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Summary: Bryophytes, including the lineages of mosses, liverworts, and hornworts, are the second‐largest photoautotroph group on Earth. Recent work across terrestrial ecosystems has highlighted how bryophytes retain and control water, fix substantial amounts of carbon (C), and contribute to nitrogen (N) cycles in forests (boreal, temperate, and tropical), tundra, peatlands, grasslands, and deserts. Understanding how changing climate affects bryophyte contributions to global cycles in different ecosystems is of primary importance. However, because of their small physical size, bryophytes have been largely ignored in research on water, C, and N cycles at global scales. Here, we review the literature on how bryophytes influence global biogeochemical cycles, and we highlight that while some aspects of global change represent critical tipping points for survival, bryophytes may also buffer many ecosystems from change due to their capacity for water, C, and N uptake and storage. However, as the thresholds of resistance of bryophytes to temperature and precipitation regime changes are mostly unknown, it is challenging to predict how long this buffering capacity will remain functional. Furthermore, as ecosystems shift their global distribution in response to changing climate, the size of different bryophyte‐influenced biomes will change, resulting in shifts in the magnitude of bryophyte impacts on global ecosystem functions. [ABSTRACT FROM AUTHOR]

Climate warming may alter predator–prey interactions and predator feeding behaviour due to increased metabolic demands. How predators meet these increased demands may depend on trade‐offs in prey energy content and body size, handling time and other functional constraints.We tested hypotheses associated with these trade‐offs with the predatory mite Stratiolaelaps scimitus, and three prey that differed in body size, energy content, and defenses (Folsomia candida, Oppia nitens, and Carpoglyphus lactis). We estimated metabolic rate, predation in choice and no choice feeding trials, movement rate, and lipid and protein content for all four species at 16°C and 24°C. We used these data to estimate the predator's energy demands and compared these to estimated energy intake in the choice feeding trials.Predators had greater metabolic demands at 24°C than at 16°C, but temperature did not affect predator or prey movement rates. Warming decreased lipid content, but not protein content, of all three prey species, leading to lower energy content for C. lactis and O. nitens, but not F. candida. In both feeding trials at 24°C, predators increased their feeding on the smaller, energy‐poor C. lactis, but not the larger, energy‐rich F. candida, resulting in lower estimated energy intake. S. scimitus did not feed on O. nitens at either temperature.Predators increasingly fed on small‐bodied prey under warming and not the large‐bodied prey despite the potential for greater energetic gains from larger prey. We posit that predators minimized energy lost during feeding through lower handling costs associated with C. lactis, rather than maximize energy gain. We conclude that selection of prey based on body size changes with temperature as a trade‐off for predators to balance increased metabolic demands. As predators provide top‐down control and regulate energy flow through the consumption of their prey, changes to predator feeding behaviour with climate warming may affect food web dynamics and ecosystem‐level processes. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Ecologists have long debated the properties that confer stability to complex, species-rich ecological networks. Species-level soil food webs are large and structured networks of central importance to ecosystem functioning. Here, we conducted an analysis of the stability properties of an up-to-date set of theoretical soil food web models that account both for realistic levels of species richness and the most recent views on the topological structure (who is connected to whom) of these food webs. The stability of the network was best explained by two factors: strong correlations between interaction strengths and the blocked, nonrandom trophic structure of the web. These two factors could stabilize our model food webs even at the high levels of species richness that are typically found in soil, and that would make random systems very unstable. Also, the stability of our soil food webs is well-approximated by the cascade model. This result suggests that stability could emerge from the hierarchical structure of the functional organization of the web. Our study shows that under the assumption of equilibrium and small perturbations, theoretical soil food webs possess a topological structure that allows them to be complex yet more locally stable than their random counterpart. In particular, results strongly support the general hypothesis that the stability of rich and complex soil food webs is mostly driven by correlations in interaction strength and the organization of the soil food web into functional groups. The implication is that in real-world food web, any force disrupting the functional structure and distribution pattern of interaction strengths (i.e., energy fluxes) of the soil food webs will destabilize the dynamics of the system, leading to species extinction and major changes in the relative abundances of species. [ABSTRACT FROM AUTHOR]

A checklist of the oribatid mite species from two boreal fens in Northern Ontario, Canada is presented. 174 peat soil samples, collected between 2015–2020, yielded a heterogeneous assemblage of 80 species, 57 genera and 33 families. Species richness and diversity were significantly higher in a Sphagnum-dominated fen (69 species) compared to a Carex-dominated fen (51 species), and although 40 species were found at both sites, overall composition was significantly different between the two sites. We also present an update to the seminal work of Behan-Pelletier and Bissett (1994) on Oribatida of Canadian peatlands with 45 new species records for peatlands. Records for the parthenogenetic families Brachychthoniidae Thor, 1934 and Suctobelbidae Jacot, 1938 were considerably expanded, but other families such as Punctoribatidae, Thor, 1937 remain poorly represented in Canadian peatlands. Taken together, species richness estimates range from 86–105 species based on our sampling and the number of undescribed species recorded suggests that the oribatid mite fauna still need further examination to encompass their actual biodiversity in peatlands. We report that the oribatid mite fauna of Canadian peatlands comprise 186 species that includes all published records as of February 2021 and species presented here. [ABSTRACT FROM AUTHOR]

As extreme climate events become more frequent and intense, short-term temperature responses of ectothermic organisms can lead to decreased performance and survival. However, organisms may acclimate to these conditions through behavioural and physiological mechanisms as exposure time increases. We used a reciprocal temperature (16 °C and 24 °C) transplant experiment to determine how feeding rate and body size of an apex soil mite predator (Stratiolaelaps scimitus) (formerly Hypoaspis miles) consuming prey (Carpoglyphus lactis) (dried-fruit-mite) changed along a gradient of acclimation time (1, 3, and 7 days, with control). In the control treatments, mites reared at 24 °C fed more, but were smaller than mites reared at 16 °C. When transferred to new temperature conditions, predators that experienced cooling events had reduced feeding efficiencies driven by decreased feeding performance, despite an absence of metabolic costs, while under warming events, predators also had reduced feeding activity, but feeding increased with acclimation time. Yet predators lost more weight the longer they were exposed to warming, and continued to experience reduced feeding efficiencies (i.e., lack of weight gain after feeding); this result suggests increased metabolic costs at higher temperatures and provides a mechanism for community downsizing under warming. Overall, our results suggest that ectothermic predators can acclimate to warming events with increased exposure time, but both warming and cooling events decrease overall performance. [ABSTRACT FROM AUTHOR]

Soil food web models are a powerful tool for calculating the carbon and nitrogen mineralized by different soil organisms. Two limitations of the current models are that they use (a) fixed parameters for determining the relative efficiency of carbon and nitrogen conversion and (b) a generic set of trophic species (i.e. nodes).We propose a new method for analysing soil food webs that varies production efficiency and diet mechanistically with resource stoichiometry. Then, we calculated how the lumping or splitting of trophic species affects carbon and nitrogen mineralization for both net mineralization rates as well as the distribution of mineralization (i.e. sources of mineralization). Our models with additional stoichiometric details better represent organisms that consume basal resources with high C:N ratios.This is important because we show that lumping together trophic species at low trophic levels, which often differ in C:N ratios (i.e. microbial taxa), causes the largest deviations in estimates of carbon and nitrogen mineralization. One reason for the large effect of C:N ratio is that it impacts diet and production efficiency in our stoichiometric model. Conversely, lumping together species at higher trophic levels causes the largest errors when those species have different production and assimilation efficiencies. Finally, we demonstrate that differences in death rate and biomass are mostly important when lumping species that have different diets.We suggest that C:N ratios are especially important when grouping microbial taxa because microbial C:N ratios vary widely and microbes feed at low trophic levels where differences in C:N ratio mattered the most. Conversely lumping higher consumers will be most problematic when they have differences in the conversion efficiencies. We provide an approach to calculate structural error and report it with parameter uncertainty. Then, we demonstrate, using oribatid mites as an example, that considering the life history of different taxa can help us group organisms more efficiently into trophic species. In doing so, we provide a way to reduce and report the uncertainty in soil food web models and to stimulate future empirical work measuring key life history parameters. A free Plain language summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Rare, long‐distance dispersal events are a key process in generating and maintaining patterns in biological diversity and species distributions across space and time. The 9.0 magnitude earthquake that struck the eastern coast of Japan in 2011, and the subsequent 38 m high tsunami washed large amounts of shoreline debris into the Pacific Ocean that led to a large‐scale biological rafting event carrying nearly 300 marine species to the western shores of North America. Whether oceanic, trans‐Pacific dispersal via rafting generates long distance dispersal events for small, flightless, terrestrial species is unknown. By sampling beach debris associated with known hot‐spots of tsunami debris along the north and east shores of Graham Island, Haida Gwaii, Canada, I document significantly dissimilar invertebrate communities associated with tide‐line beach debris and the occurrence of several putative Japanese species of soil‐dwelling mites (Acari: Oribatida). Previous explanations of Haida Gwaii's unique flora and fauna have been attributed to a proximity to the Beringian land bridge and the accumulated evidence of near‐offshore glacial refugia during the last glacial period. However, my research also suggests that stochastic, trans‐Pacific rafting events contribute to the biodiversity and biogeography of soil communities on the west coast of North America. [ABSTRACT FROM AUTHOR]

Questions: Climate warming has been demonstrated to shift peatland plant community composition from Sphagnum mosses to vascular plants in Sphagnum‐dominated peatlands. However, fewer studies have determined how increasing temperature affects vegetation patterns in Carex‐dominated peatlands. As plants are important determinants of carbon storage potential in peatlands, we aim to determine how climate warming alters plant community composition in peatlands of two different vegetation types. Location: Boreal peatlands in north–central Ontario, Canada. Methods: In a Sphagnum‐ and a Carex‐dominated peatland over two growing seasons, we instigated passive warming using clear open‐topped chambers, providing a modest increase (1–2°C) in temperature. In replicated plots we examined shifts in plant community composition using the point intercept method, and total above‐ground biomass using Leaf Area Index (LAI) against non‐warmed control plots. Results: While there was no difference in species diversity between control and warmed plots in either fen site, warming significantly increased above‐ground biomass in the Carex‐dominated fen and decreased moss abundance in the Sphagnum‐dominated fen. Both fens also displayed significantly different plant community composition between warming and control plots, and increased heterogeneity under warming. Conclusion: Peatlands are important global carbon stores and the plant community contributes to their carbon storage; Sphagnum mosses, in particular, are linked to high peatland carbon storage potential. Previous studies in Sphagnum‐dominated peatlands have shown concomitant declines in Sphagnum biomass and increases in vascular plant biomass, and in the short term, we show only a decline in Sphagnum. At both sites the increase in plant community heterogeneity suggests that climate warming effects on plant community composition in boreal peatlands may be more unpredictable than the literature suggests. Furthermore, this study demonstrates that plant community shifts occur even under modest warming scenarios. [ABSTRACT FROM AUTHOR]

Bumble bees are declining globally, largely due to habitat loss driven by agricultural intensification. Within agriculturally dominated landscapes, semi‐natural habitats (e.g. meadows, wetland edges) are fragmented, increasing the value of uncropped agricultural field margins for providing a source of food, nesting, and hibernation resources to bumble bees.We compared bumble bee communities sampled in agricultural field margins and semi‐natural habitats across Southwestern Ontario, Canada in order to assess differences in habitat quality. We then examined the effect of floral resources and soil characteristics on the bumble bee communities present in each site, independent of the habitat type classification.Our data revealed that bumble bee abundance, diversity, and community composition did not differ between habitat types. However, when examined independently of habitat type, bumble bee abundance and diversity increased with floral abundance, floral diversity, the number of rodent holes, and sandy soil texture.These results suggest that agricultural field margins are not inherently degraded bumble bee habitat and have the potential to provide food and nesting resources comparable to semi‐natural habitats in a fragmented agricultural landscape. Ensuring field margins contain the necessary floral resources and soil characteristics for bumble bees has implications for conservation and mitigating habitat loss caused by the agricultural fields themselves. [ABSTRACT FROM AUTHOR]

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Summaries of taxonomic knowledge are provided for all acarine groups in Canada, accompanied by references to relevant publications, changes in classification at the family level since 1979, and notes on biology relevant to estimating their diversity. Nearly 3000 described species from 269 families are recorded in the country, representing a 56% increase from the 1917 species reported by Lindquist et al. (1979). An additional 42 families are known from Canada only from material identified to family- or genus-level. Of the total 311 families known in Canada, 69 are newly recorded since 1979, excluding apparent new records due solely to classification changes. This substantial progress is most evident in Oribatida and Hydrachnidia, for which many regional checklists and family-level revisions have been published. Except for recent taxonomic leaps in a few other groups, particularly of symbiotic mites (Astigmata: feather mites; Mesostigmata: Rhinonyssidae), knowledge remains limited for most other taxa, for which most species records are unpublished and may require verification. Taxonomic revisions are greatly needed for a large majority of families in Canada. Based in part on species recorded in adjacent areas of the USA and on hosts known to be present here, we conservatively estimate that nearly 10,000 species of mites occur in Canada, but the actual number could be 15,000 or more. This means that at least 70% of Canada's mite fauna is yet unrecorded. Much work also remains to match existing molecular data with species names, as less than 10% of the ~7500 Barcode Index Numbers for Canadian mites in the Barcode of Life Database are associated with named species. Understudied hosts and terrestrial and aquatic habitats require investigation across Canada to uncover new species and to clarify geographic and ecological distributions of known species. [ABSTRACT FROM AUTHOR]

In the ecological literature, a ‘home-field advantage’ (HFA) describes the phenomenon where plant litters are broken down more quickly in their native versus a foreign environment due to a hypothesized specialised decomposer-litter relationship. Climate change is expected to spatially shift plant communities at an imbalanced rate compared to their decomposers, resulting in previously unexperienced above- and belowground pairings. Understanding decomposition dynamics has implications for global climate and carbon models, yet a clear predictive framework for the HFA has not been proposed. The ecological HFA concept is borrowed from the sports realm where extensive research has found a consistent, greater-than-random chance that teams in sports competitions win games played at their home venue because players are in better physical and psychological states. While research continues to show the sports HFA present in all types of sports independent of playing level or region, the ecological HFA has been shown inconsistently and cannot currently be generalised across scales and ecosystems. In this review, we map the ecological HFA onto a framework used to interpret the HFA in sports. First, we identify and outline the ‘game’ of decomposition, the ‘teams’ of decomposer organisms, how plants ‘coach’ this game, and also how ecological researchers are involved in their role as game ‘officials’. Second, we place parallels between the game location factors established in the sports analogy and their ecological counterparts to reveal a greater mechanistic understanding of the ecological HFA. Here we explore microbial adaptation to abiotic environments, the role of historical resource inputs, and how degree of ecosystem contrast and definitional ambiguity affect the HFA. In doing so, we discuss how microbial functional breadth, plant strategy and temporal effects play into the HFA. Using the sports HFA framework provides a novel and promising approach to understanding the ecological HFA that has been lacking, and helps identify potential factors that may not traditionally have been considered. Our framework incorporates multiple theories and views the HFA as a ‘team effort’ involving multiple components. [ABSTRACT FROM AUTHOR]

Considerable progress has been made in ecological and evolutionary genetics with studies demonstrating how genes underlying plant and microbial traits can influence adaptation and even 'extend' to influence community structure and ecosystem level processes. Progress in this area is limited to model systems with deep genetic and genomic resources that often have negligible ecological impact or interest. Thus, important linkages between genetic adaptations and their consequences at organismal and ecological scales are often lacking. Here we introduce the Sphagnome Project, which incorporates genomics into a long-running history of Sphagnum research that has documented unparalleled contributions to peatland ecology, carbon sequestration, biogeochemistry, microbiome research, niche construction, and ecosystem engineering. The Sphagnome Project encompasses a genus-level sequencing effort that represents a new type of model system driven not only by genetic tractability, but by ecologically relevant questions and hypotheses. [ABSTRACT FROM AUTHOR]

The notion that plants are tightly coupled to their belowground environment so that decomposition occurs faster in their place of origin is now a widely tested hypothesis known as the home-field advantage (HFA). Microbial adaptation to the most prevalent plant litter is the hypothesis proposed to explain decomposition results in a number of HFA studies but fails to corroborate results of many others, highlighting the need for a more comprehensive understanding of decomposition dynamics at local scales. Boreal peatlands are important ecosystems for carbon storage that are expected to be significantly affected by climate change, thus understanding decomposition dynamics in Boreal peatland systems is of global relevance. We performed a reciprocal transplant experiment using pure and mixed litters of two dominant peatland plant types ( Sphagnum moss and Carex sedge) present in differing densities at two sites differing in nutrient status in a Boreal peatland complex. Aboveground (temperature, relative humidity) and belowground (pH, moisture, available nitrogen) environmental characteristics were measured, and initial litter quality (C, N, S) was assessed with decomposition (mass loss) quantified after one year. We use linked HFA equations that help account for differences in litter quality and site conditions. While Carex lost greater overall mass than Sphagnum , both Carex and Sphagnum demonstrate a HFA, but only where they were the dominant plant of each site. This result held for both pure and mixed litters, suggesting microbial specificity to the most prevalent plant type, yet mixed litters moderated the strength of the HFA. While our results provide novel insights to plant-soil linkages and mixed litter interactions in Boreal peatlands, mechanisms underpinning microbial specificity to plant litter in these ecosystems requires further investigation. [ABSTRACT FROM AUTHOR]

Hollows and hummocks of boreal peatlands differ in water table position, pH, plant community composition and biochemical properties that might affect the structure of their fungal communities. The community composition of fungi at three depths (0–5 cm, 15–20 cm, 30–35 cm) in hollows and hummocks of a nutrient-poor fen in northern Ontario, Canada were assessed by Illumina sequencing of 28S amplicons. Our metabarcoding results revealed statistically distinct fungal community composition between hollows and hummocks. Hollows contained a more diverse fungal community than hummocks. However, the middle horizon of hollows and the bottom horizon of hummocks were comparable in terms of fungal biodiversity. These layers were identified as the areas bearing the most diverse community composition of fungi, most likely driven by their similarly respective distance from the water table position. This optimum area is expected to be most affected following water table drawdown under future climate change conditions. [ABSTRACT FROM AUTHOR]

The predominant input of available nitrogen (N) in boreal forest ecosystems originates from moss-associated cyanobacteria, which fix unavailable atmospheric N2, contribute to the soil N pool, and thereby support forest productivity. Alongside climate warming, increases in atmospheric CO2 concentrations are expected in Canada's boreal region over the next century, yet little is known about the combined effects of these factors on N fixation by forest floor cyanobacteria. Here we assess changes in N fixation in a common forest floor, moss-associated cyanobacterium, Nostoc punctiforme Hariot, under elevated CO2 conditions over 30 days and warming combined with elevated CO2 over 90 days. We measured rates of growth and changes in the number of specialized N2 fixing heterocyst cells, as well as the overall N fixing activity of the cultures. Elevated CO2 stimulated growth and N fixation overall, but this result was influenced by the growth stage of the cyanobacteria, which in turn was influenced by our temperature treatments. Taken together, climate change factors of warming and elevated CO2 are expected to stimulate N2 fixation by moss-associated cyanobacteria in boreal forest systems. [ABSTRACT FROM AUTHOR]

Metabarcoding has become an important tool in the discovery of biodiversity, including fungi, which are the second most speciose group of eukaryotes, with diverse and important ecological roles in terrestrial ecosystems. We have designed and tested new PCR primers that target the D1 variable region of nuclear large subunit (LSU) ribosomal DNA; one set that targets the phylum Ascomycota and another that recovers all other fungal phyla. The primers yield amplicons compatible with the Illumina MiSeq platform, which is cost-effective and has a lower error rate than other high throughput sequencing platforms. The new primer set LSU200A-F/LSU476A-R (Ascomycota) yielded 95–98% of reads of target taxa from environmental samples, and primers LSU200-F/LSU481-R (all other fungi) yielded 72–80% of target reads. Both primer sets have fairly low rates of data loss, and together they cover a wide variety of fungal taxa. We compared our results with these primers by amplifying and sequencing a subset of samples using the previously described ITS3_KYO2/ITS4_KYO3 primers, which amplify the internal transcribed spacer 2 (ITS2) of Ascomycota and Basidiomycota. With approximately equivalent read depth, our LSU primers recovered a greater number and phylogenetic diversity of sequences than the ITS2 primers. For instance, ITS3_KYO2/ITS4_KYO3 primers failed to pick up any members of Eurotiales, Mytilinidiales, Pezizales, Saccharomycetales, or Venturiales within Ascomycota, or members of Exobasidiomycetes, Microbotryomycetes, Pucciniomycetes, or Tremellomycetes within Basidiomycota, which were retrieved in good numbers from the same samples by our LSU primers. Among the OTUs recovered using the LSU primers were 127 genera and 28 species that were not obtained using the ITS2 primers, although the ITS2 primers recovered 10 unique genera and 16 species that were not obtained using either of the LSU primers These features identify the new primer sets developed in this study as useful complements to other universal primers for the study of fungal diversity and community composition. [ABSTRACT FROM AUTHOR]

The increased prevalence of smaller-bodied species under warmer conditions (community downsizing) is hypothesized as an ecologically critical consequence of climate change, leading to changes in trophic transfer efficiency, and rates of nutrient and energy flux within ecosystems. This study used 100 intact peat-soil mescosms to measure changes in belowground biodiversity under three manipulated climate variables: elevated temperature, elevated CO 2 , and altered water table. Changes in species richness, abundance, community composition and body size spectra were used to determine whether climate change factors led to community downsizing, and elucidate any underlying mechanisms. Warming was the primary driver of compositional shifts in belowground fauna communities with the strongest effect among the smaller-bodied, non-sexually reproducing species. Increases in abundance driven by enhanced reproduction in small-bodied species rather than an increased extinction-rate among large-bodied predators was the basis of the observed downsizing. The overall consequences of warming-induced changes in belowground systems on ecosystem function are still unclear. However, as body size is intricately linked to metabolism, observed community downsizing suggests reductions in food web trophic transfer efficiency with consequences for nutrient and energy dynamics in belowground systems. [ABSTRACT FROM AUTHOR]

I present the systematics and distribution of a new species of oribatid mite in the genus Metrioppia Grandjean, 1931 (Oribatida: Peloppiidae) from western North America. Metrioppia walbranensisnew species is diagnosed on the basis of adult morphology using the following character states: shape and dentition of the rostrum, length of lamellae, shape of lamellar cusps, length of the interlamellar setae, and number of posterior notogastral setae. The known distribution of M. walbranensis is provided based on sampling and museum collections. Metrioppia walbranensis has been collected only from a small number of locations on south-west Vancouver Island, British Columbia, Canada, while its congener M. oregonensis Woolley and Higgins, 1969 has been collected widely within the Pacific Northwest, including sites on Vancouver Island. However, the two species do not appear to co-occur. Nucleotide sequence of the COI gene firmly places Metrioppia within the family Peloppiidae. [ABSTRACT FROM PUBLISHER]