Biodiversity across trophic levels drives multifunctionality in highly diverse forests

Microbial taxonomic diversity and functional genes mirror soil ecosystem multifunctionality in nonferrous metal mining areas

The pollution of metal ions triggers great risks of damaging biodiversity and biodiversity-driven ecosystem multifunctioning, whether microbial functional gene can mirror ecosystem multifunctionality in nonferrous metal mining areas remains largely unknown. Macrogenome sequencing and statistical tools are used to decipher linkage between functional genes and ecosystem multifunctioning. Soil samples were collected from subdams in a copper tailings area at various stages of restoration. The results indicated that the diversity and composition of soil bacterial communities were more sensitive than those of the fungal and archaeal communities during the restoration process. The mean method revealed that nutrient, heavy metal, and soil carbon, nitrogen, and phosphorus multifunctionality decreased with increasing bacterial community richness, whereas highly significant positive correlations were detected between the species richness of the bacterial, fungal, and archaeal communities and the multifunctionality of the carbon, nitrogen, and phosphorus functional genes and of functional genes for metal resistance in the microbial communities. SEM revealed that soil SWC and pH were ecological factors that directly influenced abiotic factor-related EMF; microbial diversity was a major biotic factor influencing the functional gene multifunctionality of the microbiota; and different abiotic and biotic factors associated with EMF had differential effects on whole ecosystem multifunctionality. These findings will help clarify the contributions of soil microbial diversity and functional genes to multifunctionality in degraded ecosystems.

Functional redundancy compensates for decline of dominant ant species

Evidence is accumulating of declines in widespread, abundant insect species. The consequences of these losses for ecosystem functioning are predicted to be severe but remain poorly tested in real-world ecosystems. Here we tested the relative importance of functional redundancy versus complementarity in conferring stability of multifunctional performance in the face of dominant insect species decline. We conducted an experimental manipulation of functional trait-space occupancy within naturally occurring ant communities in Australia. Experimental suppression of dominant ant species in multiple trait groupings caused a counterintuitive increase in multifunctional performance, which was associated with an increase in species richness. The resident ant community had high functional redundancy, contributing to rapid compensatory dynamics following suppression. However, colonization by new species with increased trait complementarity drove higher multifunctional performance. This increased multifunctionality probably occurred via reduced interspecific competition but at the cost of increased sensitivity of ecosystem multifunctionality to further species loss. Our findings show that functional redundancy can buffer multifunctional performance of a community against decline of dominant insect species but suggest that future stability of ecosystem multifunctionality depends more on functional complementarity and altered competitive interactions.

Ecosystem multifunctionality in temperate forests of South Korea is primarily controlled by structural diversity and potential moisture availability with synergy effects between ecosystem functions

Assessing and improving ecosystem multifunctionality (EMF) is essential to achieving the goals of enhancing human well-being and sustainable development. This study aims to quantify EMF and to identify its influencing factors, including biotic (tree species diversity, functional dominance, and stand structural diversity) and abiotic factors (topography, climate, and soil), and stand age. We used South Korea's 7th National Forest Inventory data to analyze 630 natural forest plots consisting of coniferous, broadleaved, and mixed stands. We categorized 12 ecosystem function-related variables to quantify EMF. Multimodel averaging and piecewise structural equation modeling were implemented to identify the main variables that affect EMF and to quantify their interrelationships and strengths. Additionally, we quantified the strength of interactions between ecosystem functions. Our findings indicate that high plant richness and old forests led to high stand structural diversity, which has a direct positive effect on EMF. Additionally, reducing water stress increased the availability of plant resources, which also has a positive effect on EMF. The mechanism controlling EMF differed according to forest stand type. In particular, we did not observe dominant plant functional traits controlling EMF in mixed stands due to the mixture of functional traits of coniferous and broadleaved trees. Finally, the interactions among ecosystem functions demonstrated a stronger synergy effect, with most functions contributing to an increase in EMF, though the degree of impact varied depending on the forest stand type. Our analysis indicates that we must comprehensively consider biodiversity and stand age as well as stand structural diversity to promote EMF. Moreover, forest management strategies should account for the interaction between plant functional traits and ecosystem functions along with environmental gradients is essential.

The contrasting roles of fungal and bacterial diversity and composition in shaping the multifunctionality of rhizosphere and bulk soils across large-scale bamboo forests

Soil microbes regulate nutrient cycling, organic matter decomposition, and other processes, thereby maintaining soil multifunctionality (SMF). However, the relationship between microbial characteristics and soil multifunctionality has primarily been studied in bulk soils, with less attention to rhizosphere soils. Moreover, this relationship remains unclear within a single forest type across large scales. In this study, we selected six sites across the distribution range of moso bamboo (Phyllostachys edulis (Carrière) J. Houz.) in China to quantify the relationship between microbial communities and soil multifunctionality in both rhizosphere and bulk soil, and to evaluate how abiotic factors influence this relationship. Our results showed that microbial diversity was negatively correlated with SMF, while the key microbial drivers (bacteria or fungi) of SMF varied between soil compartments (i.e., rhizosphere and bulk soil). Soil variables influenced SMF in bulk soils by affecting bacterial diversity and fungal composition, whereas in rhizosphere soils, soil variables influenced SMF primarily by affecting fungal diversity and composition, suggesting that different characteristics of bacterial and fungal communities drive SMF. Climatic factors exert a more significant influence on the multifunctionality of rhizosphere soils compared to bulk soils. Considering the intricate interplay between plants and soil microbes, our study highlights the importance of integrating SMF and microbial community structure within distinct soil compartments.

Belowground energy fluxes determine tree diversity effects on above- and belowground food webs

Worldwide tree diversity loss raises concerns about functional and energetic declines across trophic levels. In this study, we coupled 160 above- and belowground food webs, quantifying energy fluxes to microorganisms and invertebrates in a tree-mycorrhiza diversity experiment, to test how tree diversity affects fluxes of energy above and below the ground. The experiment differentiates three mycorrhizal type treatments: only AM tree species (with arbuscular mycorrhizae), only EcM tree species (with ectomycorrhizae; one, two, and four tree species), or mixtures of both AM and EcM tree species (AM+EcM; two and four tree species). Our results indicate that most energy initially flowed through belowground communities, with soil microorganisms contributing 97.7% of total energy and belowground fauna accounting for 60.9% of energy to animals. Consequently, belowground fauna fueled surface (62.3% of predation) and aboveground (30.5% of predation) predators. Tree diversity increased ecosystem multifunctionality (indicated by total and averaged energy fluxes) by ∼30% and energy across most trophic levels in EcM tree communities, while it shifted food webs from fast (such as bacterial-dominated) to slow (such as fungal-dominated) channels in AM tree communities. Tree diversity primarily impacted energy fluxes through belowground communities and strengthened the coupling of above- and belowground food webs, with increasing importance of belowground prey for predators at the soil surface and above the ground. These findings highlight that tree diversity and mycorrhizal types drive above- and belowground ecosystem functioning via belowground energy fluxes.

Positive effects of species mixing on biodiversity of understory plant communities and soil health in forest plantations

Mixed-species plantations are increasingly recognized for their potential to maintain forest biodiversity and soil health; however, a comprehensive assessment of their global effectiveness is lacking. To fill this knowledge gap, we conducted a meta-analysis of 7,045 paired observations between mixed-species and monoculture plantations, derived from 311 studies across diverse forest ecosystems worldwide. Our results show that mixed-species plantations significantly increased understory plant biomass, cover, and species richness by 32.6%, 55.4%, and 32.2%, respectively, compared to monocultures. Furthermore, the Shannon and Pielou diversity indices increased by 28.2% and 8.6%, respectively, and the Simpson index increased by 9.6%. When understory shrub and herbaceous species were considered separately, species mixing had significantly positive effects on shrub diversity but had no effect on herbaceous diversity. Moreover, mixed-species plantations markedly improved soil physical and chemical properties compared to monocultures. These improvements include increases in soil nutrient content (9.6 to 17.8%) and nutrient availability (14.7 to 33.5%), soil microbial biomass (17.2 to 28.8%), and soil carbon sequestration (7.2 to 19.9%). These enhancements were particularly pronounced in plantations that included legumes. Our findings reveal that the benefits of species mixing are influenced by climatic conditions, geographic location, and stand age, with the most substantial effects observed in temperate regions and mature stands. This study underscores the critical role of mixed-species plantations in promoting sustainable forest management and mitigating the ecological limitations of monocultures.

Bacteriophage-Bacteria Interactions Promote Ecological Multifunctionality in Compost-Applied Soils

Bacteriophages (phages) influence biogeochemical cycling in soil ecosystems by mediating bacterial metabolism. However, the participation of phages in soil's overall ecological functions (multifunctionality) remains unclear. Hence, this study investigated the potential for phages and bacterial communities to shape the multifunctionality of compost-applied soils. The findings revealed that cow compost and vermicompost applications enhanced the soil's multifunctionality; consequently, the highest multifunctionality was observed in the soil with vermicompost application (p < 0.05). The composition and diversity of bacteria and phages, as well as the abundance of functional genes of bacteria and phages related to carbon, nitrogen, phosphorus and sulphur metabolism, were dramatically altered following the application of both compost types. Moreover, the impact of phage diversity on soil multifunctionality is crucial for multi-threshold calculations. Structural equation modelling indicated that the effects of bacterial diversity on soil multifunctionality following compost application were paramount, with a path coefficient of 0.88 (p < 0.01). The rise in phage diversity and the enrichment of functional genes indirectly led to a dramatic increase in the soil's ecological multifunctionality by affecting the host bacteria's metabolic processes. These results offer a novel avenue to improve soil's functions and environmental services by transforming the phage community composition and functions of soils.

Plant diversity increases diversity and network complexity rather than alters community assembly processes of leaf-associated fungi in a subtropical forest

Plant diversity significantly impacts ecosystem processes and functions, yet its influence on the community assembly of leaf fungi remains poorly understood. In this study, we investigated leaf epiphytic and endophytic fungal communities in a Chinese subtropical tree species richness experiment, ranging from 1 to 16 species, using amplicon sequencing to target the internal transcribed spacer 1 region of the rDNA. We found that the community assembly of epiphytic and endophytic fungi was predominantly governed by stochastic processes, with a higher contribution of dispersal limitation on epiphytic than on endophytic fungal communities but a higher contribution of selection on endophytic than on epiphytic fungal communities. The plant-epiphytic fungus interaction network was more complex (e.g., more highly connected and strongly nested but less specialized and modularized) than the plant-endophytic fungus interaction network. Additionally, tree species richness was positively correlated with the network complexity and diversity of epiphytic (α-, β- and γ-diversity) and endophytic (β- and γ-diversity) fungi, but was not associated with the contribution of the stochastic and deterministic processes on the community assembly of epiphytic and endophytic fungi. This study highlights that tree species diversity enhances the diversity and network complexity, rather than alters the ecological processes in community assembly of leaf-associated fungi.

Unraveling the Influence of Structural Complexity, Environmental, and Geographic Factors on Multi-Trophic Biodiversity in Forested Landscapes

Multi-trophic diversity is often overlooked in land management decisions due to the absence of cost- and time-effective assessment methods. Here, we introduce a new method to calculate a combined terrain and canopy structural complexity metric using LiDAR data, enabling the prediction of multi-trophic diversity-a combined diversity metric that integrates diversity across trophic levels. We selected 34 forested sites of the National Ecological Observatory Network to test the model by using observed data on plant presence, beetle pitfall trap, and bird count to calculate multi-trophic diversity. Our results show that multi-trophic diversity increases with increasing structural complexity, but this relationship differs across different forest types. The environmental and geographic factors account for about 40% variability in multi-trophic diversity, which further increases to about 60% when combined with structural complexity. This research offers a powerful approach to evaluate biodiversity at a landscape scale using remotely sensed data and highlights the importance of considering multi-trophic diversity in land management decisions.

ITS amplicon sequencing revealed that rare taxa of tea rhizosphere fungi are closely related to the environment and provide feedback on tea tree diseases

The rhizospheres of plants and soil microorganisms are intricately interconnected. Tea trees are cultivated extensively on the karst plateau of Guizhou Province, China; however, the understanding of the interactions among fungal communities, community taxa, and diseases impacting tea tree in the soil rhizosphere is limited. Our aim is to offer insights for the advancement of modern agriculture in ecologically fragile karst tea gardens, as well as microbiomics concepts for green and sustainable environmental development. This study utilized the internal transcribed spacer high-throughput sequencing technology to explore the symbiotic relationship between rhizosphere fungi and plant disease feedback in multiple tea estates across the Guizhou Plateau. The ecological preferences and environmental thresholds of fungi were investigated via environmental variables. Furthermore, a correlation was established between different taxa and individual soil functions. Research has indicated that tea leaf blight disrupts symbiotic connections among fungal groups. For various taxa, we found that numerous taxa consistently maintained core positions within the community, whereas rare taxa were able to stabilize due to a high proportion of positive effects. Additionally, abundant taxa presented a wider range of environmental feedback, whereas the rare taxon diversity presented a stronger positive association with the soil Z score. This study contributes to our understanding of the importance of rare taxa in plant rhizosphere soil processes. Emphasis should be placed on the role of rare taxa in pest and disease control within green agriculture while also strengthening systematic development and biogeographical research related to rare taxa in this region.IMPORTANCEIn this study, based on internal transcribed spacer high-throughput sequencing, fungal communities in the rhizosphere soil of tea trees and their interactions with the environment in karst areas were reported, and the symbiotic relationships of different fungal taxa and their feedback to the environment were described in detail by using the knowledge of microbial ecology. On this basis, it was found that tea tree diseases affect the symbiotic relationships of fungal taxa. At the same time, we found that rare taxa have stronger cooperative relationships in response to environmental changes and explored their participation in soil processes based on fungal trait sets. This study will provide basic data for the development of modern agriculture in tea gardens and theoretical basis for the sustainable prevention and control of tea tree diseases.

Diversity and interactions of rhizobacteria determine multinutrient traits in tomato host plants under nitrogen and water disturbances

Coevolution within the plant holobiont extends the capacity of host plants for nutrient acquisition and stress resistance. However, the role of the rhizospheric microbiota in maintaining multinutrient utilization (i.e. multinutrient traits) in the host remains to be elucidated. Multinutrient cycling index (MNC), analogous to the widely used multifunctionality index, provides a straightforward and interpretable measure of the multinutrient traits in host plants. Using tomato as a model plant, we characterized MNC (based on multiple aboveground nutrient contents) in host plants under different nitrogen and water supply regimes and explored the associations between rhizospheric bacterial community assemblages and host plant multinutrient profiles. Rhizosphere bacterial community diversity, quantitative abundance, predicted function, and key topological features of the co-occurrence network were more sensitive to water supply than to nitrogen supply. A core bacteriome comprising 61 genera, such as Candidatus Koribacter and Streptomyces, persisted across different habitats and served as a key predictor of host plant nutrient uptake. The MNC index increased with greater diversity and higher core taxon abundance in the rhizobacterial community, while decreasing with higher average degree and graph density of rhizobacterial co-occurrence network. Multinutrient absorption by host plants was primarily regulated by community diversity and rhizobacterial network complexity under the interaction of nitrogen and water. The high biodiversity and complex species interactions of the rhizospheric bacteriome play crucial roles in host plant performance. This study supports the development of rhizosphere microbiome engineering, facilitating effective manipulation of the microbiome for enhanced plant benefits, which supports sustainable agricultural practices and plant health.

The activation of Parageobacillus toebii in hyperthermophilic composting was depended on the bioavailability of raw materials

Hyperthermophilic composting (HTC) with excellent disposal effect is a novel composting technology by inoculating exogenous thermophilic microorganisms. However, the role of exogenous thermophilic microorganisms in HTC remains debated, especially for the applicability of different compost feedstocks. In this study, the role of Parageobacillus toebii during HTC using chicken and pig manure was investigated. The addition of P. toebii could raise the maximum temperature to 78.2 °C and obviously enhanced maturation effect in chicken manure composting. However, the enhancement effect of P. toebii was weaker in pig manure compost, and the maximum temperature only reached 73 °C. Addition of P. toebii could stimulated functional microbial communities for C&N transformation, increased temperature, and promoted the growth of thermophilic microorganisms in chicken manure composting. Component analyses showed that chicken manure had higher bioavailability compared to pig manure. Correlation analysis indicated that P. toebii activated as a "leader", stimulating metabolic activity among functional microbial communities and enhancing organic matter degradation for heat release, while its activation depended on the bioavailability of the raw material. This study provides important insights into the role and application of exogenous microorganisms in promoting HTC.

Soil Plastisphere Reinforces the Adverse Effect of Combined Pollutant Exposure on the Microfood Web

Microbial interactions form microfood webs, crucial for ecological functions. The steady state of these webs, shaped by cooperation and competition among trophic levels, prevents pathogen proliferation and invasion, maintaining soil health. Combined pollutants pose a widespread environmental issue, exerting significant pressure on microfood webs. However, understanding how these webs respond to combined pollutants in soil plastispheres, an emerging niche, remains limited. This study explores trophic interactions among bacteria, fungi, and protists, examining their effects on potential pathogens in three soil types amended with Cu or disinfectant, along with their plastispheres, using a microcosm experiment. Pollutant exposure disrupts trophic-level interactions through bottom-up and top-down regulation in soils and plastispheres, respectively. Microfood web network topology parameters prove more sensitive to pollutant stress than indicators from a single trophic-level community composition. Combined exposure causes greater disruption to the microfood web than exposure to a single pollutant (Cu or didecyl dimethylammonium chloride (DDAC)). Plastisphere reinforces negative impacts of combined pollutant exposure on the microfood web network, escalating potential pathogenic bacteria. Overall, this study deepens our understanding of microfood web responses under pollutant pressure in soil plastispheres and provides valuable insights for health risk assessments of soil combined pollutants.

Ecosystem stability relies on diversity difference between trophic levels

The stability of ecological communities has a profound impact on humans, ranging from individual health influenced by the microbiome to ecosystem services provided by fisheries. A long-standing goal of ecology is the elucidation of the interplay between biodiversity and ecosystem stability, with some ecologists warning of instability due to loss of species diversity while others arguing that greater diversity will instead lead to instability. Here, by considering a minimal two-level ecosystem with multiple predator and prey species, we show that stability does not depend on absolute diversity but rather on diversity differences between levels. We found that increasing diversity in either level first destabilizes but then stabilizes the community (i.e., a reentrant stability transition). We therefore find that it is the diversity difference between levels that is the key to stability, with the least stable communities having similar diversities in different levels. An analytical stability criterion is derived, demonstrating quantitatively that the critical diversity difference is determined by the correlation between how one level affects another and how it is affected in turn. Our stability criterion also applies to consumer-resource models with other forms of interaction such as cross-feeding. Finally, we show that stability depends on diversity differences in ecosystems with three trophic levels. Our finding of a nonmonotonic dependence of stability on diversity provides a natural explanation for the variety of diversity-stability relationships reported in the literature, and emphasizes the significance of level structure in predicting complex community behaviors.

Phylogenetic Diversity of Plant and Insect Communities on Islands

Interactions between plants and insects have long fascinated scientists. While some plants rely on insects for pollination and seed dispersal, insects rely on plants for food or as a habitat. Despite extensive research investigating pair-wise species interactions, few studies have characterized plant and insect communities simultaneously, making it unclear if diverse plant communities are generally associated with diverse insect communities. This work aims to better understand the historical and evolutionary relationships between plant and insect phylogenetic diversity (PD) on islands. We hypothesized that phylogenetically diverse plant communities (i.e., high PD) support diverse insect communities, with the relationship varying with island isolation, area, age, and latitude. Species lists for plants and insects were compiled from the published literature, and plant PD was calculated using ´standardized mean pairwise distance´ (SES.MPD) and ´standardized mean nearest taxon distance´ (SES.MNTD). For insects, PD was estimated using the number of genera, families, and orders. We found that plant diversity in evolutionary recent times (SES.MNTD) is associated with recent insect diversity (number of genera), but no relationship was found between plant and insect diversity across whole phylogenies (plant SES.MPD vs. number of insect families). Distant islands generally support high PD of plants (high SES.MPD and SES.MNTD) and insects (low number of genera). Plant and insect PD was generally high on small islands, except for plant SES.MPD revealing no relationship with island size. Insect PD was somewhat higher on young islands (low number of families), whereas there was no relationship between island age and plant PD. Plant SES.MPD was higher on high latitude islands, yet we did not find significant relationships between the latitude and the metrics of insect PD or plant SES.MNTD. These findings suggest that protecting high plant PD may also help conserve high insect PD, with a focus on small and distant islands as potential hotspots of phylogenetic diversity across multiple taxa.

Plant diversity enhances ecosystem multifunctionality via multitrophic diversity

Ecosystem functioning depends on biodiversity at multiple trophic levels, yet relationships between multitrophic diversity and ecosystem multifunctionality have been poorly explored, with studies often focusing on individual trophic levels and functions and on specific ecosystem types. Here, we show that plant diversity can affect ecosystem functioning both directly and by affecting other trophic levels. Using data on 13 trophic groups and 13 ecosystem functions from two large biodiversity experiments-one representing temperate grasslands and the other subtropical forests-we found that plant diversity increases multifunctionality through elevated multitrophic diversity. Across both experiments, the association between multitrophic diversity and multifunctionality was stronger than the relationship between the diversity of individual trophic groups and multifunctionality. Our results also suggest that the role of multitrophic diversity is greater in forests than in grasslands. These findings imply that, to promote sustained ecosystem multifunctionality, conservation planning must consider the diversity of both plants and higher trophic levels.

Multitrophic Diversity of the Biotic Community Drives Ecosystem Multifunctionality in Alpine Grasslands

Biodiversity and ecosystem multifunctionality are currently hot topics in ecological research. However, little is known about the role of multitrophic diversity in regulating various ecosystem functions, which limits our ability to predict the impact of biodiversity loss on human well-being and ecosystem multifunctionality. In this study, multitrophic diversity was divided into three categories: plant, animal, and microbial communities (i.e., plant diversity, rodent diversity, and bacterial and fungal diversity). Also, 15 ecosystem functions were divided into four categories-water conservation, soil fertility, nutrient cycling and transformation, and community production-to evaluate the significance of biotic and abiotic variables in maintaining ecosystem multifunctionality. Results indicated that species diversity at multiple trophic levels had a greater positive impact on ecosystem multifunctionality than species diversity at a single trophic level. Notably, the specific nature of this relationship depended on the niche breadths of plants, indicating that plants played a key role in linking above and belowground trophic levels. Abiotic factors such as altitude and pH directly acted on ecosystem multifunctionality and could explain changes in ecosystem functions. Overall, our study offers valuable insights into the critical role of multitrophic species diversity in preserving ecosystem multifunctionality within alpine grassland communities, as well as strong support for the importance of biodiversity protection.

Testing the ectomycorrhizal-dominance hypothesis for ecosystem multifunctionality in a subtropical mountain forest

Mycorrhizal associations are key mutualisms that shape the structure of forest communities and multiple ecosystem functions. However, we lack a framework for predicting the varying dominance of distinct mycorrhizal associations in an integrated proxy of multifunctionality across ecosystems. Here, we used the datasets containing diversity of mycorrhizal associations and 18 ecosystem processes related to supporting, provisioning, and regulating services to examine how the dominance of ectomycorrhiza (EcM) associations affects ecosystem multifunctionality in subtropical mountain forests in Southwest China. Meanwhile, we synthesized the prevalence of EcM-dominant effects on ecosystem functioning in forest biomes. Our results demonstrated that elevation significantly modified the distributions of EcM trees and fungal dominance, which in turn influenced multiple functions simultaneously. Multifunctionality increased with increasing proportion of EcM associations, supporting the ectomycorrhizal-dominance hypothesis. Meanwhile, we observed that the impacts of EcM dominance on individual ecosystem functions exhibited different relationships among forest biomes. Our findings highlight the importance of ectomycorrhizal dominance in regulating multifunctionality in subtropical forests. However, this ectomycorrhizal feedback in shaping ecosystem functions cannot necessarily be generalized across forests. Therefore, we argue that the predictions for ecosystem multifunctionality in response to the shifts of mycorrhizal composition could vary across space and time.

Soil conditions modify species diversity effects on tree functional trait expression

Examples of positive effects of biodiversity on ecosystem functions have kept accumulating in the last two decades, and functional traits are considered suitable tools to explain their underlying mechanisms. However, traits are rarely studied at the scale where these mechanisms (e.g., complementarity) are likely to originate, that is, between two interacting individuals. In an 18-month greenhouse experiment, we investigated how species diversity (i.e., monospecific or heterospecific tree pairs) affects within-individual leaf traits expression and variation and how this effect is modified by soil conditions. While resource addition through phosphorus fertilization partly strengthened the diversity effects, inoculation of soil microbiota (potentially leading to increased resource accessibility) resulted in counter effects. Hence, in contrast to our expectations, we did not find synergistic effects of the two soil treatments, but we found distinct effects on species following an acquisitive or conservative growth strategy. Overall, our study showed that the effect of species diversity on young trees' adaptability and resource-use strategy needs to be considered alongside soil biotic and abiotic aspects. The influence of soil conditions on species diversity effects is essential to understand mechanisms behind complementarity at the individual level, which ultimately translate to the community scale.

Long-term chemical and organic fertilization induces distinct variations of microbial associations but unanimous elevation of soil multifunctionality

Intricate microbial associations contribute greatly to the multiple functions (multifunctionality) of natural ecosystems. However, the relationship between microbial associations and soil multifunctionality (SMF) in artificial ecosystems, particularly in agricultural ecosystem with frequent fertilization, remains unclear. In this study, based on a 28-year paddy field experiment, high-throughput sequencing and networks analysis was performed to investigate changes in soil microbial (archaea, bacteria, fungi, and protists) associations and how these changes correlate with SMF under long-term fertilization. Compared to no fertilization (CK), both chemical fertilization with N, P, and K (CF) and chemical fertilization plus rice straw retention (CFR) treatments showed significantly higher soil nutrient content, grain yield, microbial abundance, and SMF. With the exception of archaeal diversity, the CF treatment exhibited the lowest bacterial, fungal, and protist diversity, and the simplest microbial co-occurrence network. In contrast, the CFR treatment had the lowest archaeal diversity, but the highest bacterial, fungal, and protist diversity. Moreover, the CFR treatment exhibited the most complex microbial co-occurrence network with the highest number of nodes, edges, and interkingdom edges. These results highlight that both chemical fertilization with and without straw retention caused high ecosystem multifunctionality while changing microbial association oppositely. Furthermore, these results indicate that rice straw retention contributes to the development of the soil microbiome and ensures the sustainability of high-level ecosystem multifunctionality.

Sustainable land management enhances ecological and economic multifunctionality under ambient and future climate

The currently dominant types of land management are threatening the multifunctionality of ecosystems, which is vital for human well-being. Here, we present a novel ecological-economic assessment of how multifunctionality of agroecosystems in Central Germany depends on land-use type and climate. Our analysis includes 14 ecosystem variables in a large-scale field experiment with five different land-use types under two different climate scenarios (ambient and future climate). We consider ecological multifunctionality measures using averaging approaches with different weights, reflecting preferences of four relevant stakeholders based on adapted survey data. Additionally, we propose an economic multifunctionality measure based on the aggregate economic value of ecosystem services. Results show that intensive management and future climate decrease ecological multifunctionality for most scenarios in both grassland and cropland. Only under a weighting based on farmers' preferences, intensively-managed grassland shows higher multifunctionality than sustainably-managed grassland. The economic multifunctionality measure is about ~1.7 to 1.9 times higher for sustainable, compared to intensive, management for both grassland and cropland. Soil biodiversity correlates positively with ecological multifunctionality and is expected to be one of its drivers. As the currently prevailing land management provides high multifunctionality for farmers, but not for society at large, we suggest to promote and economically incentivise sustainable land management that enhances both ecological and economic multifunctionality, also under future climatic conditions.

Geologically younger ecosystems are more dependent on soil biodiversity for supporting function

Soil biodiversity contains the metabolic toolbox supporting organic matter decomposition and nutrient cycling in the soil. However, as soil develops over millions of years, the buildup of plant cover, soil carbon and microbial biomass may relax the dependence of soil functions on soil biodiversity. To test this hypothesis, we evaluate the within-site soil biodiversity and function relationships across 87 globally distributed ecosystems ranging in soil age from centuries to millennia. We found that within-site soil biodiversity and function relationship is negatively correlated with soil age, suggesting a stronger dependence of ecosystem functioning on soil biodiversity in geologically younger than older ecosystems. We further show that increases in plant cover, soil carbon and microbial biomass as ecosystems develop, particularly in wetter conditions, lessen the critical need of soil biodiversity to sustain function. Our work highlights the importance of soil biodiversity for supporting function in drier and geologically younger ecosystems with low microbial biomass.

Tree diversity enhances predation by birds but not by arthropods across climate gradients

Tree diversity can promote both predator abundance and diversity. However, whether this translates into increased predation and top-down control of herbivores across predator taxonomic groups and contrasting environmental conditions remains unresolved. We used a global network of tree diversity experiments (TreeDivNet) spread across three continents and three biomes to test the effects of tree species richness on predation across varying climatic conditions of temperature and precipitation. We recorded bird and arthropod predation attempts on plasticine caterpillars in monocultures and tree species mixtures. Both tree species richness and temperature increased predation by birds but not by arthropods. Furthermore, the effects of tree species richness on predation were consistent across the studied climatic gradient. Our findings provide evidence that tree diversity strengthens top-down control of insect herbivores by birds, underscoring the need to implement conservation strategies that safeguard tree diversity to sustain ecosystem services provided by natural enemies in forests.

Transnational conservation to anticipate future plant shifts in Europe

To meet the COP15 biodiversity framework in the European Union (EU), one target is to protect 30% of its land by 2030 through a resilient transnational conservation network. The European Alps are a key hub of this network hosting some of the most extensive natural areas and biodiversity hotspots in Europe. Here we assess the robustness of the current European reserve network to safeguard the European Alps' flora by 2080 using semi-mechanistic simulations. We first highlight that the current network needs strong readjustments as it does not capture biodiversity patterns as well as our conservation simulations. Overall, we predict a strong shift in conservation need through time along latitudes, and from lower to higher elevations as plants migrate upslope and shrink their distribution. While increasing species, trait and evolutionary diversity, migration could also threaten 70% of the resident flora. In the face of global changes, the future European reserve network will need to ensure strong elevation and latitudinal connections to complementarily protect multifaceted biodiversity beyond national borders.

Compared with soil fungal diversity and microbial network complexity, soil bacterial diversity drives soil multifunctionality during the restoration process

Understanding factors driving soil multifunctionality can help with terrestrial ecosystem restoration. Soil microbial diversity and network complexity are two important factors influencing ecosystem multifunctionality. However, their effects on soil multifunctionality are still unclear. Based on high-throughput sequencing, we analyzed soil microbial alpha diversity and network complexity and their relative impacts on soil multifunctionality during the aerial seeding restoration process from 1983 to 2017 in Mu Us sandy land, China, a region threatened by desertification. Our results showed soil bacterial and fungal alpha diversity and multifunctionality increased with aerial seeding restoration. We found the community composition of soil bacteria and fungi changed with restoration periods. The keystone species of the soil bacterial network changed during restoration, while those of the soil fungal network remained unchanged. Soil bacterial and fungal species mainly maintained positive associations throughout the restoration periods. Soil bacterial network complexity initially decreased before increasing with restoration, while soil fungal network complexity increased continuously. Soil multifunctionality was found to have significantly positive correlations with soil fungal network complexity and soil bacterial alpha diversity. Compared with soil fungal alpha diversity and soil microbial network complexity, soil bacterial alpha diversity significantly promoted soil multifunctionality. Our research highlights the critical impact that soil bacterial alpha diversity plays in soil multifunctionality in restored ecosystems threatened by desertification.

Trophic interactions in soil micro-food webs drive ecosystem multifunctionality along tree species richness

Rapid biodiversity losses under global climate change threaten forest ecosystem functions. However, our understanding of the patterns and drivers of multiple ecosystem functions across biodiversity gradients remains equivocal. To address this important knowledge gap, we measured simultaneous responses of multiple ecosystem functions (nutrient cycling, soil carbon stocks, organic matter decomposition, plant productivity) to a tree species richness gradient of 1, 4, 8, 16, and 32 species in a young subtropical forest. We found that tree species richness had negligible effects on nutrient cycling, organic matter decomposition, and plant productivity, but soil carbon stocks and ecosystem multifunctionality significantly increased with tree species richness. Linear mixed-effect models showed that soil organisms, particularly arbuscular mycorrhizal fungi (AMF) and soil nematodes, elicited the greatest relative effects on ecosystem multifunctionality. Structural equation models revealed indirect effects of tree species richness on ecosystem multifunctionality mediated by trophic interactions in soil micro-food webs. Specifically, we found a significant negative effect of gram-positive bacteria on soil nematode abundance (a top-down effect), and a significant positive effect of AMF biomass on soil nematode abundance (a bottom-up effect). Overall, our study emphasizes the significance of a multitrophic perspective in elucidating biodiversity-multifunctionality relationships and highlights the conservation of functioning soil micro-food webs to maintain multiple ecosystem functions.

Modelling the effects of climate and management on the distribution of deadwood in European forests

Deadwood is a key old-growth element in European forests and a cornerstone of biodiversity conservation practices in the region, recognized as an important indicator of sustainable forest management. Despite its importance as a legacy element for biodiversity, uncertainties remain on the drivers of deadwood potentials, its spatial distribution in European forests and how it may change in the future due to management and climate change. To fill this gap, we combined a comprehensive deadwood dataset to fit a machine learning and a Bayesian hurdle-lognormal model against multiple environmental and socio-economic predictors. We deployed the models on the gridded predictors to forecast changes in deadwood volumes in Europe under alternative climate (RCP4.5 and RCP8.5) and management scenarios (biodiversity-oriented and production-oriented strategies). Our results show deadwood hotspots in montane forests of central Europe and unmanaged forests in Scandinavia. Future climate conditions may reduce deadwood potentials up to 13% under a mid-century climate, with regional losses amounting to up to 22% in Southern Europe. Nevertheless, changes in management towards more biodiversity-oriented strategies, including an increase in the share of mixed forests and extended rotation lengths, may mitigate this loss to a 4% reduction in deadwood potentials. We conclude that adaptive management can promote deadwood under changing environmental conditions and thereby support habitat maintenance and forest multifunctionality.

Core microbiota drive multi-functionality of the soil microbiome in the Cinnamomum camphora coppice planting

BACKGROUND

Cinnamomum camphora (L.) Presl (C. camphora) is an evergreen broad-leaved tree cultivated in subtropical China. The use of C. camphora as clonal cuttings for coppice management has become popular recently. However, little is known about the relationship between soil core microbiota and ecosystem multi-functionality under tree planting. Particularly, the effects of soil core microbiota on maintaining ecosystem multi-functionality under C. camphora coppice planting remained unclear.

MATERIALS AND METHODS

In this study, we collected soil samples from three points (i.e., the abandoned land, the root zone, and the transition zone) in the C. camphora coppice planting to investigate whether core microbiota influences ecosystem multi-functions.

RESULTS

The result showed a significant difference in soil core microbiota community between the abandoned land (AL), root zone (RZ), and transition zone (TZ), and soil ecosystem multi-functionality of core microbiota in RZ had increased significantly (by 230.8%) compared to the AL. Soil core microbiota played a more significant influence on ecosystem multi-functionality than the non-core microbiota. Moreover, the co-occurrence network demonstrated that the soil ecosystem network consisted of five major ecological clusters. Soil core microbiota within cluster 1 were significantly higher than in cluster 4, and there is also a higher Copiotrophs/Oligotrophs ratio in cluster 1. Our results corroborated that soil core microbiota is crucial for maintaining ecosystem multi-functionality. Especially, the core taxa within the clusters of networks under tree planting, with the same ecological preferences, had a significant contribution to ecosystem multi-functionality.

CONCLUSION

Overall, our results provide further insight into the linkage between core taxa and ecosystem multi-functionality. This enables us to predict how ecosystem functions respond to the environmental changes in areas under the C. camphora coppice planting. Thus, conserving the soil microbiota, especially the core taxa, is essential to maintaining the multiple ecosystem functions under the C. camphora coppice planting.

Hypoxia and salinity constrain the sediment microbiota-mediated N removal potential in an estuary: A multi-trophic interrelationship perspective

Reactive nitrogen (N) enrichment is a common environmental problem in estuarine ecosystems, while the microbial-mediated N removal process is complicated for other multi-environmental factors. Therefore, A systematic investigation is necessary to understand the multi-trophic microbiota-mediated N removal characteristics under various environmental factors in estuaries. Here, we studied how multiple factors affect the multi-trophic microbiota-mediated N removal potential (denitrification and anammox) and N2O emission along a river-estuary-bay continuum in southeastern China using the environmental DNA (eDNA) approach. Results suggested that hypoxia and salinity were the dominant environmental factors affecting multi-trophic microbiota-mediated N removal in the estuary. The synergistic effect of hypoxia and salinity contributed to the loss of taxonomic (MultiTaxa) and phylogenetic (MultiPhyl) diversity across multi-trophic microbiota and enhanced the interdependence among multi-trophic microbiota in the estuary. The N removal potential calculated as the activities of key N removal enzymes was also significantly constrained in the estuary (0.011), compared with the river (0.257) and bay (0.461). Structural equation modeling illustrated that metazoans were central to all sediment N removal potential regulatory pathways. The top-down forces (predation by metazoans) restrained the growth of heterotrophic bacteria, which may affect microbial N removal processes in the sediment. Furthermore, we found that the hypoxia and salinity exacerbated the N2O emission in the estuary. This study clarifies that hypoxia and salinity constrain estuarine multi-trophic microbiota-mediated N removal potential and highlights the important role of multi-trophic interactions in estuarine N removal, providing a new perspective on mitigating estuarine N accumulation.

Soil microbial diversity and network complexity drive the ecosystem multifunctionality of temperate grasslands under changing precipitation

Soil microbiomes play a critical role in regulating ecosystem multifunctionality. However, whether and how soil protists and microbiome interactions affect ecosystem multifunctionality under climate change is unclear. Here, we transplanted 54 soil monoliths from three typical temperate grasslands (i.e., desert, typical, and meadow steppes) along a precipitation gradient in the Mongolian Plateau and examined their response to nighttime warming, decreased, and increased precipitation. Across the three steppes, nighttime warming only stimulated protistan diversity by 15.61 (absolute change, phylogenetic diversity) but had no effect on ecosystem multifunctionality. Decreased precipitation reduced bacterial (8.78) and fungal (22.28) diversity, but significantly enhanced soil microbiome network complexity by 1.40. Ecosystem multifunctionality was reduced by 0.23 under decreased precipitation, which could be largely attributed to the reduced soil moisture that negatively impacted bacterial and fungal communities. In contrast, increased precipitation had little impact on soil microbial communities. Overall, both bacterial and fungal diversity and network complexity play a fundamental role in maintaining ecosystem multifunctionality in response to drought stress. Protists alter ecosystem multifunctionality by indirectly affecting microbial network complexity. Therefore, not only microbial diversity but also their interactions (regulated by soil protists) should be considered in evaluating the responses of ecosystem multifunctionality, which has important implications for predicting changes in ecosystem functioning under future climate change scenarios.

Geographical, climatic, and soil factors control the altitudinal pattern of rhizosphere microbial diversity and its driving effect on root zone soil multifunctionality in mountain ecosystems

Shifts in rhizosphere soil microorganisms of dominant plants' response to climate change profoundly impact mountain soil ecosystem multifunctionality; relatively little is known about the relationship between them and how they depend on long-term environmental drivers. Here, we conducted analyses of rhizosphere microbial altitudinal pattern, community assembly, and co-occurrence network of 6 dominant plants in six typical vegetation zones ranging from 1350 to 2900 m (a.s.l.) in Helan Mountains by absolute quantitative sequencing technology, and finally related the microbiomes to root zone soil multifunctionality ('soil multifunctionality' hereafter), the environmental dependence of the relationship was explored. It was found that the altitudinal pattern of rhizosphere soil bacterial and fungal diversities differed significantly. Higher co-occurrence and more potential interactions of Stipa breviflora and Carex coninux were found at the lowest and highest altitudes. Bacterial α diversity, the identity of some dominant bacterial and fungal taxa, had significant positive or negative effects on soil multifunctionality. The effect sizes of positive effects of microbial diversity on soil multifunctionality were greater than those of negative effects. These results indicated that the balance of positive and negative effects of microbes determines the impact of microbial diversity on soil multifunctionality. As the number of microbes at the phylum level increases, there will be a net gain in soil multifunctionality. Our study reveals that geographical and climatic factors can directly or modulate the effects of soil properties on rhizosphere microbial diversity, thereby affecting the driving effect of microbial diversity on soil multifunctionality, and points to the rhizosphere bacterial diversity rather than the fungi being strongly associated with soil multifunctionality. This work has important ecological implications for predicting how multiple environment-plant-soil-microorganisms interactions in mountain ecosystems will respond to future climate change.

Habitat fragmentation increases specialization of multi-trophic interactions by high species turnover

Habitat fragmentation is altering species interactions worldwide. However, the mechanisms underlying the response of network specialization to habitat fragmentation remain unknown, especially for multi-trophic interactions. We here collected a large dataset consisting of 2670 observations of tri-trophic interactions among plants, sap-sucking aphids and honeydew-collecting ants on 18 forested islands in the Thousand Island Lake, China. For each island, we constructed an antagonistic plant-aphid and a mutualistic aphid-ant network, and tested how network specialization varied with island area and isolation. We found that both networks exhibited higher specialization on smaller islands, while only aphid-ant networks had increased specialization on more isolated islands. Variations in network specialization among islands was primarily driven by species turnover, which was interlinked across trophic levels as fragmentation increased the specialization of both antagonistic and mutualistic networks through bottom-up effects via plant and aphid communities. These findings reveal that species on small and isolated islands display higher specialization mainly due to effects of fragmentation on species turnover, with behavioural changes causing interaction rewiring playing only a minor role. Our study highlights the significance of adopting a multi-trophic perspective when exploring patterns and processes in structuring ecological networks in fragmented landscapes.

Ecosystem consequences of invertebrate decline

Human activities cause substantial changes in biodiversity.1,2 Despite ongoing concern about the implications of invertebrate decline,3,4,5,6,7 few empirical studies have examined the ecosystem consequences of invertebrate biomass loss. Here, we test the responses of six ecosystem services informed by 30 above- and belowground ecosystem variables to three levels of aboveground (i.e., vegetation associated) invertebrate community biomass (100%, 36%, and 0% of ambient biomass) in experimental grassland mesocosms in a controlled Ecotron facility. In line with recent reports on invertebrate biomass loss over the last decade, our 36% biomass treatment also represented a decrease in invertebrate abundance (-70%) and richness (-44%). Moreover, we simulated the pronounced change in invertebrate biomass and turnover in community composition across the season. We found that the loss of invertebrate biomass decreases ecosystem multifunctionality, including two critical ecosystem services, aboveground pest control and belowground decomposition, while harvested plant biomass increases, likely because less energy was channeled up the food chain. Moreover, communities and ecosystem functions become decoupled with a lower biomass of invertebrates. Our study shows that invertebrate loss threatens the integrity of grasslands by decoupling ecosystem processes and decreasing ecosystem-service supply.

Heavy metal effects on multitrophic level microbial communities and insights for ecological restoration of an abandoned electroplating factory site

The response of soil microbes to heavy metal pollution provides a metric to evaluate the soil health and ecological risks associated with heavy metal contamination. However, a multitrophic level perspective of how soil microbial communities and their functions respond to long-term exposure of multiple heavy metals remains unclear. Herein, we examined variations in soil microbial (including protists and bacteria) diversity, functional guilds and interactions along a pronounced metal pollution gradient in a field surrounding an abandoned electroplating factory. Given the stressful soil environment resulting from extremely high heavy metal concentrations and low nutrients, beta diversity of protist increased, but that of bacteria decreased, at high versus low pollution sites. Additionally, the bacteria community showed low functional diversity and redundancy at the highly polluted sites. We further identified indicative genus and "generalists" in response to heavy metal pollution. Predatory protists in Cercozoa were the most sensitive protist taxa with respect to heavy metal pollution, whereas photosynthetic protists showed a tolerance for metal pollution and nutrient deficiency. The complexity of ecological networks increased, but the communication among the modules disappeared with increasing metal pollution levels. Subnetworks of tolerant bacteria displaying functional versatility (Blastococcus, Agromyces and Opitutus) and photosynthetic protists (microalgae) became more complex with increasing metal pollution levels, indicating their potential for use in bioremediation and restoration of abandoned industrial sites contaminated by heavy metals.

Multitrophic arthropod diversity mediates tree diversity effects on primary productivity

Forests sustain 80% of terrestrial biodiversity and provide essential ecosystem services. Biodiversity experiments have demonstrated that plant diversity correlates with both primary productivity and higher trophic diversity. However, whether higher trophic diversity can mediate the effects of plant diversity on productivity remains unclear. Here, using 5 years of data on aboveground herbivorous, predatory and parasitoid arthropods along with tree growth data within a large-scale forest biodiversity experiment in southeast China, we provide evidence of multidirectional enhancement among the diversity of trees and higher trophic groups and tree productivity. We show that the effects of experimentally increased tree species richness were consistently positive for species richness and abundance of herbivores, predators and parasitoids. Richness effects decreased as trophic levels increased for species richness and abundance of all trophic groups. Multitrophic species richness and abundance of arthropods were important mediators of plant diversity effects on tree productivity, suggesting that optimizing forest management for increased carbon capture can be more effective when the diversity of higher trophic groups is promoted in concert with that of trees.

How nutrient loading leads to alternative stable states in microbially mediated N-cycle pathways: A new insight into bioavailable nitrogen removal in urban rivers

Excessive nutrients have disrupted pathways of microbial-mediated nitrogen (N) cycle in urban rivers and caused bioavailable N to accumulate in sediments, while remedial actions sometimes fail to recover degraded river ecosystems even when environmental quality has been improved. It is not sufficient to revert the ecosystem to its original healthy state by restoring the pre-degradation environmental conditions, as explained by alternative stable states theory. Understanding the recovery of disrupted N-cycle pathways from the perspective of alternative stable states theory can benefit effective river remediation. Previous studies have found alternative microbiota states in rivers; however, the existence and implications of alternative stable states in microbial-mediated N-cycle pathway remain unclear. Here, high-throughput sequencing and N-related enzyme activities measurement were combined in the field investigation to provide empirical evidence for the bi-stability in microbially mediated N-cycle pathways. According to the behavior of bistable ecosystems, the existence of alternative stable states in microbial-mediated N-cycle pathway have been shown, and nutrient loading, mainly total nitrogen and total phosphorus, were identified as key driver of regime shifts. In addition, potential analysis revealed that reducing nutrient loading shifted the N-cycle pathway to a desirable state characterized by high ammonification and nitrification, probably avoiding the accumulation of ammonia and organic N. It should be noted that the improvement of microbiota status can facilitate the recovery of the desirable pathway state according to the relationship between microbiota states and N-cycle pathway states. Keystone species, including Rhizobiales and Sphingomonadales, were discerned by network analysis, and the increase in their relative abundance may facilitate the improvement of microbiota status. The obtained results suggested that the nutrient reduction should be combined with microbiota management to benefit the bioavailable N removal in urban rivers, therefore providing a new insight into alleviating adverse effects of the nutrient loading on urban rivers.

Will a large complex system be productive?

While the relationship between food web complexity and stability has been well documented, how complexity affects productivity remains elusive. In this study, we combine food web theory and a data set of 149 aquatic food webs to investigate the effect of complexity (i.e. species richness, connectance, and average interaction strength) on ecosystem productivity. We find that more complex ecosystems tend to be more productive, although different facets of complexity have contrasting effects. A higher species richness and/or average interaction strength increases productivity, whereas a higher connectance often decreases it. These patterns hold not only between realized complexity and productivity, but also characterize responses of productivity to simulated declines of complexity. Our model also predicts a negative association between productivity and stability along gradients of complexity. Empirical analyses support our predictions on positive complexity-productivity relationships and negative productivity-stability relationships. Our study provides a step forward towards reconciling ecosystem complexity, productivity and stability.

Decreased soil multifunctionality is associated with altered microbial network properties under precipitation reduction in a semiarid grassland

Our results reveal different responses of soil multifunctionality to increased and decreased precipitation. By linking microbial network properties to soil functions, we also show that network complexity and potentially competitive interactions are key drivers of soil multifunctionality.

Growth of grasses and forbs, nutrient concentration, and microbial activity in soil treated with microbeads

Microplastics have emerged as an important threat to terrestrial ecosystems. To date, little research has been conducted on investigating the effects of microplastics on ecosystem functions and multifunctionality. In this study, we conducted the pot experiments containing five plant communities consisting of Phragmites australis, Cynanchum chinense, Setaria viridis, Glycine soja, Artemisia capillaris, Suaeda glauca, and Limonium sinense and added polyethylene (PE) and polystyrene (PS) microbeads to the soil (contained a mixture of 1.5 kg loam and 3 kg sand) at two concentrations of 0.15 g/kg (lower concentration, hereinafter referred to as PE-L and PS-L) and 0.5 g/kg (higher concentration, hereinafter referred to as PE-H and PS-H) to explore the effects of microplastics on total plant biomass, microbial activity, nutrient supply, and multifunctionality. The results showed that PS-L significantly decreased the total plant biomass (p = 0.034), primarily by inhibiting the growth of the roots. β-glucosaminidase decreased with PS-L, PS-H, and PE-L (p < 0.001) while the phosphatase was noticeably augmented (p < 0.001). The observation suggests that the microplastics diminished the nitrogen requirements and increased the phosphorus requirements of the microbes. The decrease in β-glucosaminidase diminished ammonium content (p < 0.001). Moreover, PS-L, PS-H, and PE-H reduced the soil total nitrogen content (p < 0.001), and only PS-H considerably reduced the soil total phosphorus content (p < 0.001), affecting the ratio of N/P markedly (p = 0.024). Of interest, the impacts of microplastics on total plant biomass, β-glucosaminidase, phosphatase, and ammonium content did not become larger at the higher concentration, and it is observable that microplastics conspicuously depressed the ecosystem multifunctionality, as microplastics depreciated single functions such as total plant biomass, β-glucosaminidase, and nutrient supply. In perspective, measures to counteract this new pollutant and eliminate its impact on ecosystem functions and multifunctionality are necessary.

Resource-dependent biodiversity and potential multi-trophic interactions determine belowground functional trait stability

BACKGROUND

For achieving long-term sustainability of intensive agricultural practices, it is pivotal to understand belowground functional stability as belowground organisms play essential roles in soil biogeochemical cycling. It is commonly believed that resource availability is critical for controlling the soil biodiversity and belowground organism interactions that ultimately lead to the stabilization or collapse of terrestrial ecosystem functions, but evidence to support this belief is still limited. Here, we leveraged field experiments from the Chinese National Ecosystem Research Network (CERN) and two microcosm experiments mimicking high and low resource conditions to explore how resource availability mediates soil biodiversity and potential multi-trophic interactions to control functional trait stability.

RESULTS

We found that agricultural practice-induced higher resource availability increased potential cross-trophic interactions over 316% in fields, which in turn had a greater effect on functional trait stability, while low resource availability made the stability more dependent on the potential within trophic interactions and soil biodiversity. This large-scale pattern was confirmed by fine-scale microcosm systems, showing that microcosms with sufficient nutrient supply increase the proportion of potential cross-trophic interactions, which were positively associated with functional stability. Resource-driven belowground biodiversity and multi-trophic interactions ultimately feedback to the stability of plant biomass.

CONCLUSIONS

Our results indicated the importance of potential multi-trophic interactions in supporting belowground functional trait stability, especially when nutrients are sufficient, and also suggested the ecological benefits of fertilization programs in modern agricultural intensification. Video Abstract.

Multifunctionality and maintenance mechanism of wetland ecosystems in the littoral zone of the northern semi-arid region lake driven by environmental factors

The relationship between biodiversity and ecosystem multifunctionality (BEMF) has become an ecological research hot spot in recent years. Changes in biodiversity are non-randomly distributed in space and time in natural ecosystems, and the BEMF relationship is affected by a combination of biotic and abiotic factors. These complex, uncertain relationships are affected by research scale and quantification and measurement indicators. This paper took the Daihai littoral zone wetlands in Inner Mongolia as the research object to reveal the dynamic succession of wetland vegetation and ecosystem function change characteristics and processes during the shrinkage of the lake. The main findings were as follows: the combined effect of aboveground (species and functions) and belowground (bacteria and fungi) diversity was greater than the effect of single components on ecosystem multifunctionality (EMF) (R² = 80.00 %). Soil salinity (EC) had a direct negative effect on EMF (λ = -0.22), and soil moisture (SM) had a direct positive effect on EMF (λ = 0.19). The results of the hierarchical partitioning analysis showed that plant species richness (Margalef index) was the ideal indicator to explain the EMF and C, N, and P cycling functions in littoral zone wetlands with explanations of 12.25 %, 7.31 %, 7.83 %, and 5.33 %, respectively. The EMF and C and P cycles were mainly affected by bacterial diversity, and the N cycle was mainly affected by fungal abundance in belowground biodiversity. Margalef index and sand content affected EMF through cascading effects of multiple nutrients (FDis, CWM_RV, CWM_LCC, and bacterial and fungal abundance and diversity) in littoral zone wetlands. This paper provides a reference for exploring the multifunctionality maintenance mechanisms of natural littoral zone wetland ecosystems in the context of global change, and it also provides important theoretical support and basic data for the implementation of ecological restoration in Daihai lake.

Insect decline in forests depends on species' traits and may be mitigated by management

Insects are declining, but the underlying drivers and differences in responses between species are still largely unclear. Despite the importance of forests, insect trends therein have received little attention. Using 10 years of standardized data (120,996 individuals; 1,805 species) from 140 sites in Germany, we show that declines occurred in most sites and species across trophic groups. In particular, declines (quantified as the correlation between year and the respective community response) were more consistent in sites with many non-native trees or a large amount of timber harvested before the onset of sampling. Correlations at the species level depended on species' life-history. Larger species, more abundant species, and species of higher trophic level declined most, while herbivores increased. This suggests potential shifts in food webs possibly affecting ecosystem functioning. A targeted management, including promoting more natural tree species composition and partially reduced harvesting, can contribute to mitigating declines.

Soil biota diversity and plant diversity both contributed to ecosystem stability in grasslands

Understanding the effects of diversity on ecosystem stability in the context of global change has become an important goal of recent ecological research. However, the effects of diversity at multiple scales and trophic levels on ecosystem stability across environmental gradients remain unclear. Here, we conducted a field survey of α-, β-, and γ-diversity of plants and soil biota (bacteria, fungi, and nematodes) and estimated the temporal ecosystem stability of normalized difference vegetation index (NDVI) in 132 plots on the Mongolian Plateau. After climate and soil environmental variables were controlled for, both the α- and β-diversity of plants and soil biota (mainly via nematodes) together with precipitation explained most variation in ecosystem stability. These findings evidence that the diversity of both soil biota and plants contributes to ecosystem stability. Model predictions of the future effects of global changes on terrestrial ecosystem stability will require field observations of diversity of both plants and soil biota.

Microbial community structure and denitrification responses to cascade low-head dams and their contribution to eutrophication in urban rivers

Low-head dams are one of the most common hydraulic facilities, yet they often fragment rivers, leading to profound changes in aquatic biodiversity and river eutrophication levels. Systematic assessments of river ecosystem structure and functions, and their contribution to eutrophication, are however lacking, especially for urban rivers where low-head dams prevail. In this study, we address this gap with a field survey on microbial community structure and ecosystem function, in combination with hydrological, environmental and ecological factors. Our findings revealed that microbial communities showed significant differences among the cascade impoundments, which may be due to the environment heterogeneity resulting from the cascade low-head dams. The alternating lentic-lotic flow environment created by the low-head dams caused nutrient accumulation in the cascade impoundments, enhancing environmental sorting and interspecific competition relationships, and thus possibly contributing to the reduction in sediment denitrification function. Decreased denitrification led to excessive accumulation of nutrients, which may have aggravated river eutrophication. In addition, structural equation model analysis showed that flow velocity may be the key controlling factor for river eutrophication. Therefore, in the construction of river flood control and water storage systems, the location, type and water storage capacity of low-head dams should be fully considered to optimize the hydrodynamic conditions of rivers. To summarize, our findings revealed the cumulative effects of cascade low-head dams in an urban river, and provided new insights into the trade-off between construction and decommissioning of low-head dams in urban river systems.

Direct and indirect effects of dominant plants on ecosystem multifunctionality

Biodiversity is essential for the provision of multiple ecosystem functions simultaneously (ecosystem multifunctionality EMF). Yet, it remains unclear whether and how dominant plant species impact EMF. Here, we aimed at disentangling the direct from indirect above- and belowground pathways by which dominant plant species influence EMF. We evaluated the effects of two dominant plant species (Dasiphora fruticosa, and the toxic perennial plant Ligularia virgaurea) with expected positive and negative impacts on the abiotic environment (soil water content and pH), surrounding biological communities (plant and nematode richness, biomass, and abundance in the vicinity), and on the EMF of alpine meadows, respectively. We found that the two dominant plants enhanced EMF, with a positive effect of L. virgaurea on EMF greater than that of D. fruticosa. We also observed that dominant plants impacted on EMF through changes in soil water content and pH (indirect abiotic effects), but not through changes in biodiversity of surrounding plants and nematodes (indirect biotic pathway). Our study suggests that dominant plants may play an important role in promoting EMF, thus expanding the pervasive mass-ratio hypothesis originally framed for individual functions, and could mitigate the negative impacts of vegetation changes on EMF in the alpine meadows.

Tree dissimilarity determines multi-dimensional beta-diversity of herbivores and carnivores via bottom-up effects

Global biodiversity decline and its cascading effects through trophic interactions pose a severe threat to human society. Establishing the impacts of biodiversity decline requires a more thorough understanding of multi-trophic interactions and, more specifically, the effects that loss of diversity in primary producers has on multi-trophic community assembly. Within a synthetic conceptual framework for multi-trophic beta-diversity, we tested a series of hypotheses on neutral and niche-based bottom-up processes in assembling herbivore and carnivore communities in a subtropical forest using linear models, hieratical variance partitioning based on linear mixed-effects models (LMMs) and simulation. We found that the observed taxonomic, phylogenetic and functional beta-diversity of both herbivorous caterpillars and carnivorous spiders were significantly and positively related to tree dissimilarity. Linear models and variance partitioning for LMMs jointly suggested that as a result of bottom-up effects, producer dissimilarities were predominant in structuring consumer dissimilarity, the strength of which highly depended on the trophic dependencies on producers, the diversity facet examined, and data quality. Importantly, linear models for standardized beta-diversities against producer dissimilarities implied a transition between niche-based processes such as environmental filtering and competitive exclusion, which supports the role of bottom-up effect in determining consumer community assembly. These findings enrich our mechanistic understanding of the 'Diversity Begets Diversity' hypothesis and the complexity of higher-trophic community assembly, which is fundamental for sustainable biodiversity conservation and ecosystem management.

Functional and phylogenetic relationships link predators to plant diversity via trophic and non-trophic pathways

Human-induced biodiversity loss negatively affects ecosystem function, but the interactive effects of biodiversity change across trophic levels remain insufficiently understood. We sampled arboreal spiders and lepidopteran larvae across seasons in 2 years in a subtropical tree diversity experiment, and then disentangled the links between tree diversity and arthropod predator diversity by deconstructing the pathways among multiple components of diversity (taxonomic, phylogenetic and functional) with structural equation models. We found that herbivores were major mediators of plant species richness effects on abundance, species richness, functional and phylogenetic diversity of predators, while phylogenetic, functional and structural diversity of trees were also important mediators of this process. However, the strength and direction differed between functional, structural and phylogenetic diversity effects, indicating different underlying mechanisms for predator community assembly. Abundance and multiple diversity components of predators were consistently affected by tree functional diversity, indicating that the variation in structure and environment caused by plant functional composition might play key roles in predator community assembly. Our study highlights the importance of an integrated approach based on multiple biodiversity components in understanding the consequences of biodiversity loss in multitrophic communities.

Contrasting influences of two dominant plants, Dasiphora fruticosa and Ligularia virguarea, on aboveground and belowground communities in an alpine meadow

Soil organisms are abundant, phylogenetically and functionally diverse, and interact to catalyse and regulate critical soil processes. Understanding what structures belowground communities is therefore fundamental to gaining insight into ecosystem functioning. Dominant plants have been shown to influence belowground communities both directly and indirectly through changes in abiotic and biotic factors. In a field study, we used piecewise structural equation modelling to disentangle and compare the effects of a dominant allelopathic plant, Ligularia virgaurea, and a dominant facilitative plant, Dasiphora fruticosa, on understory plant, soil microbial and nematode community composition in an alpine meadow on the Tibetan plateau. Dasiphora fruticosa was associated with changes in edaphic variables (total nitrogen, soil organic carbon, pH and ammonium), understory plant and soil bacterial communities, whereas Ligularia virguarea was associated with increased soil ammonium content and soil fungal richness relative to dominant plant-free control plots. Moreover, nematode richness was significantly greater under D. fruticosa, with no change in nematode community composition. By contrast, nematode richness under Ligularia virgaurea was similar to that of dominant plant-free control plots, but nematode community composition differed from the control. The effects of both plants were predominantly direct rather than mediated by indirect pathways despite the observed effects on understory plant communities, soil properties and microbial assemblages. Our results highlight the importance of plants in determining soil communities and provide new insight to disentangle the complex above- and belowground linkages.

Tree species and genetic diversity increase productivity via functional diversity and trophic feedbacks

Addressing global biodiversity loss requires an expanded focus on multiple dimensions of biodiversity. While most studies have focused on the consequences of plant interspecific diversity, our mechanistic understanding of how genetic diversity within plant species affects plant productivity remains limited. Here, we use a tree species × genetic diversity experiment to disentangle the effects of species diversity and genetic diversity on tree productivity, and how they are related to tree functional diversity and trophic feedbacks. We found that tree species diversity increased tree productivity via increased tree functional diversity, reduced soil fungal diversity, and marginally reduced herbivory. The effects of tree genetic diversity on productivity via functional diversity and soil fungal diversity were negative in monocultures but positive in the mixture of the four tree species tested. Given the complexity of interactions between species and genetic diversity, tree functional diversity and trophic feedbacks on productivity, we suggest that both tree species and genetic diversity should be considered in afforestation.

The Effect of Environmental Factors on the Diversity of Crane Flies (Tipulidae) in Mountainous and Non-Mountainous Regions of the Qinghai-Tibet Plateau and Surrounding Areas

Tipulidae, one of the most diverse families of Diptera, is widely distributed in the world. The adults have weak flight ability, making it an ideal model for studying the formation of insect diversity. This study aims to explore the species diversity and endemism of Tipulidae in the Qinghai-Tibet Plateau and the surrounding areas, as well as analyze the relationships between the diversity pattern and 25 environmental factors in mountainous and non-mountainous regions. To this end, we collected 2589 datasets for the distribution of 1219 Tipulidae species, and found three areas with high diversities of Tipulidae around the QTP, including the Sikkim-Yadong area, Kamen River Basin, and Gongga Mountain. Further R, generalized additive model (GAM), and stepwise multiple regression analysis indicated that the richness and endemism of Tipulidae is mainly influenced by the warmest quarter precipitation and topographic heterogeneity in mountainous regions, but in non-mountainous regions, the richness is mostly affected by the precipitation seasonality, while there is no regularity in the relationship between endemism and environmental factors. In addition, the richness model in mountainous regions was in conformity with the results of GAM.