Changes In Soil Bacterial Community Research Articles

Topsoil Bacterial Community Changes and Nutrient Dynamics Under Cereal Based Climate-Smart Agri-Food Systems.

Soil microorganisms play a critical role in soil biogeochemical processes, nutrient cycling, and resilience of agri-food systems and are immensely influenced by agronomic management practices. Understanding soil bacterial community and nutrient dynamics under contrasting management practices is of utmost importance for building climate-smart agri-food systems. Soil samples were collected at 0–15 cm soil depth from six management scenarios in long-term conservation agriculture (CA) and climate-smart agriculture (CSA) practices. These scenarios (Sc) involved; ScI-conventional tillage based rice-wheat rotation, ScII- partial CA based rice-wheat-mungbean, ScIII- partial CSA based rice-wheat-mungbean, ScIV is partial CSA based maize-wheat-mungbean, ScV and ScVI are CSA based scenarios, were similar to ScIII and ScIV respectively, layered with precision water & nutrient management. The sequencing of soil DNA results revealed that across the six scenarios, a total of forty bacterial phyla were observed, with Proteobacteria as dominant in all scenarios, followed by Acidobacteria and Actinobacteria. The relative abundance of Proteobacteria was 29% higher in rice-based CSA scenarios (ScIII and ScV) and 16% higher in maize-based CSA scenarios (ScIV and ScVI) compared to conventional-till practice (ScI). The relative abundance of Acidobacteria and Actinobacteria was respectively 29% and 91% higher in CT than CSA based rice and 27% and 110% higher than maize-based scenarios. Some taxa are present relatively in very low abundance or exclusively in some scenarios, but these might play important roles there. Three phyla are exclusively present in ScI and ScII i.e., Spirochaetes, Thermi, and Euryarchaeota. Shannon diversity index was 11% higher in CT compared to CSA scenarios. Maize based CSA scenarios recorded higher diversity indices than rice-based CSA scenarios. Similar to changes in soil bacterial community, the nutrient dynamics among the different scenarios also varied significantly. After nine years of continuous cropping, the soil organic carbon was improved by 111% and 31% in CSA and CA scenarios over the CT scenario. Similarly, the available nitrogen, phosphorus, and potassium were improved by, respectively, 38, 70, and 59% in CSA scenarios compared to the CT scenario. These results indicate that CSA based management has a positive influence on soil resilience in terms of relative abundances of bacterial groups, soil organic carbon & available plant nutrients and hence may play a critical role in the sustainability of the intensive cereal based agri-food systems.

Biochar-induced changes in soil microbial affect species of antimony in contaminated soils

Antimony (Sb) is a highly toxic heavy metal, and the amount of Sb in the soil is increasing due to anthropogenic activities. Recently, biochar (BC) has been used for remediation of Sb-contaminated soil, therefore, understanding the effect of BC-induced changes in soil microbial on the change of Sb speciation will help to elucidate the mechanism of BC in immobilization/mobilization of Sb in contaminated soils.Sb-contaminated soil with 10 wt % of Wheat straw-derived BC (SBC) and fruit (apple) tree-derived BC (FBC) and control was incubated for 130 days. Changes of soil bacterial community composition and Sb oxidation gene induced by BC were explored during the incubation. Dynamic change of Sb speciation was assessed by the citric acid extraction. The redundancy analysis (RDA) and spearman analysis (PCA) was used to analyze the relationship between Sb immobilization/mobilization and change of soil bacterial community induced by BC. The soil properties change induced by BC affected soil bacterial community composition, and Sb mobilization was strongly related to the change of soil bacterial community composition. The relative abundance of Sb oxidation gene increased in the soil amended by BC, which proved that oxidation of Sb(III) after 20 d incubation with SBC and 50 d incubation with FBC incubation.It is noteworthy that the application of BC has a potential mobilizing risk for Sb and both the change of soil bacteria and soil chemical properties play an important role in Sb mobilization. The possible risks induced by BC should be considered before applying the BC to Sb contaminated soil.

Critical transition of soil bacterial diversity and composition triggered by nitrogen enrichment.

Soil bacterial communities are pivotal in regulating terrestrial biogeochemical cycles and ecosystem functions. The increase in global nitrogen (N) deposition has impacted various aspects of terrestrial ecosystems, but we still have a rudimentary understanding of whether there is a threshold for N input level beyond which soil bacterial communities will experience critical transitions. Using high-throughput sequencing of the 16S rRNA gene, we examined soil bacterial responses to a long-term (13yr), multi-level, N addition experiment in a temperate steppe of northern China. We found that plant diversity decreased in a linear fashion with increasing N addition. However, bacterial diversity responded nonlinearly to N addition, such that it was unaffected by N input below 16g N·m-2 ·yr-1 , but decreased substantially when N input exceeded 32g N·m-2 ·yr-1 . A meta-analysis across four N addition experiments in the same study region further confirmed this nonlinear response of bacterial diversity to N inputs. Substantial changes in soil bacterial community structure also occurred between N input levels of 16 to 32g N·m-2 ·yr-1 . Further analysis revealed that the loss of soil bacterial diversity was primarily attributed to the reduction in soil pH, whereas changes in soil bacterial community were driven by the combination of increased N availability, reduced soil pH, and changes in plant community structure. In addition, we found that N addition shifted bacterial communities toward more putatively copiotrophic taxa. Overall, our study identified a threshold of N input level for bacterial diversity and community composition. The nonlinear response of bacterial diversity to N input observed in our study indicates that although bacterial communities are resistant to low levels of N input, further increase in N input could trigger a critical transition, shifting bacterial communities to a low-diversity state.

Successional trajectory of bacterial communities in soil are shaped by plant-driven changes during secondary succession

This study investigated the potential role of a nitrogen-fixing early-coloniser Alnus Nepalensis D. Don (alder) in driving the changes in soil bacterial communities during secondary succession. We found that bacterial diversity was positively associated with alder growth during course of ecosystem development. Alder development elicited multiple changes in bacterial community composition and ecological networks. For example, the initial dominance of actinobacteria within bacterial community transitioned to the dominance of proteobacteria with stand development. Ecological networks approximating species associations tend to stabilize with alder growth. Janthinobacterium lividum, Candidatus Xiphinematobacter and Rhodoplanes were indicator species of different growth stages of alder. While the growth stages of alder has a major independent contribution to the bacterial diversity, its influence on the community composition was explained conjointly by the changes in soil properties with alder. Alder growth increased trace mineral element concentrations in the soil and explained 63% of variance in the Shannon-diversity. We also found positive association of alder with late-successional Quercus leucotrichophora (Oak). Together, the changes in soil bacterial community shaped by early-coloniser alder and its positive association with late-successional oak suggests a crucial role played by alder in ecosystem recovery of degraded habitats.

Effects of Italian ryegrass residues as green manure on soil properties and bacterial communities under an Italian ryegrass (Lolium multiflorum L.)-rice (Oryza sativa L.) rotation

Green manure shows promise for the relief of the environmental pressure caused by successive farming and excessive applications of fertilizers. Soil microbes play an important role in the decomposition of green manure. However, few studies focused on the relationship between the release of nutrients and bacterial community diversity when different rates of green manure are applied. The aim of this study was to evaluate the dynamic changes in soil bacterial communities and nutrient release during the decomposition of the green manure Italian ryegrass (Lolium multiflorum L.) residues in a new type Italian ryegrass-rice (Oryza sativa L.) rotation (IRR) system in South China. Six different rates (P0–P5) of Italian ryegrass were added to rice-growing red soil (Ferralic Cambisol) and allowed to decompose for 40 d (sampled every 10 d). Nutrient release and soil properties were determined during the decomposition and Illumina reads of the 16S rRNA gene amplicons were used to analyse changes in the bacterial communities. The addition of residues increased both nutrient concentrations (e.g., total nitrogen, available nitrogen and available potassium) and the relative abundance of microbes involved in nutrient cycling (e.g., Proteobacteria, Bacteroidetes, Acidobacteria, and Gemmatimonadetes). Italian ryegrass residues had much faster rates of decomposition at 1–10 d, 11–20 d, and 21–30 d (from 183.2 to 238.1 g kg–1, on average) than that (45.6 g kg–1) at 31–40 d. Overall, the high green manure decomposition rates were accompanied by high similarities in bacterial community structures during decomposition. The nutrient cycle efficiency and bacterial community diversity were higher when the soils were treated with 40,170–44,895 kg ha–1 (P3–4) of green manure than other treatments. The average Shannon index values following the 44,895 kg ha–1 (P4) treatment were the highest among the different rates of residue application, and they were 6.42 at 10 d, 6.37 at 20 d, 6.29 at 30 d, and 6.53 at 40 d. The highest soil total nitrogen concentrations of 1.4–2.0 g kg–1 were obtained following the 40,170 kg ha–1 (P3) treatment, and seedling biomass increased the most under P3 treatment. In addition, soil total nitrogen and available potassium concentrations were significantly correlated with rice seedling biomass. This study demonstrates that the management of green manure application based on the IRR system facilitates rice growth by improving bacterial communities (composition and diversity) and soil fertility, and it provides a new perspective on the links between potential microbial community functions and organic agro-ecosystems.

Soil fertility and crop production are fostered by micro-nano bubble irrigation with associated changes in soil bacterial community

The improvement of aeration conditions in the rhizosphere is beneficial for crop growth and productivity. However, its effects on the soil microbial community are less known. Due to microbial sentivity to environmental changes, transporting micro-nano bubble water (MNBW) to the crop rhizosphere is expected to shift soil microbial community. A two-year MNBW irrigation field experiment consisting of two mixing ratios of MNBW and groundwater (high level of MNBW, 1:0 and low level of MNBW, 1:4), and a control treatment (CK, groundwater without MNBs), was conducted in a sugarcane plantation station at Guangxi, China. The results indicated that MNBW irrigation, particularly with the high level, changed the composition and potential functionality of the soil bacterial community, reduced its diversity and altered microbial co-occurrence patterns. Structural equation modeling (SEM) demonstrated that MNBW irrigation directly affected soil microbial community and soil fertility, and indirectly promoted sugarcane yield. Overall, this study highlighted that the application of MNBW improved plant yield, and this response was strongly associated with a better nutritional content of MNBW irrigated soils and changes in the bacterial community.

Changes in soil bacterial community as affected by soil compaction, soil water content and plant roots

The present study assessed the effects of compaction on temporal dynamics of soil microbial communities and whether these changes were influenced by the presence of plant roots and soil water content. A pot trial comprised three levels of compaction (1.1 gcm-3 – un-compacted; 1.25 gcm-3 – moderately-compacted; 1.4 gcm-3 – heavily-compacted), two levels of irrigation regimes (60 and 80% FC), and two soil conditions (planted soil versus free root soil) was established. Soil microbial attributes investigated included bacterial activity and diversity, which were obtained from five sampling times (5; 10; 15; 20; 30 days). The results showed that bacterial activity and diversity changes over time and were higher in un-compacted soil treatment at day-20. Bacterial activity and diversity were higher in moderately-compacted soil with high soil moisture level (80% FC). Microbial activity and diversity were weakly correlated with the presence of plant roots particularly when soil was heavily compacted. Given the changes of microbial communities that followed changes in soil moisture availability, it was, therefore, concluded that management of the timing of irrigation inputs is needed in order to maintain microbial communities in soil.

Soil bacterial communities in grasslands revegetated using Elymus nutans are largely influenced by soil pH and total phosphorus across restoration time

AbstractSoil microbial communities have been considered indicators of soil quality and fertility changes in restored ecosystems. Little is known, however, about how these communities change over time after restoration in terms of activity, structure, and diversity. We evaluated the soil bacterial communities of 4‐, 8‐, and 12‐year‐old Elymus nutans revegetated grasslands located in the Qinghai–Tibetan Plateau. Soil bacterial diversity and composition significantly changed in the 8‐ and 12‐year‐old grasslands compared with the 4‐year‐old grassland. Surprisingly, soil bacterial communities transitioned from Proteobacteria‐ and Acidobacteria‐dominant communities in the 4‐year‐old grassland to Cyanobacteria‐dominant communities in the 8‐ and 12‐year‐old grasslands. Furthermore, the phylum of Cyanobacteria accounted for a high percentage of bacterial community (>48%) in the 8‐ and 12‐year‐old grasslands. Network analyses showed that most of the interactions were identified as positive among bacterial species, but Cyanobacteria were often negatively associated with other species. In addition, there was a slight increase in P acquisition enzymes (acid phosphatase activity) and a decline in N acquisition enzymes (soil urease and nitratase activities) with the increasing dominance of Cyanobacteria. Additionally, soil pH and total phosphorus had positive relationships with soil bacterial composition and diversity, whereas soil bacterial diversity and P acquisition enzymes were negatively related to soil bacterial composition. Overall, our results indicated that significant changes in soil bacterial communities might occur in response to the cultivation period of cultivated grassland and highlighted the importance of soil pH, TP, and P acquisition enzymes in microbe‐mediated ecological processes of cultivated grassland on the Qinghai–Tibetan Plateau.

Comparison of soil bacterial community and functional characteristics following afforestation in the semi-arid areas.

Changes in soil bacterial communities, which are crucial for the assessment of ecological restoration in Chinese plantations, have never been studied in the “Three North Shelterbelt” project in the semi-arid areas. We used high-throughput sequencing of the 16S rDNA gene to investigate the soil bacterial community diversity, structure, and functional characteristics in three plantation forests, including Populus × canadensis Moench (PC), Pinus sylvestris var. mongolica (PS), and Pinus tabuliformis (PT). In addition, soil environment factors were measured. There were distinct differences in soil characteristics among different plantation forests. Compared to PS and PT, PC had a higher soil pH, dissolved organic carbon (DOC), and available P, as well as a lower C/N ratio. Furthermore, afforestation with different tree species significantly altered the abundance of Proteobacteria, and Chloroflexi in the soil, and its influence on the bacterial diversity indices. The bacterial community compositions and functional groups related to C and N cycling from PS, and PT were grouped tightly, indicating that the soil bacterial phylogenetic distance of PS and PT were closer than that between PS plus PT and PC. Our results implied that the soil characteristics, as well as the diversity, compositions and functions related to C and N cycling of soil bacterial community obviously differed from the following afforestation, especially between PC and PS plus PT, which in turn enormously established the correlation between the soil microbial community characteristics and the afforestation tree species.

Short-term response of the soil bacterial community to differing wildfire severity in Pinus tabulaeformis stands

In recent years, the investigation of fire disturbance of microbial communities has gained growing attention. However, how the bacterial community varies in response to different severities of fire at different soil depths is largely unknown. We utilized Illumina MiSeq sequencing to illustrate the changing patterns of the soil bacterial community following low-, moderate- and high-severity wildfire in the topsoil (0–10 cm) and subsoil (10–20 cm), 6 months after the fire. Acidobacteria, Proteobacteria, Actinobacteria, Verrucomicrobia and Chloroflexi were the dominant phyla among all samples. Bacterial alpha diversity (i.e. Shannon and Simpson indices) in the topsoil was significantly higher than that in the subsoil after a high-severity wildfire. Non-metric multidimensional scaling (NMDS) analysis and permutational multivariate analysis of variance (PERMANOVA) revealed significant differences in the bacterial community structure between the two soil layers. Soil pH, ammonium nitrogen (NH4+-N) and total nitrogen were the main factors in shaping the bacterial community structure, of which soil pH was the most robust in both soil layers. Our study reveals that wildfire results in short-term changes in soil bacterial community. However, a long-term monitoring of microbial variation after burning is also essential.

Alterations in soil bacterial community in relation to Spartina alterniflora Loisel. invasion chronosequence in the eastern Chinese coastal wetlands

In order to better understand the variations in soil bacterial community and associated drivers following plant invasion, we investigated changes in soil bacterial community along with 9-, 13-, 20- and 23-year-old Spartina alterniflora Loisel. (SA) invasion in comparison with bare flat (BF) in the eastern Chinese coastal wetlands, based on analyses of quantitative polymerase chain reaction (qPCR) and Illumina MiSeq DNA sequencing of 16S rRNA gene. The SA invasion significantly elevated soil bacterial abundance and diversity relative to BF, with the highest levels in 9-year-old SA soil, which gradually decreased with SA invasion from 9 to 23 years. The abundance of copiotrophic Proteobacteria, β-proteobacteria, and Bacteroidetes generally diminished along with SA invasion chronosequence. While, changes in abundance of oligotrophic Chloroflexi, Acidobacteria, Nitrospirae and Planctomycetes exhibited opposite trends. Our data suggest that soil nutrient substrates, and physiochemical properties (soil pH and/or moisture) primarily drive the shifts in soil bacterial abundance, diversity, and community composition along with SA invasion chronosequence in the costal wetlands of eastern China. Overall, soil bacterial abundance and diversity peaked in 9-year-old SA community, with soil bacterial community composition changing from copiotrophic to oligotrophic groups along with SA invasion chronosequence.

Changes in soil bacterial communities in response to the fairy ring fungus Agaricus gennadii in the temperate steppes of China

Fairy rings (FRs), mysterious circles of fungal fruiting bodies that occur in open grassy areas, have long been reported, but scientists know little about their effects on the physiochemical properties of soil and the associated bacterial communities. We investigated three concentric zones of Agaricus gennadii FRs in June, August and October 2016 in a temperate steppe of China outside of rings (OUT), within rings (IN) and adjacent to fruiting bodies (ON) to determine the effects of FR fungus on soil properties and bacterial community structure. Significantly higher aboveground biomass was only observed in the ON zone because of an increase in available soil P (P < 0.05). Soil total N, total P and inorganic N were lower in the ON and IN zones than in the OUT zone. The bacterial Shannon and Chao 1 indices were significantly higher in samples associated with the rings in August and October (P < 0.05). At the family level, only the abundance of Microbacteriaceae was significantly higher in the ON zone than in the OUT zone during the three-month study period (P < 0.05), indicating that species of the Microbacteriaceae are associated with Agaricus gennadii FRs. Moreover, the changes of soil pH and soil available P caused by FRs were found to be better indicators of changes in soil bacterial communities than total N, total P and inorganic N in soil.

Higher phylogenetic diversity prevents loss of functional diversity caused by successive drying and rewetting cycles.

Microbial communities regulate nutrient cycling in soil, thus the impact of climate change on the structure and function of these communities can cause an imbalance of nutrients in the environment. Structural and functional changes of soil bacterial communities in two contrasting biomes in Brazil, the Atlantic Forest and the Tropical Dry Forest (Caatinga), were studied by simulating, in microcosms, rainfall and drought events. Soil samples were collected in three Brazilian states: Bahia, Pernambuco and São Paulo, in a total of four sampling sites. Analysis of 16S rRNA amplicon libraries revealed changes in microbial communities after three drying-rewetting cycles (60-30% water holding capacity). Alpha diversity indexes were obtained for bacterial communities, as well as the functional diversity index (Shannon) based on the activity of the following enzymes: acid and alkaline phosphatase, arylsulfatase, dehydrogenase, cellulase, amylase, urease and phytase. In general, the soils of Caatinga showed a decrease in the diversity indexes studied, conversely, however, the soils of Atlantic Forest were found to be more resistant during the drying-rewetting cycles. Functional diversity was significantly different for the two biomes, with a decrease in Caatinga soils, while Atlantic Forest samples demonstrated a greater stability of enzymatic activity. Further, the Atlantic Forest samples showed more resistance when compared to samples from Caatinga. The results found in this study have confirmed the hypothesis that biomes, independent of climate, when subjected to successive events of drought and rewetting exhibit structural and metabolic changes.

Response of soil microbial community dynamics to Robinia pseudoacacia L. afforestation in the loess plateau: a chronosequence approach

The objective was to analyze soil microbial community dynamics and their responses to changes in vegetation and soil properties after Robinia pseudoacacia afforestation along a chronosequence. We investigated changes in vegetation communities, soil properties and soil microbial communities 5, 15, 25, and 35 years (Y) after R. pseudoacacia afforestation on cropland on the Loess Plateau. Soil microbial community compositions were analyzed using 16S rRNA and ITS high-throughput gene sequencing. The diversity and richness of understory vegetation community decreased with restoration stage, and available phosphorus and ammonium contents in soil were consistently low. The bacterial communities converted from Acidobacteria- to Proteobacteria-dominant communities within 25-Y but transitioned again to Acidobacteria-dominant communities at the 35-Y sites. Ascomycota and Zygomycota were the dominant fungal phyla at all sites. Compared to the cropland, fungal community composition changed at the 5-Y sites and the bacterial community composition changed at the 25-Y sites. R. pseudoacacia afforestation significantly altered soil bacteria richness rather than its diversity. The planted R. pseudoacacia rapidly altered the soil fungal community composition and altered bacterial community composition at the 25-Y. The changes in soil bacterial communities were driven by the phyla of Actinobacteria, Gemmatimonadetes and Nitrospirae and lagged behind the changes in vegetation communities. Phosphorus was a principal factor in shaping microbial community composition.

Changes in bacterial diversity associated with bioremediation of used lubricating oil in tropical soils.

Used lubricating oil (ULO) is a widespread contaminant, particularly throughout tropical regions, and may be a candidate for bioremediation. However, little is known about the biodegradation potential or basic microbial ecology of ULO-contaminated soils. This study aims to determine the effects of used ULO on bacterial community structure and diversity. Using a combination of culture-based (agar plate counts) and molecular techniques (16S rRNA gene sequencing and DGGE), we investigated changes in soil bacterial communities from three different ULO-contaminated soils collected from motorcycle mechanical workshops (soil A, B, and C). We further explored the relationship between bacterial community structure, physiochemical soil parameters, and ULO composition in three ULO-contaminated soils. Results indicated that the three investigated soils had different community structures, which may be a result of the different ULO characteristics and physiochemical soil parameters of each site. Soil C had the highest ULO concentration and also the greatest diversity and richness of bacteria, which may be a result of higher nutrient retention, organic matter and cation exchange capacity, as well as freshness of oil compared to the other soils. In soils A and B, Proteobacteria (esp. Gammaproteobacteria) dominated the bacterial community, and in soil C, Actinobacteria and Firmicutes dominated. The genus Enterobacter, a member of the class Gammaproteobacteria, is known to include ULO-degraders, and this genus was the only one found in all three soils, suggesting that it could play a key role in the in situ degradation of ULO-contaminated tropical Thai soils. This study provides insights into our understanding of soil microbial richness, diversity, composition, and structure in tropical ULO-contaminated soils, and may be useful for the development of strategies to improve bioremediation.

Changes in soil bacterial communities in an evergreen broad-leaved forest in east China following 4 years of nitrogen addition

Purpose Evergreen broad-leaved forest ecosystems are common in east China, where they are both ecologically and economically important. However, nitrogen (N) addition over many years has had a detrimental effect on these ecosystems. The objective of this research was to evaluate the effect of 4 years of N addition on microbial communities in an evergreen broad-leaved forest in southern Anhui, China.

Liming in the sugarcane burnt system and the green harvest practice affect soil bacterial community in northeastern São Paulo, Brazil.

Here we show that both liming the burnt sugarcane and the green harvest practice alter bacterial community structure, diversity and composition in sugarcane fields in northeastern São Paulo state, Brazil. Terminal restriction fragment length polymorphism fingerprinting and 16S rRNA gene cloning and sequencing were used to analyze changes in soil bacterial communities. The field experiment consisted of sugarcane-cultivated soils under different regimes: green sugarcane (GS), burnt sugarcane (BS), BS in soil amended with lime applied to increase soil pH (BSL), and native forest (NF) as control soil. The bacterial community structures revealed disparate patterns in sugarcane-cultivated soils and forest soil (R=0.786, P=0.002), and overlapping patterns were shown for the bacterial community structure among the different management regimes applied to sugarcane (R=0.194, P=0.002). The numbers of operational taxonomic units (OTUs) found in the libraries were 117, 185, 173 and 166 for NF, BS, BSL and GS, respectively. Sugarcane-cultivated soils revealed higher bacterial diversity than NF soil, with BS soil accounting for a higher richness of unique OTUs (101 unique OTUs) than NF soil (23 unique OTUs). Cluster analysis based on OTUs revealed similar bacterial communities in NF and GS soils, while the bacterial community from BS soil was most distinct from the others. Acidobacteria and Alphaproteobacteria were the most abundant bacterial phyla across the different soils with Acidobacteria Gp1 accounting for a higher abundance in NF and GS soils than burnt sugarcane-cultivated soils (BS and BSL). In turn, Acidobacteria Gp4 abundance was higher in BS soils than in other soils. These differential responses in soil bacterial community structure, diversity and composition can be associated with the agricultural management, mainly liming practices, and harvest methods in the sugarcane-cultivated soils, and they can be detected shortly after harvest.

Biochar alters the soil microbiome and soil function: results of next‐generation amplicon sequencing across Europe

AbstractWide‐scale application of biochar to soil has been suggested as a mechanism to offset increases inCO2emissions through the long‐term sequestration of a carbon rich and inert substance to the soil, but the implications of this for soil diversity and function remain to be determined. Biochar is capable of inducing changes in soil bacterial communities, but the exact impacts of its application are poorly understood. Using three European sites [UK SRC, short rotation coppice, French grassland (FR) and ItalianSRF, short rotation forestry (IT)] treated with identical biochar applications, we undertook 16S andITSampliconDNAsequencing. In addition, we carried out assessments of community change over time and N and P mobilization in theUK. Significant changes in bacterial and community structure occurred due to treatment, although the nature of the changes varied by site.STAMPdifferential abundance analysis showed enrichment ofGemmatimonadeteandAcidobacteriainUKbiochar plots 1 year after application, whilst control plots exhibited enrichedGemmataceae, IsosphaeraceaeandKoribacteraceae. Increased mobility of ammonium and phosphates was also detected after 1 year, coupled with a shift from acid to alkaline phosphomonoesterase activity, which may suggest an ecological and functional shift towards a more copiotrophic ecology. Italy also exhibited enrichments, in both theProteobacteria(driven by an increase in the orderRhizobiales) and theGemmatimonadetes. No significant change in the abundance of individual taxa was noted inFR, although a small significant change in unweightedUNIFRACoccurred, indicating variation in the identities of taxa present due to treatment. Fungalβdiversity was affected by treatment inITandFR, but was unaffected inUKsamples. The effects of time and site were greater than that of biochar application inUKsamples. Overall, this report gives a tantalizing view of the soil microbiome at several sites across Europe and suggests that although application of biochar has significant effects on microbial communities, these may be small compared with the highly variable soil microbiome that is found in different soils and changes with time.

Effects of Short-Term Warming and Altered Precipitation on Soil Microbial Communities in Alpine Grassland of the Tibetan Plateau.

Soil microbial communities are influenced by climate change drivers such as warming and altered precipitation. These changes create abiotic stresses, including desiccation and nutrient limitation, which act on microbes. However, our understanding of the responses of microbial communities to co-occurring climate change drivers is limited. We surveyed soil bacterial and fungal diversity and composition after a 1-year warming and altered precipitation manipulation in the Tibetan plateau alpine grassland. In isolation, warming and decreased precipitation treatments each had no significant effects on soil bacterial community structure; however, in combination of both treatments altered bacterial community structure (p = 0.03). The main effect of altered precipitation specifically impacted the relative abundances of Bacteroidetes and Gammaproteobacteria compared to the control, while the main effect of warming impacted the relative abundance of Betaproteobacteria. In contrast, the fungal community had no significant response to the treatments after 1-year. Using structural equation modeling (SEM), we found bacterial community composition was positively related to soil moisture. Our results indicate that short-term climate change could cause changes in soil bacterial community through taxonomic shifts. Our work provides new insights into immediate soil microbial responses to short-term stressors acting on an ecosystem that is particularly sensitive to global climate change.

LONG-TERM EFFECTS OF SWINE wastewater AND MINERAL FERTILIZER ASSOCIATION ON SOIL MICROBIOTA

ABSTRACT Swine wastewater (SW) application in agricultural soils may affect its microbial community in a long term. The objective of this study was to evaluate prospective changes in soil bacterial community after eight years continuous application of swine wastewater. The wastewater doses tested were 0; 100; 200 and 300 m3 ha-1, being applied from the beginning of the experiment and with or without recommended fertilization. Three soil samples were taken from each plot for determinations of basal respiration, microbial biomass and metabolic quotient. We also performed DGGE analysis and made a correlation between soil chemical conditions and microbial activity. Microbial community underwent significant structural changes from swine wastewater applications. Higher SW doses (200 and 300 m3 ha-1) influenced significantly (p &lt;0.05) and benefitted certain bacteria groups.