Background 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?”. Methods We used a published systematic map protocol to identify studies addressing the effects of herbivores on Arctic vegetation. We conducted searches for relevant literature in online databases, search engines and specialist websites. Literature was screened to identify eligible studies, defined as reporting primary data on herbivore impacts on Arctic plants and plant communities. We extracted information on variables that describe the ecological context of the studies, from the studies themselves and from geospatial data. We synthesized the findings narratively and created a Shiny App where the coded data are searchable and variables can be visually explored. Review findings We identified 309 relevant articles with 662 studies (representing different ecological contexts or datasets within the same article). These studies addressed vertebrate herbivory seven times more often than invertebrate herbivory. Geographically, the largest cluster of studies was in Northern Fennoscandia. Warmer and wetter parts of the Arctic had the largest representation, as did coastal areas and areas where the increase in temperature has been moderate. In contrast, studies spanned the full range of ecological context variables describing Arctic vertebrate herbivore diversity and human population density and impact. Conclusions The current evidence base might not be sufficient to understand the effects of herbivores on Arctic vegetation throughout the region, as we identified clear biases in the distribution of herbivore studies in the Arctic and a limited evidence base on invertebrate herbivory. In particular, the overrepresentation of studies in areas with moderate increases in temperature prevents robust generalizations about the effects of herbivores under different climatic scenarios.

1. 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, largescale vegetation transitions are underway in response to warming, and there is an urgent need to understand how these changes affect soil biodiversity and function.2. 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.3. 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. 4. 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.

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.

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