Changes in Bacterial and Fungal Communities across Compost Recipes,Preparation Methods,and Composting Times

Compost production is a critical component of organic waste handling, and compost applications to soil are increasingly important to crop production. However, we know surprisingly little about the microbial communities involved in the composting process and the factors shaping compost microbial dynamics. Here, we used high-throughput sequencing approaches to assess the diversity and composition of both bacterial and fungal communities in compost produced at a commercial-scale. Bacterial and fungal communities responded to both compost recipe and composting method. Specifically, bacterial communities in manure and hay recipes contained greater relative abundances of Firmicutes than hardwood recipes with hay recipes containing relatively more Actinobacteria and Gemmatimonadetes. In contrast, hardwood recipes contained a large relative abundance of Acidobacteria and Chloroflexi. Fungal communities of compost from a mixture of dairy manure and silage-based bedding were distinguished by a greater relative abundance of Pezizomycetes and Microascales. Hay recipes uniquely contained abundant Epicoccum, Thermomyces, Eurotium, Arthrobotrys, and Myriococcum. Hardwood recipes contained relatively abundant Sordariomycetes. Holding recipe constant, there were significantly different bacterial and fungal communities when the composting process was managed by windrow, aerated static pile, or vermicompost. Temporal dynamics of the composting process followed known patterns of degradative succession in herbivore manure. The initial community was dominated by Phycomycetes, followed by Ascomycota and finally Basidiomycota. Zygomycota were associated more with manure-silage and hay than hardwood composts. Most commercial composters focus on the thermophilic phase as an economic means to insure sanitation of compost from pathogens. However, the community succeeding the thermophilic phase begs further investigation to determine how the microbial dynamics observed here can be best managed to generate compost with the desired properties.     

Growth,mineral nutrition and mycorrhizal colonization of red clover and cucumber plants grown in a soil amended with composted urban wastes

The utility of an urban solid waste, either freshly composted or vermicomposted, for improvement of plant growth in a soil B horizon was investigated. Growth, mineral nutrition and arbuscular mycorrhizal (AM) colonization of cucumber and red clover plants were studied in an experiment carried out under controlled growing conditions, using different mixtures of soil and composts as plant substrates. Soil inoculation with the AM fungus Acaulospora sp. did not benefit growth of plants when soil was used as the only substrate, possibly due to its poor fertility. Results showed that neither mycorrhizal plant species grew when soil was mixed with composted urban waste or when compost was used as the only substrate. However, amendment of soil with 10 or 50% vermicompost significantly increased dry matter yields of red clover and cucumber plants, compared to treatments where soil was the only substrate. Addition of vermicompost also increased Olsen-P and other mineral elements in soil and shoot P, Ca, Mg, Cu, Mn and Zn concentrations, but caused a significant reduction on root length colonized by AM fungi in red clover plants. It is concluded that application of high amounts of vermicompost from composted urban wastes to soils might cause a significant reduction of activity of AM fungi, which must be taken into account when using these organic amendments in agricultural systems.     

Transformation of buffalo manure by composting or vermicomposting to rehabilitate degraded tropical soils

The addition of composted buffalo manure may lead to qualitative and quantitative improvement of the organic matter content of degraded tropical agricultural soils in Northern Vietnam. The objectives of this study were to follow the biochemical changes occurring during composting of buffalo manure with and without earthworms during 3 months and to study the effect of the end products (compost and vermicompost) on soil biochemical parameters and plant growth after two months of incubation under controlled conditions in an open pot experiment. Our conceptual approach included characterisation of organic matter of the two composts before and after addition to soil by elemental, isotopic analysis and analytical pyrolysis and comparison with conventional fertilisation. We also analysed for lignin content and composition.Our results showed that composting in the presence of earthworms led to stronger transformation of buffalo manure than regular composting. Vermicompost was enriched in N-containing compounds and depleted in polysaccharides. It further contained stronger modified lignin compared to regular compost. In the bulk soil, the amendment of compost and vermicompost led to significant modification of the soil organic matter after 2 months of exposure to natural weather conditions. The lignin component of SOM was unaffected whatever the origin of the organic amendment. Compost and vermicompost amendments both enhanced aggregation and increased the amount of organic matter in water stable aggregates. However, vermicompost is preferable to compost due to its beneficial effect on plant growth, while having similar positive effects on quantity and quality of SOM.     

Biochar co-compost improves nitrogen retention and reduces carbon emissions in a winter wheat cropping system

Organic amendments, such as compost and biochar, mitigate the environmental burdens associated with wasting organic resources and close nutrient loops by capturing, transforming, and resupplying nutrients to soils. While compost or biochar application to soil can enhance an agroecosystem's capacity to store carbon and produce food, there have been few field studies investigating the agroecological impacts of amending soil with biochar co-compost, produced through the composting of nitrogen-rich organic material, such as manure, with carbon-rich biochar. Here, we examine the impact of biochar co-compost on soil properties and processes by conducting a field study in which we compare the environmental and agronomic impacts associated with the amendment of either dairy manure co-composted with biochar, dairy manure compost, or biochar to soils in a winter wheat cropping system. Organic amendments were applied at equivalent C rates (8 Mg C ha⁻¹). We found that all three treatments significantly increased soil water holding capacity and total plant biomass relative to the no-amendment control. Soils amended with biochar or biochar co-compost resulted in significantly less greenhouse gas emissions than the compost or control soils. Biochar co-compost also resulted in a significant reduction in nutrient leaching relative to the application of biochar alone or compost alone. Our results suggest that biochar co-composting could optimize organic resource recycling for climate change mitigation and agricultural productivity while minimizing nutrient losses from agroecosystems.     

Diverse microbial communities in non-aerated compost teas suppress bacterial wilt

Non-aerated compost teas (NCTs) are water extracts of composted organic materials and are used to suppress soil borne and foliar disease in many pathosystems. Greenhouse trials were used to test the effectiveness of NCTs to suppress potato bacterial wilt caused by Ralstonia solanacearum on plants grown in soils inoculated with a virulent isolate of the pathogen (biovar II). NCTs prepared from matured compost sources: agricultural waste (AWCT), vermicompost (VCT) and solid municipal waste (SMWCT) were evaluated at three initial application times (7 days before inoculation, at time of inoculation and 7 days after inoculation) prior to weekly applications, in a randomized complete-block design. AWCT applied initially at the time of inoculation resulted in the greatest disease suppression, with the disease severity index 2.5-fold less than the non-treated plants and the “area under the disease progress curve” (AUDPC) 3.2-fold less. VCT and SMWCT were less suppressive than AWCT regardless of initial application time. Next generation sequencing of the v4 region of 16S rRNA gene and the internal transcribed spacer region (ITS1) revealed that diversity and composition of the bacterial and fungal communities across the NCTs varied significantly. Dominant bacterial phyla such as Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, Verrucomicrobia, Chloroflexi, Planctomycetes, Acidobacteria, and a fungal phylum Ascomycota were detected in all NCTs. AWCT had optimum physico-chemical measurements with higher bacterial Shannon diversity indices (H) and fungal richness (S) than the other treatments. We conclude that bacterial wilt of potatoes grown in controlled conditions can be suppressed by a non-aerated compost tea with a high microbial diversity when applied at planting and weekly thereafter.     

Distinct microbial communities associated with buried soils in the Siberian tundra

Cryoturbation, the burial of topsoil material into deeper soil horizons by repeated freeze–thaw events, is an important storage mechanism for soil organic matter (SOM) in permafrost-affected soils. Besides abiotic conditions, microbial community structure and the accessibility of SOM to the decomposer community are hypothesized to control SOM decomposition and thus have a crucial role in SOM accumulation in buried soils. We surveyed the microbial community structure in cryoturbated soils from nine soil profiles in the northeastern Siberian tundra using high-throughput sequencing and quantification of bacterial, archaeal and fungal marker genes. We found that bacterial abundances in buried topsoils were as high as in unburied topsoils. In contrast, fungal abundances decreased with depth and were significantly lower in buried than in unburied topsoils resulting in remarkably low fungal to bacterial ratios in buried topsoils. Fungal community profiling revealed an associated decrease in presumably ectomycorrhizal (ECM) fungi. The abiotic conditions (low to subzero temperatures, anoxia) and the reduced abundance of fungi likely provide a niche for bacterial, facultative anaerobic decomposers of SOM such as members of the Actinobacteria, which were found in significantly higher relative abundances in buried than in unburied topsoils. Our study expands the knowledge on the microbial community structure in soils of Northern latitude permafrost regions, and attributes the delayed decomposition of SOM in buried soils to specific microbial taxa, and particularly to a decrease in abundance and activity of ECM fungi, and to the extent to which bacterial decomposers are able to act as their functional substitutes.     

Effects of Different Chinese Hickory Husk Returning Modes on Soil Nutrition and Microbial Community in Acid Forest Soil

Chinese hickory (Carya cathayensis Sarg.) is an important economic forest in Southeastern China. A large amount of hickory husk waste is generated every year but with a low proportion of returning. Meanwhile, intensive management has resulted in soil degradation of Chinese hickory plantations. This study aims to investigate the effects of three Chinese hickory husk returning modes on soil amendment, including soil acidity, soil nutrition, and microbial community. The field experiment carried out four treatments: control (CK), hickory husk mulching (HM), hickory husk biochar (BC), and hickory husk organic fertilizer (OF). The phospholipid fatty acid (PLFA) biomarker method was employed to determine the soil microbial community. After one year of treatment, the results showed that: (i) HM and BC significantly increased soil pH by 0.33 and 1.71 units, respectively; (ii) HM, BC and OF treatments significantly increased the soil organic carbon, alkaline nitrogen, available phosphorous, and available potassium. The OF treatment demonstrated the most significant improvement in the soil nutrient; (iii) The soil microbial biomass significantly increased in the HM, BC and OF treatments, and all microbial groups showed an increasing trend. HM treatment increased the fungal/bacterial ratio (F/B). The OF treatment significantly decreased the Shannon-Wiener diversity (H’) and evenness index (J) of the microbial community (P < 0.05). Considering the treatments effects, costs, and ease of operation, our recommended returning modes of Chinese hickory husk are mulching and organic fertilizer produced by composting with manure.     

枯草芽胞杆菌菌肥对有机冬瓜根区土壤微生态的影响

【背景】微生物肥料已广泛应用于我国有机作物的种植,其对有机种植土壤微生态的影响尚需科学评测。【目的】高通量测序技术可用于精确分析土壤微生物群落,从细菌、真菌群落结构和多样性的角度阐释枯草芽胞杆菌菌肥对有机农田根区土壤微生物群落的影响。【方法】在有机农田轮作种植条件下,施用枯草芽胞杆菌菌肥后提取冬瓜根区土壤基因组DNA,通过PCR扩增建立文库,利用IlluminaMiSeq高通量测序技术,并结合相关生物信息学方法分析土壤细菌16SrRNA基因V3-V4区和真菌ITS1区的多样性指数及群落结构;测定根区土壤化学性质及酶活性,分析有机冬瓜果实品质,并作相关分析。【结果】从6个有机冬瓜根区土壤样本中获得14199个细菌操作分类单元(OTU)和3378个真菌OTU,细菌和真菌文库测序覆盖率分别在98%、99%以上。枯草芽胞杆菌菌肥会在一定程度上提高土壤细菌种群多样性而降低真菌种群多样性,丰富了细菌群落结构,但显著降低了真菌群落丰富度(P0.05);并减少了根区土壤特有细菌和真菌物种。变形菌门、厚壁菌门和放线菌门是优势细菌,子囊菌门是优势真菌;枯草芽胞杆菌菌肥会提高绿弯菌门和子囊菌门的相对丰度,比例分别为46.23%、10.01%;降低变形菌门和担子菌门的相对丰度,比例分别为11.14%、74.72%。枯草芽胞杆菌菌肥显著降低了土壤pH,显著提高了有机冬瓜果实总氨基酸、可溶性固形物等营养成分含量(P0.05)。【结论】施用枯草芽胞杆菌菌肥改变有机冬瓜根区土壤细菌和真菌的丰富度和多样性,降低了土壤pH,提高了有机冬瓜果实品质。     

Assessing the impact of composting and vermicomposting on bacterial community size and structure, and microbial functional diversity of an olive-mill waste

The aim of this study was to couple biochemical and molecular methodologies for evaluating the impact of two recycling technologies (composting and vermicomposting) on a toxic organic waste. To do this, six enzyme activities controlling the key metabolic pathways of the breakdown of organic matter, real-time PCR assays targeting 16S rRNA genes, and denaturing gradient gel electrophoresis (DGGE) profiling-sequence analysis of PCR-amplified 16S rRNA fragments have been used to determine the functional diversity, bacterial number, and bacterial community structure, respectively, in a mixture of olive waste and sheep manure, and in the derived compost and vermicompost. Both the recycling technologies were effective in activating the microbial parameters of the toxic waste, the vermicomposting being the best process to produce greater bacterial diversity, greater bacterial numbers and greater functional diversity. Although several identical populations were detected in the processed and non-processed materials, each technology modified the original microbial communities of the waste in a diverse way, indicating the different roles of each one in the bacterial selection.     

减施化肥配施有机肥对荔枝园土壤微生物区系的影响

有机肥替代部分化肥对荔枝生产有提质增效作用。为进一步探讨荔枝土壤微生物学机制,本试验以19年生“妃子笑”荔枝为对象,以化肥处理(CF)为对照,研究2018—2020连续两年减施化肥(平均减施化肥总养分21.5%)配施羊粪(OF)和配施生物有机肥处理(BIO)对土壤微生物多样性、群落组成及差异微生物等的影响,为荔枝科学施肥提供理论指导。结果表明: 与CF相比,连续两年OF和BIO处理均可有效提高荔枝产量和品质,产量平均增幅分别为23.1%和39.0%。土壤有机质含量和pH值均明显提高,土壤有效磷、有效钾、有效钙、有效镁、有效铁、有效锰、有效铜和有效锌含量均有不同程度增加。施用两种有机肥均能提高根际土壤细菌和真菌多样性,对非根际土壤影响不明显,同时改变土壤微生物群落结构,增加拟杆菌门、变形菌门和芽单胞菌门等富营养型细菌类群,减少酸杆菌门、绿弯菌门等贫营养型细菌类群。与CF相比,OF处理下MND1属和BIO处理下TK10属、芽单胞菌属、黄色杆菌属、木霉属、毛匍孢霉属的相对丰度均显著提高,并与产量呈显著正相关关系。综上,在荔枝上连续两年采用有机肥替代部分化肥可有效提高土壤pH值和养分有效性,增加根际土壤微生物丰富度和多样性,改变土壤微生物群落结构,从而形成更有利于产量提高和品质提升的微生物区系。     

Effects of pulp mill solids and three composts on early growth of tomatoes

Compost has been proposed as a means of simultaneously diverting organic materials from landfills while producing a valuable product that improves tilth, organic matter content and nutrient supply of agricultural soils. Composts manufactured from different source materials may have markedly different properties however, even if they meet all regulatory requirements. We compared the capacity of composts made from three different combinations of organic wastes (horse manure and bedding, mink farm wastes, municipal solid waste (MSW) and sewage sludge) along with clarifier solids from a chemo-thermomechanical pulp mill, to enhance the growth of tomato (Lycopersicon esculentum L.) seedlings grown in nutrient-poor organic potting soil. Germination and seedling emergence of tomatoes, cress (Lapidium sativum L.) or radish (Raphanus sativus L.) were tested to assess phytotoxicity of the four amendments. Mink farm compost and horse manure compost stimulated root and shoot growth of tomato seedlings but MSW compost and pulp mill solids were strongly inhibitory. MSW compost and unamended potting soil also inhibited seedling emergence and pulp mill solids produced stunting and deformities in radish and cress seedlings. Both toxic constituents and nutrient imbalances may be responsible for the growth-inhibiting effects of these amendments. Application of pulp mill solids to agricultural soil without composting may lead to deleterious effects on vegetable crops.     

添加高粱根茬根际土对连作黄瓜生长和根际微生物的影响

为了分析添加高粱根茬根际土对连作黄瓜生长和根际微生物群落特征的影响,本研究通过盆栽试验,采用荧光定量PCR和高通量测序技术分析土壤细菌和真菌群落组成的差异。试验共设4个处理: CK(不施肥),T₁(单施化肥),T₂(优化施肥),T₃(优化施肥+高粱根茬根际土)。结果表明: 与其他处理相比,T₃处理促进了黄瓜生长发育,提高了土壤中16S rRNA和ITS rRNA基因数量。与T₁处理相比,T₂和T₃处理明显提高了细菌群落的丰富度和多样性,不同处理间真菌群落的丰富度和多样性差异不明显。添加高粱根茬根际土在一定程度上改变了基于门、属水平上的细菌和真菌群落结构。其中,细菌中提高了酸杆菌门和拟杆菌门的丰度,降低了变形菌门、厚壁菌门、硝化螺旋菌门和芽孢杆菌属的丰度;真菌中提高了担子菌门、木霉菌属和假散囊菌属的丰度,降低了镰刀菌属和绿僵菌属的丰度。冗余分析表明,土壤硝态氮和有机质含量分别是影响细菌和真菌群落结构差异的关键因子。添加高粱根茬根际土不仅提高了连作黄瓜土壤微生物数量和细菌多样性,而且增加了有益菌木霉菌属的丰度,降低了致病镰刀菌的丰度和数量,保障了黄瓜存活率,为缓解黄瓜连作障碍提供了一条切实可行的解决途径。     

云南文山健康三七种植年限对根际微生物群落的影响

【背景】三七的连作障碍与微生物区系失衡有一定关联,了解种植年限对三七微生物区系的影响,判断根际微生物区系是否失衡,对三七连作障碍的防治具有重要意义。【目的】探究文山不同种植年限健康三七根际土壤细菌和真菌群落结构、多样性差异,以及与种植年限之间的关联,为后续缓解三七连作障碍提供理论依据。【方法】采集一年生、二年生和三年生健康三七根际土壤,采用16S rRNA基因和ITS序列进行高通量测序。对测序结果进行分析,比较一年生、二年生和三年生健康三七根际土壤细菌和真菌的多样性和群落分布规律及与种植年限的关联。【结果】一年生健康三七根际细菌和真菌群落的α指数均显著高于二年生和三年生。通过β多样性分析发现,一年生健康三七根际土壤中真菌群落结构与其他年限的真菌群落结构有较大差异。相关性分析结果表明,真菌的均匀度和香农指数与种植年限呈现显著的负相关性,其余指数不显著相关。三七根际丰富度前三的门和属,除Acidobacteria和Aquicella丰富度随着三七种植年限的增加而显著增加外,其余群落丰度都与种植年限呈负相关。细菌中Bacteroidetes、Proteobacteria和真菌中Ascomycota、Basidiomycota、Chytridiomycota的丰富度随着种植年限增加而降低。在属水平上,细菌中Opitutus和真菌中Mortierella、Clitopilus、Pholiota的丰富度随着三七种植年限的增加而降低。在二年生三七根际土壤中病原真菌Alternaria、Cylindrocarpon、Fusarium和Pestalotiopsis的丰富度低于一年生和三年生,而有益真菌Mucor和Bacillus的丰富度却呈相反趋势。同时,有益细菌Flavobacterium和有益真菌Myxocephala、Aspergillus的丰富度随着种植年限的增加呈下降趋势。【结论】三七种植年限的增加,会引起三七根际微生物区系失衡,增加根际病原真菌属的丰度,同时降低一些有益真菌属的丰度。     

Organic amendments and land management affect bacterial community composition, diversity and biomass in avocado crop soils

Background and aims

The avocado-producing area of southern Spain includes conventional orchards and organic orchards that use different organic amendments. To gain insight into the effects of these amendments, physicochemical properties and microbial communities of the soil were analysed in a representative set of commercial and experimental orchards.

Methods

The population size of several groups of culturable microorganisms was determined by plating on different selective media. Bacterial community structure was studied by denaturing gradient gel electrophoresis (DGGE)

Results

Commercial composts showed the largest effects, especially the animal compost, enhancing the population sizes of some microbial groups and affecting bacterial community structure in superficial and deep soil layers. Moreover, animal and vegetal compost, manure and blood meal addition are related to high bacterial diversity in the superficial soil layer.

Conclusions

All of the organic amendments used in this study affect soil properties in one or more of the characteristics that were analysed. Culturable microbial population data revealed the most evident effects of some of the organic treatments. However, molecular analysis of soil bacterial communities by DGGE allowed the detection of the influence of all of the analysed amendments on bacterial community composition. This effect was stronger in the superficial layer of the avocado soil.     

Changes in Soil Microbial Community Structure Influenced by Agricultural Management Practices in a Mediterranean Agro-Ecosystem

Agricultural practices have proven to be unsuitable in many cases, causing considerable reductions in soil quality. Land management practices can provide solutions to this problem and contribute to get a sustainable agriculture model. The main objective of this work was to assess the effect of different agricultural management practices on soil microbial community structure (evaluated as abundance of phospholipid fatty acids, PLFA). Five different treatments were selected, based on the most common practices used by farmers in the study area (eastern Spain): residual herbicides, tillage, tillage with oats and oats straw mulching; these agricultural practices were evaluated against an abandoned land after farming and an adjacent long term wild forest coverage. The results showed a substantial level of differentiation in the microbial community structure, in terms of management practices, which was highly associated with soil organic matter content. Addition of oats straw led to a microbial community structure closer to wild forest coverage soil, associated with increases in organic carbon, microbial biomass and fungal abundances. The microbial community composition of the abandoned agricultural soil was characterised by increases in both fungal abundances and the metabolic quotient (soil respiration per unit of microbial biomass), suggesting an increase in the stability of organic carbon. The ratio of bacteria:fungi was higher in wild forest coverage and land abandoned systems, as well as in the soil treated with oat straw. The most intensively managed soils showed higher abundances of bacteria and actinobacteria. Thus, the application of organic matter, such as oats straw, appears to be a sustainable management practice that enhances organic carbon, microbial biomass and activity and fungal abundances, thereby changing the microbial community structure to one more similar to those observed in soils under wild forest coverage.     

Effects of Different Organic Manures on the Biochemical and Microbial Characteristics of Albic Paddy Soil in a Short-Term Experiment

This study aimed to evaluate the effects of chemical fertilizer (NPK), NPK with livestock manure (NPK+M), NPK with straw (NPK+S), and NPK with green manure (NPK+G) on soil enzyme activities and microbial characteristics of albic paddy soil, which is a typical soil with low productivity in China. The responses of extracellular enzyme activities and the microbial community diversity (determined by phospholipid fatty acid analysis [PLFA] and denaturing gradient gel electrophoresis [DGGE]) were measured. The results showed that NPK+M and NPK+S significantly increased rice yield, with NPK+M being approximately 24% greater than NPK. The NPK+M significantly increased soil organic carbon (SOC) and available phosphate (P) and enhanced phosphatase, β-cellobiosidase, L-leucine aminopeptidase and urease activities. The NPK+S significantly increased SOC and available potassium (K) and significantly enhanced N-acetyl-glucosamidase, β-xylosidase, urease, and phenol oxidase activities. The NPK+G significantly improved total nitrogen (N), ammonium N, available P, and N-acetyl-glucosamidase activity. The PLFA biomass was highest under NPK+S, followed by NPK+M and NPK+G treatments. Principal component analysis (PCA) of the PLFA indicated that soils with NPK+M and NPK+S contained higher proportions of unsaturated and cyclopropane fatty acids (biomarkers of fungi and gram-negative bacteria) and soil under NPK+G contained more straight chain saturated fatty acids (representing gram-positive bacteria). PCA of the DGGE patterns showed that organic amendments had a greater influence on fungal community. Cluster analysis of fungal DGGE patterns revealed that NPK+G was clearly separated. Meanwhile, the bacterial community of NPK+M treatment was the most distinct. RDA analysis revealed changes of microbial community composition mostly depended on β-xylosidase, β-cellobiosidase activities, total N and available K contents. The abundances of gram-negative bacterial and fungal PLFAs probably effective in improving fertility of low-yield albic paddy soil because of their significant influence on DGGE profile.     

Efficiency of biochar,nitrogen addition,and microbial agent amendments in remediation of soil properties and microbial community in Qilian Mountains mine soils

Lacking systematic evaluations in soil quality and microbial community recovery after different amendments addition limits optimization of amendments combination in coal mine soils. We performed a short‐term incubation experiment with a varying temperature over 12 weeks to assess the effects of three amendments (biochar: C; nitrogen fertilizer at three levels: N‐N1~N3; microbial agent at two levels: M‐M1~M2) based on C/N ratio (regulated by biochar and N level: 35:1, 25:1, 12.5:1) on mine soil properties and microbial community in the Qilian Mountains, China. Over the incubation period, soil pH and MBC/MBN were significantly lower than unamended treatment in N addition and C + M + N treatments, respectively. Soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), available potassium (AK), microbial biomass carbon (MBC), and nitrogen (MBN) contents increased significantly in all amended treatments (p < .001). Higher AP, AK, MBC, MBN, and lower MBC/MBN were observed in N2‐treated soil (corresponding to C/N ratio of 25:1). Meanwhile, N2‐treated soil significantly increased species richness and diversity of soil bacterial community (p < .05). Principal coordinate analysis further showed that soil bacterial community compositions were significantly separated by N level. C‐M‐N treatments significantly increased the relative abundance (>1%) of the bacterial phyla Bacteroidetes and Firmicutes, and decreased the relative abundance of fungal phyla Chytridiomycota (p < .05). Redundancy analysis illustrated the importance of soil nutrients in explaining variability in bacterial community composition (74.73%) than fungal composition (35.0%). Our results indicated that N addition based on biochar and M can improve soil quality by neutralizing soil pH and increasing soil nutrient contents in short‐term, and the appropriate C/N ratio (25:1) can better promote microbial mass, richness, and diversity of soil bacterial community. Our study provided a new insight for achieving restoration of damaged habitats by changing microbial structure, diversity, and mass by regulating C/N ratio of amendments.     

生物质调理剂对川西北高寒草地沙化土壤养分和微生物群落特征的影响

将农牧废弃物进行资源化处置制成生物质调理剂,用于沙化土壤改良是目前川西北沙化草地生态治理的有效途径之一。为了阐明不同原料调理剂在川西北高寒沙化草地上的实际应用效果,本研究以不施用调理剂为对照(CK),设置施用量均为12 t·hm^-2的菌渣(JZ)、秸秆(JG)和生物炭(SWT) 3种调理剂,分析了调理剂施用对土壤养分和微生物群落特征及其相互关系的影响。结果表明: 与对照相比,各种生物质调理剂均显著增加了土壤速效养分和活性有机碳含量,增幅在23.0%～521.6%,其中施用秸秆调理剂(JG)的效果最佳,增幅为65.1%～521.6%。因生物质调理剂只在第一年施入,第二年的土壤速效养分和活性有机碳含量均较第一年整体下降了4.5%～92.3%,而土壤有机碳含量和微生物生物量碳均较第一年整体上升了5.6%～458.0%。生物质调理剂改变了微生物属水平优势菌属的相对丰度,其中,JG处理对细菌菌群的影响较大,JG和JZ处理对真菌菌群的影响较大。与CK相比,JG处理显著降低了土壤细菌和真菌的多样性,其中,Shannon指数显著降低了2.9%和31.8%,而Simpson指数显著提高了175.0%和320.9%。冗余分析显示,土壤速效养分和活性有机碳含量是影响微生物群落组成的重要因素,其中,土壤硝态氮含量和微生物生物量碳对细菌群落组成的影响较大,共解释了65.9%的群落变化,土壤速效钾含量和微生物生物量碳对真菌群落组成的影响较大,共解释了83.2%的群落变化。综合比较,秸秆调理剂能显著增加土壤速效养分和活性有机碳含量,有利于有益细菌和真菌微生物菌属的生长,可以作为提升川西北地区高寒草地沙化土壤质量的推广措施。     

不同施肥模式对雷竹林土壤真菌群落特征的影响

为探明施肥处理对雷竹林土壤真菌群落特征的影响,采用末端限制性片段长度多态性(T-RFLP)和荧光定量PCR技术,分析有机肥(M)、化肥(CF)、化肥配施有机肥(CFM)、化肥配施有机肥加覆盖(CFMM)及不施肥(CK)处理土壤真菌群落结构和数量特征.结果表明:施肥显著影响真菌群落结构与多样性,表层(0～20 cm)土壤中M、CFMM处理与CK,亚表层(20～40 cm)土壤中CF、CFMM处理与CK之间真菌群落结构均存在明显差异;且表层土壤中CF、CFMM处理真菌Shannon指数和均匀度指数显著低于CK.M、CFM处理表层土壤真菌数量显著高于CK.土壤有机质、全氮、铵态氮和速效钾含量显著影响了真菌群落结构的变异;全氮、铵态氮、硝态氮含量与真菌数量均呈显著正相关.表明雷竹林表层和亚表层土壤中真菌群落对施肥处理的响应存在明显差异,表层土壤真菌群落明显受有机质添加的影响,而亚表层则对化肥投入较为敏感;施肥对真菌群落多样性的影响主要集中在表层土壤.     

植茶年限对土壤微生物群落结构及多样性的影响

为探明植茶年限对土壤微生物群落结构及多样性的影响,以0、20、25、38和48年茶园土壤表层(0～20 cm)、亚表层(20～40 cm)土壤样品为研究对象,采用T-RFLP技术及qPCR方法对土壤细菌(B)、真菌(F)群落进行分析。结果表明: 植茶后土壤理化性质明显改变,随植茶年限的增加土壤有机碳、碱解氮及有效磷含量呈先升高后降低的趋势,表层土壤有机碳和全氮含量均显著高于亚表层土壤。不同植茶年限土壤细菌群落组分存在差异且多样性指数随植茶年限的增加呈下降趋势,而不同植茶年限土壤真菌群落组分差异不明显且多样性指数无显著差异。总体来看,土壤细菌群落对植茶年限的响应比真菌群落敏感。随植茶年限的增加,茶园土壤微生物群落有从F/B较低的“细菌型”向F/B较高的“真菌型”转变的趋势。