Justine Karst

Justine Karst
University of Alberta | UAlberta · Department of Renewable Resources

Professor

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74
Publications
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Introduction
Skills and Expertise

Publications

Publications (74)
Article
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...
Article
The abundance of fine roots and leaves in forests typically peaks during mid‐succession and then declines. If fine root area declines more rapidly than leaf area, this could contribute disproportionately to stand decline. However, trees also partner with symbiotic ectomycorrhizal (EcM) fungi that facilitate nutrient acquisition of fine roots. Ectom...
Article
1. 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. 2. We used annual basal area increment of trees and previously descr...
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Full-text available
Viewing plant species by their mycorrhizal type has explained a range of ecosystem processes. However, mycorrhizal type is confounded with plant phylogeny and the environments in which mycorrhizal partners occur. To circumvent these confounding effects, “dual-mycorrhizal” plant species may be potential models for testing the influence of mycorrhiza...
Article
Global change has altered nitrogen availability in boreal forest soils. As ectomycorrhizal fungi play critical ecological functions, shifts in their abundance and community composition must be considered in the response of forests to changes in nitrogen availability. Furthermore, ectomycorrhizas are symbiotic, so the response of ectomycorrhizal fun...
Article
Forest disturbances can alter mycorrhizal fungal communities with consequences for subsequent plant establishment and growth. One possible mitigation strategy to promote forest recovery following disturbances is inoculation with soil from late‐successional forests. However, whether these soil transfers change the composition of resident fungal comm...
Article
1. Fungal communities can influence the productivity, composition, and survival of trees through cycling nutrients, providing resources, and altering pathogens. Thus, shifts in fungal communities could impact forests by altering interactions between trees and their environments. Fungal community composition may be shaped by stochastic and determini...
Article
Extensive tree mortality in forests can change the community composition of soil fungi altering seedling establishment, a process critical to forest restoration. Disturbances that result in the loss of ectomycorrhizal fungi, in particular, may impede the establishment of tree species reliant on these symbionts for their survival. Inoculation of see...
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Full-text available
Plant root symbionts, namely mycorrhizal fungi, can be characterized using a variety of methods, but most of these rely on DNA. While Sanger sequencing still fulfills particular research objectives, next‐generation sequencing currently dominates the field, thus understanding how the two methods differ is important for identifying both opportunities...
Article
The long-lived five-needle pines, Pinus flexilis (limber pine) and Pinus longaeva (Great Basin bristlecone pine) can co-occur and may form symbiotic partnerships with the same species of ectomycorrhizal fungi. These shared symbiotic relationships may facilitate the persistence of these pine species. Throughout their lives, P. flexilis and P. longae...
Article
Anthropogenic nitrogen (N) and sulfur (S) deposition can change above- and belowground biodiversity, including root-associated fungi that are tightly linked to plant fitness. We investigated the effect of eleven years of N and S addition on the diversity of root-associated fungal pathogens and mutualists, including ectomycorrhizal fungi (EMF), dark...
Article
In some reclamation practices following bitumen mining in the Canadian boreal forest, overburden containing low concentrations of hydrocarbons are buried under suitable soils. Residual hydrocarbons may influence the growth of trees used in afforestation of reclaimed sites, thus determining whether roots interact with buried bitumen is key to predic...
Article
Disturbances are frequent events across the Canadian boreal forest and can affect both below and above ground ecosystem processes. How disturbances change belowground 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 i...
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Full-text available
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...
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Full-text available
Spatial patterns can inform us of forest recruitment, mortality, and tree interactions through time and disturbance. Specifically, successional trajectories of self-thinning and heterospecific negative density dependence can be interpreted from the spatial arrangement of forest stems. We conducted a 50-year spatial analysis of a forest undergoing s...
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With large forested urban areas, the city of Edmonton, Alberta, Canada, faces high annual costs of replacing trees injured by deicing salts that are commonly used for winter road maintenance. Ectomycorrhizal fungi form symbiotic associations with tree roots that allow trees to tolerate the detrimental effects of polluted soils. Here, we examined my...
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Full-text available
Understanding soil systems is critical because they form the structural and nutritional foundation for plants and thus every terrestrial habitat and agricultural system. In this paper, we encourage increased use of mathematical models to drive forward understanding of interactions in soil ecological systems. We discuss several distinctive features...
Article
The trajectory of forests establishing on reclaimed oil sands mines in the Canadian boreal forest is uncertain. Soil microbes, namely mycorrhizal fungi, partly underlie successional trajectories of plant communities, yet their role in restoration is often overlooked. Here, we test the relative importance of common management tools used in restorati...
Data
APPENDIX S1. Generating mock communities for fluorescent amplified fragment length polymorphism analysis.
Data
APPENDIX S4. Species resolved in mock communities of “Pine” and “Mixedwood” forest ecosites.
Data
APPENDIX S2. Common species present in two common ecosites of boreal forest in northern Alberta, Canada. These species formed two pools from which mock communities were subsampled.
Data
APPENDIX S3. Subsampled communities comprising mock communities designed to test influence of species richness on detection success using fluorescent amplified fragment length polymorphisms.
Data
APPENDIX S5. Comparison of fragment lengths (number of base pairs) for three cpDNA regions (the trnT‐trnL intergenic spacer, the trnL intron, and the trnL‐trnF intergenic spacer) across studies: (A) the current study compared to Randall et al. (2014), and (B) the current study compared to Taggart et al. (2011).
Article
Full-text available
Premise of the Study Identifying roots to species is challenging, but is a common problem in ecology. Fluorescent amplified fragment length polymorphisms (FAFLPs) can distinguish species within a mixed sample, are high throughput, and are inexpensive. To broaden the use of this tool across ecosystems, unique size profiles must be established for sp...
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Full-text available
Variation in tree recruitment, mortality, and growth can alter forest community composition and structure. Because tree recruitment and mortality events are generally infrequent, long‐time scales are needed to confirm trends in forests. We performed a 50‐yr demographic census of a forest plot located on the southern edge of the Canadian boreal fore...
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Full-text available
Ectomycorrhizal fungi are an important component to ecosystem function in the boreal forest. Underlying factors influencing fungal community composition and richness, such as host identity and soil type have been studied, but interactions between these factors have been less explored. Furthermore, mixed-species stands may have additive or synergist...
Article
Understanding how reclamation practices influence plant community assembly and succession is an important step in developing realistic indicators and targets for reclamation of oil sands mine sites to upland forest ecosystems. We currently have a poor understanding of factors affecting plant community assembly and succession in reclaimed oil sands...
Article
Aim At continental scales, abiotic factors such as climate are typically used to explain differences in plant ranges. Although biotic interactions also underlie the biogeography of plants, the importance of plant‐associated microbes is often overlooked when predicting ranges. In particular, symbiotic microbes may influence the distribution of plant...
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Full-text available
Local adaptation, the differential success of genotypes in their native versus foreign environments, can influence ecological and evolutionary processes, yet its importance is difficult to estimate because it has not been widely studied, particularly in the context of interspecific interactions. Interactions between ectomycorrhizal (EM) fungi and t...
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Western North American landscapes are rapidly being transformed by forest die-off caused by mountain pine beetle (Dendroctonus ponderosae), with implications for plant and soil communities. The mechanisms that drive changes in soil community structure, particularly for the highly prevalent ectomycorrhizal fungi in pine forests, are complex and inte...
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Full-text available
How carbon (C) flows through plants into soils is poorly understood. Carbon exuded comes from a pool of non-structural carbohydrates (NSC) in roots. Simple models of diffusion across concentration gradients indicate that the more C in roots, the more C should be exuded from roots. However, the mechanisms underlying the accumulation and loss of C fr...
Article
Background: Local adaptation, the differential success of genotypes in their native versus foreign environment, arises from various evolutionary processes, but the importance of concurrent abiotic and biotic factors as drivers of local adaptation has only recently been investigated. Local adaptation to biotic interactions may be particularly impor...
Article
1. Phenology-induced changes in carbon assimilation by trees may affect carbon stored in fine roots and as a consequence, alter carbon allocated to ectomycorrhizal fungi. Two competing models exist to explain carbon mobilization by ectomycorrhizal fungi. Under the ‘saprotrophy model’, decreased allocation of carbon may induce saprotrophic behaviour...
Article
Full-text available
Plants form belowground associations with mycorrhizal fungi in one of the most common symbioses on Earth. However, few large-scale generalizations exist for the structure and function of mycorrhizal symbioses, as the nature of this relationship varies from mutualistic to parasitic and is largely context-dependent. We announce the public release of...
Conference Paper
Higher fitness of genotypes in their native environment relative to a foreign environment, or local adaptation, can drive the maintenance of genetic diversity in a species, and can also lead to population divergence and even speciation. Mycorrhizal fungi can play an important role in mediating a plant’s interaction with the local abiotic and biotic...
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Full-text available
Roots of different plant species are typically morphologically indistinguishable. Of the DNA-based techniques, fluorescent amplified-fragment length polymorphisms (FAFLPs) are considered reliable, high throughput, inexpensive methods to identify roots from mixed species samples. False-negatives, however, are not uncommon and their underlying causes...
Article
Dendroctonus ponderosae has killed millions of Pinus contorta in western North America with subsequent effects on stand conditions, including changes in light intensity, needle deposition, and the composition of fungal community mutualists, namely ectomycorrhizal fungi. It is unknown whether these changes in stand conditions will have cascading con...
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Full-text available
Plant species vary greatly in their responsiveness to nutritional soil mutualists, such as mycorrhizal fungi and rhizobia, and this responsiveness is associated with a trade-off in allocation to root structures for resource uptake. As a result, the outcome of plant competition can change with the density of mutualists, with microbe-responsive plant...
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Full-text available
The current unprecedented outbreak of mountain pine beetle ( Dendroctonus ponderosae ) in lodgepole pine ( Pinus contorta ) forests of western Canada has resulted in a landscape consisting of a mosaic of forest stands at different stages of mortality. Within forest stands, understory communities are the reservoir of the majority of plant species di...
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Full-text available
Surface mining in the Canadian boreal forest involves the removal of vegetation and soils, resulting in the local loss of biodiversity and ecosystem functioning. Ectomycorrhizal (EM) fungi are critical to ecosystem processes; however, their recovery following reclamation is not well understood. This study investigated the importance of reclamation...
Article
Aims Using a natural gradient of recent (0–4 years) mountain pine beetle (Dendroctonus ponderosae)-caused mortality in lodgepole pine (Pinus contorta) stands in west central Alberta, Canada, we tested the effects of different levels of tree mortality, and time since bark beetle infestation, on initial abiotic environmental changes, and nutrient inp...
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Full-text available
Altered disturbance regimes and novel introductions are causing rapid shifts in the distribution of pines (Pinus L.). The functionally obligate symbiosis between pines and ectomycorrhizal (EM) fungi dictates that shifts in the distribution of one partner will affect the distribution of the other. In this review, we examine evidence for three hypoth...
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Full-text available
• Premise of the study: Roots play a key role in many ecological processes, yet our ability to identify species from bulk root samples is limited. Molecular tools may be used to identify species from root samples, but they have not yet been developed for most systems. Here we present a PCR-based method previously used to identify roots of grassland...
Conference Paper
Full-text available
Background/Question/Methods Large-scale outbreaks of mountain pine beetle (Dendroctonus ponderosae) have killed millions of hectares of lodgepole pine (Pinus contorta) forests throughout North America. The rapid and widespread death of lodgepole pine will likely have cascading effects on biodiversity. The composition of soil fungal communities in...
Conference Paper
Background/Question/Methods In the Canadian boreal forest, surface mining for oil deposits has disturbed 715 square kilometers requiring subsequent reclamation. During this landscape level disturbance, critical mutualisms important for the growth and survival of boreal trees are disrupted. Specifically, ectomycorrhizas, the association between ro...
Conference Paper
Background/Question/Methods Following the mountain pine beetle (MPB; Dendroctonus ponderosae) outbreak, entire landscapes of mature Pinus contorta forests will be replaced by a new cohort of seedlings. Identifying potential limitations on seedling survival will be critical for predicting trajectories of beetle-killed stands. Toward this goal, we...
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Full-text available
• Context Soil temperature can limit tree growth and function, but it is often unaddressed in understanding the successional status of trees. • Aims We tested how soil temperature affected carbon allocation strategies of two dominant co-occurring boreal conifer species, Pinus contorta and Picea mariana. • Methods We measured nonstructural carbon (N...
Article
Encouraging natural regeneration of Populus tremuloides Michx (trembling aspen) from seed is a largely unexplored means for reintroducing the species into reclamation areas. We evaluated the effects of microsite (surface contour and substrate type) on aspen seedling establishment and growth on a reclaimed coal mine. The 4.6 ha study site was divide...
Article
Forest die-off caused by mountain pine beetle (MPB) is rapidly transforming western North American landscapes. The rapid and widespread death of lodgepole pine will likely have cascading effects on biodiversity. One group particularly prone to such declines associated with MPB are ectomycorrhizal fungi, symbiotic organisms that can depend on pine f...
Article
Forest die-off caused by mountain pine beetle (MPB) is rapidly transforming western North American landscapes. The rapid and widespread death of lodgepole pine will likely have cascading effects on biodiversity. One group particularly prone to such declines associated with MPB are ectomycorrhizal fungi, symbiotic organisms that can depend on pine f...
Conference Paper
Background/Question/Methods Landscape-scale outbreaks of the mountain pine beetle (Dendroctonus ponderosae; MPB) have erupted across western North America, killing mature lodgepole pine (Pinus contorta) trees over millions of hectares. MPB-induced mortality may influence the strength of interdependence among above (e.g., stand structure, pine lit...
Conference Paper
Background/Question/Methods In boreal forests, understory communities are the reservoir of the majority of plant species diversity, influence nutrient cycling, represent habitat and forage for wildlife, and have strong impacts on canopy succession. Consequently, understanding the factors that influence changes in understory composition is critica...
Conference Paper
Background/Question/Methods Large-scale outbreaks of mountain pine beetle (Dendroctonus ponderosae) have killed millions of hectares of lodgepole pine (Pinus contorta) forests throughout North America. In general, conifer seedling establishment in these forests is enhanced by ectomycorrhizal fungi and pine establishment in particular, is highly s...
Article
Full-text available
Similarity between seed bank and aboveground vegetation is frequently studied in order to better understand how community composition is affected by factors such as disturbance and succession. Grassland plant communities are known to be sensitive to shifts in precipitation and increases in temperature associated with climate change, but we do not k...
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We investigated the community composition and diversity of soil fungi along a sharp vegetative ecotone between Coastal Sage Scrub (CSS) and non-native annual grassland habitat at two sites in coastal California, USA. We pooled soil samples across 29 m transects on either side of the ecotone at each of the two sites and using clone libraries of fung...
Article
Context-dependent foraging behaviour is acknowledged and well documented for a diversity of animals and conditions. The contextual determinants of plant foraging behaviour, however, are poorly understood. Plant roots encounter patchy distributions of nutrients and soil fungi. Both of these features affect root form and function, but how they intera...
Article
Exotic earthworms are entering previously uninhabited soils of boreal forests, their invasion largely facilitated through human activities. As ecosystem engineers, earthworms are capable of causing dramatic changes in above- and belowground forest composition, but whether they have the same effects in all forests remains unclear. Forest composition...
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Full-text available
Many studies have confirmed the potential importance of mycorrhizas to plant growth and community structure. Needed now are studies that focus on the relative ecological importance of mycorrhizas, specifically how the effect of mycorrhizas compares with other environmental factors present in soil that may affect plant growth. In a greenhouse, we gr...
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Ecology Letters (2010) 13: 394–407 Mycorrhizal fungi influence plant growth, local biodiversity and ecosystem function. Effects of the symbiosis on plants span the continuum from mutualism to parasitism. We sought to understand this variation in symbiotic function using meta-analysis with information theory-based model selection to assess the relat...
Conference Paper
Full-text available
Background/Question/Methods Symbiotic associations between microbes and terrestrial plants have a long evolutionary history, are ubiquitous, and can have dramatic consequences for plant growth, local biodiversity, and ecosystem function. Research on the symbiosis between plants and mycorrhizal fungi has grown dramatically in recent years, generatin...
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Full-text available
Across different host plant species, the effects of mycorrhizal colonization on host growth parameters can vary, but intraspecific variation in this relationship has rarely been measured. We tested the direction and consistency of the relationship between ectomycorrhizal colonization level and growth responses across seed families of Pinus contorta...
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Full-text available
Context dependency is deemed to position the outcomes of species interactions along a continuum of mutualism to parasitism. Thus, it is imperative to understand which factors determine where a particular interspecific interaction falls along the continuum. Over the past 20 years research on the ectomycorrhizal symbiosis has resulted in sufficient i...
Article
We conducted greenhouse experiments using Douglas-fir (Pseudotsuga menziesii var. glauca) seedlings where chemical methods (fungicides) were used to prevent ectomycorrhizal colonization of single seedlings or physical methods (mesh barriers) were used to prevent formation of mycorrhizal connections between neighboring seedlings. These methods were...
Article
We evaluated the roles of the abiotic environment and dispersal in the assembly of fern communities at contrasting spatial scales within an old-growth, temperate deciduous forest. Specifically, we examined correlations among the geographic location of sampling plots separated by either 135–3515 m (mesoscale) or 4–134 m (fine scale), the abiotic env...
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Full-text available
The ability of trees dependent on arbuscular mycorrhizal (AM) fungi to establish in ectomycorrhizal forests is unknown. On northern Vancouver Island, Canada, there are sharp boundaries between mixed red cedar (Thuja plicata)-hemlock (Tsuga heterophylla) (CH) stands, and stands of hemlock and amabilis fir (Abies amabilis) (HA). We tested differences...
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Written for the Dept. of Biology. Thesis (M.Sc.). Includes bibliographical references.
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Thesis (M. Sc.)--McGill University, 2002. Includes bibliographical references.

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