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Soil food webs are at the nexus of soil biodiversity, functioning, and stability. With a research history of over 35 years, soil food-web research remains a challenging and relatively specialised field. Initially receiving wide attention after the general model of William H. Hunt and colleagues in 1987, the field diversified over the last two decades across ecosystem and community ecology, empirical and theoretical approaches, network and energy flux analyses. Here we reflect on the history, status, and trends in soil food-web research and identify major perspectives and synthesis directions. After briefly reviewing modelling approaches, structure, and quantification of functioning, we distinguish modern trends in tools that can streamline food-web research, a need for proper empirical validation, collaborative approaches to push the field forward, and conclude with application perspectives. In the light of increasing data availability and public awareness about soil biodiversity, we call for synthesis across multiple dimensions of soil food-web research (e.g. different methodologies and disciplines, various spatiotemporal scales, multiple trophic levels and phyla of life), integrating the soil food-web approach to biodiversity and environmental studies, and making it more accessible to a wider community of scientists.

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.

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.

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., Species‐level soil food webs are very large and structured networks. We analysed the stability properties of these networks. Correlation in interaction strength and organization by functional blocks stabilised soil food webs.

Global change is shown to significantly affect the C storage function of peatlands; however, a majority of previous research is focused on a single environmental stressor such as the increased temperature. As a result, little is known about the interactive effect of multiple environmental stressors on peatland C storage, especially in sedge-dominated fen peatlands. We performed a full factorial experiment of increased temperature and elevated atmospheric CO2 concentration on minerotrophic, sedge-dominated fen monoliths to experimentally examine the individual and interactive effects of simulated future climate conditions on peatland plant biomass, CO2 exchange, and pore water dissolved organic carbon (DOC) over one full growing season. Our study demonstrates that warming and elevated atmospheric CO2 significantly increased aboveground and belowground biomass, respectively, as well as the gross ecosystem production (GEP), while the DOC concentrations and respired CO2 from peatland soils only increased under warming Our results suggest that global change will increase both plant production and microbial decomposition, but with altered plant biomass allocation between aboveground and belowground. Our study provides experimental evidence for shifts in ecosystem-level carbon dynamics under global change for a sedge-dominated peatland, and suggests that while carbon stores may weaken, the carbon sink will be maintained in these types of northern peatlands if hydrological conditions are largely maintained.

In boreal peatlands, the aboveground (plant) and belowground (microbial) communities are acutely linked because the whole soil profile is partially decomposed plant matter (peat), and dictates the nutrients available to the belowground system. We characterized the aboveground and belowground communities in two boreal peatlands: a Sphagnum-dominated fen and a Carex-dominated fen. We link the plant and microbial communities by observing plant, litter and peat carbon and nitrogen values. The Sphagnum-dominated fen had greater plant diversity but provided low quality litter inputs (high carbon:nitrogen) that formed peat and that corresponded with greater fungi:bacteria and Gram-positive:Gram-negative bacteria microbial community compared to the Carex-dominated fen. The higher quality plant inputs in the Carex-dominated fen supported a 5 × greater microbial biomass that was also 2 × more active (as measure by CO2 production). In this approach we highlight that peatlands and their component plant and microbial communities play-out along a common resource-spectrum that dictates ‘fast’ vs ‘slow’ carbon and nutrient cycling (i.e., a plant–soil interaction spectrum) that can, in turn, affect carbon storage potential. As peatland plant community composition is predicted to shift and decomposition rates are expected to increase under climate change, our work highlights the importance of understanding plant–soil microbial interactions.

SummaryHere we introduce the Soil BON Foodweb Team, a cross-continental collaborative network that aims to monitor soil animal communities and food webs using consistent methodology at a global scale. Soil animals support vital soil processes via soil structure modification, direct consumption of dead organic matter, and interactions with microbial and plant communities. Soil animal effects on ecosystem functions have been demonstrated by correlative analyses as well as in laboratory and field experiments, but these studies typically focus on selected animal groups or species at one or few sites with limited variation in environmental conditions. The lack of comprehensive harmonised large-scale soil animal community data including microfauna, mesofauna, and macrofauna, in conjunction with related soil functions, limits our understanding of biological interactions in soil communities and how these interactions affect ecosystem functioning. To provide such data, the Soil BON Foodweb Team invites researchers worldwide to use a common methodology to address six long-term goals: (1) to collect globally representative harmonised data on soil micro-, meso-, and macrofauna communities; (2) to describe key environmental drivers of soil animal communities and food webs; (3) to assess the efficiency of conservation approaches for the protection of soil animal communities; (4) to describe soil food webs and their association with soil functioning globally; (5) to establish a global research network for soil biodiversity monitoring and collaborative projects in related topics; (6) to reinforce local collaboration networks and expertise and support capacity building for soil animal research around the world. In this paper, we describe the vision of the global research network and the common sampling protocol to assess soil animal communities and advocate for the use of standard methodologies across observational and experimental soil animal studies. We will use this protocol to conduct soil animal assessments and reconstruct soil food webs on the sites included in the global soil biodiversity monitoring network, Soil BON, allowing us to assess linkages among soil biodiversity, vegetation, soil physico-chemical properties, and ecosystem functions. In the present paper, we call for researchers especially from countries and ecoregions that remain underrepresented in the majority of soil biodiversity assessments to join us. Together we will be able to provide science-based evidence to support soil biodiversity conservation and functioning of terrestrial ecosystems.

Knowledge of benthic macroinvertebrate β-diversity patterns and drivers in an agricultural landscape can inform and improve watershed management decisions. Our study used multi-site and pairwise measures to determine taxonomic and functional β-diversity and associated nestedness and turnover components for benthic macroinvertebrate communities in the agricultural landscape. Total taxonomic β-diversity was mostly due to turnover, whereas total functional β-diversity was composed of turnover and nestedness more equally. Variation partitioning showed that spatial and habitat variables explained the largest proportion of variation in the total and turnover component of both taxonomic and functional β-diversity. Variation in nestedness was associated with local-scale habitat. Agricultural land cover was not a driver of β-diversity; however, extensive agricultural land cover appeared to disrupt the habitat–functional β-diversity relationship. Our findings suggest that distance among benthic macroinvertebrate communities should be considered when making land management or conservation decisions. Moreover, apparent disruption of the habitat–functional β-diversity relationship with extensive agricultural cover suggests managers should strategically target restoration activities to upland or channel areas based on catchment conditions. Finally, differences between taxonomic and functional β-diversity suggest including both measures in monitoring programs may enhance regional biodiversity assessments.

Microbes play crucial roles in global carbon cycles, particularly in peatland ecosystems that store vast quantities of carbon. Boreal peatlands are under stress from commercial extraction of peat, drainage for conversion to forestry and agricultural lands, and climate change. In this study, we identify key microbial groups and their ecological functions across peatland depth profiles and provide insight into how environmental changes related to water table may alter microbial communities. We examined the diversity and composition of prokaryotic communities across a microtopographic hummock–hollow gradient using Illumina sequencing. Communities formed a gradient of species and functional groups with depth, with overlap in functional groups at lower layers of hummocks and upper layers of hollows. Yet, overall, we found significantly different prokaryotic communities in hollows than hummocks. Surfaces of hummocks were typified by aerobic chemoorganotrophs, methanotrophs and chemoheterotrophs, mid-depths were typified by aerobic chemoorganotrophs, nitrogen-fixing bacteria and anaerobic nitrate reducers, while lower depths in hollows were typified by anaerobic and facultative anaerobic chemoorganotrophs, nitrate reducers and methanogenic archaea. Microbial composition as a function of hydrology and moisture regimes suggests that environmental changes that alter hydrological regimes (e.g., climate change, peatland draining) may alter carbon and nutrient cycling regimes.

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The use of functional information in the form of species traits plays an important role in explaining biodiversity patterns and responses to environmental changes. Although relationships between species composition, their traits, and the environment have been extensively studied on a case-by-case basis, results are variable, and it remains unclear how generalizable these relationships are across ecosystems, taxa and spatial scales. To address this gap, we collated 80 datasets from trait-based studies into a global database for metaCommunity Ecology: Species, Traits, Environment and Space; “CESTES”. Each dataset includes four matrices: species community abundances or presences/absences across multiple sites, species trait information, environmental variables and spatial coordinates of the sampling sites. The CESTES database is a live database: it will be maintained and expanded in the future as new datasets become available. By its harmonized structure, and the diversity of ecosystem types, taxonomic groups, and spatial scales it covers, the CESTES database provides an important opportunity for synthetic trait-based research in community ecology., Measurement(s)species abundance • species trait • environmental feature • latitude • longitudeTechnology Type(s)digital curationFactor Type(s)year of data collection • type of ecosystem • level of human disturbanceSample Characteristic - Environmentterrestrial natural environment • fresh water • marine biome • anthropogenic terrestrial biome • natural environment • area of mixed forest • cultivated environmentSample Characteristic - LocationEarth (planet) Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.11317790

The use of functional information in the form of species traits plays an important role in explaining biodiversity patterns and responses to environmental changes. Although relationships between species composition, their traits, and the environment have been extensively studied on a case-by-case basis, results are variable, and it remains unclear how generalizable these relationships are across ecosystems, taxa and spatial scales. To address this gap, we collated 80 datasets from trait-based studies into a global database for metaCommunity Ecology: Species, Traits, Environment and Space; “CESTES”. Each dataset includes four matrices: species community abundances or presences/absences across multiple sites, species trait information, environmental variables and spatial coordinates of the sampling sites. The CESTES database is a live database: it will be maintained and expanded in the future as new datasets become available. By its harmonized structure, and the diversity of ecosystem types, taxonomic groups, and spatial scales it covers, the CESTES database provides an important opportunity for synthetic trait-based research in community ecology., This work was funded by the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (funded by the German Research Foundation; DFG FZT 118). We thank Jitendra Gaikwad for his precious help with the technical aspects of the database storage and management through the iDiv Biodiversity Portal (https://idata.idiv.de/, https://doi.org/10.25829/idiv.286-21-2695) and the iDiv IT Support for their help in the CESTES website development (https://icestes.github.io/). The datasets provided by A. Jeliazkov were collected with financial support from the Fédération d’Ile-de-France pour la Recherche en Environnement (FIRE FR-3020). The dataset provided by R. Carvalho and F.L. Tejerina-Garro had financial support from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq No. 471283/2006-1) granted to FLTG. The datasets provided by R. van Klink, J.-Y. Humbert, R. Arlettaz and M.H.M. Menz were collected with financial support from the Swiss National Science Foundation (grants 31003A_125398/2 and 31003A_149656) awarded to RA.

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.

Fungi play a pivotal role in the carbon sequestration potential of boreal peatlands through the process of decomposition. As such, climate-driven changes in the diversity and community composition of peatland fungal communities could have substantial impacts on carbon release from these ecosystems, especially in subsurface peat that represents an important global carbon stock. We used Illumina MiSeq sequencing of rDNA to examine fungal communities after 18 months in intact peatland mesocosms subjected to conditions associated with Canada's future climate, including: warming, elevated atmospheric CO2 and lowered water table. Warming was the main driver of changes in fungal communities across three depths of the peat profile with both Ascomycota- and Basidiomycota-dominated groups becoming more homogenous under warming conditions. Specific changes in fungal functional groups, however, were temperature dependent with potential cellulose decomposers and mycorrhizal root-associated fungi from Basidiomycota dominant under warming of +4 °C, whereas there was a prevalence of potential lignocellulose decomposers and mycorrhizal root-associated fungi from Ascomycota under +8 °C warming. These climate change-induced shifts in the structure of fungal communities in favour of recalcitrant compound decomposers observed across a depth gradient, may reduce long-term carbon storage of boreal peatlands under future climate change scenarios.

Climate warming is expected to disproportionately affect high latitude and alpine systems such as boreal peatlands. Previous studies observing changes in both plant and microbial communities suggest boreal peatlands may shift from carbon sinks to sources under warming. But few studies have investigated oribatid mites (Acari: Oribatida) under climate change scenarios in peatland systems, despite oribatid mites being well represented in terms of diversity in boreal peatlands. We performed a large-scale experimental field manipulation of warming in two contrasting peatland sites in Northern Ontario, Canada, and sampled oribatid mites over four years following three years of passive warming and one full growing season of active warming. We found that warming had contrasting effects on the oribatid mite community at both peatland sites, and depended on the peatland type. Specifically, we observed an increase in species richness at the drier, Sphagnum-dominated site and a reduction in species richness at the wetter, Carex-dominated site. That said, we suggest that these outcomes arise from the same mechanism, namely warming-induced reductions in soil moisture that impacted semi-aquatic species and facilitated the establishment of new species, likely from surrounding forests. We also observed increases in small-bodied species suggesting direct metabolic effects from warming. As such, we show that peatland oribatid mite community composition is driven to an extent by interactions between temperature and moisture but dependant on peatland type. As oribatid mite communities are responsive to multiple environmental changes, and play important mid-trophic level roles in soil food webs, changes in oribatid mite community composition may have consequences for carbon flux in peatland systems.

Increasing global mean surface temperatures from climate change will coincide with longer and more frequent short-term, extreme warming events. Because of this, habitats like boreal forests are predicted to have new temperature regimes. Boreal forest soils contain a diverse array of microarthropods and nematodes, which include the main soil predators, mesostigmatic mites (Acari: Parasitiformes: Mesostigmata). Although extensive research exists on how climate warming affects oribatid mite and collembolan communities, fewer studies have examined how warming effects Mesostigmata communities. We tested the effect of short-term (three months), intensive warming (+8 °C) on Mesostigmata communities from the boreal forest using experimental mesocosms containing forest-floor material. We collected moss mats and underlying forest floor organic material from a boreal forest and incubated them within individual mesocosms at 12 °C and 20 °C for three months, where 12 °C represented the long-term average growing season temperature and 20 °C corresponds to the potential extreme surface temperature from climate warming for the region. We enumerated all extracted microarthropods and nematodes, and identified all Mesostigmata adults to the species-level. In total, we counted 24,080 nematode individuals, and 19,582 total microarthropod individuals, of which 3349 individuals (1899 adults and 1450 juveniles) were mesostigmatic mites, consisting of 14 species. Mesostigmatic juvenile and adult abundances, along with adult community-level body mass were higher under warming, which lead to a shift in community composition. Changes to Mesostigmata communities were driven by the greater abundances of parthenogenetic species, primarily Veigaia mitis (Berlese), under warming—a response that has been shown in oribatid mite communities, but not mesostigmatic communities, before. Overall, we found that warming shifted mesostigmatic mite communities in the boreal forest, which has wide ranging implications for the soil food web.

In boreal peatlands, low decomposition rate is the underlying cause of carbon sequestration. Decomposition of litter can be affected by factors relating to soil moisture and temperature, the quality of the litter, and by the biotic decomposer community, among others. Exploring how these drivers interact will provide better understanding of carbon dynamics in boreal peatlands. We measured the decomposition of three common peatland plant functional types (moss, sedge, shrub), and associated microarthropod communities using litterbags placed in hollows (wet depressions) and hummocks (dry, raised areas) of a boreal peatland in Ontario, Canada. Decomposition was significantly different between all plant litter types, and greatest in sedge, but was not significantly different between hummock and hollow microhabitats. The decomposer community displayed an opposite pattern, significantly affected by microhabitat where richness and abundance of microarthropods was greater in hollows than hummocks. Oribatid mites were the dominant microarthropod with respect to both richness and abundance. Plant litter type did not affect community structure in hollows, but was a determinant of oribatid dominance in hummocks. These results suggest that abiotic environmental conditions are the main drivers of community structure for decomposers, while plant litter quality is a more important determinant of decomposition dynamics in boreal peatlands.

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.

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.

Plant species shape soil properties such as nutrient availability and carbon storage through functional traits. Understanding the role of plant functional traits, and the relationship between aboveground and belowground systems are especially important in boreal peatlands, which are important carbon sinks. Sphagnum as a key peat-forming bryophyte has long been considered an ecosystem engineer, whereas the engineering role of graminoids, also dominant in peatlands, has not traditionally been considered. We quantified vegetation community composition, plant functional traits, and peat properties in two peatland sites differing in dominant vegetation (Sphagnum mosses and Carex sedges), and link plant traits with peat properties using ordination. We show that plant traits significantly explain many peat properties, including organochemicals that are indicators of decomposition dynamics. Specifically, Carex-dominated sites had larger amount of ‘decomposition products’ while a larger proportion of ‘undecomposed materials’ was observed in Sphagnum-dominated sites. Feedbacks in plant-soil systems are increasingly being recognised as drivers of ecosystem processes. In both peatland types, plant traits of the key ecosystem engineer drove properties of the belowground peat environment. Peat organochemical constituents between Sphagnum-dominated and Carex-dominated sites reveal differences in ecosystem function, and thus the conducive potential for carbon storage.

Foliar litter is the main input of organic carbon to many soils, and thus litter decomposition processes are integral to our understanding of carbon dynamics in soil systems. Despite the short duration of the leaching phase of decomposition, a considerable amount of mass loss can occur providing a valuable energy source for microbes, and influencing leaf litter chemistry for subsequent microbial decomposition. At the same time, differences in plant species and their functional traits play a role in decomposition dynamics, particularly in consideration of shifting plant communities or changes in leaf chemistry under climate change. Here we investigate the short-term leaching decomposition dynamics of three boreal peatland plant species ( Carex magellanica , Chamaedaphne calyculata , Sphagnum magellanicum ) grown under ambient and elevated levels of atmospheric CO 2 . Litter chemistry was significantly different among all three plant species. In addition, plant tissues grown under elevated CO 2 showed lower total C and total N than plants grown under ambient CO 2 . After leaching, however litter from plants grown under elevated CO 2 conditions were not significantly different in total C values compared to plants grown under ambient CO 2 conditions. Mass loss corresponded with the total dissolved organic carbon release across all species and was greatest in Chamaedaphne , a woody shrub; measures of carbon lability (SUVA 254 ) were significantly greater in vascular plant species compared to Sphagnum moss. Mass loss was reduced in plants grown under elevated CO 2 conditions, suggesting allocation to more non-soluble structural compounds. Placing our results within a climate change scenario where peatland plant community compositional shifts from mosses to graminoids and woody shrubs have been observed, we suggest that greater amounts of more labile carbon released from vascular plant species indicates a shift to more decomposable litters with the potential to stimulate microbial growth and activity.

This checklist of the oribatid fauna of Canada and Alaska (excluding Astigmata) includes 580 identified species in 249 genera and 96 families. The known fauna of Canada includes 556 identified species in 247 genera, and that of Alaska includes 182 species in 95 genera; 39 of the 42 oribatid superfamilies are represented. We further list ~ 300 species that are currently unidentified, and possibly undescribed. In addition, we list 42 genera that are represented only by unidentified and probably undescribed species. For each species we give combinations and synonymies, specific locations in Alaska and the Provinces and Territories of Canada, habitats, and biogeography. There are 182 identified species known for Alaska, 152 for Yukon, 122 for Northwest Territories, 58 for Nunavut; 210 for British Columbia, 213 for Alberta, 15 for Saskatchewan, 84 for Manitoba, 167 for Ontario, 210 for Québec, 110 for Nova Scotia, 77 for New Brunswick, 84 for Newfoundland and 6 for Prince Edward Island. The known fauna of Canada is smaller than that of Austria, and is approximately equivalent to that of the Czech Republic. As these countries are much smaller in size than Canada and less ecologically diverse, we consider the Canadian and Alaskan fauna are at most 25% known. The paucity of these data reflects the absence of taxonomic and faunistic studies on Oribatida in State, Provinces or Territories, and especially in the Canadian and Alaskan National Park systems and the hundreds of Provincial Parks. Despite the almost 90% increase in described species since the catalogue of Marshall et al. (1987), there is a need for focussed, coordinated research on Oribatida in the natural regions throughout Canada and Alaska, and for monographs on families and genera with large numbers of undescribed species, such as Brachychthoniidae, Damaeidae, Cepheidae, Liacaridae, Oppiidae, Suctobelbidae, Hydrozetidae, Phenopelopidae, Scheloribatidae, Haplozetidae and Galumnidae.

Soils host the vast majority of life on Earth including microorganisms and animals, and supporting all terrestrial vegetation. While soil organisms are pivotal for ecosystem functioning, the assemblages of different biota from a taxonomic and functional perspective, as well as how these different organisms interact, remains poorly known. We provide a brief overview of the taxonomic and functional diversity of all major groups of soil biota across different scales and organism sizes, ranging from viruses to prokaryotes and eukaryotes. This reveals knowledge gaps in relation to all soil biodiversity groups, which are especially evident for viruses, protists, micro- and meso-fauna. We review currently-available methods to study the taxonomic and functional diversity of soil organisms by grouping all commonly-used methods into morphological, biochemical and molecular approaches. We list potentials and limitations of the methods to reveal that there is, as yet, no single method to fully characterize the biodiversity even of a single group of soil biota. Yet, we stress that we now have the methods available to enable scientists to disentangle the taxonomic and functional diversity of virtually all soil organisms. We provide a user-friendly guide to help researchers address a wider variety of soil biodiversity in their studies by discussing and critically analysing the various potentials and limitations of diverse methods to study distinct groups of soil life. We highlight that integrative methodological approaches, ideally in collaborative interactions, are key to advancing our understanding of soil biodiversity, such as the combination of morphological and molecular approaches to overcome method-specific limitations. Together, integrative efforts can provide information on the abundance, biomass, diversity and function of several groups of soil biota simultaneously. This newly-obtained integrative information on soil biodiversity will help to define the importance of soil biodiversity in ecosystem processes, functions, and services, and serve to refine food-web and earth system models.

Plant growth forms can influence carbon cycling, particularly in carbon-rich ecosystems like northern peatlands; however, mechanistic evidence of this relationship is limited. Our aim was to determine if northern peatland plant growth forms alter belowground dissolved carbon chemistry and enhance carbon release through stimulated microbial metabolism. We used replicated, peat monoliths populated exclusively by Sphagnum mosses, graminoids, or bare peat and quantified changes in belowground dissolved organic carbon chemistry, microbial metabolism, as well as respired CO2. The graminoid growth form was significantly distinct in belowground dissolved organic carbon chemistry with carbon compound lability 20 % and 11 % greater than bare peat and Sphagnum moss respectively. The labile dissolved organic carbon stimulated the microbial community, as indicated by greater microbial metabolic activity and richness values in conjunction with 50 % higher respired CO2 fluxes under the graminoid treatment. Our results provide mechanistic evidence that peatland plant growth forms can drive carbon cycling processes by altering dissolved organic carbon chemistry to prompt cascading effects on the microbial community and carbon release — trends suggestive of microbial priming effects. Should climate change increase graminoid prevalence at the expense of Sphagnum moss northern peatland carbon store stability may be threatened by this mechanism.