Harry Olde Venterink

Biodiversity is widely expected to stabilize ecosystem functioning 1-6, but the stabilizing effect likely depends on which species constitute biodiversity. The global proliferation of non-native species is fundamentally reshaping ecological communities worldwide 7-12, but whether these compositional changes undermine biodiversity’s stabilizing role remains unresolved. Using plant community data from 142 terrestrial sites across the world and more than 11,000 local communities, we show that, compared with native plants, non-native plants weaken positive diversity–stability relationships across broad environmental gradients. Increasing non-native dominance shifts local plant communities from conservative toward more acquisitive resource-use strategies. This functional reorganization weakens the pathway through which diversity stabilizes constituent populations and thereby supports community stability, while leaving compensatory dynamics among species (species asynchrony) comparatively less affected. These findings show that native and non-native species are not functionally equivalent in their contributions to community stability, cautioning against treating non-native species as functional substitutes for native biodiversity. Our results highlight a previously underappreciated consequence of plant invasion: by altering community functional composition and disrupting the mechanisms through which diversity promotes stability, non-native species can undermine the stabilizing role of biodiversity. Limiting the spread and dominance of non-native species may therefore be critical not only for conserving native biodiversity, but also for safeguarding the capacity of plant communities to sustain ecosystem functioning under ongoing environmental change.

Pollinators are declining globally due to anthropogenic pressures, such as intensive grazing and nutrient enrichment. Yet, their combined effects on pollinators and plant‐pollinator interactions remain poorly understood, particularly in the Arctic. Here, we experimentally tested how grazing exclusion and nutrient addition shape flower‐visiting insect communities and interaction networks in a high‐productivity montane and a low‐productivity tundra grassland, in northern Fennoscandia. Grazing exclusion emerged as the primary driver across both grasslands, increasing flower‐visitor family richness, diversity, and the number of plant‐pollinator interactions. These effects were especially strong in the tundra grassland, where resource limitation is more pronounced. In contrast, nutrient addition had weaker and more context‐dependent effects, enhancing flower‐visitor richness and the number of interactions mainly in the tundra grassland and particularly when combined with grazing exclusion. At both sites, grazing exclusion and nutrient addition altered community composition, with the strongest shifts occurring under their combined effects. Despite large effects on interaction numbers, network structure responded more subtly. Weighted connectance declined with grazing exclusion, especially in the tundra, indicating that interactions became more concentrated on a subset of plant species where floral resources were abundant. In contrast, network specialization (H ₂ ’) and nestedness showed limited responses to experimental treatments, suggesting relatively stable interaction organization. Overall, our results demonstrate that grazing strongly regulates pollinator communities and interaction networks in Arctic grasslands, while nutrient enrichment plays a secondary, context‐dependent role. The pronounced sensitivity of tundra grasslands highlights their vulnerability to environmental change and underscores the importance of managing grazing pressure to sustain pollination processes in Arctic ecosystems.

Animals play an important role in elemental cycles that underpin ecosystem functioning through their foraging, movement and waste excretion. Yet animals also play a distinct but often overlooked role in the cycling of trace elements by incorporating potentially scarce trace elements into their tissues and returning significant quantities to the local environment when their carcasses decompose. This gap in our understanding of trace element cycling through animal decomposition means we lack a complete picture of the fundamental zoogeochemical processes that integrate animals within landscapes. Here, we present a perspective on the role large animals play in linking trace elemental cycles from local to landscape scales during their lives (via accumulation and excretion) and after their death (via carcass decomposition). We highlight how large vertebrates, and their decomposition, can redistribute trace elements across spatial scales and may serve as tools for managing trace elemental cycling and enhancing landscape heterogeneity.

Summary: Drought stress constrains the productivity of terrestrial ecosystems and the distribution of plant species. To withstand drought stress, plants have evolved diverse water‐use strategies. Despite the critical function of roots in whole‐plant water regulation, drought strategies have been primarily studied from an aboveground perspective, and so our knowledge of how fine‐root traits are related to aboveground hydraulic traits remains limited. Here, we compiled a dataset of primarily woody species comprising five aboveground plant hydraulic traits associated with water‐use strategies and four fine‐root traits from the root economics space (RES). We investigated how the global diversity in ecological strategies of the RES traits relates to aboveground hydraulic traits contributing to drought resistance. We found a slight trend towards acquisitive species with higher root nitrogen content and lower root tissue density having lower drought resistance in aboveground tissues. Species with thicker roots displayed a tendency towards slightly higher drought resistance than thin‐rooted species. The weakness of these relationships suggests that aboveground drought adaptations are largely independent of classical axes of fine root ecological strategies, pointing to either a decoupling between aboveground and belowground responses or a stronger coordinating role for other root traits such as maximum rooting depth or root cortex fraction in hydraulic adaptation.

Mammalian herbivores play a pivotal role in nutrient cycling and plant community composition. Their excreta and grazing activity influence plant diversity, but the relative or interactive effects of these influences are unclear. We manipulated dung quantity, quality (three herbivores with varying dung-N:P), and grazing type (bulk, selective, no) in a 3-year experiment. Neither dung quantity nor bulk grazing influenced plant diversity, despite strongly impacting plant productivity and light. Dung’s impact on plant diversity varied among herbivore species but could not be ascribed to nutrients. Effects of selective grazing on plant diversity interacted with dung type (herbivore species), depending on whether it promoted dominance of the consumed plants. Our results highlight that the interactive effects between herbivore species-specific dung characteristics and grazing activities have important indirect effects on plant diversity in terrestrial ecosystems.

Threatened and invasive plant species may appear worlds apart; however, we propose that mechanisms underlying invasive success and extinction risk among European herbaceous species constitute a continuum from successful, well-dispersing, fast-growing species to threatened, slow-growing species. We provide empirical evidence for such an extinction-invasion continuum and show that threatened and naturalized invasive plant species occur at opposite ends. Threatened species persist in phosphorus-limited nutrient-poor habitats, while naturalized and invasive species more often occur in nitrogen-limited nutrient-rich habitats. These opposing niches suggest invasive species do not directly displace threatened species; instead, species replacement and extinction result from nutrient regime shifts. Mitigating and preventing nutrient enrichment, especially phosphorus, for nature conservation protects existing nutrient niches for threatened species and limits plant invasion.

The abundance and composition of flowers within plant communities shape the resources available to flower‐visiting insects. However, it remains unclear how nutrient enrichment and changes in grazing impact plant communities and their floral resources, and whether these effects contribute to ongoing pollinator decline. We investigated how the abundance, diversity and species composition of flowers (excluding graminoids) respond to long‐term nutrient additions and grazing exclusion in two high‐latitude grasslands (tundra and montane). We used two factorial experimental designs: 1) a nutrient experiment with additions of nitrogen (N), phosphorus (P), and potassium (K with micronutrients), and 2) a grazing experiment that included combined NPK addition with and without grazing exclusion. Flower abundance was assessed in 5 × 5 m experimental plots after 6–10 years of treatments. N and P interactively affected flower abundance, with N counteracting the positive effects of P. N reduced flower abundance in the montane grassland, whereas P and K increased it. Grazing exclusion increased flower abundance, with its effect amplified under NPK addition, but this joint treatment reduced flower species richness. Grazing exclusion reduced flower species diversity, with contrasting site‐specific effects depending on NPK. N, P and K additions as well as grazing exclusion and NPK addition changed the composition of flower assemblages. At the montane grassland joint NPK addition and grazing exclusion led to strong dominance of forbs, such as Anthriscus sylvestris and Geranium sylvaticum , and grazing exclusion led to homogenisation of the flower community at the montane grassland. Our study demonstrate the importance of grazing and nutrients as key determinants of floral resources, which are vital for flower‐visiting insects. We suggest that quantifying floral resources could contribute to ecosystem status assessment. Our findings offer insights for managing and conserving pollinator habitats in the face of environmental change.

Nutrient enrichment typically causes local plant diversity declines. A common but untested expectation is that nutrient enrichment also reduces variation in nutrient conditions among localities and selects for a smaller pool of species, causing greater diversity declines at larger than local scales and thus biotic homogenization. Here we apply a framework that links changes in species richness across scales to changes in the numbers of spatially restricted and widespread species for a standardized nutrient addition experiment across 72 grasslands on six continents. Overall, we find proportionally similar species loss at local and larger scales, suggesting similar declines of spatially restricted and widespread species, and no biotic homogenization after 4 years and up to 14 years of treatment. These patterns of diversity changes are generally consistent across species groups. Thus, nutrient enrichment poses threats to plant diversity, including for widespread species that are often critical for ecosystem functions.

Ecosystems are experiencing changing global patterns of mean annual precipitation (MAP) and enrichment with multiple nutrients that potentially colimit plant biomass production. In grasslands, mean aboveground plant biomass is closely related to MAP, but how this relationship changes after enrichment with multiple nutrients remains unclear. We hypothesized the global biomass–MAP relationship becomes steeper with an increasing number of added nutrients, with increases in steepness corresponding to the form of interaction among added nutrients and with increased mediation by changes in plant community diversity. We measured aboveground plant biomass production and species diversity in 71 grasslands on six continents representing the global span of grassland MAP, diversity, management, and soils. We fertilized all sites with nitrogen, phosphorus, and potassium with micronutrients in all combinations to identify which nutrients limited biomass at each site. As hypothesized, fertilizing with one, two, or three nutrients progressively steepened the global biomass–MAP relationship. The magnitude of the increase in steepness corresponded to whether sites were not limited by nitrogen or phosphorus, were limited by either one, or were colimited by both in additive, or synergistic forms. Unexpectedly, we found only weak evidence for mediation of biomass–MAP relationships by plant community diversity because relationships of species richness, evenness, and beta diversity to MAP and to biomass were weak or opposing. Site-level properties including baseline biomass production, soils, and management explained little variation in biomass–MAP relationships. These findings reveal multiple nutrient colimitation as a defining feature of the global grassland biomass–MAP relationship.