Above- and belowground biodiversity drives soil multifunctionality along a long-term grassland restoration chronosequence

Natural Regeneration Enhances Long-Term Soil Carbon Storage in Various Fractions More Effectively Than Active Restoration: Meta-Analysis

Restoration of terrestrial ecosystems, through both natural and active approaches, is critical for enhancing soil organic carbon (SOC) storage. However, the long-term effects of these restoration approaches on soil aggregate organic carbon remain poorly understood. In this study, we conducted a global meta-analysis to assess the temporal effects of natural and active restoration on SOC and aggregate organic carbon, including macroaggregate (MAC), microaggregate (MIC), and silt-clay fraction (SCC) organic carbon. The overall global results showed that natural regeneration outperformed active restoration in enhancing SOC and MAC, with increases of 21% and 24%, respectively, higher than those of active restoration. Notably, the benefits of natural regeneration on SOC and MAC intensified over time, surpassing active restoration after 40 years. In different terrestrial ecosystems, natural regeneration showed greater effectiveness in late-stage SOC and MAC accumulation, with 72% and 61% higher in forests (> 40 years) and 64% and 63% higher in grasslands (> 20 years) compared to active restoration. In shrublands, late-stage (> 15 years) MIC accumulation was 62% higher under natural regeneration than under active restoration. In addition, natural regeneration enhanced SOC storage in deeper soil layers and in carbon-poor areas. These findings highlight the long-term superiority of natural regeneration for soil carbon sequestration, positioning it as a key strategy for sustainable ecosystem restoration and climate change mitigation.

Conventional and organic farms with more intensive management have lower soil functionality

Organic farming is often considered to be more sustainable than conventional farming. However, both farming systems comprise highly variable management practices. In this study, we show that in organic and conventional arable fields, the multifunctionality of soils decreases with increasing agricultural management intensity. Soil organic carbon content and bacterial biomass, respectively, were the strongest abiotic and biotic predictors of soil multifunctionality. Greater soil multifunctionality was associated with less-frequent inversion tillage and higher frequency of grass-legume cover cropping, and organic farming did not outperform conventional farming. Our results suggest that reducing management intensity will enhance soil multifunctionality in both conventional and organic farming. This implies that, in contexts where high-yielding, high-intensity agriculture prevails, the paradigm of sustainable intensification should be replaced by "productive deintensification."

Divergent altitudinal patterns of arbuscular and ectomycorrhizal fungal communities in a mid-subtropical mountain ecosystem

Arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (EMF) form ubiquitous symbiotic relationships with plants through co-evolutionary processes, providing multiple benefits for plant growth, productivity, health, and stress mitigation. Mountain ecosystem multifunctionality is significantly influenced by mycorrhizal responses to climate change, highlighting the importance of understanding the complex interactions between these fungi and environmental variables. In this study, we investigated five vegetation zones across an altitudinal gradient (675-2157 m a.s.l.) in Wuyi Mountain, one of the most well-preserved mid-subtropical mountain ecosystems in eastern China. Using high-throughput sequencing, we examined the altitudinal distribution patterns, community assembly mechanisms, and network interactions of soil AMF and EMF. Our analyses demonstrated significant altitudinal variations in the composition and diversity of mycorrhizal fungal communities. AMF richness peaked in the subalpine dwarf forest at intermediate elevations, whereas EMF richness was highest in the low-altitude evergreen broad-leaved forest, showing a marked decrease in the alpine meadow ecosystem. β-diversity decomposition revealed that species turnover constituted the primary mechanism of community differentiation for both fungal types, explaining >56% of the observed variation. Stochastic processes dominated community assembly, with the relative importance of dispersal limitation and drift showing distinct altitudinal patterns. Network analysis indicated that AMF networks reached maximum complexity in evergreen broad-leaved forests, while EMF networks showed similar complexity levels in coniferous forests. Among the examined factors, soil properties emerged as the predominant driver of altitudinal variations in ecosystem multifunctionality, followed by AMF communities and climatic variables. These findings provide critical insights into the ecological functions and environmental adaptations of mycorrhizal fungi, advancing our understanding of their responses to environmental changes in mountain ecosystems and informing evidence-based conservation strategies.

Roles of the soil microbiome in sustaining grassland ecosystem health on the Qinghai-Tibet Plateau

Soil microbes, as intermediaries in plant-soil interactions, are closely linked to plant health in grassland ecosystems. In recent years, varying degrees of degradation have been observed in the alpine grasslands of the Qinghai-Tibet Plateau (QTP). Addressing grassland degradation, particularly under the influence of climate change, poses a global challenge. Understanding the factors driving grassland degradation on the QTP and developing appropriate mitigation measures is essential for the future sustainability of this fragile ecosystem. In this review, we discuss the environmental and anthropogenic factors affecting grassland degradation and the corresponding impacts on soil microbe community structure. We summarize the current research on the microbiome of the QTP, in particular the effect of vegetation, climate change, grazing, and land use, respectively on the alpine grassland microbiome. The results of these studies indicate that microbially mediated soil bioprocesses are important drivers of grassland ecosystem functional recovery. Therefore, a thorough understanding of the spatial distribution characteristics of the soil microbiome in alpine grasslands is required, and this necessitates an integrated approach in which the interactions among climatic factors, vegetation characteristics, and human activities are evaluated. Additionally, we assess and summarise current technological developments and prospects for applying soil microbiome technologies in sustainable agriculture, including: (i) single-strain inoculation, and (ii) inoculation of synthetic microbial communities, (iii) microbial community transplantation. Grassland restoration projects should be carried out with the understanding that each restoration measure has a unique effect on the soil microbial activity. We propose that the sustainable development of alpine grassland ecosystems can be achieved by adopting advanced microbiome technologies and integrating microbe-based sustainable agricultural practices to maximise grassland biomass, increase soil carbon, and optimise soil nutrient cycling.

Prioritizing microbial functions over soil quality for enhanced multifunctionality in saline-sodic soil remediation

Paddy cultivation has become a widely adopted approach for saline-sodic wasteland reclamation, aiming to mitigate the food crisis and enhance soil quality. Nevertheless, the impact of long-term paddy cultivation on the interplay between soil quality, microbial metabolic functions, and soil ecosystem multifunctionality (EMF) remains unclear. Here, we evaluated soil physicochemical properties, the abundance of 132 biomarker functional genes, and soil EMF across a 78-year period of saline-sodic paddy cultivation. After 78 years of paddy cultivation, soil pH and electrical conductivity (EC) decreased by 43.38% and 93.02% compared to saline-sodic wasteland (WL), respectively. Moreover, principal component analysis was used to select a minimal dataset of soil indicators and to establish a soil quality index (SQI). Significant positive correlations were observed between SQI and rice yield, implying that soil quality was the main factor driving increases in saline-sodic farmland. The Mantel test indicates that soil microbial biomass, SQI, and the availability of nutrients exhibit a significant positive relationship with the abundance and expression of genes related to carbon (C), nitrogen (N), and phosphorus (P) cycling, encompassing crucial biogeochemical processes like hemicellulose degradation, C fixation, N degradation, and organic P mineralization. This indicates that changes in soil physicochemical properties significantly affect biogeochemical cycling in saline-sodic soils. Differences in the abundance of microbial P core functional genes explained 41.9% of variation in soil EMF, followed by key soil physicochemical indicators (EC, available potassium, microbial biomass nitrogen, etc.) selected through random forest analysis. Further, we identified a key threshold for changes in soil EMF during long-term saline-sodic paddy cultivation, with EMF increasing for the first 20 years of restoration before decreasing thereafter. Finally, partial least squares path modeling revealed the roles of microbial functional genes and SQI in driving soil EMF before and after the threshold. Soil EMF is primarily influenced by the significant negative effects of P functional genes prior to the threshold value, whereas beyond the threshold, it is mainly affected by the positive effects of C functional genes. These findings provide insights into the functional restoration and sustainable development of saline-sodic agricultural ecosystems.

Nonlinear relationship between diversity of rare and common species and ecosystem multifunctionality in alpine meadows along an altitude gradient

Biodiversity is closely related to ecosystem multifunctionality (EMF), and both are affected by environmental change. However, little is known about the impact of specific components of a biome (e.g., rare and common species) on EMF. This limits our understanding of protecting rare and common species and better utilizing multiple ecosystem services. In this study, we established 15 study plots at different elevation gradients (ranging from 2010 m to 3931 m) in the northeastern Tibetan Plateau to analyze the changes in species diversity of rare and common species in alpine meadows and their contributions to EMF. The results showed that (1) the functional richness (FRic), functional evenness (FEve), and species richness (SR) of rare species were significantly higher than those of common species. (2) The diversity of both rare and common species was significantly positively correlated with EMF across the entire elevation gradient, with the FRic of rare species explaining more of the variation in EMF (R2 = 0.73, P < 0.001). (3) EMF showed a significant negative correlation with elevation (F = -14.67, P < 0.001), with elevation explaining 88 % and 81 % of the variation in EMF in the regions with elevation <3100 m and elevation >3100 m, respectively. (4) The relationship between rare species diversity and EMF changed around 3100 m above sea level. At lower altitudes (<3000 m), common species diversity was positively correlated with EMF, while at higher altitudes (>3150 m), the positive impact of rare species diversity on EMF was more significant. This study helps to understand more carefully how rare and common species affect EMF in the context of climate change and, for the first time, emphasizes the potential and role of rare species in predicting and regulating ecosystem functions, productivity, and functional trade-offs. It is recommended to designate alpine meadow areas as protected areas, strengthen the protection of rare species in high-altitude meadows, and establish seed banks of rare species for artificial restoration. In low-altitude regions, the diversity of common species should be maintained through reasonable grazing, grazing bans and rotations, and organic fertilizers.

Soil properties, climate, and topography jointly determine plant community characteristics in marsh wetlands

Various environmental conditions influence the characteristics of plant communities within wetlands. Although the influence of key environmental factors on plant community traits within specific types of wetland ecosystems has been studied extensively, how they regulate plant communities across marsh wetland types remains poorly understood. We examined how environmental conditions influence plant communities in marsh wetlands along the lower Tumen River in northeastern China. We collected and analyzed data on the plant community characteristics (species, height, and coverage), soil physicochemical properties (organic carbon, inorganic nitrogen, and sulfur), and climatic and topographic factors (temperature, precipitation, and elevation) of 56 distinct marsh plots (29 herbaceous, 14 shrub, and 13 forested marshes) to understand how these variables correlate with plant community characteristics across marsh types. The wetland plant diversity varied, with the lowest, intermediate, and highest diversity occurring in herbaceous, shrub, and forested marshes, respectively. Climate, topography, and soil properties had crucial influences on plant diversity and biomass. Structural equation modeling showed that, in herbaceous marshes, plant biomass was primarily determined by soil and plant diversity, with climate exerting an indirect effect. In shrub marshes, soil, climate, and plant diversity directly influenced biomass. In forest marshes, soil and plant diversity directly affected biomass, whereas climate and topography had indirect effects. These findings highlight the complex interactions among environmental factors across marsh ecosystems and their influence mechanisms on biomass, aiding in formulating effective conservation and restoration strategies for marsh wetland ecosystems.

Effects of volcanic environment on Setaria viridis rhizospheric soil microbial keystone taxa and ecosystem multifunctionality

Keystone taxa are significant within ecosystem multifunctionality, as certain species fulfil essential functions such as recycling soil nutrients, promoting plant growth, influencing biogeochemical processes, and contributing to human health maintenance. However, there are still gaps regarding the relationship between microbial communities in volcanic rhizospheric soil and ecosystem multifunctionality. As a result, in this research, we employed Illumina MiSeq high-throughput sequencing to analyse the microbial community composition of rhizospheric soil from volcanic S. viridis. Compared with non-volcanic areas, volcanic soils have higher fungal alpha diversity and the absolute abundance of bacteria (16S gene copies) showed significant variation between the two successions (P < 0.0001). The network analysis further demonstrated that the microbial diversity in non-volcanic regions surpassed that of the volcanic area. The volcanic fungi network has more nodes and edges, is more complex than non-volcanic areas (Nodes: 425 vs. 770; Edges: 21844 vs. 74532), and more rhizosphere growth-promoting bacteria are enriched. Regression analysis and correlation networks showed that fungal communities were more closely associated with ecosystem multifunctionality than bacteria. This study lays the groundwork for examining the microbial keystone taxa in the rhizosphere of volcanic plants and offers valuable insights into the multifaceted functions of plant rhizospheric soil ecosystems.

Effects of cropland-to-orchard conversion on soil multifunctionality, particularly nitrogen cycling in the eastern Loess Plateau

The conversion of cropland to orchards is one of the main measures of the Grain for Green Program for soil and water conservation and ecosystem function maintenance in the eastern Loess Plateau, China. However, the patterns and influencing forces of soil multifunctionality during the conversion from cropland to orchard remain unclear. This study evaluated the responses and regulating factors of soil multifunctionality following the conversion of cropland to pomegranate (Punica granatum L.) orchard along a 10-year chronosequence. Results showed that the conversion of cropland to pomegranate trees significantly increased the L-leucine aminopeptidase enzyme activity from 4.77 to 17.69 nmol g-1 h-1. The 10-year pomegranate stand exhibited the highest nitrogen (N) cycle multifunctionality. The N cycle multifunctionality was positively correlated with soil dissolved organic carbon (C) content, soil available phosphorus content, microbial biomass C content, phospholipid fatty acid, and soil feature index (All p < 0.05). Structural equation modeling suggested that the increased N cycle multifunctionality was attributed to soil feature index rather than soil microbial C content and phospholipid fatty acid. Land-use change did not affect soil C cycle, phosphorus cycle, or soil multifunctionality. Overall, our findings reveal that cropland conversion to orchards significantly enhances soil N cycle multifunctionality, highlighting the soil feature index's role in maintaining soil function. The conversion from cropland to orchards, which has economic benefits and increases soil N cycle multifunctionality, is an effective approach of the Grain for Green Program in the Loess Plateau.

Optimizing tradeoff strategies of soil microbial community between metabolic efficiency and resource acquisition along a natural regeneration chronosequence

The tradeoff between community-level soil microbial metabolic efficiency and resource acquisition strategies during natural regeneration remains unclear. Herein, we examined variations in soil extracellular enzyme activity, microbial metabolic quotient (qCO2), and microbial carbon use efficiency (CUE) along a chronosequence of natural regeneration by sampling secondary forests at 1, 10, 20, 30, 40, and 100 years after rubber plantation (RP) clearance. The results showed that the natural logarithms of carbon (C)-, nitrogen (N)-, and phosphorus (P)-acquiring enzyme activities were 1:1.68:1.37 and 1:1.54:1.38 in the RP and secondary forests, respectively, thus demonstrating that microbial metabolism was co-limited by N and P. Moreover, the soil microbial C limitation initially increased (1-40 years) and later decreased (100 years). Overall, the qCO2 increased, decreased, and then increased again in the initial (< 10 years), middle (10-40 years), and late (100 years) successional stages, respectively. Except for specific P-acquiring enzyme activities, the changes in other indicators with natural regeneration were consistent in the dry and wet seasons. Both qCO2 and CUE were mainly predicted by microbial community composition and physiological traits. These results indicate that soil microbial communities could employ tradeoff strategies between metabolic efficiency and resource acquisition to cope with variations in resources. Our findings provide new information on tradeoff strategies between metabolic efficiency and resource acquisition during natural regeneration.

Prairie restoration promotes the abundance and diversity of mutualistic arbuscular mycorrhizal fungi

Predicting how biological communities assemble in restored ecosystems can assist in conservation efforts, but most research has focused on plants, with relatively little attention paid to soil microbial organisms that plants interact with. Arbuscular mycorrhizal (AM) fungi are an ecologically significant functional group of soil microbes that form mutualistic symbioses with plants and could therefore respond positively to plant community restoration. To evaluate the effects of plant community restoration on AM fungi, we compared AM fungal abundance, species richness, and community composition of five annually cultivated, conventionally managed agricultural fields with paired adjacent retired agricultural fields that had undergone prairie restoration 5-9 years prior to sampling. We hypothesized that restoration stimulates AM fungal abundance and species richness, particularly for disturbance-sensitive taxa, and that gains of new taxa would not displace AM fungal species present prior to restoration due to legacy effects. AM fungal abundance was quantified by measuring soil spore density and root colonization. AM fungal species richness and community composition were determined in soils and plant roots using DNA high-throughput sequencing. Soil spore density was 2.3 times higher in restored prairies compared to agricultural fields, but AM fungal root colonization did not differ between land use types. AM fungal species richness was 2.7 and 1.4 times higher in restored prairies versus agricultural fields for soil and roots, respectively. The abundance of Glomeraceae, a disturbance-tolerant family, decreased by 25% from agricultural to restored prairie soils but did not differ in plant roots. The abundance of Claroideoglomeraceae and Diversisporaceae, both disturbance-sensitive families, was 4.6 and 3.2 times higher in restored prairie versus agricultural soils, respectively. Species turnover was higher than expected relative to a null model, indicating that AM fungal species were gained by replacement. Our findings demonstrate that restoration can promote a relatively rapid increase in the abundance and diversity of soil microbial communities that had been degraded by decades of intensive land use, and community compositional change can be predicted by the disturbance tolerance of soil microbial taxonomic and functional groups.

Biodiversity drives ecosystem multifunctionality in sandy grasslands?

Plant communities and soil microbiomes play a crucial role in regulating ecosystem multifunctionality (EMF). However, whether and how aboveground plant diversity, belowground soil microbial diversity and interactions with environmental factors affect EMF in sandy grasslands under climate change conditions is unclear. Here, we selected 15 typical grassland communities from the Horqin sandy grassland along temperature and precipitation gradients, using the mean annual temperature (AMT), mean annual precipitation (AP), soil temperature (ST), soil water content (SW) and pH as abiotic factors, and plant diversity (PD) and soil microbial diversity (SD) as biodiversity indicators. The effects of biodiversity and abiotic factors on individual ecosystem functions and EMF were studied. We found that PD and its components, plant species richness (SR), species diversity (PR) and genetic diversity (GD), had significant effects on aboveground biomass (AGB) and major factors involved in ecosystem nitrogen cycling (plant leaf nitrogen content (PLN) and soil total nitrogen content (STN)) (P < 0.05). Soil fungal diversity (FR) has a greater impact on ecosystem function than soil bacteria (BR) and archaea (ABR) in sandy grasslands and mainly promotes the accumulation of soil microbial carbon and nitrogen (MBC, MBN) (P < 0.05), STC and STN (P < 0.01). PD and two types of SD (FR and ABR) significantly regulated EMF (P < 0.01). Among the abiotic factors, soil pH and SW regulated EMF (P < 0.05), and SW and ST directly drove EMF (P < 0.05). PD drove EMF significantly and indirectly (positively) through soil pH and ST (P < 0.001), while SD drove EMF weakly and indirectly (negatively) through AP and PD (P > 0.05). PD was a stronger driving force on EMF than SD. These results improve our understanding of the drivers of multifunctionality in sandy grassland ecosystems.

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.

Microbial network structure, not plant and microbial community diversity, regulates multifunctionality under increased precipitation in a cold steppe

It is known that the dynamics of multiple ecosystem functions (i. e., multifunctionality) are positively associated with microbial diversity and/or biodiversity. However, how the relationship between microbial species affects ecosystem multifunctionality remains unclear, especially in the case of changes in precipitation patterns. To explore the contribution of biodiversity and microbial co-occurrence networks to multifunctionality, we used rainfall shelters to simulate precipitation enhancement in a cold steppe in Northeast China over two consecutive growing seasons. We showed that an increased 50% precipitation profoundly reduced bacterial diversity and multidiversity, while inter-annual differences in precipitation did not shift microbial diversity, plant diversity, or multidiversity. Our analyses also revealed that increased annual precipitation significantly increased ecosystem, soil, nitrogen, and phosphorous cycle multifunctionality. Neither increased precipitation nor inter-annual differences in precipitation had a significant effect on carbon cycle multifunctionality, probably due to the relatively short period (2 years) of our experiment. The co-occurrence network of bacterial and fungal communities was the most dominant factor affecting multifunctionality, the numbers of negative interactions but not positive interactions were linked to multifunctionality. In particular, our results provided evidence that microbial network topological features are crucial for maintaining ecosystem functions in grassland ecosystems, which should be considered in related studies to accurately predict the responses of ecosystem multifunctionality to predicted changes in precipitation patterns.

Shrub expansion raises both aboveground and underground multifunctionality on a subtropical plateau grassland: coupling multitrophic community assembly to multifunctionality and functional trade-off

Introduction

Shrubs have expanded into grasslands globally. However, the relative importance of aboveground and underground diversity and the relative importance of underground community assembly and diversity in shaping multifunctionality and functional trade-offs over shrub expansion remains unknown.

Methods

In this study, aboveground and underground multitrophic communities (abundant and rare archaea, bacteria, fungi, nematodes, and protists) and 208 aboveground and underground ecosystem properties or indicators were measured at three stages (Grass, Mosaic, Shrub) of shrub expansion on the Guizhou subtropical plateau grassland to study multifunctionality and functional trade-offs.

Results

The results showed that shrub expansion significantly enhanced aboveground, underground, and entire ecosystem multifunctionality. The functional trade-off intensities of the aboveground, underground, and entire ecosystems showed significant V-shaped changes with shrub expansion. Shrub expansion improved plant species richness and changed the assembly process and species richness of soil abundant and rare subcommunities. Plant species diversity had a greater impact on multifunctionality than soil microbial diversity by more than 16%. The effect of plant species diversity on functional trade-offs was only one-fifth of the effect of soil microbial diversity. The soil microbial species richness did not affect multifunctionality, however, the assembly process of soil microbial communities did. Rather than the assembly process of soil microbial communities, the soil microbial species richness affected functional trade-offs.

Discussion

Our study is the first to couple multitrophic community assemblies to multifunctionality and functional trade-offs. Our results would boost the understanding of the role of aboveground and underground diversity in multifunctionality and functional trade-offs.

Grazing alters the relationship between alpine meadow biodiversity and ecosystem multifunctionality

The relationship between biodiversity and ecosystem multifunctionality (EMF) depends on changes in environmental disturbance. Plant and soil biological diversity can mediate EMF, but how these change in response to grazing disturbance remains unknown. Here we present an 8-year experiment on sheep grazing control in alpine grasslands in Gannan Tibetan Autonomous Prefecture, Gansu Province, China. Plant species richness, FRic (functional richness), PD (Faith's phylogenetic diversity), soil biological diversity (bacterial, fungal, and ciliate diversity), and multiple ecosystem functions were measured and calculated. The results showed that increasing grazing intensity caused a decrease in biodiversity and EMF and that biodiversity and ecosystem function differed significantly (P < 0.05) between grazing intensities. EMF was positively correlated with species richness, functional diversity, and soil bacterial diversity (P < 0.05), with 23.6 %, 10.8 %, and 12.1 % of EMF explained by changes in grazing intensity, respectively. The interaction terms of grazing intensity, plant species richness, and soil biological diversity were negatively correlated with EMF (P < 0.05). This shift in the relationship between plant or soil biological diversity and EMF occurs at a grazing intensity index of around 0.7, i.e., the impact of plant species richness on EMF is more significant when the grazing intensity index is below 0.67. The effect of soil biological diversity on EMF is more substantial when the grazing intensity index is above 0.86. Conclusion: High grazing intensity directly affects soil bulk density and pH and indirectly affects EMF by regulating plant species richness and soil biological diversity changes. Loss of plant and soil biological diversity can have extreme consequences under low and high grazing intensity disturbance conditions. Therefore, we must develop biodiversity conservation strategies for external disturbances to mitigate the effects of land use practices such as grazing disturbances.

Ecosystem multifunctionality and soil microbial communities in response to ecological restoration in an alpine degraded grassland

Linkages between microbial communities and multiple ecosystem functions are context-dependent. However, the impacts of different restoration measures on microbial communities and ecosystem functioning remain unclear. Here, a 14-year long-term experiment was conducted using three restoration modes: planting mixed grasses (MG), planting shrub with Salix cupularis alone (SA), and planting shrub with Salix cupularis plus planting mixed grasses (SG), with an extremely degraded grassland serving as the control (CK). Our objective was to investigate how ecosystem multifunctionality and microbial communities (diversity, composition, and co-occurrence networks) respond to different restoration modes. Our results indicated that most of individual functions (i.e., soil nutrient contents, enzyme activities, and microbial biomass) in the SG treatment were significantly higher than in the CK treatment, and even higher than MG and SA treatments. Compared with the CK treatment, treatments MG, SA, and SG significantly increased the multifunctionality index on average by 0.57, 0.23 and 0.76, respectively. Random forest modeling showed that the alpha-diversity and composition of bacterial communities, rather than fungal communities, drove the ecosystem multifunctionality. Moreover, we found that both the MG and SG treatments significantly improved bacterial network stability, which exhabited stronger correlations with ecosystem multifunctionality compared to fungal network stability. In summary, this study demonstrates that planting shrub and grasses altogether is a promising restoration mode that can enhance ecosystem multifunctionality and improve microbial diversity and stability in the alpine degraded grassland.

Changes in grassland soil types lead to different characteristics of bacterial and fungal communities in Northwest Liaoning, China

Introduction

Soil microbial communities are critical in regulating grassland biogeochemical cycles and ecosystem functions, but the mechanisms of how environmental factors affect changes in the structural composition and diversity of soil microbial communities in different grassland soil types is not fully understood in northwest Liaoning, China.

Methods

We investigated the characteristics and drivers of bacterial and fungal communities in 4 grassland soil types with 11 sites across this region using high-throughput Illumina sequencing.

Results and Discussion

Actinobacteria and Ascomycota were the dominant phyla of bacterial and fungal communities, respectively, but their relative abundances were not significantly different among different grassland soil types. The abundance, number of OTUs, number of species and diversity of both bacterial and fungal communities in warm and temperate ecotone soil were the highest, while the warm-temperate shrub soil had the lowest microbial diversity. Besides, environmental factors were not significantly correlated with soil bacterial Alpha diversity index. However, there was a highly significant negative correlation between soil pH and Shannon index of fungal communities, and a highly significant positive correlation between plant cover and Chao1 index as well as Observed species of fungal communities. Analysis of similarities showed that the structural composition of microbial communities differed significantly among different grassland soil types. Meanwhile, the microbial community structure of temperate steppe-sandy soil was significantly different from that of other grassland soil types. Redundancy analysis revealed that soil total nitrogen content, pH and conductivity were important influencing factors causing changes in soil bacterial communities, while soil organic carbon, total nitrogen content and conductivity mainly drove the differentiation of soil fungal communities. In addition, the degree of connection in the soil bacterial network of grassland was much higher than that in the fungal network and soil bacterial and fungal communities were inconsistently limited by environmental factors. Our results showed that the microbial community structure, composition and diversity of different grassland soil types in northwest Liaoning differed significantly and were significantly influenced by environmental factors. Microbial community structure and the observation of soil total nitrogen and organic carbon content can predict the health changes of grassland ecosystems to a certain extent.

Investigating the recovery in ecosystem functions and multifunctionality after 10 years of natural revegetation on fly ash technosol

Technogenic soil (technosol) developed from coal fly ash (FA) landfilling has been considered a critical environmental problem worldwide. Drought-tolerant plants often naturally grow on FA technosol. However, the impact of these natural revegetations on the recovery of multiple ecosystem functions (multifunctionality) remains largely unexplored and poorly understood. Here we assessed the response of multifunctionality, including nutrient cycling (i.e., carbon, nitrogen, and phosphorus), carbon storage, glomalin-related soil protein (GRSP), plant productivity, microbial biomass carbon (MBC), microbial processes (soil enzyme activities), and soil chemical properties (pH and electrical conductivity; EC) to FA technosol ten years' natural revegetation with different multipurpose species in Indo-Gangetic plain, and identified the key factors regulating ecosystem multifunctionality during reclamation. We evaluated four dominant revegetated species: Prosopis juliflora, Saccharum spontaneum, Ipomoea carnea, and Cynodon dactylon. We found that natural revegetation initiated the recovery of ecosystem multifunctionality on technosol, with greater recovery under higher biomass-producing species (P. juliflora and S. spontaneum) than lower biomass-producing ones (I. carnea and C. dactylon). The individual functions (11 of the total 16 variables) at higher functionality (70 % threshold) also exhibited this pattern among revegetated stands. Multivariate analyses revealed that most of the variables (except EC) significantly correlated with multifunctionality, indicating the capability of multifunctionality to consider the tradeoff between individual functions. We further performed structural equation modeling (SEM) to detect the effect of vegetation, pH, nutrients, and microbial activity (MBC and microbial processes) on ecosystem multifunctionality. Our SEM model predicted 98 % of the variation in multifunctionality and confirmed that the indirect effect of vegetation mediated by microbial activity is more important for multifunctionality than their direct effect. Collectively, our results demonstrate that FA technosol revegetation with high biomass-producing multipurpose species promotes ecosystem multifunctionality and emphasizes the significance of microbial activity in the recovery and maintenance of ecosystem attributes.

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.

Variations in Soil Nitrogen Availability and Crop Yields under a Three-Year Annual Wheat and Maize Rotation in a Fluvo-Aquic Soil

Optimum tillage practices can create a suitable soil environment, and they improve the soil nutrient status to ensure crop development and yield. In this study, we evaluated the influences of six tillage practices on soil nutrients and maize yields from 2017 to 2019 in fluvo-aquic soil in the North China Plain. The field experiment was carried out by a split design with rotary tillage (RT) and deep tillage (DT) in wheat season in the main plot and no-tillage (NT), subsoiling between the row (SBR), and subsoiling in the row (SIR) in maize season in the subplot. The results showed that the soil nutrient content was higher under the treatments with rotary tillage in the wheat season in the 0-20 cm soil layer, while in the 20-40 cm soil layer, the soil nutrient content was higher under the treatments with deep tillage in the wheat season. The integrated principal component scores indicated that the soil nutrients had improved in the second year. The ecosystem multifunctionality (EMF) index was higher with the treatments with rotary tillage in wheat season in the 0-20 cm soil layer, while it was the highest under DT-SIR at 20-40 cm. Correlation analysis showed that the soil EMF index correlated significantly (p < 0.05) with the soil nutrient content mainly in the 0-40 cm soil layer. The higher maize yield was under the treatments with deep tillage compared to that under the treatments with rotary tillage in the wheat season. The yield-increasing effect was higher under the treatments with subsoiling than those utilizing no-till in the maize season, with the highest average yield of 13,910 kg hm^-2 in the DT-SIR during the three years. Maize yield was strongly correlated with nutrients in the subsoil layer. The higher yield stability was found under RT-NT. To sum up, during the three-year experiment, rotary tillage in the wheat season combined with subsoiling in the maize season improved the soil nutrient content and the EMF index in the 0-20 cm layer, while the combination of deep tillage in the wheat season and subsoiling in the maize season improved those indices in the 20-40 cm soil layer, and increased the maize yield, the best one was under DT-SIR.

Biodiversity and soil pH regulate the recovery of ecosystem multifunctionality during secondary succession of abandoned croplands in northern China

The 'Grain-for-Green' program in China provides a valuable opportunity to investigate whether spontaneous restoration can reverse the deterioration of grassland ecosystem functions. Previous studies have focused on individual ecosystem functions, but the response of and mechanisms driving variation in ecosystem multifunctionality (EMF) during restoration are poorly understood. Here, we quantified EMF using productivity, nutrient cycling, and water regulation functions along abandoned croplands in a recovery chronosequence (5, 15 and 20 years) and in natural grasslands in the desert steppe and typical steppe. We also analyzed the effects of plant and microbial diversity and an abiotic factor (soil pH) on EMF. Our results showed that EMF increased gradually concomitant with recovery time, shifting toward EMF values comparable to those in natural grasslands in both desert and typical steppe. Similar results were found for the productivity function, the water regulation function, and soil organic carbon. However, even after 20 years of restoration, EMF did not reach the levels observed in natural grasslands. Structural equation modeling showed that the driving mechanisms of EMF differed between the two steppe types. Specifically, in the desert steppe, plant diversity, especially the diversity of perennial graminoids and perennial herbs, had a positive effect on EMF, but in the typical steppe, soil bacterial diversity had a negative effect, while soil pH had a positive effect on EMF. Our results demonstrated that spontaneous grassland restoration effectively enhanced EMF, and emphasized the importance of biodiversity and soil pH in regulating EMF during secondary succession. This work provides important insights for grassland ecosystem management in arid and semi-arid regions.

Effects of different management practices on soil microbial community structure and function in alpine grassland

Management practices, such as grazing exclusion and reseeding, have been implemented to mitigate the degradation of grassland. Low grazing intensities and reseeding increase grass production. Nevertheless, few studies have investigated the effects of these measures on the soil microbial community structure and function in the Qinghai Tibetan Plateau (QTP). To reveal the effects of management practices on soil microbes and give a reference to assess and improve ecosystems functions, we here evaluated the impact of various types of grazing (exclusion, seasonal, and traditional), reseeding (annual oat (Avena fatua) grassland (RO) and perennial artificial grassland cultivated >10 y), and integrated restoration (weed control and no-tillage reseeding) measures on soil microbial community structure and function in the QTP. The Shannon-Wiener diversity indices were highest for prokaryotes under RO and for fungi under integrated grassland restoration. Relative Actinobacteria abundance was higher under seasonal grazing than that under integrated grassland restoration. The latter had relatively higher abundances of Betaproteobacteria, Alphaproteobacteria, and Deltaproteobacteria and comparatively lower abundance of Thermoleophilia. There were significantly higher abundances of plant pathogens under seasonal grazing than those under other managements. There were significantly high proportions of pathotrophs and saprotrophs (10.0%) under seasonal and traditional grazing, respectively. The proportion of pathotrophs under integrated restoration (10.0%) was about seven-fold greater than that under grazing exclusion (1.5%). The relative differences among treatments in terms of soil water content, plant biomass, and soil C:N partially explained the differences in their prokaryotic community compositions. Increases in soil organic carbon and C:N may explain the observed changes in the soil fungal communities. The management practices affected soil microorganisms mainly by altering the soil nutrient profile. Grazing attracted specific pathotrophs and saprotrophs while repelling certain plant pathogens. Hence, modulations in soil microbial community structure and function must be considered in the process of planning for the implementation of grassland degradation management measures.

Moss-dominated biocrust-based biodiversity enhances carbon sequestration via water interception and plant-soil-microbe interactions

We investigated a nature-based solution (NbS) via incorporating biocrust into alfalfa-maize intercropping system to test carbon sequestration in seriously eroded agricultural soils. Field investigation showed that the NbS (moss-dominated biocrust + intercropping) massively lowered surface soil erosion by 94.5% and soil carbon (C) and nitrogen (N) loss by 94.7 and 96.8% respectively, while promoting rainwater interception by 82.2% relative to bare land (CK). There generally existed positive interactions between biocrust and cropping in the integrated standing biodiversity system. Enhanced plant biomass input into soils substantially promoted soil fungal community diversity and abundance under NbS (p < 0.05). This enabled NbS to evidently improve soil macroaggregate proportion and mean weight diameter. Critically, topsoil carbon storage was increased by 2.5 and 10.7%, compared with CK and pure intercropping (p < 0.05). Conclusively, the standing diversity under such NbS fostered soil C sequestration via water interception and plant-soil-microbe interactions in degraded agricultural soils.

Microbial community succession in soils under long-term heavy metal stress from community diversity-structure to KEGG function pathways

Currently, understanding the structure and function of the microbial community is the key step in artificially constructing microbial communities to control soil heavy metal pollution. Abundant/rare microbial communities play different roles in different levels of concentrations. However, the correlation between heavy metals and rare/abundant subgroups is poorly understood. In this study, we used a metagenomics approach to comprehensively investigate the evolutionary changes in microbial diversity, structure, and function under different heavy metal concentration stress in soils surrounding gold tailings. The results show that the main pollutants were Pb, As, and Zn. Indigenous microorganisms have different responses to heavy metal concentrations. Bacteria are the main components of indigenous microorganisms, mainly including Actinobacteria, Proteobacteria, Chloroflexi, and Acidobacteria. With the increase of heavy metal pollution, the relative abundance of Proteobacteria increased, and that of Actinobacteria decreased. Archaea was significantly inhibited by heavy metal stress and was more sensitive to heavy metal concentration. The response of fungi to heavy metal concentration was not obvious. The results of KEGG pathways showed that carbon fixation was inhibited with increasing heavy metal concentrations, while nitrogen metabolism was in contrast. Abundant subcommunity had a greater correlation mainly with metal resistance mechanisms, and rare subcommunity plays a key role for soil nutrient cycling such as N, S cycling in soils contaminated. Overall, this study provides a comprehensive analysis of the effects of heavy metal stress at different concentrations on microorganisms in farmland around gold tailings and reveals the relationship between heavy metals on KEGG pathways.

Effects of Land Use on the Soil Microbial Community in the Songnen Grassland of Northeast China

Land use change obviously changes the plant community composition and soil properties of grasslands and thus affects multiple functions and services of grassland ecosystems. However, the response mechanisms of soil microorganisms, key drivers of the nutrient cycle and other soil functions during changes in grassland use type and associated vegetation are not well understood. In this study, Illumina high-throughput sequencing was used to analyze the changes in the soil microbial community structure of four grassland use types: exclosure (EL), mowed land (ML), grazed land (GL), and farmland (FL) in the Songnen Plain of Northeast China. The results showed that the FL and EL had significantly higher soil total nitrogen (TN) and lower soil electrical conductivity (EC) and pH than GL and ML. In contrast, the GL and ML had higher soil bulk density (BD) and organic matter, respectively, than the other land use types. In addition, the values of the Shannon diversity and Pielou’s evenness indexes were highest in the EL of all the land use types. Based on the high-throughput sequencing results, we observed high levels of α diversity in the FL for both bacteria and fungi. A structural equation model (SEM) revealed that pH and EC had a direct and positive effect on the bacterial community structure and composition. In addition, plant taxonomic diversity (according to the Shannon diversity and Pielou’s evenness indexes) indirectly affected the bacterial community composition via soil pH and EC. Notably, fungal composition was directly and positively correlated with soil nutrients and the value of Pielou’s evenness index changed with land use type. In conclusion, soil properties and/or plant diversity might drive the changes in the soil microbial community structure and composition in different grassland use types.