Intermediate soil acidification induces highest nitrous oxide emissions.

Global potent greenhouse gas nitrous oxide (N2O) emissions from soil are accelerating, with increases in the proportion of reactive nitrogen emitted as N2O, i.e., N2O emission factor (EF). Yet, the primary controls and underlying mechanisms of EFs remain unresolved. Based on two independent but complementary global syntheses, and three field studies determining effects of acidity on N2O EFs and soil denitrifying microorganisms, we show that soil pH predominantly controls N2O EFs and emissions by affecting the denitrifier community composition. Analysis of 5438 paired data points of N2O emission fluxes revealed a hump-shaped relationship between soil pH and EFs, with the highest EFs occurring in moderately acidic soils that favored N2O-producing over N2O-consuming microorganisms, and induced high N2O emissions. Our results illustrate that soil pH has a unimodal relationship with soil denitrifiers and EFs, and the net N2O emission depends on both the N2O/(N2O + N2) ratio and overall denitrification rate. These findings can inform strategies to predict and mitigate soil N2O emissions under future nitrogen input scenarios.

Plant litter loss exacerbates drought influences on grasslands.

Plant litter is known to affect soil, community, and ecosystem properties. However, we know little about the capacity of litter to modulate grassland responses to climate change. Using a 7-yr litter removal experiment in a semiarid grassland, here we examined how litter removal interacts with a 2-yr drought to affect soil environments, plant community composition, and ecosystem function. Litter loss exacerbates the negative impacts of drought on grasslands. Litter removal increased soil temperature but reduced soil moisture and nitrogen mineralization, which substantially increased the negative impacts of drought on primary productivity and the abundance of perennial rhizomatous graminoids. Moreover, complete litter removal shifted plant community composition from grass-dominated to forb-dominated and reduced species and functional group asynchrony, resulting in lower ecosystem temporal stability. Our results suggest that ecological processes that lead to reduction in litter, such as burning, grazing, and haying, may render ecosystems more vulnerable and impair the capacity of grasslands to withstand drought events.

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-, ß-, 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 ß-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.

Phosphorus availability and planting patterns regulate soil microbial effects on plant performance in a semiarid steppe.

BACKGROUND AND AIMS: Growing evidence has suggested that plant responses to model soil microorganisms are context dependent; however, few studies have investigated the effects of whole soil microbial communities on plant performance in different abiotic and biotic conditions. To address this, we examined how soil phosphorus (P) availability and different planting patterns regulate soil microbial effects on the growth of two native plant species in a semiarid steppe. METHODS: We carried out a glasshouse experiment to explore the effects of the whole indigenous soil microbiota on the growth and performance of Leymus chinensis and Cleistogenes squarrosa using soil sterilization with different soil P availabilities and planting patterns (monoculture and mixture). Transcriptome sequencing (RNA-seq) was used to explain the potential molecular mechanisms of the soil microbial effects on C. squarrosa. KEY RESULTS: The soil sterilization treatment significantly increased the biomass of L. chinensis and C. squarrosa in both monoculture and mixture conditions, which indicated that the soil microbiota had negative growth effects on both plants. The addition of P neutralized the negative microbial effects for both L. chinensis and C. squarrosa, whereas the mixture treatment amplified the negative microbial effects on L. chinensis but alleviated them on C. squarrosa. Transcriptomic analysis from C. squarrosa roots underscored that the negative soil microbial effects were induced by the upregulation of defence genes. The P addition treatment resulted in significant decreases in the number of differentially expressed genes attributable to the soil microbiota, and some defence genes were downregulated. CONCLUSIONS: Our results underline that indigenous soil microbiota have negative effects on the growth of two dominant plant species from a semiarid steppe, but their effects are highly dependent on the soil P availability and planting patterns. They also indicate that defence genes might play a key role in controlling plant growth responses to the soil microbiota.

Epidemiological Characteristics of Visceral Leishmaniasis - Shanxi Province, China, 1950-2019.

What is already known about this topic?: Visceral leishmaniasis (VL) is the most serious form of leishmaniasis. In recent years, reported cases of VL have been gradually increasing in Shanxi Province, China. What is added by this report?: The report describes the epidemiology of VL from 1950 to 2019 in Shanxi Province and the recent trend of VL reemergence. What are the implications for public health practice?: Measures to prevent and control VL, such as health education, improving clinical diagnostics, strengthening epidemiological investigation capacity for VL cases, monitoring surveillance, and use of other evidence-based preventive measures, should be undertaken in Shanxi Province.

Grassland soil carbon sequestration: Current understanding, challenges, and solutions.

Grasslands store approximately one third of the global terrestrial carbon stocks and can act as an important soil carbon sink. Recent studies show that plant diversity increases soil organic carbon (SOC) storage by elevating carbon inputs to belowground biomass and promoting microbial necromass contribution to SOC storage. Climate change affects grassland SOC storage by modifying the processes of plant carbon inputs and microbial catabolism and anabolism. Improved grazing management and biodiversity restoration can provide low-cost and/or high-carbon-gain options for natural climate solutions in global grasslands. The achievable SOC sequestration potential in global grasslands is 2.3 to 7.3 billion tons of carbon dioxide equivalents per year (CO2e year-1) for biodiversity restoration, 148 to 699 megatons of CO2e year-1 for improved grazing management, and 147 megatons of CO2e year-1 for sown legumes in pasturelands.

Changes in Gut Microbiota by the Lactobacillus casei Anchoring the K88 Fimbrial Protein Prevented Newborn Piglets From Clinical Diarrhea.

In the last 20 years, accumulating evidence indicates that the gut microbiota contribute to the development, maturation, and regulation of the host immune system and mediate host anti-pathogen defenses. Lactobacillus casei (L.casei) is a normal flora of the gastrointestinal tract in mammals and, as a great mucosal delivery vehicle, has wide use in bioengineering. However, the diarrhea prevention role of commensal intestinal microbiota interfered by the recombinant L.casei (rL.casei) in newborn piglets is not well understood. In our study, newborn piglets orally fed with the rL.casei surface displayed the fimbrial protein K88 of enterotoxigenic Escherichia coli (ETEC) and their feces were collected for a period of time after feeding. The next-generation sequencing of these fecal samples showed that the relative abundance of L.casei was significantly increased. The oral administration of rL.casei altered the intestinal microbial community as evidenced by altered microbial diversity and microbial taxonomic composition. Remarkably, the functional enhancing of the intestinal bacterial community by rL.casei was positively correlated with membrane transport, replication, and repair (p < 0.05). The specific antibody detection indicates that high levels of anti-K88 secretory immunoglobulin A (sIgA) were induced in fecal samples and systemic immunoglobulin G was produced in serum. The diarrhea rate in piglets caused by ETEC K88 was decreased by about 24%. Thus, the oral administration of rL.casei not only activated the mucosal and humoral immune responses in vivo but also contributed to shape the intestinal probiotics in newborn piglets and to significantly reduce the diarrhea rates of newborn piglets.

Grazing Intensity Rather than Host Plant's Palatability Shapes the Community of Arbuscular Mycorrhizal Fungi in a Steppe Grassland.

Arbuscular mycorrhizal fungi (AMF) are the predominant type of mycorrhizal fungi in roots and rhizosphere soil of grass species worldwide. Grasslands are currently experiencing increasing grazing pressure, but it is not yet clear how grazing intensity and host plant grazing preference by large herbivores interact with soil- and root-associated AMF communities. Here, we tested whether the diversity and community composition of AMF in the roots and rhizosphere soil of two dominant perennial grasses, grazed differently by livestock, change in response to grazing intensity. We conducted a study in a long-term field experiment in which seven levels of field-manipulated grazing intensities were maintained for 13 years in a typical steppe grassland in northern China. We extracted DNA from the roots and rhizosphere soil of two dominant grasses, Leymus chinense (Trin.) Tzvel. and Stipa grandis P. Smirn, with contrasting grazing preference by sheep. AMF DNA from root and soil samples was then subjected to molecular analysis. Our results showed that AMF α-diversity (richness) at the virtual taxa (VT) level varied as a function of grazing intensity. Different VT showed completely different responses along the gradient, one increasing, one decreasing, and others showing no response. Glomeraceae was the most abundant AMF family along the grazing gradient, which fits well with the theory of disturbance tolerance of this group. In addition, sheep-grazing preference for host plants did not explain much of the variation in AMF α-diversity. However, the two grass species exhibited different AMF community composition in their roots and rhizosphere soils. Roots exhibited a lower α-diversity and higher ß-diversity within the AMF community than soils. Overall, our results suggest that long-term grazing intensity might have changed the abundance of functionally diverse AMF taxa in favor of those with disturbance-tolerant traits. We suggest our results would be useful in informing the choice of mycorrhizal fungi indicator variables when assessing the impacts of grassland management choices on grassland ecosystem functioning.

Linking leaf traits to the temporal stability of above- and belowground productivity under global change and land use scenarios in a semi-arid grassland of Inner Mongolia.

The biotic drivers for the temporal stability of aboveground net productivity (ANPP) in natural ecosystems are well understood. However, knowledge gaps still exist regarding the relative importance of biotic and abiotic drivers regulating the temporal stability of aboveground productivity (ANPP), belowground net productivity (BNPP), and community net productivity (NPP) under global change and land use scenarios. Thus, in this study, we aimed to study the effects of increased water and nitrogen availability on temporal stability of ANPP, BNPP, and NPP and underlying mechanisms at sites with different long-term grazing histories in typical grasslands of the Inner Mongolia. The results suggested that resource addition affected the ANPP stability, but it did not change the stability of BNPP and NPP, which were all mediated by grazing histories. Most importantly, our study further indicated that species asynchrony, primarily contributed to the stability of ANPP and NPP by weakening their variation, and species asynchrony was regulated directly by plant diversity-related variables and indirectly by soil variables which were affected by resource addition and grazing history. In addition, an increase of ANPP stimulated under resource addition was a secondary contributor to ANPP stability. Specifically, the community-weighted mean of specific leaf area (CWM SLA) regulated the ANPP stability indirectly by promoting species asynchrony, while functional diversity of leaf area and SLA both directly controlled the BNPP stability. Findings of our study demonstrate that different mechanisms drove temporal stability of above- and belowground productivity. Our study has important implications for maintaining the temporal stability of community productivity and for establishing sustainable management practices of semi-arid grasslands under global change and land use scenarios.

[Epidemiological survey of allergic rhinitis in steppe area of Xilingol League, Inner Mongolian of China].

Objective:To investigate the epidemiologic feature of allergic rhinitis （AR） in the grassland area of Xilin Gol League, in Inner Mongolia, including prevalence rate, clinical characteristics and main allergens, so as to provide scientific evidence for the prevention and treatment of AR. Methods:From May to August of 2015, in strict accordance with the requirements of epidemiological investigation, A multi-stage, stratified， random and cluster sampling method was adopted to investigate the population in three areas of Xilingol Grassland in Inner Mongolia （Xilinhot, Erlianhot and Duolun）, with a face to face questionnaire used to investigate the general situation, the main clinical symptoms and related symptoms of AR and the combined. Simultaneously, the skin prick test （SPT） of 10 common grassland allergens was carried out, and the gravity sedimentation method was used to monitor the daily pollen types and quantity in the area.SAS 9.4 software was used for data analysis． Results:A total of 2878 subjects in the cluster sample completed the questionnaire survey and allergen detection. The positive rate of SPT was 41.10% （1179/2787）, the self-reported prevalence rate of AR was 39.96%（1150/2878） and confirmed prevalence rate of AR was 22.72%（654/2878）. The most obvious clinical symptoms of AR were sneezing （91.13%, 1048/1150） and itchy nose （85.65%, 985/1150）. The most obvious clinical symptoms of ocular were itchy （55.13%, 634/1150） and tearing（42.96%，494/1150）. Fatigue and somnolence were prominent among other symptoms associated with AR. Among comorbidities, AR combined with conjunctivitis accounted for 60.52% （696/1150）, AR combined with asthma accounted for 13.57% （156/1150）. The major allergens of AR from high to low were Artemisia pollen, Chenopodium pollen, and Humulus pollen. The peak of AR symptoms mostly occuredin August.， and the peak period of allergic rhinitis symptoms coincided with the peak period of pollen quantity. Conclusion:The prevalence rate of AR in is extremely high due to the high seasonal pollen exposure in steppe area of Xilingol League in Inner Mongolian. Artemisia pollen is the main sensitized allergen.

The Murine Reg3a Stimulated by Lactobacillus casei Promotes Intestinal Cell Proliferation and Inhibits the Multiplication of Porcine Diarrhea Causative Agent in vitro.

Lactobacillus casei (L. casei), a normal resident of the gastrointestinal tract of mammals, has been extensively studied over the past few decades for its probiotic properties in clinical and animal models. Some studies have shown that some bacterium of Lactobacillus stimulate the production of antimicrobial peptides in intestinal cells to clear enteric pathogens, however, which antimicrobial peptides are produced by L. casei stimulation and its function are still not completely understood. In this study, we investigated the changes of antimicrobial peptides' expression after intragastric administration of L. casei to mice. The bioinformatics analysis revealed there were nine genes strongly associated with up-regulated DEGs. But, of these, only the antimicrobial peptide mReg3a gene was continuously up-regulated, which was also confirmed by qRT-PCR. We found out the mReg3a expressed in engineering E.coli promoted cell proliferation and wound healing proved by CCK-8 assay and wound healing assay. Moreover, the tight junction proteins ZO-1 and E-cadherin in mReg3a treatment group were significantly higher than that in the control group under the final concentration of 0.2 mg/ml both in Porcine intestinal epithelial cells (IPEC-J2) and Mouse intestinal epithelial cells (IEC-6) (p < 0.05). Surprisingly, the recombinant mReg3a not only inhibited Enterotoxigenic Escherichia coli (ETEC), but also reduced the copy number of the piglet diarrheal viruses, porcine epidemic diarrhea virus (PEDV), porcine transmissible gastroenteritis virus (TGEV), and porcine rotavirus (PoRV), indicating the antimicrobial peptides mReg3a may be feed additives to resist the potential of the intestinal bacterial and viral diarrhea disease.

A dataset of plant and microbial community structure after long-term grazing and mowing in a semiarid steppe.

Grazing and mowing are two dominant management regimes used in grasslands. Although many studies have focused on the effects of grazing intensity on plant community structure, far fewer test how grazing impacts the soil microbial community. Furthermore, the effects of long-term grazing and mowing on plant and microbial community structure are poorly understood. To elucidate how these management regimes affect plant and microbial communities, we collected data from 280 quadrats in a semiarid steppe after 12-year of grazing and mowing treatments. We measured plant species abundance, height, coverage, plant species diversity, microbial biomass, and microbial community composition (G+ and G- bacteria; arbuscular mycorrhizal and saprotrophic fungi; G+/G- and Fungi/Bacteria). In addition, we determined the soil's physical and chemical properties, including soil hardness, moisture, pH, organic carbon, total nitrogen, and total phosphorus. This is a long-term and multifactorial dataset with plant, soil, and microbial attributes which can be used to answer questions regarding the mechanisms of sustainable grassland management in terms of plant and microbial community structure.

Seasonal variation in the response of arbuscular mycorrhizal fungi to grazing intensity.

Despite existing evidence of pronounced seasonality in arbuscular mycorrhizal (AM) fungal communities, little is known about the ecology of AM fungi in response to grazing intensity in different seasons. Here, we assessed AM fungal abundance, represented by soil hyphal length density (HLD), mycorrhizal root colonization intensity (MI), and arbuscule intensity (AI) throughout three seasons (spring, summer, autumn) in a farm-scale field experiment in typical, grazed steppe vegetation in northern China. Seven levels of field-manipulated, grazing intensities had been maintained for over 13 years within two topographies, flat and slope. We also measured soil nutrients and carbon content throughout the growing season to investigate whether seasonal variation in AM fungal abundance was related to seasonal shifts in soil resource availability along the grazing gradient. We further examined the association between AM fungal metrics in the different grazing treatments through the growing season. Our results showed a pronounced seasonal shift in HLD but there was no clear seasonality in MI and AI. HLD was significantly negatively related to grazing intensity over the course of the growing season from spring to autumn. However, MI and AI were related negatively to grazing intensity only in spring. In addition, differential responses of AM fungal abundance to grazing intensity at the two topographical sites were detected. No strong evidence was found for associations between AM fungal abundance and soil resource availability. Moreover, AM fungal internal and external abundance were correlated positively under the different grazing intensities throughout the growing season. Overall, our study suggests that external AM fungal structures in soil were more responsive to seasonal variation and grazing than internal structures in roots. The findings also suggest that early grazing may be detrimental to AM fungal root colonization of newly emerged plants.

Soil acidification reduces the effects of short-term nutrient enrichment on plant and soil biota and their interactions in grasslands.

Soil nitrogen (N) and phosphorus (P) contents, and soil acidification have greatly increased in grassland ecosystems due to increased industrial and agricultural activities. As major environmental and economic concerns worldwide, nutrient enrichment and soil acidification can lead to substantial changes in the diversity and structure of plant and soil communities. Although the separate effects of N and P enrichment on soil food webs have been assessed across different ecosystems, the combined effects of N and P enrichment on multiple trophic levels in soil food webs have not been studied in semiarid grasslands experiencing soil acidification. Here we conducted a short-term N and P enrichment experiment in non-acidified and acidified soil in a semiarid grassland on the Mongolian Plateau. We found that net primary productivity was not affected by N or P enrichment alone in either non-acidified or acidified soil, but was increased by combined N and P enrichment in both non-acidified and acidified soil. Nutrient enrichment decreased the biomass of most microbial groups in non-acidified soil (the decrease tended to be greatest with combined N and P enrichment) but not in acidified soil, and did not affect most soil nematode variables in non-acidified or acidified soil. Nutrient enrichment also changed plant and microbial community structure in non-acidified but not in acidified soil, and had no effect on nematode community structure in non-acidified or acidified soil. These results indicate that the responses to short-term nutrient enrichment were weaker for higher trophic groups (nematodes) than for lower trophic groups (microorganisms) and primary producers (plants). The findings increase our understanding of the effects of nutrient enrichment on multiple trophic levels of soil food webs, and highlight that soil acidification, as an anthropogenic stressor, reduced the responses of plants and soil food webs to nutrient enrichment and weakened plant-soil interactions.

Can more carbon be captured by grasslands? A case study of Inner Mongolia, China.

Grasslands cover a large part of the Earth's surface and play an important role in the global carbon cycle. Previous studies have indicated that nearly half of the grassland vegetation cover has experienced degradation on a global scale; if this degradation is reversed, grasslands can act as potential carbon sinks. However, the question of how much more carbon (carbon gap) could be sequestrated by grassland vegetation by regulating human activities remains unanswered. Here, we present an innovative approach to assess the achievable carbon gap through focal analysis of long-term Moderate Resolution Imaging Spectroradiometer (MODIS) Net Primary Production (NPP) dataset or observed NPP (ONPP). In focal analysis, region segmentation was done to produce spatially homogeneous patches of the same types of soil, topography, and vegetation, referred to as S-T-V units, to minimize the variation in environmental conditions and their impacts on the NPP. Then, the ONPP within each S-T-V unit was rectified by offsetting the variations in potential NPP determined by the climate-oriented Miami NPP model. Hence, spatial variations in the climate-rectified ONPP (ONPPCR) in an S-T-V unit were solely determined by different human activities across locations. In a case study of the Inner Mongolia grassland of China, three focal statistics, namely mean (Mean), 95% percentile threshold (95%PCT), and maximum (Max) within each S-T-V unit were computed for ONPPCR for each year from 2000 to 2014 to assess the annual carbon uptake that was achievable by updating grassland management practices. The carbon gaps were assessed to be 11.8, 58.9, and 74.6 gC/m2 per year based on Mean, 95%PCT, and Max, respectively, compared to 65.0 gC/m2 per year based on the traditional pixel-based approach. We conclude that the carbon gap patterns identified from focal analysis are practically achievable and are more valuable in formulating policy-related decisions for grassland management. Implementing sustainable management practices that are currently being practiced at locations with high ONPPCR in neighboring degraded areas is expected to increase the carbon sequestration by grassland vegetation by one-third.

Deepened winter snow cover enhances net ecosystem exchange and stabilizes plant community composition and productivity in a temperate grassland.

Global warming has greatly altered winter snowfall patterns, and there is a trend towards increasing winter snow in semi-arid regions in China. Winter snowfall is an important source of water during early spring in these water-limited ecosystems, and it can also affect nutrient supply. However, we know little about how changes in winter snowfall will affect ecosystem productivity and plant community structure during the growing season. Here, we conducted a 5-year winter snow manipulation experiment in a temperate grassland in Inner Mongolia. We measured ecosystem carbon flux from 2014 to 2018 and plant biomass and species composition from 2015 to 2018. We found that soil moisture increased under deepened winter snow in early growing season, particularly in deeper soil layers. Deepened snow increased the net ecosystem exchange of CO2 (NEE) and reduced intra- and inter-annual variation in NEE. Deepened snow did not affect aboveground plant biomass (AGB) but significantly increased root biomass. This suggested that the enhanced NEE was allocated to the belowground, which improved water acquisition and thus contributed to greater stability in NEE in deep-snow plots. Interestingly, the AGB of grasses in the control plots declined over time, resulting in a shift towards a forb-dominated system. Similar declines in grass AGB were also observed at three other locations in the region over the same time frame and are attributed to 4 years of below-average precipitation during the growing season. By contrast, grass AGB was stabilized under deepened winter snow and plant community composition remained unchanged. Hence, our study demonstrates that increased winter snowfall may stabilize arid grassland systems by reducing resource competition, promoting coexistence between plant functional groups, which ultimately mitigates the impacts of chronic drought during the growing season.

Immunogenicity of 987P fimbriae of enterotoxigenic Escherichia coli surface-displayed on Lactobacillus casei.

As most pathogens invade the bodies through the mucosa, it is crucial to develop vaccines that induce mucosal immunity. To this end, we generated a safe and effective vaccine candidate that displayed fimbrial protein 987P of enterotoxigenic Escherichia coli (ETEC) on the surface of Lactobacillus casei (L.casei) CICC 6105 by using poly-γ-glutamate synthetase A (PgsA) as an anchoring matrix. After gavage inoculation of the recombinant strain pLA-987P/L.casei into specific-pathogen-free (SPF) BALB/c mice, high levels of mucosal immunoglobulin A (IgA) were induced in fecal samples, intestine and lung lavage fluids and systemic immunoglobulin G of IgG subclasses (IgG1, IgG2b, and IgG2a) was produced in serum. T-cell proliferation assays showed the stimulation index (SI) of the groups immunized with pLA-987P/L.casei to be significantly higher than that of the control group. The recombinant L.casei promoted T cells to produce both Th1 and Th2 cytokines, while the number of splenic IL-4 Spot forming cells (SFC) exceeded the number of IFN-γ SFC by 2.26-fold (P < .01). >83.3% of the vaccinated mice were protected from challenge with a lethal dose of virulent strain C83916. These results indicate that the recombinant L.casei expressing ETEC 987P fimbrial protein could elicit a protective immune response against ETEC 987P infection effectively.

Limited evidence for spatial resource partitioning across temperate grassland biodiversity experiments.

Locally, plant species richness supports many ecosystem functions. Yet, the mechanisms driving these often-positive biodiversity-ecosystem functioning relationships are not well understood. Spatial resource partitioning across vertical resource gradients is one of the main hypothesized causes for enhanced ecosystem functioning in more biodiverse grasslands. Spatial resource partitioning occurs if species differ in where they acquire resources and can happen both above- and belowground. However, studies investigating spatial resource partitioning in grasslands provide inconsistent evidence. We present the results of a meta-analysis of 21 data sets from experimental species-richness gradients in grasslands. We test the hypothesis that increasing spatial resource partitioning along vertical resource gradients enhances ecosystem functioning in diverse grassland plant communities above- and belowground. To test this hypothesis, we asked three questions. (1) Does species richness enhance biomass production or community resource uptake across sites? (2) Is there evidence of spatial resource partitioning as indicated by resource tracer uptake and biomass allocation above- and belowground? (3) Is evidence of spatial resource partitioning correlated with increased biomass production or community resource uptake? Although plant species richness enhanced community nitrogen and potassium uptake and biomass production above- and belowground, we found that plant communities did not meet our criteria for spatial resource partitioning, though they did invest in significantly more aboveground biomass in higher canopy layers in mixture relative to monoculture. Furthermore, the extent of spatial resource partitioning across studies was not positively correlated with either biomass production or community resource uptake. Our results suggest that spatial resource partitioning across vertical resource gradients alone does not offer a general explanation for enhanced ecosystem functioning in more diverse temperate grasslands.

Grazing simplifies soil micro-food webs and decouples their relationships with ecosystem functions in grasslands.

Livestock grazing often alters aboveground and belowground communities of grasslands and their mediated carbon (C) and nitrogen (N) cycling processes at the local scale. Yet, few have examined whether grazing-induced changes in soil food webs and their ecosystem functions can be extrapolated to a regional scale. We investigated how large herbivore grazing affects soil micro-food webs (microbes and nematodes) and ecosystem functions (soil C and N mineralization), using paired grazed and ungrazed plots at 10 locations across the Mongolian Plateau. Our results showed that grazing not only affected plant variables (e.g., biomass and C and N concentrations), but also altered soil substrates (e.g., C and N contents) and soil environment (e.g., soil pH and bulk density). Grazing had strong bottom-up effects on soil micro-food webs, leading to more pronounced decreases at higher trophic levels (nematodes) than at lower trophic levels (microbes). Structural equation modeling showed that changes in plant biomass and soil environment dominated grazing effects on microbes, while nematodes were mainly influenced by changes in plant biomass and soil C and N contents; the grazing effects, however, differed greatly among functional groups in the soil micro-food webs. Grazing reduced soil C and N mineralization rates via changes in plant biomass, soil C and N contents, and soil environment across grasslands on the Mongolian Plateau. Spearman's rank correlation analysis also showed that grazing reduced the correlations between functional groups in soil micro-food webs and then weakened the correlation between soil micro-food webs and soil C and N mineralization. These results suggest that changes in soil micro-food webs resulting from livestock grazing are poor predictors of soil C and N processes at regional scale, and that the relationships between soil food webs and ecosystem functions depend on spatial scales and land-use changes.