standards application to Canadian whitebark and limber pine recovery, and progress to date on key benchmarks.
Two of the most pervasive threats facing Eastern Deciduous Forests are the long-term overabundance of white-tailed deer and the spread of non-native invasive plants. Overbrowsing of native plants leads to the extirpation of palatable species and intensifies invasive plant spread, leading to regeneration failures. Fragmented peri-urban habitats, the transition zone between the urban and rural interface, are particularly vulnerable to overabundant deer and invasive species. Here, we evaluate the effects of deer exclusion through fencing and a single instance of invasive plant removal on understory plant community dynamics in a degraded peri-urban habitat with high deer densities. We found that 4 years following our treatments, neither excluding deer nor removing invasives or the combination promoted native plant diversity. However, deer exclusion enhanced total native cover and vertical diversity and combined treatments increased vertical native diversity and native plant heights. Our findings highlight that while fencing fails to restore native diversity, removing invasive plants reduced invasive vertical diversity, and reducing deer browsing pressure improves native cover and vertical diversity, especially in upper understory layers. In peri-urban habitats with deer overabundance, fencing, invasive removals, and the focus on restoring browse-tolerant species offers a realistic path for restoring native plant understory composition.
This study investigated the influence of agroforestry systems involving grafted harar (Terminalia chebula Retz.), soapnut (Sapin-dus mukorossi Gaertn.), and aonla (Phyllanthus emblica) on sesame (Sesamum indicum L.) productivity and soil health in the subtropical region of Himachal Pradesh. For the evaluation of sesame (Sesamum indicum), a randomized block design with four treatments and five replications was employed and seven land-use treatments including different tree-crop combinations and sole sesame cultivation were assessed with soils sampled at 0-15 cm and 15-30 cm depths. Agroforestry systems significantly enhanced sesame growth and yield compared to sole cropping. The harar + sesame system recorded the highest benefit-cost ratio (2.36), while soapnut + sesame achieved the maximum total biomass (68.32 t ha-1) and carbon stock (34.16 t ha-1). Tree-based systems improved plant height, seed weight, and overall yield with harar-based combinations showing superior performance. Soil organic carbon was significantly higher in agroforestry systems; harar + sesame recorded 2.71% at the surface layer compared to sole sesame. Chemical attributes such as electrical conductivity (0.49 dS/m), and available N (336.64 kg/ha), P (24.16 kg/ha), and K (282.40 kg/ha) were higher in agroforestry systems under harar + sesame, though values declined with depth. Microbial nitrogen (Nmic) (313.90 mg/kg), phosphorus (Pmic) (31.53 mg/kg), and carbon (Cmic) (433.66 mg/kg) was significantly higher under harar + sesame compared to sole sesame. Similarly, enzymatic activities including dehydrogenase (6.28 & micro;g/g dry soil/ha), catalase (2.95 mg KMnO4 per gram dry soil), acid (6.96 & micro;g/g dry soil/h), and alkaline phosphatase (1.82 & micro;g/g dry soil/h) also remained highest in the harar + sesame system. Across almost all parameters, soil quality decreased with increasing depth, reflecting the importance of surface-level organic matter accumulation. Overall, agroforestry enhanced soil fertility, biological activity, and system profitability, demonstrating its potential as a sustainable strategy for improving productivity and resilience in semi-arid agroecosystems.
Prescribed fire is used to reduce fuel loads in forestry, but its impact on litter and soil properties requires further understanding. We measured pH, carbon and nitrogen concentrations, C:N ratio, and stable isotope composition (δ 13 C, δ 15 N) in litter and surface soil before, one day after, and 1 year after a low-severity prescribed burn in a Mexican montane forest. Because prescribed burns primarily combust surface litter while limiting soil heating, we expected rapid litter responses and delayed soil responses. One day after the burn, litter pH increased from 4.9 to 8.4, δ 15 N increased from –3.7‰ to –0.3‰, and the C:N ratio decreased from 44 to 21. One year after the burn, litter δ 15 N decreased toward pre-burn values (–1.5‰), while the C:N ratio increased to 84, nearly double the initial value. In soil, pH did not differ significantly one day after the burn (5.1 to 5.2). Soil δ 15 N increased from –0.2‰ to 1.6‰ one day after the burn and remained enriched one year after (2.0‰). Litter and soil δ 13 C showed no significant changes across the burn chronology. δ 15 N and C:N revealed decoupled trajectories of litter and soil and can be used as sensitive indicators of fire effects in managed forests.
An energy balance model (EBM) is developed by augmenting a carbon–climate module found in Dynamic Integrated Climate and Economy to include a land carbon pool in addition to three other pools. The land pool allows us to examine the impact of potential afforestation on future temperatures and associated damages. By removing CO 2 from the atmosphere afforestation reduces global temperatures and thereby economic damages. Realistic and optimistic rates of afforestation are investigated for four scenarios of future CO 2 emissions and per capita incomes derived from the IPCC’s shared socioeconomic pathways (SSP). The emission pathways are employed in our EBM to provide a path of future temperatures that tracks well with projections from SSPs. Since afforestation reduces atmospheric CO 2 and thereby temperatures, and since economic damages are a function of temperature, sequestration of carbon in forests reduces damages and increase income. Under the SSP2 and SSP3 scenarios, afforestation has little impact on atmospheric CO 2 and damages, and minimal impact under the SSP5 scenario. Impacts of afforestation are higher when using a Weitzman damage function as opposed to Nordhaus specification. CO 2 removals by afforestation are very small relative to anthropogenic emissions to the atmosphere. Yet afforestation may provide substantial ecosystem service benefits and/or local climate mitigation benefits.
The emerald ash borer (EAB) is one of North America's most destructive invasive insects, responsible for the death of millions of ash trees since its introduction. This study documents ash mortality, regeneration dynamics, and infestations in regenerating stems after two decades of EAB presence in Canada. We analyzed data from 46 long-term monitoring plots established in 2010-2012 across four regions, two urban and two agricultural, encompassing riparian and woodland habitats. No ash trees larger than 10 cm DBH (diameter at breast height) survived beyond 7 years following the onset of EAB-induced mortality, though vigorous regeneration was observed in most sites. Reconstruction of infestation timelines indicated that EAB shifted to attacking smaller hosts only once large trees were depleted, and among regenerating stems, 42% were infested at least once and 14% experienced five or more infestations. Larval densities were generally low, suggesting reduced carrying capacity in post-invasion forests, lower EAB fecundity, and higher EAB mortality in regenerating stems. These findings highlight the complex interactions between EAB and its hosts, improving our ability to anticipate ecological outcomes and inform post-outbreak forest management strategies.
Proposed frameworks for addressing boreal forest degradation have not yet prioritized indicators for implementation, despite this being essential to cost-effective and timely application. We created a framework grounded in the literature, subjected the indicators within that framework to semi-quantitative ranking using criteria that spoke directly to applicability and relevance, and used an expert review to produce a final suite of recommended indicators. We then turned our focus to implementation, providing a case study of prioritization for application in Ontario, Canada. Advancing from forest degradation frameworks to quantifiable applications will be bolstered by collaboration across researchers and invested parties working in this field. We end by highlighting the importance of building partnerships and utilizing existing data and products to address this phenomenon in the boreal forest of Canada and elsewhere.
Evaluating genetic diversity and population structure is important for understanding adaptation, evolution, and species conservation, especially under changing environments and disease conditions. Unfortunately, shea tree ( Vitellaria paradoxa spp. paradoxa) conservation strategies in Central Africa are rarely supported by molecular genetic studies. This study applies genotyping-by-sequencing (GBS) to evaluate genetic diversity and population structure in Shea trees across three West and Central African countries, focusing on conservation implications. We generated 12 771 high-quality filtered single nucleotide polymorphism (SNP) markers in the studied population. Within-population, expected heterozygosity (H e ) was low in all sampled populations, ranging from 0.05 to 0.08, indicating poor genetic diversity. Moreover, H e of farmland trees was closer to savannah ones. Population structure analysis revealed three main clusters aligning with geographic regions, suggesting limited gene flow and distinct adaptive responses within each of the studied populations. Additionally, the molecular variance analysis indicated that most genetic variation in these samples was distributed within the populations (74.9%). In contrast to earlier studies conducted in Cameroon using microsatellite markers, which detected no population structure, this GBS study is the first to clearly distinguish admixed groups in western and northern Cameroon. Our findings offer a concrete framework for prioritizing conservation units in domestication programs.
Long-term effects of logging on plant diversity are often examined within forest stands (alpha diversity), ignoring potential impacts on regional biodiversity that stem from biotic homogenization (beta diversity). By changing environmental conditions and altering the relative importance of environmental and dispersal-based processes, clearcutting may reduce beta diversity, reducing regional forest diversity. We compared beta diversity in secondary (“mature”) and old-growth forests of Great Smoky Mountains National Park, which maintains some of the largest tracts of old-growth forest in the Eastern U.S. Mature forests had a closed canopy but experienced clearcut logging within 50-100 years prior to measurement. Within each forest type, we examined two aspects of beta diversity: 1. total variation in community structure (‘variation’), and 2. changes in community composition along gradients (‘turnover’). We found that mature stands are more homogeneous (e.g., more similar to each other) relative to old growth stands. Furthermore, turnover rates differed between mature and old-growth forests depending on growth form. Notably, spatial distance was more strongly associated with the turnover of herbaceous communities in mature stands, while site exposure (solar radiation) was a larger driver of species turnover in old growth stands for all growth forms. Our analysis suggests that clearcutting is associated with long-term homogenization relative to remnant old-growth stands.
We tested the hypothesis that leaf litter decomposition would be faster close to streams compared to further upland due to differences in microclimate and consumer assemblages. Litter bags of dried, red alder leaves were placed on the soil surface in a coastal, temperate rainforest at five distances from 1 to 40 m from the edge of seven streams. Over 11 months, litter bags were removed from each distance and site on five different sampling dates. Litter was weighed to determine ash-free dry mass, and mass loss rate calculated for each distance and date. Mass loss was slow through winter, but by summer differences with respect to distance were clear, with higher loss rates closer to streams. By 11 months, leaf litter bags closest to the streams’ edge (1 m) had a 26% higher litter mass loss than at 40 m away. We found no significant differences in the abundance of invertebrates associated with the litter with respect to distance from streams’ edges. Densities of invertebrates were dominated by oligochaetes, but there were many other taxa present. In this relatively mesic forest, proximity to streams affects microclimate, which results in higher decomposition rates, particularly during the dry summer season.
As the constructive species of subalpine forest ecosystems in the Qilian Mountains of northwest China, regeneration of Picea crassifolia (Pinaceae) from seeds plays a crucial role in maintaining forest functionality. We investigated the function of Dasiphora fruticosa (Rosaceae), a dominant shrub species in the Qilian Mountains, as a nurse plant for establishment and growth of P. crassifolia saplings. A comprehensive monitoring program was conducted to assess the effect of D. fruticosa on the establishment and growth of P. crassifolia saplings. Our results indicate that D. fruticosa shrubs positively facilitate the occurrence of P. crassifolia saplings. The linear mixed-effects model showed that P. crassifolia saplings had a significantly higher growth rate inside the D. fruticosa shrub canopy than outside, and D. fruticosa shrubs did not significantly affect the mortality percentage of P. crassifolia saplings. The height of dead P. crassifolia saplings was significantly lower than that of the surrounding D. fruticosa shrubs, indicating that these saplings died before growing above the shrub canopy. Soil moisture content under D. fruticosa shrubs was significantly higher than that outside the shrubs. In conclusion, D. fruticosa shrubs facilitate seed germination and sapling establishment of P. crassifolia and promote sapling growth, although their shading effect suggests potential competitive pressure on sapling survival as they develop.
Carolina hemlock ( Tsuga caroliniana Engelm.) is a rare conifer endemic to the southern Appalachian Mountains. Since the early to mid‐20th century, the non‐native hemlock woolly adelgid (HWA; Adelges tsugae Annand) has threatened the persistence of both Carolina and eastern hemlocks ( Tsuga canadensis (L.) Carrière) throughout the Appalachians. To assess the long‐term impacts of HWA within the context of historical growth patterns, we used dendroecological methods to reconstruct establishment dates, disturbance events, and radial growth trends for four Carolina hemlock populations in North Carolina and Tennessee. Establishment was concentrated between 1940 and 1970, after which recruitment sharply declined. Growth release analyses revealed a cyclical disturbance–recovery pattern, with major releases concentrated in the 1970s and 1990s and moderate releases distributed across decades. This cycle was disrupted following the arrival of HWA in each county. Within a decade of infestation, radial growth declined by more than 50% at some sites, and the magnitude of suppression often exceeded that observed following natural disturbance events. These persistent declines suggest long‐term physiological stress under continued pest pressure. The sustained growth suppression indicates that HWA has fundamentally altered the growth dynamics of Carolina hemlock populations. These findings underscore the urgency of conservation interventions before visible canopy decline is observed.
We evaluated the structural response to simulated wind stress applied to two coastal tree species native to the southeastern USA that have contrasting rates of windthrow during hurricanes: Baldcypress (Taxodium distichum (L.) Rich) and laurel oak (Quercus laurifolia Michx.). In a static winching study, we evaluated the stability of 30 individuals each of laurel oak and baldcypress by quantifying the critical turning moment required to cause structural failure. Baldcypress were more likely to snap than uproot, while the opposite was true for laurel oak. Baldcypress critical turning moments were higher than laurel oak based on biomass, but were similar when compared by diameter and other size proxies, and ranged from 10.9 to 43.9 kN & centerdot;m. Models that incorporated crown size and shape indicated smaller baldcypress could withstand higher wind speeds than laurel oak before failing. Unlike laurel oak, many smaller baldcypress were so flexible that they bent to the ground instead of failing. Considering future scenarios with stronger hurricane-force winds, we conclude that baldcypress will remain wind resistant and thus ecosystem services and functions provided by this species should be maintained. Conversely, laurel oak, while having similar stability to baldcypress at large diameters, is more likely to experience windthrow at smaller diameters, which suggests that their presence in built environments should be carefully evaluated.
Bamboo expansion is widely recognized as a major driver of declining native biodiversity; however, the belowground interaction between expanding bamboo and native species remain poorly understood. In this study, four expanding stages (PES, PCM, CPM, and CLS) were established in the native Cunninghamia lanceolata ( Cl)-expanding Phyllostachys edulis ( Pe) interface, and compared with their differences in terms of root vertical distribution and phenotypic plasticity. The results showed that a vertical stratification of root biomass of two species as the expansion intensified, Cl exhibited a reduction in root biomass density, coupled with increased root allocation in deeper layers. Concurrently, fine roots of Cl displayed significant increases in specific root length, root length density, and root specific surface area by expanding effect. In contrast, the root biomass of Pe remained relatively stable but exhibited significantly higher phenotypic plasticity, with dominating the nutrient-rich upper soil layers. These contrasting responses highlight the competitive advantages of P. edulis in belowground niche occupation and reveal the competitive response patterns of expanding moso bamboo and native Chinese fir from the perspective of root system. Active restoration measures should be considered to promote the growth of native trees in bamboo–Chinese fir mixed forest management.
Trembling aspen (Populous tremuloides Michx.) copses are found throughout southern Saskatchewan and provide ecosystem services. Advancing our knowledge of carbon sequestration and biodiversity conservation requires understanding the full range of services within these unique landscapes. There is increasing attention toward regional-scale or ecosystem-specific biomass equations compared to current national-scale equations. We destructively sampled 54 trembling aspen trees from across southern Saskatchewan to develop regional-scale biomass equations for the area. We developed two complementary biomass equations using generalized additive models for diameter at breast height (DBH) and height-only models with explanatory powers of 87.1% and 74.9%. We estimated 118.27 tonnes C ha-1 for copses in Saskatchewan, which is lower than the 166.0 tonnes C ha-1 in the Boreal Forest. Our work also illustrates that the developed biomass equations are more representative of southern Saskatchewan, as national-scale DBH-only biomass equations tend to overestimate and height biomass equations tend to underestimate biomass.
Forest ecosystems are increasingly threatened by invasive pests due to global trade and changing environmental conditions. Improving tree resilience through selective breeding represents an effective management strategy. We used a combination of Lymantria dispar asiatica insect rearing, host metabolomic profiling, and full-sib family effect parameter evaluation of metabolites to identify defenses with greatest genetic potential. Among conifers studied for larval development, coastal Douglas-fir was the most and Norway spruce the least favorable host. Phenolics in foliage grouped conifer species phylogenetically, whereas terpenes reflected feeding behavior of the larvae better. Analysis of Douglas-fir full-sib families revealed moderate to high family effects of phytochemicals, suggesting potential for direct improvement of resistance. However, terpene profiles of nursery versus field grown Douglas-fir and Norway spruce were highly dissimilar, illustrating environmental and ontogenetic variability of biochemical traits. Insect bioassays thus need to be directly linked to terpene profiles of tested trees and data cannot be extrapolated to the species level. This integrated framework proposes a way for identifying targeted defenses and assessing their genetic potential, supporting evidence-based strategies for developing pest-resistant forest trees under increasing biological invasions. Follow-up work is needed to enhance phenotyping capacities of targeted resistance traits and obtain breeding values for these.
Invasive insects threaten the resilience and sustainability of Canadian forests, but we lack a comprehensive national perspective on the extent of this vulnerability. We assessed Canadian forest exposure to invasive pests by quantifying host biomass intersecting with recent (1981–2010) and near-future (2021–2040) climate niches of 14 invasive insects. Of the 37 most abundant tree species in Canada, 24 were affected by at least one of the 14 focal pests. We combined spatial assessments of exposure and outbreak severity to create an integrated spatial portrait of vulnerability. Under current conditions, 3.2 billion tonnes of tree biomass could be exposed to at least one of these pests; this is projected to increase to 13.6 billion tonnes of biomass within two decades. Two vulnerability hotspots were identified: north-central British Columbia near the BC–Alberta border and the St. Lawrence Seaway near the U.S. border. To highlight the importance of surveillance and early eradication programs, we show that a re-invasion of the Asian longhorned beetle ( Anoplophora glabripennis) into Canadian forests would put six additional tree species and 3.1 billion tonnes of tree biomass at risk. This nation-wide view aims to support risk assessments, guide the prioritization of monitoring efforts, and inform adaptive forest management.
