Resistance of subarctic soil fungal and invertebrate communities to disruption of below-ground carbon supply

The supply of recent photosynthate from plants to soils is thought to be a critical mechanism regulating the activity and diversity of soil biota. In the Arctic, large-scale vegetation transitions are underway in response to warming, and there is an urgent need to understand how these changes affect soil biodiversity and function. We investigated how abundance and diversity of soil fungi and invertebrates responded to a reduction in fresh below-ground photosynthate supply in treeline birch and willow, achieved using stem girdling. We hypothesised that birch forest would support greater abundance of ectomycorrhizal (ECM) fungal species and fauna than willow shrubs, and that girdling would result in a rapid switch from ECM fungi to saprotrophs as canopy supply of C was cut, with a concomitant decline in soil fauna. Birch forest had greater fungal and faunal abundance with a large contribution of root-associated ascomycetes (ericoid mycorrhizal fungi and root endophytes) compared to willow shrub plots, which had a higher proportion of saprotrophs and, contrary to our expectations, ECM fungi. Broad-scale soil fungal and faunal functional group composition was not significantly changed by girdling, even in the third year of treatment. Within the ECM community, there were some changes, with genera that are believed to be particularly C-demanding declining in girdled plots. However, it was notable how most ECM fungi remained present after 3 years of isolation of the below-ground compartment from contemporary photosynthate supply. Synthesis. In a treeline/tundra ecosystem, distinct soil communities existed in contrasting vegetation patches within the landscape, but the structure of these communities was resistant to canopy disturbance and concomitant reduction of autotrophic C inputs

Resistance of subarctic soil fungal and invertebrate communities to disruption of below‐ground carbon supply

The supply of recent photosynthate from plants to soils is thought to be a critical mechanism regulating the activity and diversity of soil biota. In the Arctic, large-scale vegetation transitions are underway in response to warming, and there is an urgent need to understand how these changes affect soil biodiversity and function. We investigated how abundance and diversity of soil fungi and invertebrates responded to a reduction in fresh below-ground photosynthate supply in treeline birch and willow, achieved using stem girdling. We hypothesised that birch forest would support greater abundance of ectomycorrhizal (ECM) fungal species and fauna than willow shrubs, and that girdling would result in a rapid switch from ECM fungi to saprotrophs as canopy supply of C was cut, with a concomitant decline in soil fauna. Birch forest had greater fungal and faunal abundance with a large contribution of root-associated ascomycetes (ericoid mycorrhizal fungi and root endophytes) compared to willow shrub plots, which had a higher proportion of saprotrophs and, contrary to our expectations, ECM fungi. Broad-scale soil fungal and faunal functional group composition was not significantly changed by girdling, even in the third year of treatment. Within the ECM community, there were some changes, with genera that are believed to be particularly C-demanding declining in girdled plots. However, it was notable how most ECM fungi remained present after 3 years of isolation of the below-ground compartment from contemporary photosynthate supply. Synthesis. In a treeline/tundra ecosystem, distinct soil communities existed in contrasting vegetation patches within the landscape, but the structure of these communities was resistant to canopy disturbance and concomitant reduction of autotrophic C inputs

Location of studies and evidence of effects of herbivory on Arctic vegetation: a systematic map

Herbivores modify the structure and function of tundra ecosystems. Understanding their impacts is necessary to assess the responses of these ecosystems to ongoing environmental changes. However, the effects of herbivores on plants and ecosystem structure and function vary across the Arctic. Strong spatial variation in herbivore effects implies that the results of individual studies on herbivory depend on local conditions, i.e., their ecological context. An important first step in assessing whether generalizable conclusions can be produced is to identify the existing studies and assess how well they cover the underlying environmental conditions across the Arctic. This systematic map aims to identify the ecological contexts in which herbivore impacts on vegetation have been studied in the Arctic. Specifically, the primary question of the systematic map was: “What evidence exists on the effects of herbivores on Arctic vegetation?”

Natural and Indigenous sciences: reflections on an attempt to collaborate

Abstract: Natural scientists are increasingly being encouraged to engage with local and Indigenous communities when carrying out research. However, these attempts at collaboration can repeatedly bring up challenges that have their root in how the different stakeholders relate to one another throughout the research process. This essay explores the experiences of the author, an early career researcher trained in the natural sciences, in her attempts to undertake interdisciplinary collaborative work with Sámi reindeer herders in Northern Europe. Whilst underpinned with good intent of creating decolonial, collaborative and locally useful research, the practice of this work lacked awareness of how to do so effectively, leading to multiple challenges in the project. This was largely due to the author having an inadequate understanding of key relevant discourses, including research fatigue, ethics of co-authorship, mismatching timelines, mismatching expectations between academics and relevant communities and power dynamics in interpersonal relationships. These are topics that have been explored in-depth in fields such as human geography, social sciences and anthropology, yet they are insufficiently considered in the natural sciences as a whole. The purpose of this essay is two-fold. The first is to signpost natural scientists wishing to engage in collaborative research towards key texts and concepts that could aid their work. It is not an extensive review, but rather what is hopefully an accessible introduction. It is, quite simply, an essay that the author would have appreciated having access to before undertaking her work. The second is to contribute to a wider discussion around the need for a more diverse and decolonial training in the natural sciences, so we all can respond to the many changes currently occurring on our planet using knowledge generated from well-informed, meaningful and effective collaborations

Natural and Indigenous sciences: reflections on an attempt to collaborate

Natural scientists are increasingly being encouraged to engage with local and Indigenous communities when carrying out research. However, these attempts at collaboration can repeatedly bring up challenges that have their root in how the different stakeholders relate to one another throughout the research process. This essay explores the experiences of the author, an early career researcher trained in the natural sciences, in her attempts to undertake interdisciplinary collaborative work with Sámi reindeer herders in Northern Europe. Whilst underpinned with good intent of creating decolonial, collaborative and locally useful research, the practice of this work lacked awareness of how to do so effectively, leading to multiple challenges in the project. This was largely due to the author having an inadequate understanding of key relevant discourses, including research fatigue, ethics of co-authorship, mismatching timelines, mismatching expectations between academics and relevant communities and power dynamics in interpersonal relationships. These are topics that have been explored in-depth in fields such as human geography, social sciences and anthropology, yet they are insufficiently considered in the natural sciences as a whole. The purpose of this essay is two-fold. The first is to signpost natural scientists wishing to engage in collaborative research towards key texts and concepts that could aid their work. It is not an extensive review, but rather what is hopefully an accessible introduction. It is, quite simply, an essay that the author would have appreciated having access to before undertaking her work. The second is to contribute to a wider discussion around the need for a more diverse and decolonial training in the natural sciences, so we all can respond to the many changes currently occurring on our planet using knowledge generated from well-informed, meaningful and effective collaborations

Reindeer ecology in a changing Arctic: Snow, vegetation, and traditional ecological knowledge

The cumulative effects of anthropogenic development on reindeer (Rangifer tarandus, L.), and how these impacts interact with a changing climate, remain largely unknown. To fill this knowledge gap, this thesis begins by examining how presence and winter accessibility of reindeer forage is affected by silviculture in boreal forests of northern Sweden, as stands progress from clear-cut to mature forests. Original surveys show that the abundance of various lichen species generally increases with stand age, highlighting the roles of competition, grazing pressure and disturbance in this process. Snow depth is consistently shallower in old stands, and the number of ice layers in the snow column increases throughout winter, affecting the ability of reindeer to dig to ground-lying lichens. Overall, there is upto 61 % lower availability of forage in clear-cut sites compared to old stands, showing that changes in forest structure have notable impacts on reindeer grazing. Next the effects of multiple forms of land-use, individually and cumulatively, on reindeer are examined. A model is created which considers the impact of silviculture, roads, mines, hydropower stations, settlements and four climate scenarios, on reindeer populations over 50 years. All scenarios saw a loss of 54-100 % of reindeer, and only 25 % resulted in economically sustainable herd sizes for reindeer herders. Climate had the greatest impact on reindeer survival within the model. The results highlight that current and many projected future scenarios of land development create an unsustainable environment for reindeer and herders. Alongside natural science methodologies, the role of history, politics and economics in the lives of Indigenous Sámi herders are explored, arguing that to gain a fuller understanding of reindeer ecology in a changing system, it is essential to consider both the biological and human context surrounding them. The processes of trying to carry out research using both scientific and traditional ecological knowledges are discussed, providing suggestions for others undertaking interdisciplinary work in this field

Abundance and accessibility of forage for reindeer in forests of Northern Sweden: Impacts of landscape and winter climate regime

The survival of reindeer during winter, their period of greatest food stress, depends largely on the abundance and accessibility of forage in their pastures. In Northern Sweden, realized availability of forage is notably affected by snow conditions and the impacts of forestry. While these factors have been examined in isolation, their combined effect has, to the best of our knowledge to date, not been researched. In this study, vegetation surveys and analysis of snow conditions were undertaken in forest stands at various stages of recovery from clear-cutting. The variation in abundance and growth of understory species edible by reindeer, such as lichen, was noted as forests matured. The barrier effect of ice lenses in the snow was also measured in these stands. Lichen biomass was significantly affected by a combination of stand maturity, understory vegetation height, and lichen height. Soil disturbance from the processes of felling and competition in the vegetation communities recovering from this disturbance were identified as key drivers of change in lichen biomass. Overall, clear-cut forests had some of the greatest prevalence of ice lenses in the snow column, and forage availability at these sites was up to 61% less than in mature stands over 58 years in age. It is suggested that alternative silviculture methods are investigated for use in this reindeer herding region, as frequent clear-cutting and consequent reduction in the average forest stand age and maturity class may be detrimental to reindeer grazing, reducing both abundance of forage, and access to it during winter

Herbivore diversity effects on Arctic tundra ecosystems : a systematic review

Background: Northern ecosystems are strongly influenced by herbivores that differ in their impacts on the ecosystem. Yet the role of herbivore diversity in shaping the structure and functioning of tundra ecosystems has been overlooked. With climate and land-use changes causing rapid shifts in Arctic species assemblages, a better understanding of the consequences of herbivore diversity changes for tundra ecosystem functioning is urgently needed. This systematic review synthesizes available evidence on the effects of herbivore diversity on different processes, functions, and properties of tundra ecosystems. Methods: Following a published protocol, our systematic review combined primary field studies retrieved from bibliographic databases, search engines and specialist websites that compared tundra ecosystem responses to different levels of vertebrate and invertebrate herbivore diversity. We used the number of functional groups of herbivores (i.e., functional group richness) as a measure of the diversity of the herbivore assemblage. We screened titles, abstracts, and full texts of studies using pre-defined eligibility criteria. We critically appraised the validity of the studies, tested the influence of different moderators, and conducted sensitivity analyses. Quantitative synthesis (i.e., calculation of effect sizes) was performed for ecosystem responses reported by at least five articles and meta-regressions including the effects of potential modifiers for those reported by at least 10 articles. Review findings: The literature searches retrieved 5944 articles. After screening titles, abstracts, and full texts, 201 articles including 3713 studies (i.e., individual comparisons) were deemed relevant for the systematic review, with 2844 of these studies included in quantitative syntheses. The available evidence base on the effects of herbivore diversity on tundra ecosystems is concentrated around well-established research locations and focuses mainly on the impacts of vertebrate herbivores on vegetation. Overall, greater herbivore diversity led to increased abundance of feeding marks by herbivores and soil temperature, and to reduced total abundance of plants, graminoids, forbs, and litter, plant leaf size, plant height, and moss depth, but the effects of herbivore diversity were difficult to tease apart from those of excluding vertebrate herbivores. The effects of different functional groups of herbivores on graminoid and lichen abundance compensated each other, leading to no net effects when herbivore effects were combined. In turn, smaller herbivores and large-bodied herbivores only reduced plant height when occurring together but not when occurring separately. Greater herbivore diversity increased plant diversity in graminoid tundra but not in other habitat types. Conclusions: This systematic review underscores the importance of herbivore diversity in shaping the structure and function of Arctic ecosystems, with different functional groups of herbivores exerting additive or compensatory effects that can be modulated by environmental conditions. Still, many challenges remain to fully understand the complex impacts of herbivore diversity on tundra ecosystems. Future studies should explicitly address the role of herbivore diversity beyond presence-absence, targeting a broader range of ecosystem responses and explicitly including invertebrate herbivores. A better understanding of the role of herbivore diversity will enhance our ability to predict whether and where shifts in herbivore assemblages might mitigate or further amplify the impacts of environmental change on Arctic ecosystems

Herbivore diversity effects on Arctic tundra ecosystems: a systematic review

Abstract Background Northern ecosystems are strongly influenced by herbivores that differ in their impacts on the ecosystem. Yet the role of herbivore diversity in shaping the structure and functioning of tundra ecosystems has been overlooked. With climate and land-use changes causing rapid shifts in Arctic species assemblages, a better understanding of the consequences of herbivore diversity changes for tundra ecosystem functioning is urgently needed. This systematic review synthesizes available evidence on the effects of herbivore diversity on different processes, functions, and properties of tundra ecosystems. Methods Following a published protocol, our systematic review combined primary field studies retrieved from bibliographic databases, search engines and specialist websites that compared tundra ecosystem responses to different levels of vertebrate and invertebrate herbivore diversity. We used the number of functional groups of herbivores (i.e., functional group richness) as a measure of the diversity of the herbivore assemblage. We screened titles, abstracts, and full texts of studies using pre-defined eligibility criteria. We critically appraised the validity of the studies, tested the influence of different moderators, and conducted sensitivity analyses. Quantitative synthesis (i.e., calculation of effect sizes) was performed for ecosystem responses reported by at least five articles and meta-regressions including the effects of potential modifiers for those reported by at least 10 articles. Review findings The literature searches retrieved 5944 articles. After screening titles, abstracts, and full texts, 201 articles including 3713 studies (i.e., individual comparisons) were deemed relevant for the systematic review, with 2844 of these studies included in quantitative syntheses. The available evidence base on the effects of herbivore diversity on tundra ecosystems is concentrated around well-established research locations and focuses mainly on the impacts of vertebrate herbivores on vegetation. Overall, greater herbivore diversity led to increased abundance of feeding marks by herbivores and soil temperature, and to reduced total abundance of plants, graminoids, forbs, and litter, plant leaf size, plant height, and moss depth, but the effects of herbivore diversity were difficult to tease apart from those of excluding vertebrate herbivores. The effects of different functional groups of herbivores on graminoid and lichen abundance compensated each other, leading to no net effects when herbivore effects were combined. In turn, smaller herbivores and large-bodied herbivores only reduced plant height when occurring together but not when occurring separately. Greater herbivore diversity increased plant diversity in graminoid tundra but not in other habitat types. Conclusions This systematic review underscores the importance of herbivore diversity in shaping the structure and function of Arctic ecosystems, with different functional groups of herbivores exerting additive or compensatory effects that can be modulated by environmental conditions. Still, many challenges remain to fully understand the complex impacts of herbivore diversity on tundra ecosystems. Future studies should explicitly address the role of herbivore diversity beyond presence-absence, targeting a broader range of ecosystem responses and explicitly including invertebrate herbivores. A better understanding of the role of herbivore diversity will enhance our ability to predict whether and where shifts in herbivore assemblages might mitigate or further amplify the impacts of environmental change on Arctic ecosystems. </jats:sec