Wildfire risk reduction treatments such as thinning and prescribed burning are becoming commonplace across British Columbia forests in response to the increase in frequency and severity of wildfires. However, investigations of their effects on ecosystem structures and functions have been lacking to date. To help address this, we examined short-term effects of a thinning and burning treatment on predicted wildfire risk as well as carbon stocks, forest structure, and plant biodiversity in West Arm Provincial Park, near Nelson, British Columbia, Canada. The treatment met the goal of reducing the wildfire risk rating. In the short-term, forest floor depth and carbon stocks were 73% (4.1 cm) and 51% (12.20 Mg ha–1) less, respectively, in the treatment than the control. The aboveground tree carbon pool was also reduced, with average stocks in the treatment one-third that of the control (14.66 ± 8.72 Mg ha–1 versus 43.63 ± 16.56 Mg ha–1, respectively). Herb cover increased and moss cover decreased, and the species composition of the plant community changed, including an increase in plants associated with disturbances. The thin-burn treatment resulted in high tree mortality and damage rates, and simplified tree species diversity and vertical stand structure compared with the control. On our site, a thin-only treatment would have eliminated tree mortality due to follow-up burning, but would have been ineffective at reducing fire hazard based on the intensity of the applied burn. Our findings indicate the thin-burn treatment had trade-offs, where reduced fire risk came at ecological costs, highlighting the need for prescriptions to consider potential effects on carbon stocks and plant communities, and to be based on local conditions. We emphasize that our study was preliminary and that further monitoring is required to assess long-term results.

British Columbia’s interior forests have been heavily subjected to logging, burning, and beetle outbreaks for decades. Partial retention forest harvesting may be a method that could mitigate some of the negative effects of clearcut harvesting on wildlife. We conducted live trapping for small mammals at John Prince Research Forest in north-central BC to estimate species diversity, population density, and habitat use across a gradient of overstory tree retention. We detected 7 species, with diversity highest in the uncut forest (control) relative to the clearcut (control mean Shannon Index = 1.01, SE = 0.14) and partial retention treatments (30% and 60% retention, mean Shannon Indices = 0.99, 0.98; SE = 0.17, 0.17), and significantly lower in the seed tree treatment (mean = 0.63, SE = 0.17, p = 0.02). Greater population densities of North American deer mouse (Peromyscus sonoriensis) and southern red-backed vole (Myodes gapperi) in partially harvested stands, as estimated with spatially explicit capture-recapture models, support these practices for supporting populations of forest specialists. More experimental approaches to forest operations are needed across larger spatial scales, such as adaptive management of forest harvest methods with rigorous wildlife monitoring to ensure ecological objectives are met.

The future climatic niche of interior Douglas-fir (Pseudotsuga menziesii var. glauca [Mirb.] Franco) is expected to have little spatial overlap with its current range due to climate change. The resulting misalignment of the climatic niche and species distribution is expected to result in many forests becoming maladapted in their current location, thus increasing vulnerability to disturbance and reducing productivity. This novel study examined the individual and interactive effects of climatic transfer distance and silviculture systems on planted 3-year-old Douglas-fir seedlings across the natural range of interior Douglas-fir in British Columbia. Several climatic transfer distance variables were considered, and the silviculture systems tested comprised the following gradients of tree retention: 0% retention (clearcut), 10% dispersed retention (seed-tree), 30% aggregate retention, and 60% aggregate retention with thinning from below. Using linear mixed effect models, we found that survival and height were positively correlated with movements of seedlings to warmer, wetter, and more humid climates. Moisture availability had a stronger influence than temperature, indicating that seedlings transferred to warmer but more arid climates would experience decreased survival and height. Where seedlings were transferred to climates with greater frost frequency or decreased humidity, greater retention of overstory trees improved survival and height. Conversely, movements to more favorable climatic conditions (warmer and wetter) resulted in improved survival and height where overstory retention was low. Our findings suggest that genetic reshuffling of populations through assisted migration could benefit from overstory retention where stressful climatic conditions due to aridity or increased frost frequency occur.

Downed woody debris is important for biodiversity, forest regeneration, and carbon, nutrient, and water cycling, and past studies have examined how the coarse fraction is affected by climate or harvesting. In a field study in Douglas-fir dominated forests, we expand existing knowledge by investigating the interacting effects of climate and harvesting on downed woody debris of all sizes. Across a 900-km long latitudinal gradient in British Columbia, we found that coarse woody debris (CWD, >7.5 cm diameter) in humid climates contained 700% greater carbon stocks, had 500% greater volume, and was more diverse than in arid climates. Pre- and post-harvest, small and fine woody debris comprised a higher proportion of total woody debris carbon stocks in arid than moist climates, especially after clearcutting and seed tree treatments. Harvesting generally decreased total CWD volume, but it was not depleted on any site. Harvesting substantially reduced the volume of large, highly decomposed CWD except at the two most arid sites, and losses of large CWD increased with increasing tree removal. These losses were accompanied by a pulse of fresh, small diameter CWD and SWD which are short-term organic nutrient sources but have less habitat value than larger pieces and contribute to fuel loads. Because CWD was less abundant in arid than humid mature forests, care must be taken on arid sites to avoid its depletion during harvesting, especially clearcutting, where future woody debris inputs will not occur for decades.

EDITORIAL article Front. For. Glob. Change, 27 February 2024Sec. Forest Management Volume 7 - 2024 | https://doi.org/10.3389/ffgc.2024.1379302

Whitebark pine ( Pinus albicaulis Engelm.; WBP) is an endangered subalpine tree species and requires associations with ectomycorrhizal fungi (ECMF) for survival and growth. Despite this obligate dependence, there are gaps in the identification of ECMF that associate with WBP. In addition, ECMF rarely feature in assessments of recovery actions and little is known about the relationship between ECMF and the insects and pathogens affecting WBP. We used next-generation sequencing to characterize ECMF occurring in soil and mycorrhizal root tip samples from naturally occurring mature WBP trees and seedlings as well as planted WBP seedlings in the Columbia Mountains of Interior British Columbia, Canada. ECMF data was paired with data on tree age, tree health and soil conditions. Thirty-three species and twenty-one genera of ECMF were identified with medium or high confidence from mycorrhizal root tip samples. Major groups were: generalist ascomycetes [ Cenococcum , Meliniomyces (= Hyaloscypha )], Atheliales ( Piloderma, Amphinema, Tylospora ), non-ascomycetous generalists (e.g., Amphinema ), associates of high-elevation conifers (species of Cortinarius, Russula ) and Suilloids ( Suillus, Rhizopogon ). Differences in WBP ECMF with other, drier and southerly regions that have been studied previously, were consistent with a distinct forest type and an endemism hypothesis. Soil at the planting site and planted seedlings hosted a reduced ECMF community or were non-ectomycorrhizal, which can be explained by site factors and is expected to affect seedling survival. ECMF composition on mature trees was correlated with tree health, which may have implications for WBPs resistance to pathogens and signals that ECMF are affected by the decline of their host. Understanding the ecology of WBP ECMF and their relationship with tree performance is essential for WBP recovery efforts.

Clearcutting reduces proximity to seed sources and mycorrhizal inoculum potential for regenerating seedlings. Partial retention of legacy trees and protection of refuge plants, as well as preservation of the forest floor, can maintain mycorrhizal networks that colonize germinants and improve nutrient supply. However, little is known of overstory retention levels that best protect mycorrhizal inoculum while also providing sufficient light and soil resources for seedling establishment. To quantify the effect of tree retention on seedling regeneration, refuge plants, and resource availability, we compared five harvesting methods with increasing retention of overstory trees (clearcutting (0% retention), seed tree (10% retention), 30% patch retention, 60% patch retention, and 100% retention in uncut controls) in an interior Douglas-fir-dominated forest in British Columbia. Regeneration increased with proximity to legacy trees in partially cut forests, with increasing densities of interior Douglas-fir, western redcedar, grand fir, and western hemlock seedlings with overstory tree retention. Clearcutting reduced cover of ectomycorrhizal refuge plants (from 80 to 5%) while promoting arbuscular mycorrhizal plants the year after harvest. Richness of shrubs, herbs, and mosses declined with increasing harvesting intensity, but tree richness remained at control levels. The presence of legacy trees in all partially cut treatments mitigated these losses. Light availability declined with increasing overstory cover and proximity to leave trees, but it still exceeded 1,000 W m−2 in the clearcut, seed tree and 30% retention treatments. Increasing harvesting intensity reduced aboveground and belowground C stocks, particularly in live trees and the forest floor, although forest floor losses were also substantial where thinning took place in the 60% retention treatment. The loss of forest floor carbon, along with understory plant richness with intense harvesting was likely associated with a loss of ectomycorrhizal inoculum potential. This study suggests that dispersed retention of overstory trees where seed trees are spaced ~10–20 m apart, and aggregated retention where openings are <60 m (2 tree-lengths) in width, will result in an optimal balance of seed source proximity, inoculum potential, and resource availability where seedling regeneration, plant biodiversity, and carbon stocks are protected.

Disturbances have altered community dynamics in boreal forests with unknown consequences for belowground ecological processes. Soil fungi are particularly sensitive to such disturbances; however, the individual response of fungal guilds to different disturbance types is poorly understood. Here, we profiled soil fungal communities in lodgepole pine forests following a bark beetle outbreak, wildfire, clear-cut logging, and salvage-logging. Using Illumina MiSeq to sequence ITS1 and SSU rDNA, we characterized communities of ectomycorrhizal, arbuscular mycorrhizal, saprotrophic, and pathogenic fungi in sites representing each disturbance type paired with intact forests. We also quantified soil fungal biomass by measuring ergosterol. Abiotic disturbances changed the community composition of ectomycorrhizal fungi and shifted the dominance from ectomycorrhizal to saprotrophic fungi compared to intact forests. The disruption of the soil organic layer with disturbances correlated with the decline of ectomycorrhizal and the increase of arbuscular mycorrhizal fungi. Wildfire changed the community composition of pathogenic fungi but did not affect their proportion and diversity. Fungal biomass declined with disturbances that disrupted the forest floor. Our results suggest that the disruption of the forest floor with disturbances, and the changes in C and nutrient dynamics it may promote, structure the fungal community with implications for fungal biomass-C.

Forests are important for biodiversity, timber production and carbon accumulation, but these ecosystem services may be impacted by climate change. Field data collected from individual forest types occurring across a climatic gradient can contribute to forecasting these consequences. We examined how changes in temperature, precipitation and aridity affect ecosystem services in 23 mature Douglas-fir ( Pseudotsuga menziesii ) forests in nine climatic regions across a 900 km gradient in British Columbia, Canada. Using Canadian National Forest Inventory methodology, we assessed richness and diversity of plant functional groups, site index, and above- and below-ground carbon stocks. As aridity increased, ecosystem-level tree species richness declined on average from four to one species, Douglas-fir site index declined from 30 to 15 m, and ecosystem carbon storage decreased from 565 to 222 Mg ha –1 . Tree species richness was positively and herb species richness negatively correlated with carbon storage. Carbon storage by ecosystem compartment was largest in aboveground live tree biomass, declining in the following order: mineral soils > coarse woody debris and dead standing trees > forest floor > small and fine woody debris > understory plants. Mineral soil carbon at depths of 0-15 cm, 15-35 cm, and 35-55 cm increased with increasing mean annual precipitation and decreasing aridity. Our results indicate that as aridity increases and precipitation decreases, tree species richness, site index and carbon storage in existing Douglas-fir forests declines. However, assisted or natural migration of Douglas-fir into more humid regions could be associated with more diverse, productive, carbon-rich forests. This study informs carbon stock vulnerability and provides empirical data essential for carbon stock forecasts.

Trees often exist in a complex ecological system with many biological interactions. Here we examine kin interactions of Pseudotsuga menziesii var. glauca (interior Douglas-fir) both in the context of pure kin stands, in accordance with established plant kin selection and recognition studies, but also in combination with inter and intraspecific neighbors in order to observe how interactions may differ in a more complex system. Seedlings grown with kin neighbors (i.e. in stands that contained only kin) were significantly larger (biomass, height and root length) than those grown with any type of unrelated neighbor. However, of those with an unrelated neighbor, performance was better if that neighbor was interspecific (lodgepole pine rather than a stranger, or non-kin, Douglas-fir neighbor). Interestingly when Douglas-fir was grown in mixed stands, the four growth and four morphological traits of the seedlings examined paralleled neither pure stranger nor pure kin stands. This suggests that a mixed stand environment yielded cues that were uniquely different than either type of pure stand and that these seedlings are able to integrate that information and respond in a different way; for example, with increased early mycorrhizal fungal colonization. The morphological traits fine: coarse root allocation and slenderness (height relative to diameter) closely paralleled the seeding-size results, with the greatest values in pure kin stands. Whereas, fine root: needle allocation showed a kin response of less fine root allocation relative to needle mass compared to strangers, but kin seedlings had more fine root allocation when grown with a pine compared to a stranger Douglas-fir neighbor. We have demonstrated that the kin response in Douglas-fir is influenced by the complexity of the environment in which it grows, and this has significant effects on growth, morphology and mycorrhizal fungal colonization that may affect the success and resiliency of regeneration.

Temperate forests provide crucial ecosystems services as living sinks for atmospheric carbon (C) and repositories of biodiversity. Applying harvesting at intensities that minimize losses offers one means for mitigating global change. However, little is known of overstory retention levels that best conserve ecosystem services in different regional climates, and likewise as climate changes. To quantify the effect of harvest intensity on C stocks and biodiversity, we compared five harvesting intensities (clearcutting, seedtree retention, 30% patch retention, 60% patch retention, and uncut controls) across a climatic aridity gradient that ranged from humid to semi-arid in the Douglas-fir (Pseudotsuga menziesii) forests of British Columbia. We found that increased harvesting intensity reduced total ecosystem, aboveground, and live tree C stocks 1 year post-harvest, and the magnitude of these losses were negatively correlated with climatic aridity. In humid forests, total ecosystem C ranged from 50% loss following clearcut harvest, to 30% loss following large patch retention harvest. In arid forests this range was 60 to 8% loss, respectively. Where lower retention harvests are sought, the small patch retention treatment protected both C stocks and biodiversity in the arid forests, whereas the seedtree method performed as well or better in the humid forests. Belowground C stocks declined by an average of 29% after harvesting, with almost all of the loss from the forest floor and none from the mineral soil. Of the secondary pools, standing and coarse deadwood declined in all harvesting treatments regardless of cutting intensity or aridity, while C stocks in fine fuels and stumps increased. The understory plant C pool declined across all harvesting intensities in the humid forests, but increased in arid forests. Shannon's diversity and richness of tree and bryoid species declined with harvesting intensity, where tree species losses were greatest in the humid forests and bryoid losses greatest in arid forests. Shrub and herb species were unaffected. This study showed that the highest retention level was best at reducing losses in C stocks and biodiversity, and clearcutting the poorest, and while partial retention of canopy trees can reduce losses in these ecosystem services, outcomes will vary with climatic aridity.

Mycorrhizal networks are conduits for the transfer of resources between hosts. While ectomycorrhizal networks (EMN) are known to influence seedlings, their effect on adult tree growth remains unknown and may have important implications for forest responses to future climates. We used annual basal area increment of trees and previously described Rhizopogon vesiculosus and Rhizopogon vinicolor EMNs to examine an association between the number of connections between trees through an EMN and the growth of adult interior Douglas‐fir. We compared this relationship for the year the networks were mapped, in 2008, with 8 years previous and 8 years afterward. We also compared the variation in standardized growth (2000–2016) to examine the association between growth variability and EMN variables. Greater growth was positively associated with (a) the number of connections to other trees via a R. vinicolor EMN and (b) the number of genets of Rhizopogon vesiculosis by which a tree was colonized. Variation of growth (2000–2016) was negatively associated with increasing number of connections to other trees via R. vinicolor. Synthesis. These findings, for the first time, indicate that EMNs may positively influence the growth of adult trees. The difference in tree growth response between the sister fungal species highlights a novel avenue to identify interspecific and intraspecific differences between fungi occurring at different depths in the soil. Our study has important implications when considering the role of EMNs in influencing forest health and mitigating stress from environmental conditions.

Disturbances are frequent events across the Canadian boreal forest and can affect both below- and above-ground ecosystem processes. How disturbances change below-ground soil fungal communities and in-turn affect pine establishment and performance is poorly understood. Such understanding has become increasingly important in light of observed changes in disturbance regimes in recent years due to climate change. We used a greenhouse experiment to determine how soil inoculum collected from lodgepole pine stands undisturbed (control) or disturbed by fire, mountain pine beetle outbreak, logging and salvage logging affect pine seedling performance in western Canada. We first characterized whether fungal communities of seedling roots change as a function of inoculum source, and then determined whether changes in fungal community composition impact pine seedling performance (biomass and height). Root fungal communities of pine seedlings from logged and salvage logged disturbances differed from their respective paired controls, while soils from natural disturbances (fire and beetle outbreak) did not. Among disturbances, the pine root fungal communities of fire and salvage logged disturbances differed. In parallel to the root fungal communities, seedling performance also decreased when comparing logging and salvage logging disturbances to paired controls. Among disturbance treatments, seedlings from the salvage logged disturbance did not grow as big as seedlings inoculated with soils from burned forests. Synthesis and application. Our findings indicate that anthropogenic disturbances (logging and salvage logging) can have cross-generational impacts on pine seedling performance, through functional shifts in seedling root fungal community structure. Furthermore, the impacts of soil fungi on pine seedlings appear to be pronounced following salvage logging, stressing the importance of compound disturbance events. These findings may be important to land managers considering clear-cut logging or salvage logging in pine forests, particularly where soil biotic communities are likely to be one of the predominate factors in pine establishment.

Rhizopogon vesiculosus and R. vinicolor are sister fungal species; they form ectomycorrhizas exclusively with Douglas-fir roots, and they are important in forming relatively large mycorrhizal networks, but they may be vulnerable to disturbance caused by logging practices. The main objective was to determine the resilience of mycorrhizal networks 25 years following removal of large hub trees. We predicted that the targeted removal of mature trees would reduce network connectedness compared with a non-harvested neighboring forest. Rhizopogon vesiculosus was nearly absent in the non-harvested plots, whereas both species were prominent in the harvested plots. Initially, network analysis was based only on networks formed by R. vinicolor because they were well represented in both treatments. These analyses showed that the R. vinicolor-Douglas-fir MN was more densely linked in the non-harvested plots than the harvested plots. When we accounted for differences in link and node density, there was still an edge difference and a greater vulnerability to fragmentation in harvested forests than in non-harvested forests. When both Rhizopogon sister species were included in the analysis, both treatments had similar connectivity and limited vulnerability to fragmentation. This suggests that when these forests transition from a regenerating to a non-regenerating state, the Rhizopogon network will lose R. vesiculosus but will maintain link density due to the colonization with R. vinicolor.

For tree seedlings in boreal forests, ectomycorrhizal (EM) fungal networks may promote, while root competition may impede establishment. Thus, disruption to EM fungal networks may decrease seedling establishment owing to the loss of positive interactions among neighbors. Widespread tree mortality can disrupt EM networks, but it is not clear whether seedling establishment will be limited by the loss of positive interactions or increased by the loss of negative interactions with surrounding roots. Depending upon the relative influence of these mechanisms, widespread tree mortality may have complicated consequences on seedling establishment, and in turn, the composition of future forests. To discern between these possible outcomes and the drivers of seedling establishment, we determined the relative importance of EM fungal networks, root presence, and the bulk soil on the establishment of lodgepole pine and white spruce seedlings along a gradient of beetle-induced tree mortality. We manipulated seedling contact with EM fungal networks and roots through the use of mesh-fabric cylinders installed in soils of lodgepole pine forests experiencing a range of overstorey tree mortality caused by mountain pine beetle. Lodgepole pine seedling survival was higher with access to EM fungal networks in undisturbed pine forests in comparison with that in beetle-killed stands. That is, overstorey tree mortality shifted fungal networks from being a benefit to a cost on seedling survival. In contrast, overstorey tree mortality did not change the relative strength of EM fungal networks, root presence and the bulk soil on survival and biomass of white spruce seedlings. Furthermore, the relative influence of EM fungal networks, root presence, and bulk soils on foliar N and P concentrations was highly contingent on seedling species and overstorey tree mortality. Our results highlight that following large-scale insect outbreak, soil-mediated processes can enable differential population growth of two common conifer species, which may result in species replacement in the future.

Stump removal is a common forest management practice used to reduce the mortality of trees affected by the fungal pathogen-mediated root disease, Armillaria root rot, but the impact of stumping on soil fungal community structure is not well understood. This study analyzed the long-term impact of stumping and tree species composition on the abundance, diversity and taxonomic composition of soil fungal communities using internal transcribed spacer (ITS) marker-based DNA metabarcoding in a 48-year-old trial at Skimikin, British Columbia. A total of 108 samples were collected from FH (fermented and humus layers), and soil mineral horizons (A and B) from stumped and unstumped plots of six tree species treatments (pure stands and admixtures of Douglas-fir, western red-cedar and paper birch). Fungal α-diversity in the A horizon significantly increased with stumping regardless of tree species composition, while β-diversity was significantly affected by stumping in all the horizons. We also observed that the relative abundance of the saprotrophic fungal community declined while that of the ectomycorrhizal fungal community increased with stumping. In conclusion, increase in ectomycorrhizal fungal associations, which are positively associated with tree productivity, suggests that stumping can be considered a good management practice for mitigating root disease and promoting tree regeneration.

Large-scale studies that examine the responses of ectomycorrhizal fungi across biogeographic gradients are necessary to assess their role in mediating current and predicted future alterations in forest ecosystem processes. We assessed the extent of environmental filtering on interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) ectomycorrhizal fungal communities across regional gradients in precipitation, temperature, and soil fertility in interior Douglas-fir dominated forests of western Canada. We also examined relationships between fine-root traits and mycorrhizal fungal exploration types by combining root and fungal trait measurements with next-generation sequencing. Temperature, precipitation, and soil C:N ratio affected fungal community dissimilarity and exploration type abundance but had no effect on α-diversity. Fungi with rhizomorphs (e.g., Piloderma sp.) or proteolytic abilities (e.g., Cortinarius sp.) dominated communities in warmer and less fertile environments. Ascomycetes (e.g., Cenococcum geophilum) or shorter distance explorers, which potentially cost the plant less C, were favored in colder/drier climates where soils were richer in total nitrogen. Environmental filtering of ectomycorrhizal fungal communities is potentially related to co-evolutionary history between Douglas-fir populations and fungal symbionts, suggesting success of interior Douglas-fir as climate changes may be dependent on maintaining strong associations with local communities of mycorrhizal fungi. No evidence for a link between root and fungal resource foraging strategies was found at the regional scale. This lack of evidence further supports the need for a mycorrhizal symbiosis framework that is independent of root trait frameworks, to aid in understanding belowground plant uptake strategies across environments.

Variation in resource acquisition strategies enables plants to adapt to different environments and may partly determine their responses to climate change. However, little is known about how belowground plant traits vary across climate and soil gradients. Focusing on interior Douglas-fir (Pseudotsuga menziesii var. glauca) in western Canada, we tested whether fine-root traits relate to the environment at the intraspecific level. We quantified the variation in commonly measured functional root traits (morphological, chemical, and architectural traits) among the first three fine-root orders (i.e., absorptive fine roots) and across biogeographic gradients in climate and soil factors. Moderate but consistent trait-environment linkages occurred across populations of Douglas-fir, despite high levels of within-site variation. Shifts in morphological traits across regions were decoupled from those in chemical traits. Fine roots in colder/drier climates were characterized by a lower tissue density, higher specific area, larger diameter, and lower carbon-to-nitrogen ratio than those in warmer/wetter climates. Our results showed that Douglas-fir fine roots do not rely on adjustments in architectural traits to adapt rooting strategies in different environments. Intraspecific fine-root adjustments at the regional scale do not fit along a single axis of root economic strategy and are concordant with an increase in root acquisitive potential in colder/drier environments.

Tree range shifts during geohistorical global change events provide a useful real-world model for how future changes in forest biomes may proceed. In North America, during the last deglaciation, the distributions of tree taxa varied significantly as regards the rate and direction of their responses for reasons that remain unclear. Local-scale processes such as establishment, growth, and resilience to environmental stress ultimately influence range dynamics. Despite the fact that interactions between trees and soil biota are known to influence local-scale processes profoundly, evidence linking below-ground interactions to distribution dynamics remains scarce. We evaluated climate velocity and plant traits related to dispersal, environmental tolerance and below-ground symbioses, as potential predictors of the geohistorical rates of expansion and contraction of the core distributions of tree genera between 16 and 7 ka bp. The receptivity of host genera towards ectomycorrhizal fungi was strongly supported as a positive predictor of poleward rates of distribution expansion, and seed mass was supported as a negative predictor. Climate velocity gained support as a positive predictor of rates of distribution contraction, but not expansion. Our findings indicate that understanding how tree distributions, and thus forest ecosystems, respond to climate change requires the simultaneous consideration of traits, biotic interactions and abiotic forcing.

The majority of terrestrial plants associate with fungi in symbiotic resource-exchange relationships called mycorrhizae. Because of the importance of these mycorrhizal systems to ecosystem functioning, it is crucial that future resource managers and scientists have a solid understanding of mycorrhizal ecology. Limited interest of postsecondary students in plants and fungi compared with animals, combined with difficulties visualizing below-ground processes, present challenges for learning mycorrhizal concepts. To address this, we created the digital, plant-ecology-centric, action-based game Shroomroot for use in a second year, postsecondary Introduction to Soil Science course. We then assessed effects of Shroomroot on students' knowledge acquisition and engagement with the topic of mycorrhizal ecology using a pre- and post-test evaluation. Students' knowledge of mycorrhizal ecology increased significantly after playing Shroomroot, and tended to increase more for items related to Shroomroot gameplay than in rewards-based game content. Student engagement with mycorrhizal content tended to increase after gameplay. These results suggest positive potential for action-based, plant-ecology-oriented digital games in a postsecondary science curriculum. Furthermore, greater understanding of mycorrhizae has the potential to improve our multifaceted relationships with the ecosystems upon which we depend.