Influence of grass species and soil type on rhizosphere microbial community structure in grassland soils

A number of studies have reported species specific selection of microbial communities in the rhizosphere by plants. It is hypothesised that plants influence microbial community structure in the rhizosphere through rhizodeposition. We examined to what extent the structure of bacterial and fungal communities in the rhizosphere of grasses is determined by the plant species and different soil types. Three grass species were planted in soil from one site, to identify plant-specific influences on rhizosphere microbial communities. To quantify the soil-specific effects on rhizosphere microbial community structure, we planted one grass species (Lolium perenne L.) into soils from three contrasting sites. Rhizosphere, non-rhizosphere (bulk) and control (non-planted) soil samples were collected at regular intervals, to examine the temporal changes in soil microbial communities. Rhizosphere soil samples were collected from both root bases and root tips, to investigate root associated spatial influences. Both fungal and bacterial communities were analysed by terminal restriction fragment length polymorphism (TRFLP). Both bacterial and fungal communities were influenced by the plant growth but there was no evidence for plant species selection of the soil microbial communities in the rhizosphere of the different grass species. For both fungal and bacterial communities, the major determinant of community structure in rhizospheres was soil type. This observation was confirmed by cloning and sequencing analysis of bacterial communities. In control soils, bacterial composition was dominated by Firmicutes and Actinobacteria but in the rhizosphere samples, the majority of bacteria belonged to Proteobacteria and Acidobacteria. Bacterial community compositions of rhizosphere soils from different plants were similar, indicating only a weak influence of plant species on rhizosphere microbial community structure.     

Physical,Chemical, and Biological Changes in the Rhizosphere and Nutrient Availability

The rhizosphere is the soil zone adjacent to plant roots which is physically, chemically, and biologically different from bulk or non-rhizosphere soil. Adaptative mechanisms of plants influence physical (temperature, water availability, and structure), chemical [pH, redox potential, nutrient concentration, root exudates, aluminum (Al) detoxification and allelopathy], and biological properties (microbial association) in the rhizosphere. These changes affect nutrient solubility, transport, and uptake and ultimately plant growth. Major rhizosphere changes are synthesized and their influence on nutrient availability is discussed. In the last decade, significant progress has been made in understanding the rhizosphere environment and nutrient availability. However, the subject matter is very complex and more research is needed to understand the interaction between the plant, the rhizosphere environment, and nutrient availability.     

<Emphasis Type="Italic">p</Emphasis>-Coumaric can alter the composition of cucumber rhizosphere microbial communities and induce negative plant-microbial interactions

Phenolics from root exudates or decaying residues are usually referred as autotoxins of several plant species. However, how phenolics affect soil microbial communities and their functional significances are poorly understood. Rhizosphere bacterial and fungal communities from cucumber (Cucumis sativus L.) seedlings treated with p-coumaric acid, an autotoxin of cucumber, were analyzed by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer amplicons. Then, feedback effects of the rhizosphere biota on cucumber seedlings were evaluated by inoculating non-sterilized and sterilized rhizosphere soils to sterilized background soils. p-Coumaric acid decreased the bacterial diversity of rhizosphere but increased fungal diversity and altered the compositions of both the bacterial and fungal communities. p-Coumaric acid increased the relative abundances of microbial taxa with phenol-degrading capability (such as Chaetomium, Humicola, and Mortierella spp.) and microbial taxa which contained plant pathogens (such as Fusarium spp.). However, p-coumaric acid inhibited the relative abundances of Lysobacter, Haliangium, and Gymnoascus spp., whose species can have pathogen-antagonistic and/or plant-growth-promoting effects. The positive effect of cucumber rhizosphere microbiota on cucumber seedling growth was reduced by p-coumaric acid. Overall, our results showed that, besides its direct phytotoxicity, p-coumaric acid can inhibit cucumber seedling growth through generating negative plant-soil microbial interactions.     

黄河三角洲退化湿地微生物群落特性研究

Five different sites with a soluble salt gradient of 3.0--17.7 g kg-1 dry soil from the coast to the inland were selected, and the microbial population size, activity and diversity in the rhizospheres of five common plant species and the adjacent bulk soils (non-rhizosphere) were compared in a degraded wetland of the Yellow River Delta, Shandong Province, China to study the effects of soil environment (salinity, seasonality, depth, and rhizosphere) on microbial communities and the wetland’s ecological function, thus providing basic data for the bioremediation of degraded wetlands. There was a significant negative linear relationship between the salinity and the total number of microorganisms, overall microbial activity, or culturable microbial diversity. Salinity adversely affected the microbial community, and higher salinity levels resulted in smaller and less active microbial communities. Seasonal changes were observed in microbial activity but did not occur in the size and diversity. The microbial size, activity and diversity decreased with increasing soil depth. The size, activity and diversity of culturable microorganisms increased in the rhizospheres. All rhizospheres had positive effects on the microbial communities, and common seepweed had the highest rhizosphere effect. Three halophilic bacteria (Pseudomonas mendocina, Burkholderia glumae, and Acinetobacter johnsonii) were separated through BIOLOG identification, and common seepweed could be recommended for bioremediation of degraded wetlands in the Yellow River Delta.     

Rhizosphere effects on soil bacterial abundance and diversity in the Yellow River Deltaic ecosystem as influenced by petroleum contamination and soil salinization

In this study, we compared the differences of bacterial abundance and diversity between rhizosphere and surrounding bulk soils under soil salinization and petroleum contamination in the Yellow River Delta on a 110-km-distance scale. In comparison with bulk soils, rhizosphere soils were mainly characterized by lower salinity and higher water content in saline soils. For bacterial abundance, the numbers of total bacteria and hydrocarbon degraders were significantly higher in rhizosphere soils than those in bulk soils. Although there was no significant difference in total petroleum hydrocarbon (TPH) concentration between the two types of soils, TPH had distinctly different effects on bacterial abundance in rhizosphere and bulk soils. TPH concentration was the major determinant of total bacterial abundance and had positive effects on abundances of hydrocarbon degraders. However, the abundances of total bacteria and hydrocarbon degraders in bulk soils were primarily determined by soil salinity and water content. Great abundance of rhizosphere bacteria suggested that plant roots could alleviate the stresses from soil salinization and provide more favorable microhabitats for bacterial growth. TPH had positive effects on bacterial diversity of both rhizosphere and bulk soils. Our results support the view that petroleum in the environments functions as both toxic chemicals and carbon sources to soil bacteria. Great abundance and diversity of total bacteria in plant rhizospheres would potentially improve the roles of bacteria in maintaining ecosystem functioning in the degraded ecosystems. Our results would improve our understanding of the relationships between rhizosphere effects and multiple environmental stresses that control the development of bacterial community in fragile anthropologically-affected ecosystems.     

连作对再植枸杞根际细菌群落多样性和群落结构的影响研究

受枸杞道地产区土地资源等因素限制,连作障碍已成为影响枸杞产业发展的重要原因之一,导致严重的经济损失.研究连作条件下枸杞农田土壤生态系统微生物群落的演替规律对枸杞产业的可持续发展具有重要的理论意义.以宁夏银川市南梁农场连作多年的枸杞地为研究对象,利用Illumina MiSeq测序技术分析了连作对再植枸杞根际/非根际细菌群落的影响.结果表明,连作地显著抑制再植枸杞苗地径的增加,且其土壤pH较对照样地显著降低(p<0.05).测序结果证实,与对照样地相比,连作地再植枸杞根际土壤细菌物种数显著降低(p<0.05),细菌群落α多样性下降(p>0.05).主坐标分析表明,连作和对照样地间枸杞非根际细菌群落结构无明显差异,但连作显著改变再植枸杞根际细菌的群落结构.对细菌群落丰度的统计分析发现,连作地枸杞根际浮霉菌门、非根际假单胞菌门的相对丰度较对照样地显著降低(p<0.05).此外,冗余分析结果表明:枸杞园土壤pH和有效磷含量是影响枸杞非根际土壤细菌群落结构变化的主要因素,分别解释了41.8%和35.4%的群落结构变化(p<0.05),其他土壤因子无统计学意义,但土壤理化因子对再植枸杞根际细菌群落结构变化的影响均未达显著水平.这些结果证实连作能够显著抑制再植枸杞生长、影响再植枸杞根际细菌群落结构和多样性,干扰枸杞与土壤细菌群落间的互作关系.这些研究结果将为解析枸杞连作障碍机制提供理论基础.     

不同作物间作对黄瓜病害及土壤微生物群落多样性的影响

分别采用RAPD和T-RFLP技术,研究了小麦、毛苕子和三叶草分别与黄瓜间作对黄瓜病害、黄瓜根际土壤微生物群落多样性和黄瓜产量的影响。结果表明,小麦、毛苕子与黄瓜间作均能提高黄瓜根际土壤微生物群落多样性,其中,小麦-黄瓜间作对黄瓜根际土壤微生物群落多样性的影响最为突出;3种作物分别与黄瓜间作均显著提高了黄瓜产量(p<0.01),其中小麦-黄瓜间作的产量优势最强;同时,3种作物分别与黄瓜间作均降低了黄瓜角斑病、白粉病、霜霉病和枯萎病的病情指数和尖孢镰刀菌的数量。间作有利于提高土壤微生物群落的多样性、减轻病害、提高黄瓜产量。     

Effects of pine roots on microorganisms,fauna, and nitrogen availability in two soil horizons of a coniferous forest spodosol

Summary We investigated the effects of pitch pine seedling roots on extractable N, microbial growth rate, biomass C and N, and nematodes and microarthropods in microcosms with either organic (41% C, 1.14% N) or mineral (0.05% C, 0.01% N) horizon soils of a spondosol. Root quantity was manipulated by varying plant density (0, 1, 2, or 4 seedlings) and rhizosphere soil was separated from non-rhizosphere soil by a 1.2 m mesh fabric. In the rhizosphere of organic soil horizons, moisture, microbial growth rate, biomass C and N, and extractable N declined as root density was increased, but there was little effect on nematodes or microarthropods. High levels of extractable N remained after 5 months, suggesting that N mineralization was stimulated during the incubation. In the rhizosphere of mineral soil horizons, microbial growth rate, and nematode and microarthropod abundances increased at higher root density, and in the absence of roots faunal abundance approached zero. Faunal activity was concentrated in the rhizosphere compared to non-rhizosphere soil. In organic soil horizons, roots may limit microbial activity by reducing soil moisture and/or N availability. However, in mineral soil horizons, where nutrient levels are very low, root inputs can stimulate microbial growth and faunal abundance by providing important substrates for microbial growth. Our results demonstrate a rhizosphere effect for soil fauna in the mineral soil, and thus extends the rhizosphere concept to components of the soil community other than microbes for forest ecosystems. Although our results need to be verified by field manipulations, we suggest that the effects of pine roots on nutrient cycling processes in coniferous forests can vary with soil nutrient content and, therefore, position in the soil profile.     

Phosphorus Speciation and Nutrient Stoichiometry in the Soil-Plant System During Primary Ecological Restoration of Copper Mine Tailings

The effects of plant vegetation on phosphorus(P) speciation, pH, total carbon concentration, total nitrogen concentration, and alkaline phosphatase activities were investigated to explore the P uptake strategy of plants in low-P soil and to determine the nutrient stoichiometric ratio changes in the rhizosphere of plants(Imperata cylindrica, Miscanthus floridulus, Zoysia sinica, Artemisia lavandulaefolia, Indigofera pseudotinctoria, and Conyza canadensis) which had grown for approximately 15 years in copper mine tailings, East China. The results showed that the average pH values in the rhizosphere decreased by 0.06–1.37 compared with those in the non-rhizosphere. The alkaline phosphatase activities of the rhizosphere were significantly higher than those in the non-rhizosphere.The mean concentrations of aluminum(Al)-and iron(Fe)-bound P and Ca_2-P(CaHPO_4) in the rhizosphere of all plants were 5.4% to 87.7%, 49.2% to 214.2%, and 86.6% to 147.6% higher than those in the non-rhizosphere, respectively. Except for Ca_8-P(Ca_8H_2(PO_4)_6)and Ca_(10)-P(Ca_(10)(PO_4)_6(OH)_2) in the rhizosphere, all kinds of inorganic P forms were negatively correlated with pH. Significant correlation was also observed among the concentrations of dominant forms of inorganic P, C, and N and alkaline phosphatase activities in the rhizosphere. Among the studied species, I. pseudotinctoria showed the most significant effect on enhancing soil available P concentration. The stoichiometric ratios of C:P and N:P were apparently higher in the rhizosphere than the non-rhizosphere, whereas these ratios were far below the ratios commonly observed in Chinese soils. These results indicated that the plant growth effectively affected P fractions possibly by changing pH, C and N concentrations, and alkaline phosphatase activity, in the rhizosphere in copper mine tailings.     

Glucose uptake by maize roots and its transformation in the rhizosphere

The flow of carbon from roots into the rhizosphere represents a significant C loss from plants. However, roots have the capacity to recapture low molecular weight C from soil although this is in direct competition with soil microorganisms. The aim of this study was to investigate the behaviour of glucose in rhizosphere and non-rhizosphere soil, the plant's potential to recapture sugars from soil and translocation and utilization of the recaptured sugars. In microcosms containing maize plants we injected ¹⁴C-glucose into the rhizosphere and followed its uptake into plants, upward and downward transport in the plant and soil, evolution as ¹⁴CO₂ and incorporation into the soil microbial biomass. These fluxes were compared with non-rhizosphere soil. Glucose was rapidly mineralized in soil and the rate of turnover was significantly greater in the rhizosphere in comparison to non-rhizosphere soil. The amount of glucose captured by the maize plants was low (<10% of the total ¹⁴C-glucose added) in comparison to that captured by the soil microbial biomass. Only small amounts of the ¹⁴C-glucose were transported to the shoot (0.6% of the total). The degree of glucose capture by maize roots whilst in competition with soil microorganisms was similar to similar experiments performed for amino acids. We conclude that while plant roots can recapture low molecular weight C from the rhizosphere, intense competition from soil microorganisms may reduce the efficiency of this process.     

抗盐碱转基因大豆对根际与非根际土壤氨氧化古菌多样性的影响

采用PCR—DGGE技术,研究了抗盐碱转基因大豆（SRTS）对根际与非根际土壤氨氧化古菌（AOA）群落多样性的影响。结果表明,在非根际土壤中,SRTS的氨氧化古菌DGGE条带数、多样性指数显著高于其受体亲本黑农35和其他两种大豆处理,而均匀度指数较低;在根际土壤中,SRTS的DGGE条带数和多样性指数均高于其受体亲本,但并不显著,其均匀度指数则显著高于其他处理;每种大豆自身根际与非根际比较显示,SRTS非根际氨氧化古菌DGGE条带数、多样性指数明显高于根际,均匀度指数却低于根际,而其受体亲本与其他两个处理反之。聚类分析结果表明,SRTS的DGGE带谱与其他大豆处理差异较大,且自身非根际与根际处理差异显著,与其受体亲本黑农35相似性很低。测序结果表明,在SRTS处理中特有条带12、15和优势条带13、14均属于Uncultured crenarchaeote。在盐碱土壤生态系统中,SRTS提高了非根际土壤氨氧化古菌群落的多样性,但对根际土壤中氨氧化古菌的群落多样性有一定的抑制作用。     

Differences between soil solutions obtained from rhizosphere and non-rhizosphere soils by water displacement and soil centrifugation

Soil solution was obtained from potted rhizosphere or non-rhizosphere soils by water displacement or soil centrifugation. The pH of the displaced solutions was lower than that of bulk soils when solutions were obtained from non-rhizosphere soil, although it increased as plants grew. This increase probably reflected true changes in rhizosphere pH, generated by the uptake by plants of N0₃-N. In contrast, the pH of soil centrifugates was usually close to that of the bulk soils, implying that buffering by colloids had occurred during sampling. Concentrations of elements in solutions from non-rhizosphere soil were similar for both methods when soils were incubated at ambient pCO₂. However, when non-rhizosphere soils were incubated at elevated pCO₂, displacement solutions had lower pH values, and much larger concentrations of elements, compared to soil centrifugates. Comparison of mass flow of elements versus actual plant uptake showed that Ca and Mg accumulated, while K, Zn and Cd were depleted from the rhizosphere. Displacement solutions showed this accumulation or depletion of the elements more clearly than soil centrifugates. These differences were attributed to the fact that, at constant soil moisture, the rhizosphere developed mainly in larger pores, which were sampled by displacement. With centrifugation, a mixture of pore sizes was sampled, so that rhizosphere solution was only obtained when all of the soil had become rhizosphere. Soil centrifugates obtained after 22 days of growth also contained higher concentrations of organic carbon than displacement solutions, indicating contamination due to the disruption of roots and/or micro-organisms. We conclude that water displacement is suitable for sampling solution from light to medium textured rhizosphere or non-rhizosphere soils and that soil centrifugation is only of limited suitability.     

Soil bacterial community response to sulfadiazine in the soil–root zone

Sulfonamide antibiotics reach soil via manure and adversely affect microbial diversity. Clear effects of these bacteriostatic, growth‐inhibiting antibiotics occur in the presence of a parallel input of microbial activity stimulating manure. Natural hot spots with already increased soil microbial activity are located in the rhizosphere, comprising microorganism such as Pseudomonas with plant growth promoting and pathogenic strains. The hypothesis was therefore that the antibiotic activity of sulfonamides is promoted in the rhizosphere even in the absence of manure, followed by shifts of the natural plant‐specific microbial community structure. This was evaluated by a laboratory experiment with Salix fragilis L. and Zea mays L. After 40 d of incubation, sub‐areas such as non‐rhizosphere soil, rhizosphere soil and plant roots were sampled. Effects on microbial community structure were analyzed using 16S rRNA gene fragment patterns of total bacteria community and Pseudomonas. Selected exoenzymes of N‐, P‐, and C‐cycling were used to test effects on microbial functions. Compared to the factors soil sub‐area and sulfadiazine (SDZ) content, plant species had the largest influence on the bacterial community structure and soil exoenzyme activity pattern. This was also reflected by an up to 1.5‐fold higher acid phosphatase activity in samples from maize‐ compared to willow‐planted soil. We conclude that antibiotic effects on the bacterial community structures are influenced by the antibiotic concentration and root influence.     

Effect of Capsicum annuum cultivated in sub-alkaline soil on bacterial community and activities of cultivable plant growth promoting bacteria under field conditions

In literature, it remains little explored the soil–plant relationships within Capsicum agroecosystem. We studied how chili peppers plants contribute to influence microbial diversity. Across the bulk and rhizosphere soils of three genotypes of Capsicum annuum, the structure, the diversity and the abundance of bacteria was evaluated by means of DNA-based culture-independent approach. Furthermore, 515 bacterial strains isolated from the bulk and rhizosphere soil, were used to investigate the effect of C. annuum on four plant growth promoting bacteria (PGPB) abilities. Our results indicated that the three genotypes influence differently the physical-chemical and microbial properties of soil around the roots. Bacterial abundance resulted in increasing with different trend rhizospheres to bulk soil ratio; however, bacterial diversity was significantly higher only in the rhizosphere of one genotype. Only the indolic compounds production was stimulated in the rhizosphere of the three cultivars. Inhibition of Fusarium oxysporum was stimulated just with one genotype, where 53 of rhizosphere isolates showed more than 10% of inhibition. 165 of isolates produced siderophores and the major part belonged to the high production level. Interactions between PGPB features revealed that anti-phytopathogenic activity was not associated with the others characteristics; however, phosphate solubilization was associated with both siderophores and indolic compounds productions.     

Investigating microbial community structure in soils by physiological, biochemical and molecular fingerprinting methods

Several biochemical and molecular methods are used to investigate the microbial diversity and changes in microbial community structure in rhizospheres and bulk soils resulting from changes in management. We have compared the effects of plants on the microbial community, using several methods, in three different types of soils. Pots containing soil from three contrasting sites were planted with Lolium perenne (rye grass). Physiological (Biolog), biochemical (PLFA) and molecular (DGGE and TRFLP) fingerprinting methods were employed to study the change in soil microbial communities caused by the growth of rye grass. Different methods of DNA extraction and nested PCR on TRFLP profiles were examined to investigate whether they gave different views of community structure. Molecular methods were used for both fungal and bacterial diversity. Principal component analysis of Biolog data suggested a significant effect of the plants on the microbial community structure. We found significant effects of both soil type and plants on microbial communities in PLFA data. Data from TRFLP of soil bacterial communities showed large effects of soil type and smaller but significant effects of plants. Effects of plant growth on soil fungal communities were measured by TRFLP and DGGE. Multiple Procrustes analysis suggested that both methods gave similar results, with only soil types having a significant effect on fungal communities. However, TRFLP was more discriminatory as it generated more ribotype fragments for each sample than the number of bands detected by DGGE. Neither methods of DNA extraction nor the nested PCR had any effect on the evaluation of soil microbial community structure. In conclusion, the different methods of microbial fingerprinting gave qualitatively similar results when samples were processed consistently and compatible statistical methods used. However, the molecular methods were more discriminatory than the physiological and biochemical approaches. We believe results obtained from this experiment will have a major impact on soil microbial ecology in general and rhizosphere–microbial interaction studies in particular, as we showed that the different fingerprinting methods for microbial communities gave qualitatively similar results.     

健康与罹患青枯病的番茄土壤细菌群落特征比较

应用实时荧光定量PCR及MiSeq高通量测序技术,全面地研究了连作番茄田块中健康与感染青枯病植株周围土体及根际土壤细菌群落结构和组成.结果表明:健康番茄土体土壤的pH及全碳含量显著高于感病番茄土体土壤;土体及根际土壤的细菌群落结构和组成明显不同于感病番茄土体及根际土壤细菌群落.与感病番茄根际相比,健康番茄根际细菌的数量...     

不同作物根际土壤微生物的群落结构特征分析

为探究根际微生物群在支持植物生长、发育和健康方面的重要作用,本研究在2017年7月采集同一农田中大豆[Glycine max (L.) Merr.]、玉米[Zea mays)、花生(Arachis hypogaea L.]、四季豆[Phaseolus vulgaris L.]、豇豆[Vigna unguiculata (L.) Walp]、番薯[Ipomoea batatas (L.) Lam.]和芋艿[Colocasia esculenta (L.) Schoot]7种不同作物,通过Illumina MiSeq测序技术和磷脂脂肪酸(PLFA)对这7种不同作物的根际微生物群落结构和组成进行了分析。结果显示,不同作物根际土壤微生物的PLFA种类和组成差异显著,但均以表征革兰氏阴性菌、革兰氏阳性菌和真菌的特征脂肪酸为主。花生根际土中微生物的PLFAs含量最高,花生根际土中的真菌细菌比(F/B)显著高于其他作物,且其革兰氏阳性菌与革兰氏阴性菌比(G⁺/G^-)最低。尽管在门水平,变形菌门、放线菌门、酸杆菌门和厚壁菌门是7种作物根际微生物的主要优势门,但是在纲水平和目水平不同作物根际微生物组成存在差异。Alpha多样性分析表明,大豆根际的OTU丰富度(Chao1,P<0.001)和细菌群落多样性(Shannon,P<0.001)在7种作物中最高。非度量多维尺度分析(NMDS)表明,根际微生物群落结构在OTU和PLFAs水平下均以不同作物形成聚类,不同聚类间的差异显著。根际敏感微生物的筛选和比较进一步说明不同作物对根际微生物的选择具有差异性,群落中某些特定菌群优势度存在区别,不同作物具有不同敏感微生物的选择倾向。本研究为构建健康的植物根际微生物群落以促进植物育种提供了基础。     

湿地植物铅的富集特征及根际铅移动性的影响因素研究

【目的】 揭示湿地植物铅的富集特征及根际铅移动性影响因素的作用机理,为人工湿地修复重金属污染水体提供理论指导和依据。 【方法】 通过根箱法研究了五种挺水湿地植物 (大叶皇冠草、黑籽荸荠、圆币草、草龙、小婆婆纳) 根际 pH、氧化还原电位 (Eh)、Fe2+ 和 Fe3+ 浓度、铅 (Pb) 的化学形态及移动性的变化。 【结果】 与非根际相比,五种植物根际pH下降,Fe2+ 和 Fe3+ 浓度显著下降,Eh显著升高,Pb的移动性显著降低 (P<0.05)。与非根际相比,根际pH下降幅度为 0.1～0.4个单位,根际Fe2+和 Fe3+浓度下降幅度为0.6～2.7 mmol/kg。土壤中铅的存在形态主要以残渣态为主 (36.39%～47.54%),其次是铁锰氧化物结合态 (30.16%～41.64%)、有机质结合态 (8.85%～15.08%) 和碳酸盐结合态 (6.89%～12.46%)。五种湿地植物根际Pb的移动性降低的主要原因是根际碳酸盐结合态Pb含量显著下降,其中大叶皇冠草受根际pH、Eh、Fe3+和Fe2+的影响导致其根际Pb移动性降低效应最为显著。 【结论】 五种供试植物Pb主要分布在根部;根表富集的铁膜数量显著高于锰膜数量;供试植物根际Fe3+含量与Pb的移动性因子呈极显著正相关,湿地植物根系铁氧化能力对降低其根际重金属的移动性有重要作用。本研究为人工湿地修复重金属污染水体提供了有力的理论依据。      

耕作制度对紫色水稻土根际与非根际土壤有机碳矿化的影响

以稻田免耕长期定位试验点为平台,研究耕作制度对紫色水稻土根际与非根际土壤有机碳矿化的影响。结果表明,不同耕作制度下稻田土壤有机碳日均矿化量均表现前期快速下降而后逐渐趋于平稳,培养结束时有机碳日均矿化量仅为第1天的3.1%～6.7%;另外,实行稻油轮作可有效降低土壤有机碳矿化速率。垄作免耕(中稻-油菜)处理有机碳日均矿化量、累积矿化量及矿化强度均为根际大于非根际土壤,而其他处理则是根际小于非根际土壤。稻田根际与非根际土壤有机碳平均日均矿化量随培养时间均符合幂函数变化规律,在62d培养期内,除第1天外,非根际土壤平均日均矿化量均大于根际土壤平均日均矿化量,差异变幅范围为67.0%～98.7%。各处理稻田根际与非根际土壤有机碳日均矿化量、累积矿化量和矿化强度均与其相应pH显著相关;根际与非根际土壤间有机碳日均矿化量和累积矿化量差异均与其微生物生物量碳、氮含量显著相关。     

套作对黄瓜根际土壤细菌群落结构的多样性影响

以设施蔬菜中的主要栽培种类黄瓜为研究对象,以毛葱、蒜为套作作物,利用T-RFLP(末端限制性片段长度多态性,Terminal Restriction Fragment Length Polymorphism)技术对套作黄瓜根际土壤细菌群落结构多样性进行了研究。结果表明:套作改变了黄瓜根际土壤细菌群落结构的多样性和优势菌群结构。套种毛葱的黄瓜根际土壤细菌群落结构多样性高于套种蒜的黄瓜根际土壤细菌群落结构多样性;在黄瓜定植前和拉秧期,套作处理的土壤细菌群落结构多样性有比对照高的趋势,而在根瓜期和盛瓜期套作处理的土壤细菌群落结构多样性有比对照低的趋势;毛葱的套作效果最佳,蒜套作次之。套作提高了黄瓜产量。