土壤微生物在植物获得养分中的作用

大量施用化肥是当今农业的一个重要特征。化肥为粮食增产做出了巨大贡献,同时也带来一系列问题,如土壤酸化、水体富营养化、温室气体排放、资源耗竭等,直接威胁着农业可持续发展。土壤微生物是陆地生态系统植物多样性和生产力的重要驱动者,直接参与了植物获得养分和土壤养分循环两个过程。因此,通过调控土壤微生物的功能,有望降低农业对化肥的过分依赖。介绍了共生固氮菌、菌根真菌和根际促生菌对植物获得养分能力的影响及其机制,分析了土壤微生物对土壤氮、磷循环的影响及其与土壤养分生物有效性、养分损失的关系。依据这些知识,提出了改善植物营养、降低化肥施用的土壤微生物途径。虽然大量试验已证明了土壤微生物在改善植物营养中的重要作用,但是大面积应用土壤微生物技术来改善植物营养还存在不少问题。随着以后对这方面研究的加强以及上述问题的不断解决,土壤微生物有望在降低化肥施用量和维持农业可持续发展中做出重要贡献。     

Minerals in the rhizosphere: overlooked mediators of soil nitrogen availability to plants and microbes

Non-native earthworms are a continued source of environmental change in the northeastern United States that may affect trace metals in the plant-soil system, with largely unknown effects. We assessed earthworm impacts on exchangeable and strong acid extractable (total) concentrations and pools of Al, Fe, Cu, Zn, Mo, Pb in non-point source polluted, forest soil horizons (Organic, A, and B) and foliar metals concentrations in young (<?3 years) Acer saccharum and Polystichum acrostichoides at four proximal forests in the Finger Lakes Region of New York. We observed decreasing total trace metal Organic horizon pools and increasing total trace metal A horizon concentrations as a function of increasing earthworm biomass. Earthworms had limited effects on exchangeable concentrations in A and B horizons and total metal concentrations in the B horizon. Foliar trace metal concentrations in Acer were better explained by earthworm biomass than soil concentrations but foliar concentrations for Polystichum were poorly predicted by both earthworm biomass and soil metal concentrations. Our results suggest that earthworms can affect trace metal uptake by some plants, but not by increasing soil trace metal exchangeability or from changing soil properties (pH, %SOM, or cation exchange capacity). Instead, non-native earthworms may indirectly alter understory plant uptake of trace metals.     

漓江河岸带不同水文环境土壤微生物与土壤养分的耦合关系

基于漓江河岸带典型地段内砾石滩、草地、灌草地和疏林地等4类水文环境梯度上的土壤样品分析,探讨了漓江河岸带土壤养分、微生物数量及微生物量等的变化特征及耦合关系。结果表明:土壤养分含量、土壤微生物数量及微生物量等在不同水文环境下均有显著差异。随着水淹时间的减少,土壤含水量、pH值、有效氮、有效磷和有效钾均呈先增后减的趋势,最大值多出现在灌草地,最小值多出现在砾石滩,而土壤微生物总量、细菌、放线菌数量和微生物量也为先增后减趋势,其数量或含量在灌草地最多,砾石滩最少。简单相关分析表明漓江河岸带各微生物指标与土壤有效氮、有效磷及速效钾相关性较强,与土壤全氮、全磷和全钾的相关性较弱。冗余分析表明土壤有效氮、有效磷和含水量是影响微生物总数、细菌数量、微生物量碳、微生物量氮和微生物量磷的重要因素,而有机质和全氮是影响放线菌数量的重要因素。研究结果说明适当的水文干扰有利于河岸带土壤养分的积累,对土壤微生物数量及其生物量也有显著促进作用;土壤有机质和有效养分含量(有效氮、有效磷等)与微生物数量及微生物量关系密切,其含量很大程度影响着微生物数量及其活性。在漓江河岸带生态保护和评估等研究过程中应充分考虑不同水文环境下的土壤微生物和养分的变化特征及耦合关系。     

退化落叶松人工林近自然化改造对土壤微生物及养分的影响

落叶松人工纯林生产力和地力下降是目前林业生产亟待解决的问题,尤其是第2代人工林,通过近自然化改造是否能提高土壤肥力,改善土壤微生物多样性及养分,缺乏深入的研究.本文对第2代落叶松人工纯林近自然化改造2年内土壤微生物群落的多样性和结构变化以及土壤养分变化进行了调查.结果显示:林隙大小与土壤微生物多样性有较强的相关性,小林隙(25 m2)土壤微生物多样性比大林隙(100 m2)高;改造后第1年,小林隙土壤微生物多样性显著提高,Shannon指数、丰富度指数和均匀度指数均高于大林隙和对照(未间伐);第2年各处理间差异不显著;2年的3个指数比较发现,Shannon指数和丰富度指数均是第1年明显高于第2年,而均匀度指数变化相反,说明第1年土壤微生物的物种多样性较高但分布不均匀.在种类遗传相似性方面,小林隙与对照更为接近,大林隙可能由于小气候变化较大致使土壤微生物变化较剧烈.改造后第1年土壤养分含量显著增加,尤其是有效P,大林隙增幅达80％,小林隙达52％,有效N的含量也有所增加,有效K含量增加不明显.第2年土壤养分含量有所下降,但大、小林隙下降的格局不同,大林隙有效P含量下降极显著,小林隙养分下降不显著.本研究为近自然化改造的可行性及其科学实施提供了依据.     

扎龙季节性湿草甸土壤养分和土壤微生物特性

以扎龙自然湿地典型季节性湿草甸为试验对象,研究了土壤微生物特性和土壤养分空间分布规律及其主要影响因子.结果表明:土壤养分、微生物群落数量、微生物量碳、氮均呈现明显的垂直分布特征;土壤酶活性的空间分布因受多种因素影响而表现复杂.逐步线性回归分析表明:土壤微生物生物量碳、氮均分别与β-葡萄糖苷酶、脲酶、磷酸酶显著相关(P<0.05);有机碳与放线菌数量、过氧化氢酶活性显著相关(P<0.05);速效钾、全氮、水解性氮、C/N分别与放线菌数量、细菌数量、β-葡萄糖苷酶活性、土壤微生物生物量氮显著相关(P<0.05);全P、pH与土壤微生物活性无显著相关关系(P>0.05).采用主成分分析构建了湿地土壤养分的评价模型及微生物学预测模型.     

Effects of intercropping sugarcane and soybean on growth, rhizosphere soil microbes, nitrogen and phosphorus availability

The effects of sugarcane plantation intercropped with soybean on plant growth, yield, enzyme activity, nitrogen and phosphorus contents, the microbe quantity of rhizosphere soil were investigated. Results showed that dry weight of biomass and yield under sugarcane/soybean intercropping were increased by 35.44 and 30.57 % for sugarcane, and decreased by 16.12 and 9.53 % (100-grain weight) for soybean, respectively. The nitrogenase activity of intercropping soybean nodule was significantly increased by 57.4 % as compared with that in monoculture models. The urease activities of intercrops sugarcane and soybean were promoted by 89 and 81 % as compared to that of the monoculture models, respectively. The effective nitrogen and phosphorus contents of rhizospheric soil of intercrops sugarcane and soybean were increased by 66 and 311.7 %, respectively, as compared to those in the monoculture system. Microbe number of rhizosphere soil in the intercropping pattern increased significantly as compared to those in the monoculture models. The quantities of bacteria, fungi, and actinomyces increased by 42.62, 14.5 and 78.5 % in the intercropping sugarcane, while the intercropping soybean increased by 188, 183 and 73 %, respectively. Therefore, growing sugarcanes in combination with soybean can be considered a good agriculture management practice, helping to promote plant growth, yield and increase soil nutrients.     

多伦县土壤营养元素有效态含量的影响因素研究

在对该区土壤进行全面调查、分析、评价的基础上,对影响土壤中元素有效态含量的因素如土壤类型、地貌类型、土地利用类型,以及砂化等进行讨论。结果表明,这些因素均影响到元素有效态含量。过度开垦和放牧是造成土壤沙化和肥力下降的主要原因。研究认为全理利用土地资源,实行退耕还草、还林、改善生态,以控制沙化和优化农、林、牧结构比,并结合配方施肥。则是提高粮食、牧草单产及经济效益的关键。     

Soil microbes and plant fertilization

With respect to the adverse effects of chemical fertilization on the environment and their related expenses, especially when overused, alternative methods of fertilization have been suggested and tested. For example, the combined use of chemical fertilization with organic fertilization and/or biological fertilization is among such methods. It has been indicated that the use of organic fertilization with chemical fertilization is a suitable method of providing crop plants with adequate amount of nutrients, while environmentally and economically appropriate. In this article, the importance of soil microbes to the ecosystem is reviewed, with particular emphasis on the role of plant growth-promoting rhizobacteria, arbuscular mycorrhizal fungi, and endophytic bacteria in providing necessary nutrients for plant growth and yield production. Such microbes are beneficial to plant growth through colonizing plant roots and inducing mechanisms by which plant growth increases. Although there has been extensive research work regarding the use of microbes as a method of fertilizing plants, it is yet a question how the efficiency of such microbial fertilization to the plant can be determined and increased. In other words, how the right combination of chemical and biological fertilization can be determined. In this article, the most recent advances regarding the effects of microbial fertilization on plant growth and yield production in their combined use with chemical fertilization are reviewed. There are also some details related to the molecular mechanisms affecting the microbial performance and how the use of biological techniques may affect the efficiency of biological fertilization.     

Soil microbial biomass influence on strontium availability in mine soil

Abstract

The main aim of our work was to assess whether strontium (Sr) affects soil microbial biomass size and activity, and the involvement of said biomass in the availability process of the metal. In addition, information concerning the distribution and mobility of the stable element within ecosystems may allow the prediction of the behaviour of its radioisotope counterpart, ⁹⁰Sr. Samples were collected in the surroundings of a strontium mine and characterised for total and diethylene triamine pentaacetic acid (DTPA)-extractable Sr, total organic C (TOC), microbial biomass C (MBC), MBC/TOC ratio and metabolic quotient (qCO₂). Moreover, MBC and DTPA-extractable Sr were measured during a 45-day incubation experiment of samples soils amended with maize. Overall, increased levels of total Sr had a negative effect on both TOC and MBC. DTPA-extractable Sr was significantly correlated to MBC/TOC suggesting a possible role of soil microbial biomass in the mobilisation of the element. The synthesis of new microbial biomass after soil amendment was negatively affected by the initial content of DTPA-extractable Sr. Conversely, there was a linear positive relationship between newly formed MBC and DTPA-extractable Sr during the incubation, indicating that soil microbial biomass may promote the mobilisation of Sr. These findings indicate that soil amendment with easily degradable organic substrate significantly increases Sr mobility and availability.     

曲靖植烟土壤养分空间变异及土壤肥力适宜性评价

采用GPS技术在云南曲靖烟区布置了2088个采样点,测定其耕作层(0～20 cm)土壤主要养分含量,利用经典统计方法和地统计学方法对植烟土壤养分状况的总体特征和空间变异特征进行分析,并采用模糊数学方法对植烟土壤肥力适宜性进行综合评价.结果表明:曲靖植烟土壤pH、有机质、有效硫和水溶性氯含量适宜,全氮和碱解氮含量偏高,速效钾、有效钙、有效镁、有效铜、有效铁、有效锌、有效钼和有效锰含量丰富,速效磷含量中等,全磷、全钾和有效硼含量偏低;区域内植烟土壤养分指标均表现为各向异性分布,其中速效磷和有效硼的空间变异主要受随机性因素的影响,其他养分指标的空间变异是结构性因素和随机性因素共同作用的结果.植烟土壤肥力适宜性指数为优的区域缺乏,为良的区域占8.0%,一般的区域占51.6%,中等的区域占39.0%,为差的区域占1.4%.     

Soil nutrients and water availability interact to influence willow growth and chemistry but not leaf beetle performance

We investigated the effects of soil nutrient and water availability on the growth and chemistry of the silky willow (Salix sericea Marshall), and on the performance of the imported willow leaf beetle (Plagiodera versicolora Laichartig). Our major aims were to determine whether there are nutrient–water interactions on plant traits and whether this leads to parallel interactions for herbivore performance. We used a 2 × 3 fully factorial design, which consisted of high and low nutrient treatments crossed with dry, field capacity, and flooded water treatments. We found that nutrient additions increased plant growth, but only in field capacity and flooded conditions (nutrient–water interaction). Leaf nitrogen content also depended on the interaction between soil nutrients and water: nutrient addition resulted in a larger increase in foliar nitrogen in the field capacity treatment than in the flooded and dry treatments. Of the two phenolic glycosides measured, salicortin and 2′‐cinnamoylsalicortin, only one was affected by the treatments. 2′‐cinnamoylsalicortin concentration was lower in the high nutrient–dry treatment compared with the other treatments. In contrast to plant responses, there were no interactions found for larval or pupal weight or development time. Nutrient addition led to an increase in female pupal weight, and foliar N was positively correlated with female pupal weight and negatively correlated with female development time. In addition, leaf water was positively correlated with female development time. The lack of interactions for insect performance may stem from the small absolute differences in foliar nitrogen content associated with the interaction between the nutrients and water. Taken together, our results suggest that nutrient–water interactions influence plant traits that are potentially important for insect performance (leaf nitrogen and water), but these interactions do not produce parallel interactions in beetle performance.     

Residual effect of iron-nickel interactions on the availability of nutrients

Summary Residual value of micronutrients pair (Fe × Ni) has been investigated in a Cu-deficient and P-responsive red soil by growing a second crop of maize in which maize had already been grown with factorial combination of 4 levels of Fe and Ni. Dry matter yield (shoots) has been found to be lower (50%) in comparison to first year. Due to combined Fe and Ni treatments the concentration and uptake of Fe by shoots increased significantly while reverse was the case in roots, showing synergistic effect of Ni on Fe absorption and its significant translocation to shoots. Concentration and uptake of Mn by shoots and roots decreased at higher levels of Fe and Ni. Concentration of P in shoots decreased whereas concentration and uptake of Zn by shoots remained unchanged. Under the combined effect of Fe × Ni, maize roots contained more of nutrients as compared to shoots. Thus roots appear to be responsible for the recycling of micro and macronutrients in soils.     

子午岭典型植被凋落叶-土壤养分与酶活性特征

对黄土高原子午岭任家台林区内刺槐、油松、侧柏等3种人工林以及桦树、辽东栎等两种天然次生林的凋落叶C、N、P含量、林下土壤基本理化性质和碱性磷酸酶、脲酶、蔗糖酶3种酶的活性进行分析,并研究凋落叶C、N、P含量与土壤C、N、P含量之间的相关关系,以及土壤基本理化性质与酶活性之间的相关关系,为该区植被恢复效果评价提供科学依据与参考。结果发现:刺槐、辽东栎凋落叶碳氮比值显著低于其他植被,凋落叶分解速率相对较快;辽东栎土壤有机碳、全氮含量最高,分别为19.18、1.60g/kg,刺槐土壤全磷含量最高(0.61g/kg);土壤酶活性主要受土壤有机碳、全氮、容重及p H影响,与土壤全磷相关性不显著;人工林中,侧柏土壤中3种酶活性均高于其他植被,且侧柏凋落叶碳氮比值相对较低,分解速率较快,相比于刺槐作为造林树种更占优势。     

Influence of nutrients and currents on the genomic composition of microbes across an upwelling mosaic

Metagenomic data sets were generated from samples collected along a coastal to open ocean transect between Southern California Bight and California Current waters during a seasonal upwelling event, providing an opportunity to examine the impact of episodic pulses of cold nutrient-rich water into surface ocean microbial communities. The data set consists of ∼5.8 million predicted proteins across seven sites, from three different size classes: 0.1–0.8, 0.8–3.0 and 3.0–200.0 μm. Taxonomic and metabolic analyses suggest that sequences from the 0.1–0.8 μm size class correlated with their position along the upwelling mosaic. However, taxonomic profiles of bacteria from the larger size classes (0.8–200 μm) were less constrained by habitat and characterized by an increase in Cyanobacteria, Bacteroidetes, Flavobacteria and double-stranded DNA viral sequences. Functional annotation of transmembrane proteins indicate that sites comprised of organisms with small genomes have an enrichment of transporters with substrate specificities for amino acids, iron and cadmium, whereas organisms with larger genomes have a higher percentage of transporters for ammonium and potassium. Eukaryotic-type glutamine synthetase (GS) II proteins were identified and taxonomically classified as viral, most closely related to the GSII in Mimivirus, suggesting that marine Mimivirus-like particles may have played a role in the transfer of GSII gene functions. Additionally, a Planctomycete bloom was sampled from one upwelling site providing a rare opportunity to assess the genomic composition of a marine Planctomycete population. The significant correlations observed between genomic properties, community structure and nutrient availability provide insights into habitat-driven dynamics among oligotrophic versus upwelled marine waters adjoining each other spatially.     

Soil microbes under threat in the Amazon Rainforest

Soil microorganisms are sensitive indicators of land-use and climate change in the Amazon, revealing shifts in important processes such as greenhouse gas (GHG) production, but they have been overlooked in conservation and management initiatives. Integrating soil biodiversity with other disciplines while expanding sampling efforts and targeted microbial groups is crucially needed.     

The effects of olive mill waste compost and poultry manure on the availability and plant uptake of nutrients in a highly saline soil

The effects of a compost (produced from by-products of the olive oil industry) and a poultry manure on mineral ion solubility and exchangeability in a highly saline agricultural soil (electrical conductivity for a 1:5 soil:water extract=1.85 dS m(-1)) from Murcia (SE Spain) were studied. The organic amendments did not change significantly the soil electrical conductivity or the soluble Na(+), Ca(2+) or Mg(2+). Only soluble K(+) increased, due to the K(+) supplied by the amendments. The cation exchange capacity increased in treated soils, the exchange complex being mainly saturated with Ca(2+), Mg(2+) and K(+). However, Na(+) was not retained in the exchange sites, and the sodium absorption ratio remained low. The compost and manure increased markedly the shoot growth of the salt-tolerant Beta maritima L. (sea beet) and Beta vulgaris L. (sugar beet). For B. maritima, this seemed to be related to decreases in the shoot concentrations of Na(+) and Cl(-) and increases in K(+) and H(2)PO(4)(-). In the case of B. vulgaris, increases in shoot H(2)PO(4)(-) and B and, for manure-treated soil, a decrease in shoot Na(+) may have been involved. Cultivation of tomato (Lycopersicon esculentum Mill. cv. Moneymaker) in the soil used previously for B. vulgaris indicated that the effects of the manure on tissue cation concentrations were longer-lasting than those of the compost.     

土壤微生物RAPD分析体系的优化研究

采用正交实验设计,对影响土壤微生物RAPD扩增体系的Mg2+、dNTP浓度及引物浓度进行了研究,同时对退火温度、延伸时间及循环次数进行摸索。结果表明,适宜土壤微生物PCR扩增反应在25μl体积中进行,包括7ng土壤微生物DNA样品、20pm随机引物l、.5uTaq酶、3.0mmol.L-1Mg-CL2和0.2mmol.L-1dNTP。PCR扩增反应进程如下:94℃3min,使土壤DNA变性;然后再进行39个循环,每个循环包括94℃1min,37℃40s,72℃90s,结束后72℃延伸7min。     

Effects of mercury compounds on soil microbes

Summary Even low concentrations of mercury compounds in agar media strongly decreased the number of soil microbes that could be isolated on these media.Mercury compounds added to the soil in very high concentrations inhibited CO₂-evolution, dehydrogenase activity, and nitrification. In contrast, the number of microbes increased somewhat in a clay soil treated with HgCl₂. Phenylmercury acetate had a stronger inhibiting effect than HgCl₂. In sandy soil the microbial processes were inhibited more strongly than in clay soil.Mercury compounds present in the soil or added in low concentrations are not expected to seriously disturb organic-matter breakdown, nitrogen mineralization, or the soil-microbe numbers.