Alter Soil Microbial Community Research Articles

Interactions of long-term grazing and woody encroachment can shift soil biogeochemistry and microbiomes in savanna ecosystems

Semi-arid grasslands and savannas in the southern Great Plains USA are extensively used for livestock grazing. Over the past century, Juniperus (juniper) and Quercus (oak) species abundance have increased due to intensive grazing and reduced fire frequency. We investigated the interactions between livestock grazing history (none, moderate, heavy) and vegetation cover (grassland, juniper, oak) using a ∼ 70-year grazing experiment in west-central Texas. We explored effects on soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), microbial community composition, and function. SOC and TN were 50–150 % higher under juniper and oak compared to grasslands, and 10–30 % lower in grazed vs. ungrazed areas. Vegetation × grazing interaction showed greater SOC and TN loss under oak than juniper or grasslands. Ungrazed controls had higher soil TP than grazed areas, with oak and juniper soils having more TP than grasslands. Bacterial and fungal communities differed between grassland and woody vegetation. Grazing affected only bacterial communities. SOC, TN, TP accounted for differences in community structure. Abundances of genes related to methane, nitrogen, sulfur metabolisms, and dominant fungal trophic modes were linked to soil C, N, P ratios. These findings highlight how long-term livestock grazing and woody plant encroachment influence soil C, N, P cycles, altering soil microbial community structure and function. This study provides insights for savanna ecosystem management and integrating land cover effects into biogeochemical models for global change scenarios.

Direct and indirect effects of Basta®, a glufosinate-based herbicide, on banana plantation soil microbial diversity and function

Herbicide applications have doubled over the past 30 years to control weeds, but their use may influence soil microbial communities, which mediate important ecosystem services. Here, we characterised the direct effects of a single application of Basta® (glufosinate), at 1× and 2× the recommended rate (5 and 10 kg product ha−1), as well as the indirect effects of vegetation loss on the diversity and function of soil microbial communities within a banana plantation. A 10-month pre-experimental period using Basta® to remove additional vegetation from half of the experimental area created conditions for assessing the indirect herbicide effects. Direct assessments on soil microbial communities began when the Basta® herbicide treatments were applied to the areas with and without vegetation and continued over multiple time-points, for 56 days. Herbicide treatment had no significant direct impacts on basal, and substrate induced respiration rates, or the potential activities of microbial enzymes as inferred from fluorescein diacetate hydrolysis (FDA) and β-glucosidase assays. Similarly, phylogenetic marker gene sequencing indicated that Basta® application did not significantly influence the diversity of soil bacterial or fungal communities. Indirectly, Basta® had a greater influence on the soil microbial activity and functions by removing understory vegetation cover around banana plants. This suggested that continual use of herbicides to reduce soil vegetation cover under bananas had a greater impact on soil microbial communities than a single application of the herbicide. Furthermore, the presence or absence of vegetation cover, significantly altered the abundance of Fusarium oxysporum, plus an additional eight bacterial and ten fungal taxa. Our results indicated that a single application of glufosinate as Basta® at the recommended or double the recommended rate, did not adversely affect soil microbial communities or their activities in banana plantations directly. However, application of herbicides, such as Basta® in crops like banana, indirectly alters soil microbial communities and their activities through loss of vegetation cover and should only be used as a component of an integrated weed management system.

Polyethylene microplastics alter soil microbial community assembly and ecosystem multifunctionality

Although pervasive microplastics (MPs) pollution in terrestrial ecosystems invites increasing global concern, impact of MPs on soil microbial community assembly and ecosystem multifunctionality received relatively little attention. Here, we manipulated a mesocosm experiment to investigate how polyethylene MPs (PE MPs; 0, 1%, and 5%, w/w) influence ecosystem functions including plant production, soil quality, microbial community diversity and assembly, enzyme activities in carbon (C), nitrogen (N) and phosphorus (P) cycling, and multifunctionality in the maize–soil continuum. Results showed that PE MPs exerted negligible effect on plant biomass (dry weight). The treatment of 5% PE MPs caused declines in the availability of soil water, C and P, whereas enhanced soil pH and C storage. The activity of C-cycling enzymes (α/β-1, 4-glucosidase and β-D-cellobiohydrolase) was promoted by 1% PE MPs, while that of β-1, 4-glucosidase was inhibited by 5% PE MPs. The 5% PE MPs reduced the activity of N-cycling enzymes (protease and urease), whereas increased that of the P-cycling enzyme (alkaline phosphatase). The 5% PE MPs shifted soil microbial community composition, and increased the number of specialist species, microbial community stability and networks resistance. Moreover, PE MPs altered microbial community assembly, with 5% treatment decreasing dispersal limitation proportion (from 13.66% to 9.96%). Overall, ecosystem multifunctionality was improved by 1% concentration, while reduced by 5% concentration of PE MPs. The activity of α/β-1, 4-glucosidase, urease and protease, and ammonium-N content were the most important predictors of ecosystem multifunctionality. These results underscore that PE MPs can alter soil microbial community assembly and ecosystem multifunctionality, and thus development and implementation of practicable solutions to control soil MPs pollution become increasingly imperative in sustainable agricultural production.

Microbial Community Shifts with Soil Properties and Enzyme Activities in Inter-/Mono-Cropping Systems in Response to Tillage

No-till and cereal–legume intercropping have been recognized as favorable cropping practices to increase crop yields while maintaining soil quality in arid and semiarid environments, but the biological mechanisms are poorly understood. The present study aimed to determine the response of yields, soil properties, enzyme activities, and microbial community diversity and composition in mono- and inter-cropping under conventional and no-tillage conditions. We initiated a field experiment in Wuwei, a typical arid area of China, in 2014. Soil was sampled in August 2022 and, yields, soil properties, enzyme activities, and the microbial community diversity and composition were determined in the maize and pea strips in inter- and mono-cropping systems. Results revealed that the maize and pea strips in the no-till intercropping significantly increased yields, total and organic carbon stocks, decreased NO3−-N, and obtained the highest total and organic P in the soil. No-tillage significantly enhanced the Shannon index and Pielou evenness of the bacterial community and total microbial community over conventional tillage, with the α-diversity of the bacterial community and total microbial community distinctly higher in the NTIM treatment than in the CTIM treatment. The α-diversity of the total microbial community was significantly related to yield, soil IC and OC, and the α-diversity of the archaea community was significantly related to soil TC, TC/TP, TN/TP, and BX. Meanwhile, the α-diversity of the eukaryote community was significantly related to soil yield, soil TC/TP. Both no-tillage and intercropped maize significantly increased the abundance of archaea phylum Thaumarchaeota and bacterial phylum Nitrospirae, and were significantly positively associated with soil OC and NH4+-N, benefiting nitrogen fixation of intercropped pea from the atmosphere under the no-tillage cereal/legume intercropping. No-till intercropping was conducive to the accumulation of organic carbon, while decreasing the abundance of Proteobacteria, Acidobacteria, and Verrucomicrobia. Limited soil enzyme activities (ACP, ALP, DP, NAG, BG, AG, CB) led to decreases in organic carbon turnover and utilization. Intercropping altered soil microbial community diversity and composition due to changes in soil properties and enzyme activities. These findings suggest that no-tilled cereal–legume intercropping is a sustainable cropping practice for improving soil properties and enhancing microbial (archaea, bacterial, eukaryota) diversity, but the persistence is not conducive to rapid turnover of soil nutrients due to limited enzyme activities.

Plastic residues alter soil microbial community compositions and metabolite profiles under realistic conditions

Wide usage of plastic coupled with mismanagement has created a humongous environmental hazard threatening entire ecosystems. To date, the potential effects of plastic debris-induced soil nutrition substance changes and the relevant microbial metabolic behavior remain unclear. Here, we studied the effect of plastic films polyethylene and polylactic acid in differential soil environments (farmland, woodland, and wetland) for 120 days. Soil enzyme activities (urease, neutral phosphatase, and catalase) and nutrition substance (NH4+-N, available P, available K, and soil organic matter) present obvious variations in polylactic acid groups compared to polyethylene-treated samples. 16S rRNA gene sequencing indicates that several bacteria abundance such as Bacteroidales, Actinobacteriota, Nitrososphaeraceae, Pyrinomonadalcs, Muribaculaceae, exhibited obvious up-regulation or down-regulation, and simultaneously, the carbon, nitrogen, and phosphorus cycling relevant species Bryobacter, Bradyrhizobium, and Sphingomonas, expressed wider margin of down-regulation in abundance in plastic treatment soil samples. As a result, the abundance of metabolites including sugar, amino acid, and fatty acids, which may associated with nutrition substance metabolic pathways, were significantly altered in the stress of plastic. These findings provide valuable information on the environmental effects of plastics, and the relationships of subsequent nutrition substance changes and microbial metabolic behavior.

The responses of soil Cd fractions to disinfestation regimes associated with microbial communities

While reductive soil disinfestation (RSD)-related practices have been shown to mediate soil cadmium (Cd) fraction to a certain extent, the underlying mechanisms remain unclear. Here, a pot experiment was conducted to investigate the effects of various reductive soil disinfestation regimes on Cd fraction and its driving mechanisms underlying them. Five Cd fractions, soil physicochemical properties as well as microbial communities were simultaneously measured. Results revealed that, relative to the control treatment, all RSD-related regimes contributed to decrease exchangeable Cd fraction (EX-Cd) by transforming it to unexchangeable Cd fractions (RES-Cd CB/OX-Cd fractions) (P < 0.05). RSD with Hermetia illucens L. feces treatment (abbr.: HI treatment) had the greatest reduction rate (9.7 %), which higher than that of other treatment (3.5 % and 2.6 %), this largely attributed to more functional genera in association with Cd fixation and Fe (III) reduction enriched. In addition, soil disinfestation regimes altered soil microbial community composition and structure, which was a critical factor responsible for the changes of soil Cd fraction. Correlation analysis showed that the changes of Cd fraction were closely related to biotic and abiotic factors. Both pH and soil organic material were main abiotic factors, while microbial groups, including Bacteroidetes, Hydrogenedentes (Hydrogenispora), Ascomycota, Acidobacteria and Verrucucomicrobia were key biotic factors for Cd conversion and immobilization. The validation experiment in four vegetables further confirmed that RSD-related regimes were indeed favorable for decreasing soil availability and plant uptake of Cd by improving soil pH, and HI treatment showed optimal remediation and utilization potential to Cd-contaminated soils. Together, the results provide a theoretical basis and reference for the RSD-related disinfestation regimes in remediation of Cd-contaminated soils, and highlighted the significant potential of Hermetia illucens L. feces as a novel addition in RSD technology for reducing available Cd from soils.

Long-term plastic film mulching altered soil physicochemical properties and microbial community composition in Shiyang River Basin, Northwest China

Plastic film mulching (PM) is used widely to improve crop water productivity in the arid regions of Northwest China. However, there are increasing concerns about the potential harm to soil health due to the presence of residue plastic film (RPF) mixed into the soil after long-term field mulching. In our study, we investigated the density of RPF in farmland topsoil (0 to 40 cm) (Exp. I) by analyzing 75 soil samples collected from 15 fields with varying durations of PM (ranging from 3 to 27 years). In addition, we examined the impact of long-term PM and PM + BM (BM, biodegradable film mulching) on soil health (Exp. II) based on an 8-year field experiment. The results illustrated that the weight of RPF ranged from 42.7 to 165.9 kg ha−1 after 3 to 27 years of mulching, with 10 out of 15 fields exceeded the national standard of China (75 kg ha−1). Compared with no film mulching treatment (NM), the long-term PM treatment significantly increased aggregate stability, while significantly decreased soil pH and the enzymatic activities of sucrase by 1.5 % and 33.4 %, respectively. Further, the Chao1, Shannon and Pielou's indices of bacteria significantly decreased after 8 years of PM. Compared with PM and NM, PM + BM treatment significantly improved the Chao1, Shannon and Pielou's indices of bacteria and altered the relative abundance of dominant bacterial and fungal phyla. The principal coordinates analysis (PCoA) revealed significant changes in the soil bacterial and fungal community structure under PM + BM, with the soil fungal community displaying higher sensitivity to PM + BM compared to PM. No significant differences were observed in soil organic matter (SOM), soil microbial biomass C (MBC), soil microbial biomass N (MBN) contents and the enzymatic activities of soils between PM + BM and PM treatments. Overall, BM could be a promising alternative to polyethylene plastic film for improving soil health and is recommended for farming practice in the arid regions of Northwest China.

The effect of prescribed fires on abiotic and biotic factors in the southern region of Puerto Rico

Field fires can modify soil nutrient cycling and alter soil microbial communities (SMC), although the latter is not well understood. In the southern region of Puerto Rico, field fires have become a significant problem during the dry season. To mimic the effects of a field fire, we performed prescribed fires on a hillside at the Juana Díaz Agricultural Experiment substation in October 2015 and March 2017. A complete randomized block design was established in Yauco soil (Typic calciustolls) that included the following treatments: negative control (unburned), positive control (burned plots, no remediation), mulching treatment (burned plots remediated with Leucaena spp. mulch), and surfactant treatment (burned plots remediated with a surfactant). In the first burning (2015), soil samples were collected before burning and at 30, 180, and 420 days after burning (DAB). In the second burning (2017), soil samples were collected at 30, 90, and 270 DAb. soil physicochemical properties and microbial community structure were assessed using phospholipid fatty acid (PLFA) analysis. Overall, burning increased soil exchangeable Ca2+ (except after 30 DAB in the second burning) and decreased exchangeable K+ when compared to unburned soils. compared to unburned plots, total fungal PLFA was significantly lower in burned plots with or without mulch and surfactant treatments, and total bacterial PLFA did not differ between burned and unburned plots after 30 days. Total microbial biomass was significantly (P&lt;0.05) higher in mulch and surfactant treated burned soil compared to unburned and burned plots without treatment after 90 DAB (2017) and 420 (2015) DAB. The use of mulch and surfactant treatments in prescribed burning fields increased microbial communities 90 DAB. This study emphasizes short-term changes in microbial communities and suggests they are highly resilient to disturbances after prescribed fires.

The response of soil respiration to land‐use change depends on soil microbial community being regulated by edaphic factors in the Loess Plateau, China

AbstractLand‐use change has significant influences on soil respiration (Rs) in terrestrial ecosystems. Soil microbes play critical roles in soil carbon cycling. Nevertheless, the specific mechanism of how changes in soil microbial properties are linked to the variation of Rs rate during land‐use change still remains poorly understood, especially in the Loess Plateau, China. Here, the characteristics of Rs rate and soil microbial community following the land‐use change from farmland to plantation/grassland were analyzed via an automated soil CO2 flux system and high‐throughput 16S rDNA gene sequencing. The afforestation altered soil microbial diversity and community composition, which was mainly explained by soil pH, temperature, organic matter, nitrate, alkali‐hydrolyzed nitrogen, and available phosphorus. The biomarkers of Bacteroidetes, Firmicutes, and Thaumarchaeota were found in farmland soil at the phylum level. The afforestation also significantly decreased Rs rate, which was closely related to Shannon's index, Simpson's index, and some microbial taxa, such as Bacteroidetes, Firmicutes, Nitrospirae, and Acidobacteria. Bacteroidetes, and Firmicutes were particularly expected to be important drivers of high Rs rate in farmland soil. Moreover, the microbial interaction was probably also an important factor affecting Rs rate. Our results indicate that the response of Rs to land‐use change depends on soil microbial community being regulated by soil physicochemical properties in the Loess Plateau, China.

Disturbance of eucalypt forests alters the composition, function, and assembly of soil microbial communities.

Forest disturbance has well-characterized effects on soil microbial communities in tropical and northern hemisphere ecosystems, but little is known regarding effects of disturbance in temperate forests of the southern hemisphere. To address this question, we collected soils from intact and degraded Eucalyptus forests along an east-west transect across Tasmania, Australia, and characterized prokaryotic and fungal communities using amplicon sequencing. Forest degradation altered soil microbial community composition and function, with consistent patterns across soil horizons and regions of Tasmania. Responses of prokaryotic communities included decreased relative abundance of Acidobacteriota, nitrifying archaea, and methane-oxidizing prokaryotes in the degraded forest sites, while fungal responses included decreased relative abundance of some saprotrophic taxa (e.g. litter saprotrophs). Forest degradation also reduced network connectivity in prokaryotic communities and increased the importance of dispersal limitation in assembling both prokaryotic and fungal communities, suggesting recolonization dynamics drive microbial composition following disturbance. Further, changes in microbial functional groups reflected changes in soil chemical properties-reductions in nitrifying microorganisms corresponded with reduced NO3-N pools in the degraded soils. Overall, our results show that soil microbiota are highly responsive to forest degradation in eucalypt forests and demonstrate that microbial responses to degradation will drive changes in key forest ecosystem functions.

Seasonality and bacterial community assembly processes dominate prairie ecosystem service disruption during invasion

Invasive plants alter soil microbial communities and ecosystem services reducing the Earth's carrying capacity for humans. Many ecosystem services are underpinned by soil microbial communities, and these communities arise from assembly processes that are likely altered by invasion. We evaluated the hypothesis that invasive effects on grassland ecosystem services arise from changes in microbial community assembly processes caused by invasion. We sampled 515 plots at a native Rough Fescue prairie undergoing invasion by nine invasive species of which smooth brome (Bromus inermis) is a dominant member. Each week, for 26 weeks, we monitored invasion effects on vascular plant communities, ecosystem services, as well as bacterial and fungal community structures. Invasive effects on ecosystem services interacted with seasonal (plant green-up, peak biomass, and plant senescence) effects and consistently disrupted ecosystem service provision. Invasion increased heterogenous selection in fungal communities but otherwise had minor effects on assembly process. Only ∼20% of community composition could be ascribed to deterministic filters which hindered our ability to conclusively link invasion to assembly processes. Assembly processes explained changes in ecosystem services with bacterial assembly accounting for 2.5% of food, 4% of climate, 9% of conservation and 5.5% of fertility services. Fungal communities were less consistent in their effects on ecosystem services with only food (3%) and water (4%) services influenced by fungal assembly. After seasonality (27%), bacterial assembly processes (4%) accounted for the largest effect on ecosystem services, overshadowing invasion (2%) and fungal assembly (2%). At this 130-ha site, after seasonal effects, bacterial assembly processes had the largest effect on ecosystem services with plant invasion placing a distant third.

Response of heavy-metal and antibiotic resistance genes and their related microbe in rice paddy irrigated with treated municipal wastewaters

Paddy irrigation with secondary effluents from municipal wastewater treatment plants (MWTPs) is a well-established practice to alleviate water scarcity. However, the reuse might lead to more complicated contamination caused by interactions between residual antibiotics in effluents and heavy metals in paddy soil. To date, no information is available for the potential effects of dual stress of heavy metals and antibiotics on heavy-metal resistance genes (MRGs) and antibiotic resistance genes (ARGs). Here, this study investigated the response of heavy metal and antibiotic resistance genes, and related microorganisms to the dual threat of antibiotics and heavy metals under the long-term MWTP effluent irrigation for rice paddy using metagenome. The results showed that there was not a negative effect on rice consumption if MWTP effluent was used to irrigate rice for a long time. The concentration of antibiotics could reshape the ARGs and MRG profiles in rice paddy soil. The findings revealed the co-occurrence of ARGs and MRGs in rice paddy soils, thus highlighting the need for simultaneous elimination of antibiotics and heavy metals to effectively reduce ARGs and MRGs. Acn and sul1 genes encoding Iron and sulfonamides resistance mechanisms are the most abundant MRG and ARG, respectively. Network analysis revealed the possibility that IntI1 plays a role in the co-transmission of MRG and ARG to host microbes, and that Proteobacteria are the most dominant hosts for MRG, ARG, and integrons. The presence of antibiotics in irrigated MWTP effluents has been found to stimulate the proliferation of heavy metal and antibiotic resistances by altering soil microbial communities. This study will enhance our comprehension of the co-selection between ARGs and MRGs, as well as reveal the concealed environmental impacts of combined pollution. The obtained results have important implications for food safety and human health in rice.

Urbanization reduces soil microbial network complexity and stability in the megacity of Shanghai

Urbanization is altering the co-occurrence networks of ecological communities that are critical to maintaining ecosystem functions and services. Soil microbial communities play key roles in various ecosystem processes, but how soil microbial co-occurrence networks respond to urbanization is unclear. Here we analyzed co-occurrence networks in soil archaeal, bacterial, and fungal communities from 258 soil sampling sites across the megacity of Shanghai along large urbanization gradients. We found that topological features of microbial co-occurrence networks were strongly altered by urbanization. In particular, microbial communities in more urbanized land-use and highly impervious land cover had less connected and more isolated network structures. These structural variations were accompanied by the dominance of connectors and module hubs affiliated with the Ascomycota in fungi and Chloroflexi in bacteria, and there were greater losses in efficiency and connectivity in urbanized than in remnant land-use in simulated disturbances. Furthermore, even though soil properties (especially soil pH and organic carbon) were major factors shaping topological features of the microbial networks, urbanization still uniquely explained a proportion of the variability, particularly those describing network connections. These results demonstrate that urbanization has clear direct and indirect effects on microbial networks and provide novel insights into how urbanization alters soil microbial communities.

Natural restoration alters soil microbial community structure, but has contrasting effects on the diversity of bacterial and fungal assemblages in salinized grasslands

Natural restoration has often been considered an effective measure for rehabilitating degraded ecosystems. However, its impact on the structure and diversity of soil microbial communities, particularly within a salinized grassland during its restoration succession, remains unclear. In this study, we examined the effects of natural restoration on the Shannon-Wiener diversity index, Operational Taxonomic Units (OTU) richness, and structure of the soil microbial community of a sodic-saline grassland in China using high-throughput amplicon sequencing data from representative successional chronosequences. Our results indicated that natural restoration resulted in a significant mitigation of the grassland salinization (pH from 9.31 to 8.32 and electrical conductivity from 393.33 to 136.67 μs·cm−1) and a significant alteration of the soil microbial community structure of the grassland (p < 0.01). However, the effects of natural recovery differed in terms of the abundance and diversity of bacteria and fungi. For example, the relative abundance of the bacterial phyla Acidobacteria increased by 116.45 % in the topsoil and 339.03 % in the subsoil, while that of the fungal phyla Ascomycota decreased by 8.86 % in the topsoil and 30.18 % in the subsoil. There was no significant effect of restoration on bacterial diversity, but fungal diversity increased by 15.02 % in the Shannon-Wiener index and 62.20 % in the OTU richness in the topsoil. Model-selection analysis further corroborated that the alteration of the soil microbial structure by natural restoration may be due to the fact that the bacteria could adapt to the alleviated salinized grassland soil and the fungi could adapt to the improved soil fertility of the grasslands. Overall, our results contribute to an in-depth understanding of the impacts of natural restoration on soil microbial diversity and community structure in salinized grasslands during the long-term successional course. This may also help to apply natural restoration as a greener practice option for managing degraded ecosystems.

Contrasting sensitivity of soil bacterial and fungal community composition to one year of water limitation in Scots pine mesocosms.

The soil microbiome is crucial for regulating biogeochemical processes and can thus strongly influence tree health, especially under stress conditions. However, little is known about the effect of prolonged water deficit on soil microbial communities during the development of saplings. We assessed the response of prokaryotic and fungal communities to different levels of experimental water limitation in mesocosms with Scots pine saplings. We combined analyses of physicochemical soil properties and tree growth with DNA metabarcoding of soil microbial communities throughout four seasons. Seasonal changes in soil temperature and soil water content and a decreasing soil pH strongly influenced the composition of microbial communities but not their total abundance. Contrasting levels of soil water contents gradually altered the soil microbial community structure over the four seasons. Results indicated that prokaryotic communities were less resistant to water limitation than fungal communities. Water limitation promoted the proliferation of desiccation-tolerant, oligotrophic taxa. Moreover, water limitation and an associated increase in soil C/N ratio induced a shift in the potential lifestyle of taxa from symbiotic to saprotrophic. Overall, water limitation appeared to alter soil microbial communities involved in nutrient cycling, pointing to potential consequences for forest health affected by prolonged episodes of drought.

Litter inputs exert greater influence over soil respiration and its temperature sensitivity than roots in a coniferous forest in north-south transition zone

The changes in carbon inputs of litter and roots to forest soils caused by climate change will result in a serious cascade effect on soil respiration and its temperature sensitivity (Q10). To differentiate and quantify the effects of surface litter and living roots on soil respiration and Q10, and further explore the role of abiotic factors and microbial properties on soil respiration and Q10, a short-term (two years) detritus input and removal treatment experiment was conducted in a coniferous forest of central China. Soil temperature, soil moisture, C/N, microbial biomass and community composition were analyzed to explore the drive mechanisms of soil respiration and Q10 in response to carbon inputs. The results showed that litter addition increased soil respiration by 22 %, while litter or roots removal did not affect soil respiration, which might be ascribed to the “priming effects” mediated by fresh plant litter. We also found that litter addition increased Q10, while litter removal decreased Q10. Litter addition significantly enhanced the microbial biomass for any single functional group and altered soil microbial community composition. Structural equation model further proved that microbial biomass and community composition exerted stronger impacts on Q10 than do soil abiotic factors. Soil moisture, microbial biomass and community structure were main factors in predicting soil respiration. The study highlights the important role of litter inputs compared with living roots in carbon cycling in short-term and deepens our understanding on the complex relationships among soil respiration, soil micro-environment and microbial community composition.

Inoculations of phosphate-solubilizing bacteria alter soil microbial community and improve phosphorus bioavailability for moso bamboo (Phyllostachys edulis) growth

Moso bamboo plantations suffer from phosphorus (P) limitations. A better understanding of soil P cycling contributes to the sustainable management and development of the bamboo forests. In this study, different phosphate-solubilizing bacteria (PSB) were applied to soils to stimulate bamboo growth, and the metagenomics method was employed to investigate the changes in soil microbial communities and relative abundances of functional genes. Meanwhile, soil properties and bamboo biomass and physiological indices were also quantitatively analyzed. The PSB inoculations changed soil P fractions and significantly elevated available P (AP) content by stimulating phosphatase activity and functional genes involved in P-transformation. The PSB inoculations significantly stimulated soil acid phosphatase activities and enhanced the relative abundances of functional genes associated with inorganic P-solubilization and organic P-mineralization. Moreover, increased soil available nutrients were beneficial to the moso bamboo growth, and the bamboo biomass in the different treatments increased by from 32.43 % to 69.04 % compared with the control treatment. Significant increases in root activity, carotenoid, chlorophyll a and total chlorophyll contents after the PSB inoculations also contributed to moso bamboo growth. The PSB strain inoculations shaped soil microbial communities and increased microbial connections. Besides adjusting soil P supplies and functional genes, the PSB also promoted the moso bamboo growth by increasing soil mineral N, AK and bamboo chlorophyll contents and stimulating functional microorganisms. Our study could provide a theoretical basis to improve soil nutrient utilization for moso bamboo with the PSB inoculations.

Nanoplastics alter ecosystem multifunctionality and may increase global warming potential.

Although the presence of nanoplastics in aquatic and terrestrial ecosystems has received increasing attention, little is known about its potential effect on ecosystem processes and functions. Here, we evaluated if differentially charged polystyrene (PS) nanoplastics (PS-NH2 and PS-SO3 H) exhibit distinct influences on microbial community structure, nitrogen removal processes (denitrification and anammox), emissions of greenhouse gases (CO2 , CH4 , and N2 O), and ecosystem multifunctionality in soils with and without earthworms through a 42-day microcosm experiment. Our results indicated that nanoplastics significantly altered soil microbial community structure and potential functions, with more pronounced effects for positively charged PS-NH2 than for negatively charged PS-SO3 H. Ecologically relevant concentration (3 g kg-1 ) of nanoplastics inhibited both soil denitrification and anammox rates, while environmentally realistic concentration (0.3 g kg-1 ) of nanoplastics decreased the denitrification rate and enhanced the anammox rate. The soil N2 O flux was always inhibited 6%-51% by both types of nanoplastics, whereas emissions of CO2 and CH4 were enhanced by nanoplastics in most cases. Significantly, although N2 O emissions were decreased by nanoplastics, the global warming potential of total greenhouse gases was increased 21%-75% by nanoplastics in soils without earthworms. Moreover, ecosystem multifunctionality was increased 4%-12% by 0.3 g kg-1 of nanoplastics but decreased 4%-11% by 3 g kg-1 of nanoplastics. Our findings provide the only evidence to date that the rapid increase in nanoplastics is altering not only ecosystem structure and processes but also ecosystem multifunctionality, and it may increase the emission of CO2 and CH4 and their global warming potential to some extent.

Changes in soil fertility and microbial communities following cultivation of native grassland in Horqin Sandy Land, China: a 60-year chronosequence

BackgroundGrassland conversion to cropland is a prevailing change of land use in traditionally nomadic areas, especially in the Mongolian Plateau. We investigated the effects of grassland conversion followed by continuous cultivation on soil properties and microbial community characteristics in Horqin Sandy Land, a typical agro-pastoral transition zone of Northern China. Soil samples were collected from the topsoil (upper 20 cm) across a 60-year cultivation chronosequence (5, 15, 25, 35 and 60 years) and unconverted native grassland. Soil physico-chemical properties were determined and high-throughput sequencing was used to assess microbial community diversity and composition.ResultsGrassland cultivation resulted in changes to soil properties in both the short and longer term. Initially, it significantly increased soil bulk density (BD), electrical conductivity (EC), soil total nitrogen (TN), available phosphorus (AP) and available potassium (AK) concentrations, while reducing soil water content (SWC) and soil organic carbon content (SOC). Over the next 35–55 years of continuous cultivation, the trend for most of these characteristics was of reversion towards values nearer to those of native grassland, except for SOC which remained highly depleted. Cultivation of grassland substantially altered soil microbial communities at phylum level but there was no significant difference in microbial α-diversity between native grassland and any cropland. However, soil bacterial and fungal community structures at phylum level in the croplands of all cultivation years were different from those in the native grasslands. Heatmaps further revealed that bacterial and fungal structures in cropland tended to become more similar to native grassland after 15 and 25 years of cultivation, respectively. Redundancy analysis indicated that SOC, EC and BD were primary determinants of microbial community composition and diversity.ConclusionsThese findings suggest that agricultural cultivation of grassland has considerable effects on soil fertility and microbial characteristics of Horqin Sandy Land. Intensive high-yield forage grass production is proposed as an alternative to avoid further native grassland reclamation, while meeting the grazing development needs in the ethnic minority settlements of eco-fragile regions.

Taxonomical and functional responses of microbial communities from forest soils of differing tree species diversity to drying-rewetting cycles

The predicted increases in drought in many forest ecosystems may alter soil microbial community diversity and activity, which may further depend on tree species richness. Shifts in microbial community composition and activity could engender changes in ecosystem function, notably, in soil greenhouse gas emissions and C storage. Using soils from mono-specific and mixed three-species forest stands from across Europe, we performed a microcosm experiment to test how soil microbial taxonomic and catabolic diversity are affected by repeated drying-rewetting (DRW) cycles and tree species mixing. We used Illumina sequencing and MicroResp™ analyses to explore community-level changes between microbial functional groups. DRW decreased bacterial richness and carbon substrate use diversity and increased fungal Shannon diversity. Additionally, microbial communities exposed to DRW changed their consumption of 11 out of 15 substrates significantly, suggesting microbial functional shifts. The legacy effect of tree species mixing influenced the structure of the microbial communities (i.e. taxonomic differential abundance) although, community weighted mean (CWM) values of absorptive root traits appeared to affect more strongly microbial richness, relative abundance, and Shannon diversity. No significant tree species mixing:DRW interaction was found for most microbial variables, except for the use of certain substrates and potentially differential abundance. Our data from a laboratory experiment with soils from different forest ecosystems underline that drought may cause shifts in microbial taxonomic and catabolic diversity, while tree species influences primarily taxonomic diversity through root traits.