Woody vegetation encroachment in unmanaged semi-natural grasslands leads to a decline in plant diversity and alters community composition. Livestock grazing reinstatement can reverse this succession. However, despite their importance for terrestrial biodiversity and ecosystem processes, the dynamics of associated soil microbial communities are not well understood. We examined plant and soil microbial communities, including fungal (arbuscular mycorrhizal, ectomycorrhizal, pathogenic, saprotrophic) and prokaryotic (rhizobia, non-rhizobial bacteria, archaea) communities, in mountain grasslands in the central Pyrenees experiencing different degrees of management and overgrowth by woody vegetation. We found that plant richness declines and plant community composition changes substantially during woody encroachment. Analogous trends were observed in soil microbial communities, with AM fungal and bacterial communities showing the most distinct successional trajectories. A notable contrast was the significant increase in the richness of ECM fungi under the developing pine canopy. Livestock grazing reinstatement influenced soil microbial community composition but did not significantly affect plant community composition. Plant and soil microbial communities change synchronously during woody plant encroachment following livestock grazing cessation. Changes in plant communities are most pronounced, but strongly correlated changes also occur among AM fungi, pathogenic fungi and rhizobia, which have strong functional links with plants as symbionts or antagonists. Responses to restored livestock grazing were more apparent in soil microbial communities than plant communities, probably reflecting differences in diaspore persistence or dispersal efficiency.

Despite extensive research, stabilizing mechanisms in ecosystems remain uncertain. Taylor's power law (TPL) is a pervasive ecological pattern that describes how variance scales with mean abundance (sigma(2) = a mu(b)). While TPL has been widely studied within populations, its role across species within communities and its implications for stability remain largely unexplored. A TPL scaling factor (b) < 2 implies an unexplored stabilizing effect of dominant species (hereafter the 'dominance effect'), where community stability arises from dominant species being relatively more stable than subordinates. This study aims to explore the influence of TPL exponent b on the dominance effect on stability and identify the biotic and abiotic community factors shaping it. Using data from over 9000 permanent vegetation plots globally, we investigated within-community TPL, linked it to the dominance effect, and examined drivers of b values. Results reveal a strong contribution of b, together with species evenness, to dominance effects on stability. A ubiquitous TPL (mode R-2 = 0.92) with a consistent b < 2 highlights widespread dominance effects. Lower b values were linked to resource-conservative strategies and climatic seasonality, reinforcing the role of environmental filtering in stability. These findings highlight the widespread dominance effect on community temporal stability, particularly driven by woody, large-seeded species in cold, seasonal climates. Moreover, results identify the TPL exponent b as a powerful indicator of dominant species' stabilizing effects, complementing the well-known role of species diversity.

Urbanisation has led to reduced exposure to environmental microbiota, potentially with negative consequences for human health. The biodiversity hypothesis suggests that contact with diverse environmental microorganisms, particularly soil-dwelling Gammaproteobacteria, is associated with immune regulation and may reduce allergy risk. We investigated this hypothesis in Tartu, an Estonian city (ca. 100,000 inhabitants) in Northern Europe, by integrating citywide ecological data with clinical information. Using a cohort of 148 children, we assessed the relationship between atopy (atopic sensitisation, a tendency to develop allergic diseases) and proximity to urban green spaces with high Gammaproteobacteria diversity. This spatial linkage was possible through an intensive citywide soil microbial eDNA survey covering 743 green spaces.We found that children living closer to green spaces characterised by high soil Gammaproteobacteria diversity had a significantly lower probability of atopy than those living farther away. Additionally, atopy was positively associated with the wealth of the neighbourhood and negatively associated with the abundance of urban grasslands. The diversity of Gammaproteobacteria was positively associated with plant diversity and the nearby presence of urban woodlands and negatively associated with soil fertility (potassium concentration). Notably, children's daycare yards exhibited higher Gammaproteobacteria diversity than public green areas.These findings support the biodiversity hypothesis in an urban context and highlight the importance of microbial exposure in early life, offering insights for integrating microbial biodiversity into urban design and public health policy. In particular, urban planning strategies that promote plant diversity, preserve urban grasslands and woodlands, and support biodiverse daycare environments may enhance public health.

Grasses, including major cereal crops, associate with arbuscular mycorrhizal (AM) fungi to varying degrees depending on environmental conditions. Understanding mechanisms driving this environment-induced variation in mycorrhization, i.e. plant AM plasticity, is necessary to predict grass-mycorrhizal responses to global change factors, such as nutrient enrichment, and to resolve the role of AM symbiosis in cereal crop production. We compared AM plasticity in four cereal crops by testing the effect of nitrogen (N) fertilization on AM colonization and root PLFA 16:1ω5 concentration. To assess whether mycorrhization patterns reflect root functional traits, we compared specific root length among species. To determine whether plants regulate AM colonization qualitatively (by selectively associating with certain AM taxa) or quantitatively (by collectively suppressing colonization across taxa), we investigated directional shifts and variability in AM community structure in response to N fertilization. AM colonization varied between cereal species and was reduced by N fertilization, but we found limited evidence for interspecific differences in AM plasticity. Winter wheat appeared less AM responsive and associated more with uncultured AM fungi compared to the three spring-sown cereal species, oat, spring wheat and spring barley. Fertilization did not affect AM community composition, and within-species variation in AM community β-dispersion did not covary with variation in AM colonization or PLFA 16:1ω5 concentration. These results support the view that host plants regulate arbuscular mycorrhization quantitatively rather than through taxonomic selectivity. We propose AM plasticity as a plant-mycorrhizal trait to be used for more accurate predictions of plant environmental responses in eco-physiological and agroecological research.

Aim Understanding why some plant species are abundant or widely distributed is a long-standing aim of plant ecology. This research investigated whether the position of herbaceous plant species within the plant economics spectrum (aboveground and belowground) and along the mycorrhizal collaboration gradient could explain their local abundance, geographic occupancy, and global abundance.Location Global.Methods We used two published sources of global plant community data (sPlotOpen and the global biodiversity initiative facility; GBIF) to determine whether the local abundance, geographic occupancy, and global abundance of herbaceous plant species can be explained by their above- and belowground traits and estimates of mycorrhizal dependence and flexibility.Results Both above- and belowground traits were only weakly associated with local abundance, while geographic occupancy was associated with small plant size and traits indicating fast return on investment in aboveground tissues. Geographic occupancy was also related to belowground traits, being positively associated with specific root length and negatively associated with root diameter, and weakly positively associated with mycorrhizal flexibility. The traits associated with global abundance largely mirrored those associated with occupancy.Main Conclusions Our analysis suggests that the local success of herbaceous plants is context-specific and there are no universal traits globally underlying high local abundance. By contrast, geographic occupancy aligns strongly with belowground traits, including specific root length and root diameter. The wide success of fine-rooted species may be related to nutrient enrichment during biogeographic history and in recent increasingly anthropogenic conditions.

This study investigates how agricultural disturbance influences arbuscular mycorrhizal (AM) fungal diversity, biomass, and community niche structure. Utilizing niche concepts, we show that the AM fungal communities in intensively managed soils exhibited larger niche volumes and an increased proportion of culturable taxa, which negatively impacted biomass production. This process was primarily driven by the reduction in specialist taxa, indicating a functional homogenization of the community. Intensively disturbed low-biomass AM fungal communities were composed of species that can persist under low host abundance. Our findings reveal that intensive management disturbance significantly decreased AM fungal species richness and biomass simultaneously. Preserving AM fungal diversity is essential for maintaining their biomass and functionality, underscoring the detrimental effects of intensive agricultural practices on these critical soil organisms and their potential consequences for soil health and ecosystem functioning.

Ecological niche volumes are hypothesised to decrease with latitude, with species distribution primarily shaped by abiotic factors at high latitudes and biotic factors at low latitudes. Similar patterns are expected along elevational gradients. We tested these predictions using global distribution and niche data for arbuscular mycorrhizal (AM) fungi. We found that temperature niche volumes increased with latitude, while precipitation niche volumes decreased, reflecting greater temperature and lower precipitation variability with increasing latitude. Niche differentiation in communities declined with latitude, suggesting a shift towards habitat filtering, driven primarily by similar temperature niches. Additionally, community niche structure along elevational gradients largely mirrored patterns observed in relation to latitude. These findings highlight the key role of abiotic filtering in structuring communities at high latitudes and suggest that similar ecological principles govern niche dynamics and community composition across latitudinal and elevational gradients.

Plant coexistence and diversity-productivity relationships are often studied separately, yet both are shaped by the same biotic interactions. Here we focus on how host-specificity among soil pathogens and mutualists alters niche and fitness differences among plant species, subsequently modifying biodiversity effects on productivity. Specialist pathogens can generate niche differences through density-dependent processes, thereby stabilizing plant coexistence and enhancing complementarity effects. Specialist mutualists can instead destabilize coexistence and lead to variable effects on productivity. The effects of generalist microbes are less predictable, depending on relationships between plant traits determining microbial interactions (e.g., defense traits) and those determining competitive ability and biomass production. This review underscores the significance of plant-microbial interactions in bridging the mechanisms underlying species coexistence and biodiversity-ecosystem functioning relationships.

Because of the growing human population, increasing agricultural yields is becoming increasingly more important. However, various environmental crises have led society to demand a reduction in the environmental damage caused by agriculture. Until now, the economic and ecological aspects of plant cultivation have developed largely independently. Here, we propose a novel ecological intensification index (EII) that integrates both economic and ecological goals, measured in relative units as the realized proportion of a possible maximum value. The EII can incorporate multiple ecological and/or economic measures with different weights to balance societal needs, environmental concerns, and scientific knowledge. Using the EII will provide a quantitative target for breeders, agronomists, and farmers to catalyze innovation toward a minimal ecological impact of agriculture.

Mycorrhiza is a symbiotic association between plant root and fungus, contributing to plant mineral nutrition and defence against antagonists. The mycorrhizal collaboration niche characterizes the position of plant species along a gradient of reliance on mycorrhiza. In this Perspective, we introduce the plant mycorrhizal traits that describe these niches and explore upscaling them to describe community-scale and macroecological-scale structure, including relationships with ecosystem function. Plant mycorrhizal type, status, dependency and root colonization rate characterize mycorrhizal niche optima, whereas flexibility and variation of root colonization rate, indicating the plasticity of plants in their reliance on mycorrhiza, describe mycorrhizal niche width. Abundance-weighted community means of plant mycorrhizal traits offer a way of upscaling trait information and examining mycorrhizal niche structure across communities and biomes. An illustrative analysis indicated that the share of highly mycorrhiza-reliant plant species decreases in biomes of more recent biogeographic origin at high latitudes. Arbuscular mycorrhizal plants become less prevalent, and those remaining tend to be flexible. The highest overall flexibility is observed in anthropogenic semi-natural grasslands, whereas, contrastingly, natural grasslands exhibit low overall mycorrhizal flexibility. Further advances in the field will be underpinned by the development of standardized approaches for measuring mycorrhizal traits. The mycorrhizal symbiosis between plants and fungi is critical to the success of both partners. This Perspective explores how plant reliance on mycorrhizae varies across ecological scales and how the relationship shifts with changing ecological conditions.

Anthropogenic biodiversity decline threatens the functioning of ecosystems and the many benefits they provide to humanity1. As well as causing species losses in directly affected locations, human influence might also reduce biodiversity in relatively unmodified vegetation if far-reaching anthropogenic effects trigger local extinctions and hinder recolonization. Here we show that local plant diversity is globally negatively related to the level of anthropogenic activity in the surrounding region. Impoverishment of natural vegetation was evident only when we considered community completeness: the proportion of all suitable species in the region that are present at a site. To estimate community completeness, we compared the number of recorded species with the dark diversity-ecologically suitable species that are absent from a site but present in the surrounding region2. In the sampled regions with a minimal human footprint index, an average of 35% of suitable plant species were present locally, compared with less than 20% in highly affected regions. Besides having the potential to uncover overlooked threats to biodiversity, dark diversity also provides guidance for nature conservation. Species in the dark diversity remain regionally present, and their local populations might be restored through measures that improve connectivity between natural vegetation fragments and reduce threats to population persistence.

Earth’s climate is tightly connected to carbon and nitrogen exchange between the atmosphere and ecosystems. Wet peatland ecosystems take up carbon dioxide in plants and accumulate organic carbon in soil but release methane. Man-made drainage releases carbon dioxide and nitrous oxide from peat soils. Carbon and nitrous gas exchange and their relationships with environmental conditions are poorly understood. Here, we show that open peatlands in both their wet and dry extremes are greenhouse gas sinks while peat carbon/nitrogen ratios are high and prokaryotic (bacterial and archaeal) abundances are low. Conversely, peatlands with moderate soil moisture levels emit carbon dioxide and nitrous oxide, while prokaryotic abundances are high. The results challenge the current assumption of a uniform effect of drainage on greenhouse gas emissions and show that the peat microbiome of greenhouse-gas sources differs fundamentally from sinks.

The distylous plant Primula veris has long served as a model species for studying heterostyly, that is the occurrence of multiple floral morphs within a population to ensure outcrossing. Habitat loss, reduced plant population sizes, and climate change have raised concerns about the impact of these factors on morph ratios and the related consequences on fitness of heterostylous species. We studied the deviation of floral morphs of P. veris from isoplethy (i.e. equal frequency) in response to plant population size, landscape context and climatic factors, based on a pan-European citizen science campaign involving observations from 28 countries. In addition, we examined the relative frequency of morphs to determine whether landscape and climatic factors disrupt morph frequencies or whether a specific morph has an advantage over the other. Theory predicts equal frequencies of short-styled S-morphs and long-styled L-morphs in populations at equilibrium. However, data from >3000 populations showed a substantial morph deviation from isoplethy and a significant excess of S-morphs (9% higher compared to L-morphs). Deviation of morph frequency from equilibrium was substantially stronger in smaller populations and was not affected by morph identity. Higher summer precipitation and land use intensity were associated with an increased prevalence of S-morphs. Five populations containing individuals exhibiting short homostyle phenotypes (with the style and anthers in low positions) were found. Genotyping of the individuals at CYP734A50 gene of the S locus, which determines the length of the style and the position of anthers of P. veris, revealed no mutations in this region. Our results based on an unprecedented geographic sampling suggest that changes in land use and climate may be responsible for non-equilibrium morph frequencies. This large-scale citizen science initiative sets foundations for future studies to clarify whether the unexpected excess of S-morphs is due to partial intra-morph compatibility, disruption of heterostyly or survival advantage of S-morphs. Synthesis. Human-induced environmental change may affect biodiversity indirectly through altering reproductive traits, which can also lead to reduced fitness and genetic diversity. Further research should consider the possible role of pollinators in mediating the ecological and evolutionary consequences of recent landscape and climatic shifts on plant reproductive traits.

Soil microbes drive ecosystem function and play a critical role in how ecosystems respond to global change. Research surrounding soil microbial communities has rapidly increased in recent decades, and substantial data relating to phospholipid fatty acids (PLFAs) and potential enzyme activity have been collected and analysed. However, studies have mostly been restricted to local and regional scales, and their accuracy and usefulness are limited by the extent of accessible data. Here we aim to improve data availability by collating a global database of soil PLFA and potential enzyme activity measurements from 12,258 georeferenced samples located across all continents, 5.1% of which have not previously been published. The database contains data relating to 113 PLFAs and 26 enzyme activities, and includes metadata such as sampling date, sample depth, and soil pH, total carbon, and total nitrogen. This database will help researchers in conducting both global- and local-scale studies to better understand soil microbial biomass and function.

The Andean paramo, hereafter “paramo”, is a Neotropical high-mountain region between the treeline and permanent snowline (3500–4800 m) and is considered the world’s coolest biodiversity hotspot. Because of paramo’s high humidity, solar radiation and temperature variation, mycorrhizal symbiosis is expected to be essential for plants. Existing theory suggests that replacement of arbuscular mycorrhizal (AM) by ectomycorrhizal (ECM) and then ericoid mycorrhizal plants (ERM) can be expected with increasing elevation. Previous findings also suggest that non-(NM) and facultatively mycorrhizal (FM) species predominate over obligatory mycorrhizal (OM) species at high elevations. However, these expectations have never been tested outside of the northern temperate zone. We addressed the distribution and environmental drivers of plant mycorrhizal types (AM, ECM and ERM) and statuses (NM, FM and OM) along the paramo’s elevational gradient. We used vegetation plots from the VegParamo database, climatic and edaphic data from online repositories, and up-to-date observation information about plant mycorrhizal traits at species and genus level, the latter being proposed as hypotheses. AM plants were dominant along the entire gradient, and ERM plants were most abundant at the lowest elevations (2500–3000 m). The share of FM plants increased and that of OM plants decreased with elevation, while NM plants increased above 4000 m. Temperature and soil pH were positively related to the abundance of AM plants and negatively to ERM plants. Our results reveal patterns that contrast with those observed in temperate northern-hemisphere ecosystems.

Mycorrhizal symbiosis, specifically arbuscular mycorrhiza, is one of Earth's oldest and most widespread symbiosis. Existing evidence suggests that plant species differ in their associations with mycorrhizal partners, with different species reported to be always (obligately mycorrhizal, OM), sometimes (facultatively mycorrhizal, FM) or never (non-mycorrhizal, NM) associating with arbuscular mycorrhizal (AM) fungi and this plant reliance on AM fungi is called plant mycorrhizal status. However, very little is known about how host plant mycorrhizal status shapes the network topology of interacting AM fungi. Here, we use a standardized sampling scheme to test whether plant species with different mycorrhizal statuses differ in mean AM fungal hyphal colonization and various indices of the AM fungal networks such as nestedness rank and resource range. We collected the roots and rhizosphere soil of 19 plant species representing five families. Each plant species was sampled from three distinct habitats. We determined AM fungal colonization in the roots and AM fungal community composition in roots and rhizosphere soil using molecular methods. We found that previously reported NM plant species had lower mean AM fungal colonization than FM plant species, but no differences were found between FM and OM plant species. Network analyses indicated that AM fungal communities in the roots of FM plant species had higher nestedness rank and resource range than networks associated with OM plant species, suggesting that OM plant species are more generalist regarding partner selection and interact with a wider range of fungal partners. Our results suggest that plant mycorrhizal status conveys useful information about the characteristics of AM fungal interaction networks, revealing that plant species consistently associated with AM fungi are less selective towards their fungal partners.Read the free Plain Language Summary for this article on the Journal blog.

Studies of niche differentiation and biodiversity often focus on a few niche dimensions due to the methodological challenge of describing hyperdimensional niche space. However, this may limit our understanding of community assembly processes. We used the full spectrum of realized niche types to study arbuscular mycorrhizal fungal communities: distinguishing abiotic and biotic, and condition and resource, axes. Estimates of differentiation in relation to different niche types were only moderately correlated. However, coexisting taxon niches were consistently less differentiated than expected, based on a regional null model, indicating the importance of habitat filtering at that scale. Nonetheless, resource niches were relatively more differentiated than condition niches, which is consistent with the effect of a resource niche-based coexistence mechanism. Considering niche types, and in particular distinguishing resource and condition niches, provides a more complete understanding of community assembly, compared with studying individual niche axes or the full niche.

We discuss which plant species are likely to become winners, that is achieve the highest global abundance, in changing landscapes, and whether plant-associated microbes play a determining role. Reduction and fragmentation of natural habitats in historic landscapes have led to the emergence of patchy, hybrid landscapes, and novel landscapes where anthropogenic ecosystems prevail. In patchy landscapes, species with broad niches are favoured. Plasticity in the degree of association with symbiotic microbes may contribute to broader plant niches and optimization of symbiosis costs and benefits, by downregulating symbiosis when it is unnecessary and upregulating it when it is beneficial. Plasticity can also be expressed as the switch from one type of mutualism to another, for example from nutritive to defensive mutualism with increasing soil fertility and the associated increase in parasite load. Upon dispersal, wide mutualistic partner receptivity is another facet of symbiont plasticity that becomes beneficial, because plants are not limited by the availability of specialist partners when arriving at new locations. Thus, under conditions of global change, symbiont plasticity allows plants to optimize the activity of mutualistic relationships, potentially allowing them to become winners by maximizing geographic occupancy and local abundance.

European dry thin-soil calcareous grasslands (alvars) are species-rich semi-natural habitats. Cessation of traditional management, such as mowing and grazing, leads to shrub and tree encroachment and the local extinction of characteristic alvar species. While soil microbes are known to play a critical role in driving vegetation and ecosystem dynamics, more information is needed about their composition and function in grasslands of different dynamic stages. Here we assess the composition of soil fungal, prokaryotic, and plant communities using soil environmental DNA from restored alvar grasslands in Estonia. The study areas included grasslands that had experienced different degrees of woody encroachment prior to restoration (woody plant removal and grazing), as well as unmanaged open grasslands. We found that, in general, different taxonomic groups exhibited correlated patterns of between-community variation. Previous forest sites, which had prior to restoration experienced a high degree of woody encroachment by ectomycorrhizal Scots pine, were compositionally most distinct from managed open grasslands, which had little woody vegetation even prior to restoration. The functional structure of plant and fungal communities varied in ways that were consistent with the representation of mycorrhizal types in the ecosystems prior to restoration. Compositional differences between managed and unmanaged open grasslands reflecting the implementation of grazing without further management interventions were clearer among fungal, and to an extent prokaryotic, communities than among plant communities. While previous studies have shown that during woody encroachment of alvar grassland, plant communities change first and fungal communities follow, our DNA-based results suggest that microbial communities reacted faster than plant communities during the restoration of grazing management in alvar grassland. We conclude that while the plant community responds faster to cessation of management, the fungal community responds faster to restoration of management. This may indicate hysteresis, where the eventual pathway back to the original state (grazed ecosystem) differs from the pathway taken towards the alternative state (abandoned semi-natural grassland ecosystem).