Phospholipid Fatty Acid Signatures Research Articles

Comparison of leaf litter decomposition and microbial decomposer communities in fringe and riverine mangroves in French Guiana

Mangroves are highly productive and changing forests located in the intertidal zone of tropical regions. Leaf litter decomposition represents a substantial part of their carbon sink abilities. Little is known about the potential effect of climate change on this key process of ecosystem functioning. This study compared leaf litter microbial decay between fringe and riverine Avicennia germinans stands. A direct and reciprocal transplant experiment using litterbags was setup in French Guiana to test 3 hypotheses: (i) the activities and abundance of microbial decomposers are lowest in the fringe mangroves due to exposure to saline water and tidal immersion; (ii) for these reasons, litter decomposes faster in riverine stands; and (iii) according to the home-field advantage hypothesis, litter decomposes more rapidly in the environment from which it originates. Remaining litter masses, abundance of litter microbial community (phospholipid fatty acid signatures (PLFA)), and their functional capability (enzyme activities and Biolog) were assessed. Litter directly transplanted in riverine stands showed higher enzymatic activity (+ 77%), catabolic diversity (+ 10%), and microbial biomass (+ 60%) than litter transplanted directly in fringe stands. In contrast, both riverine and fringe derived litter showed faster decay at the fringe (14% mass loss) than riverine site (4% mass loss) between 30 and 45 days. Here, environmental conditions associated with different distances from the sea such as salinity and inundation regimes, rather than microbial features are suggested as main factors affecting decomposition process. Expected sea level rise in the coastal Guianas may therefore modify the mangroves productivity in the coming decades.

Fatty acid signatures of sediment microbial community in the chronically polluted mangrove ecosystem

Phospholipid fatty acid (PLFA) analysis was used to examine variation in the distribution of microbial communities in heavily polluted mangrove sediments of Thane creek, west coast of India. A total of 40 individual PLFAs representing 11 functional groups were identified in the sediment and were mainly dominated by saturated fatty acids (anaerobic prokaryotes) >50%. Significant dominance of PUFA, 16:3 ω6c (34.2%) indicators of micro-eukaryotes, in subsurface depth (p < 0.05) suggests input from the remnants of marine microalgae. Declined mean relative abundance of fungi (<6%) and actinomycetes (<1%) were detected in the sediment indicating their sensitivity to anthropic stressors. Homogenous profile of microbial diversity indicating active bioturbation. Cumulative metabolic stress evident from SAT/MUFA (>1), B/F (>1) and G+/G– (<1) ratio and prolonged hypoxia to be prevalent in the creek during the study. In conclusion, PLFA signatures can thus be used as potential biomarkers of environmental monitoring and proxy for interpreting ecosystem health.

Effects of different patterns of maize-straw application on soil microorganisms, enzyme activities, and grain yield

ABSTRACT The present study aimed to assess the influences of corn straw application on the soil microbial organisms, soil enzyme activities and the grain yield. Four treatments were evaluated: (i) The straw was ploughed into soil using a fence hydraulic turning plow with ploughing depth of 30-40 cm(PD). (ii) The self-developed straw deep returning machine was used to bury 30-40 cm in the sub-surface layer of soil (SD). (iii) The straw was mulched and no tillage sowing(M). (iv)Without straw application(CK). Soil samples of different deep(0-20 cm, 20-40 cm soil layer) were taken during the corn growth stage to determinesoil biological characteristics.Our results suggested that soil microorganisms were not increased by straw mulching. Straw deep ploughing and returning (PD treatment) could effectively improve the phospholipid fatty acids(PLFAs) of bacteria, actinomycetes, and fungi, the activities of urease,invertase,dehydrogenase and polyphenoloxidase, even the grain yield. In 20-40 cm subsoil layer, the effects were more obvious than those of topsoil. The mean yield of PD treatment was higher than SD,M and CK. The results showed that the PLFA signatures and soil enzyme were both sensitive to the changes of soil environment condition by the application of straw. In the actual field production, we should adopt the appropriate way of straw returning to the field to achieve not only the improvement of soil quality, but also the increase of grain yield.

Effect of land use and carbonates on organic matter stabilization and microbial communities in Mediterranean soils

Soil organic matter (SOM) is sensitive to land use and to physico-chemical soil properties as well soil microbial communities controlling SOM stabilization. Our study aimed at exploring how carbonates of Mediterranean soils – known to stabilize SOM by enhancing soil aggregation and binding SOM by calcium – are affecting SOM and microbial communities under different land uses. In soils with and without carbonates sampled in forests, cultivated and abandoned fields, we have fractionated SOM-pools according to particle sizes and determined C mineralization rates and polyvalent cations in these fractions. In agreement with larger scale assessments in the Mediterranean, our results show that SOM contents are greater in forest than in agricultural soils, but that the differences among land use types depend on carbonate contents. While SOM contents are greater in carbonated soils of forests, cultivated soils have low SOM levels independent of the carbonate content, presumably due to a reduced protection of particulate SOM by century-long intense tillage. Forest soils contain particularly large amounts of SOM associated with the coarser soil fraction. In this fraction, C mineralization was smallest in the carbonated forest soil, possibly due to a low SOM quality indicated by high C/N ratios and low δ15N values. Greater contents of Ca, Fe and Al in carbonated soils also suggests that stabilization through Ca and phyllosilicates was important. Mineralization of sand-associated SOM was highest in cultivated and abandoned soils, which is indicative for a small SOM stabilization, which in turn might restrict SOM accumulation after land abandonment. Microbial communities assessed by phospho-lipid fatty acid signatures and microbial carbon use efficiency were more closely associated with land use than with carbonate content – a pattern that reflects the distribution of C pools among size fractions which differed more strongly among land use types than between soils with and without carbonates.

Bioindicators and nutrient availability through whole soil profile under orange groves after long-term different organic fertilizations

We investigated long-term (18 years) effects of three organic (cow manure (CM), poultry manure (PM), compost from agro-industry orange wastes (OW)) and one inorganic fertilization (IF) on various soil biological indicators (microbial biomass C, soil respiration, total phospholipid fatty acids (PLFAs), total bacteria, Gram-positive and Gram-negative bacteria and fungi) and nutrient contents (total and extractable organic C, total and mineral N, available P and K) along the profile of a Typic Haplustept under orange Mediterranean orchards. All fertilizers were added on the same N content basis (190 kg N ha−1 per year). Variables related to carbon cycling gradually worsened with depth, regardless of treatment, but at any soil depth they improved according to IF OW > PM > IF. Organic manures favoured Gram-negative bacteria, especially between 35 and 55 cm depth, whereas Gram-positive bacteria flourished better under inorganic fertilization up to 55 cm. Organic fertilizers increased microbial biomass C, compared with IF, with CM being the most efficient, i.e. inducing the greatest C use efficiency, in turn coupled with a greater amount of fungi compared to bacteria. This is crucial from the environmental viewpoint, since fungi better contribute to soil C storage. PLFAs signatures of microbial communities reflected the differences in resources availability determined by soil depth and fertilizer type; indeed, fungi and Gram-negative bacteria responded more promptly to nutrient contents than other microbial groups. Oligotrophic conditions in deeper soil horizons increased the metabolic quotient, an indicator of stress conditions.

鄱阳湖湿地土壤微生物群落结构沿地下水位梯度分异特征

PDF HTML阅读 XML下载 导出引用 引用提醒 鄱阳湖湿地土壤微生物群落结构沿地下水位梯度分异特征 DOI: 10.5846/stxb201705220946 作者: 作者单位: 中国科学院地理科学与资源研究所,中国科学院地理科学与资源研究所,中国科学院地理科学与资源研究所,中国科学院地理科学与资源研究所,中国科学院地理科学与资源研究所,中国科学院地理科学与资源研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41471088）；地方合作项目（鄱阳湖水生态综合模型研究及开发） Variation in the distribution of soil microbial community structure along ground water level gradients in the Poyang Lake Wetland Author: Affiliation: Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了揭示地下水位梯度对湿地土壤微生物群落的影响，在鄱阳湖典型碟形湖泊白沙湖洲滩湿地设置了200m×300m大样地，沿地下水位梯度划分4个样带（从湖岸到湖心依次为GT-A，GT-B，GT-C，GT-D），采集了不同梯度带的土壤样品，利用磷脂脂肪酸法分析其土壤微生物群落结构分异特征。结果表明，随着地下水位抬升，土壤pH和沙粒含量升高，而有机碳、容重、粘粒和粉粒含量降低。与地下水位最低的梯度（GT-A）相比，地下水位在地表上下波动（GT-D）时，土壤微生物量碳氮及其分配比例分别增加了2.82、4.30、5.77和7.15倍；土壤微生物总量、细菌生物量、放线菌生物量、革兰氏阳性细菌及革兰氏阴性细菌生物量分别增长了106.8%、117.2%、74.9%，107.9%和207.2%。洲滩地下水位梯度的升高增加了土壤微生物群落的环境压力，进而降低了其群落结构的多样性。土壤微生物群落结构组成与土壤pH、含水量、沙粒含量以及碳氮比呈显著相关关系，而土壤微生物商则主要受pH和土壤质地的影响。以上结果表明地下水位梯度所引起的土壤微环境变化对微生物量、土壤有机碳周转和群落结构均产生了深刻影响。 Abstract:To reveal the response of soil microbial community structure to the changes of ground water level, a 200m×300m field experimental site was setup in the beach of Baisha Lake, a typical shallow lake of the Poyang Lake Wetlands. This site included 4 ground water levels:GT-A, GT-B, GT-C, GT-D (moving from shore to center). Phospholipid fatty acids (PLFA) analysis was applied to determine the microbial community structure. Results showed when ground water level raised from GT-A to GT-D, soil pH and sand content increased and soil organic carbon (SOC), bulk density, clay and silt particle contents decreased. Compared to GT-A, microbial biomass carbon (MBC), microbial biomass nitrogen(MBN), and their allocation ratio of GT-D were significantly more by 2.82, 4.30, 5.77 and 7.15 time. The abundances of total PLFAs, bacterial, actinomyces, gram-positive bacteria and gram-negative bacteria increased 106.8%, 117.2%, 74.9%, 107.9% and 207.2%. The raise in ground water level enhanced the environmental stress on the microbial community, resulting in a decrease in microbial bio-diversity. Soil pH, moisture, sand contents as well as the C:N ratio have significant correlations with PLFA signatures. Further, the microbial quotient (MBC/SOC) is mainly influenced by soil pH and texture. In summary, the results show significant effects of ground water level on both soil microbial biomass and community structure during the dry season. 参考文献 相似文献 引证文献

Interactive effects of temperature and moisture on composition of the soil microbial community

SummaryA wealth of knowledge exists on the response of soil processes to variation in environmental factors such as temperature and moisture, but the response from the soil microbial communities that control these processes remains poorly understood. We carried out a full factorial incubation experiment to investigate the single and interactive effects of temperature (10, 17, 24, 31 and 38°C) and moisture (20, 40, 60, 80 and 100% water holding capacity (WHC)) on composition of the soil microbial community characterized by the phospholipid fatty acids (PLFAs) method. The single and interactive effects of temperature and moisture were statistically significant (P &lt; 0.05) for almost all the selected PLFA signatures, including fungi (F), bacteria (B), Gram‐positive bacteria (G+), Gram‐negative bacteria (G−), actinomycetes (ACT) and the bacterial stress index (BSI). Although the F/B ratio increased and the G+/G− ratio decreased with increasing temperature, they were not significantly affected by moisture and its interaction with temperature. In general, the concentrations of fungal PLFAs were smaller at higher temperatures, but not altered by changes in moisture. In contrast, the concentrations of bacterial PLFAs were larger at higher temperatures and moderate moisture contents. Although we manipulated temperature and moisture in the incubation, the treatments and the treatment‐altered soil properties (dissolved organic carbon (DOC) and inorganic nitrogen (ION)) together explained 18% of the total variation in selected PLFA signatures and the temperature effect contributed the most (12%). Significant correlations between community composition variables (F, B and F/B) and soil properties (DOC and ION) indicated substantive indirect effects of temperature and moisture on the composition of the soil microbial community by altering substrate availability. Our results suggest that soil microbial communities might shift towards a more bacteria‐dominated composition under warmer temperatures and moderate moisture conditions in subtropical forest regions.Highlights How do temperature and moisture independently and interactively affect soil microbial community composition? Concentrations of bacterial PLFAs were larger at higher temperatures and moderate moisture. Concentrations of fungal PLFAs were smaller at higher temperatures, but did not respond to moisture differences. Increased soil carbon and nitrogen availability mainly benefitted bacteria under higher temperatures and moderate moisture.

Assessing Biological Impacts of Land Reclamation in a Mining Region in Canada: Effects of Dolomitic Lime Applications on Forest Ecosystems and Microbial Phospholipid Fatty Acid Signatures

The ability of an ecosystem to withstand serious disturbances may depend in part on the diversity of the system, with soil microbiological communities being coupled to their associated vegetation. The main objectives of the present study were (1) to determine the association between soil microbial diversity, abundance, and activities with diversity and sustainability of remediated mining-damaged ecosystems in Northern Ontario, and (2) to assess the effects of dolomitic lime applications on aboveground and belowground biodiversity and community structures. Results revealed that liming increases soil pH, cation exchange capacity (CEC), forest tree species diversity and abundance, and the overall ecosystem health even 25 to 35 years after dolomite applications. The mean Shannon index value was significantly higher in limed compared to unlimed sites. Tree species richness was 4.0, 6.0, and 7.7 for unlimed, limed, and reference sites, respectively. Overall, the mean health index revealed a significant improvement in population health in limed sites (index score = 7) compared to unlimed areas (index score = 4). Soil microbial biomass and respiration were also increased by liming. Surprisingly, the main component of soil microbial biomass in limed, unlimed, and reference sites within the vicinity of the restored lands was bacteria (mostly Gram (−). Significant difference was also observed between limed, unlimed, and reference sites for arbuscular mycorrhizal fungi, Gram (−) bacteria, Gram (+) bacteria, anaerobe, and actinomycetes abundance. The ratios between fungi and bacteria and among other phospholipid fatty acid (PLFA) measures were extremely low suggesting that the targeted region is still under environmental stress. No apparent associations among soil microbial biomass, soil respiration, and forest plant diversity or abundance were observed. Soil pH levels and organic matter amounts and quality appear to be the main factors affecting these parameters. Molecular analysis of main tree species within the impacted region revealed no change in genetic variation among plant populations on either limed or unlimed lands contaminated with metals over two generations.

南亚热带红椎和格木人工幼龄林土壤微生物群落结构特征

PDF HTML阅读 XML下载 导出引用 引用提醒 南亚热带红椎和格木人工幼龄林土壤微生物群落结构特征 DOI: 10.5846/stxb201411242328 作者: 作者单位: 中国林科院森环森保所,中国林科院森环森保所,中国林科院森环森保所,四川省林业科学研究院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科技支撑计划项目（2012BAD22B01） Characteristics of soil microbial community structure in two young plantations of Castanopsis hystrix and Erythrophleum fordii in subtropical China Author: Affiliation: Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry,Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用氯仿熏蒸浸提法和磷脂脂肪酸法（Phospholipids fatty acid，PLFA）研究了我国南亚热带地区非固氮树种红椎（Castanopsis hystrix）和固氮树种格木（Erythrophleum fordii）人工幼龄林土壤微生物生物量与微生物群落结构特征。结果表明，在旱季和雨季，红椎幼龄林土壤微生物总PLFAs量，细菌PLFAs量、放线菌PLFAs量及丛枝菌根真菌PLFAs量均大于格木幼龄林。红椎幼龄林土壤PLFA Shannon多样性指数（HPLFA）在旱季和雨季均大于格木幼龄林。主成分分析表明，土壤微生物群落结构组成受到林分类型和季节的双重影响。冗余分析表明，土壤硝态氮（NO3--N）含量、土壤含水量、pH及土壤微生物生物量氮（MBN）与特征磷脂脂肪酸之间呈显著相关关系。以上结果表明固氮树种格木与非固氮树种红椎人工幼龄林对土壤微生物生物量和群落结构的影响存在显著差异。 Abstract:The effects of two plantation stands of non-N-fixing Castanopsis hystrix and N-fixing Erythrophleum fordii on soil microbial biomass and microbial community structure in south subtropical China were studied by fumigation-extraction and phospholipid fatty acid (PLFA) analyses. The results showed that soil pH, soil N status (total N, NH4+-N and NO3--N), soil microbial total PLFAs, bacterial PLFAs, actinomycetes PLFAs and arbuscular mycorrhizal fungi PFLAs were significantly influenced by plantation type and season, while only season significantly influenced soil microbial biomass carbon and fungal PLFAs, but soil microbial biomass nitrogen(MBN) was not significantly affected by plantation type and season. The content of soil NH4+-N and NO3--N in C. hystrix plantation were significantly higher than those in E. fordii plantation during both the dry and rainy seasons. In addition, the amounts of soil microbial total PLFAs and bacterial, actinomycete, and arbuscular mycorrhizal fungi PFLAs in C. hystrix plantation were significantly higher than those in E. fordii plantation during both the seasons as well. Furthermore, the richness and Shannon diversity index of soil microbial PLFAs were significantly altered by plantation type, Shannon diversity index of soil microbial PLFAs in C. hystrix plantation was significantly higher than that in E. fordii plantation during both the seasons. Principal component analysis indicated that variations in the soil microbial community structure were affected by both the plantation types and seasons. Redundancy analysis of soil microbial community structure and environmental factors showed that NO3-, soil water content, soil pH, and microbial biomass nitrogen had significant correlations with PLFA signatures. Thus, our study results showed significantly different effects of non-N-fixing C. hystrix and N-fixing E. fordii plantation stands on the soil microbial biomass and community structure. Overall, soil pH and N status may be the main factors that could regulate soil microbial biomass and community structure in the studied plantations. 参考文献 相似文献 引证文献

Transition to second generation cellulosic biofuel production systems reveals limited negative impacts on the soil microbial community structure.

Currently we lack knowledge on how the soil microbial community responds to the transition from traditional grain production to cellulosic feedstock production systems with residue removal for biofuel production. Implementation of second-generation biofuel production systems could create a challenge in meeting the goal of providing cellulose biomass if the processes impact soil's function as part of ecosystem services. Our goal was to assess the transition period as we move from a grain harvest system with residue return into biomass production systems with both residue and grain removal. The existing traditional systems were continuous corn (CC) and corn–soybean rotations (corn–soybean–corn (R1) or soybean–corn–soybean (R2)). The biomass production systems include a previously established mixed tall grass prairie dominated by big bluestem (Andropogon gerardii; PR) where the above ground biomass is now harvested when it had been previously burned, corn–soybean rotations transitioned to residue recovery based on: Miscanthus×giganteus (MS), dual-purpose sorghum (Sorghum bicolor; SG), upland switchgrass (Panicum virgatum; c.v. Shawnee; SW) and a tilled continuous corn changed to continuous no-till corn (Zea mays; CR) with the residue removed. Over a three-year transition period, biological indicators of soil health included microbial biomass and community structure profile using phospholipid fatty acid (PLFA) biochemical markers, and an assessment of the saprotrophic fungal diversity using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction amplified ITS rRNA genetic marker. Over the course of the transition, bacterial biomass dominated soils in the annual systems of CC, R1, R2, CR and SG, and the perennial system of MS. While fungal biomass dominated soils under PR. Fungal PLFA signatures and ITS-DGGE profiles demonstrated similarity between PR and the transitioned SW system, and to a lesser extent SG. In contrast, MS did not statistically alter the microbial biomass, community structure or fungal diversity away from patterns observed in the corn–soybean system. Our findings support microbial community stability and resilience as we found no negative impacts in any of the biomass recovery systems (PR, MS, SG, SW and CR) relative to the traditional systems (CC, R1 and R2), as indicated by measures of soil health. We did find that the selection of the plant types used in the biomass system could have a significant impact on the structure of both bacterial and fungal communities. With respect to soil health indicators including the fungal community, our findings suggest the dual-purpose SG system provides an encouraging alternative to continuous maize when considering plant biomass production. The selection of this dedicated perennial biomass system offers an avenue to enhance indicators of soil health and associated ecosystem services while supporting the bioenergy economy.

The effect of cowpea (Vigna unguiculata) with root mucilage on phenanthrene (PHE) dissipation and microbial community composition using phospholipid fatty acid (PLFA) analysis and artificial neural network (ANN) modeling

The objective of this study was to evaluate the effects of cowpea with root mucilage on phenanthrene (PHE) dissipation and microbial community composition. The experiment was conducted using three cowpea breeding lines (Vigna unguiculata) that differed in mucilage production. The highest PHE dissipation rate was achieved in soils planted with high root mucilage producing cowpea C1 inoculated with Bradyrhizobium, leading to 91.6% PHE disappearance in 5 weeks. Relative changes in microbial populations of different treatments were investigated by monitoring PLFA signatures. Data was analyzed by principle component analysis (PCA) and by construction of artificial neural network (ANN). Based on the PCA profiles, the ten treatments were separated into four groups. The ANN results demonstrated that fungal biomass were significantly influenced by root mucilage produced by cowpea (C1), and gram positive to gram negative bacteria ratios were shown to have a positive correlation with the presence of Phenanthrene (PHE) via a Kohonen self-organizing map (KSOM). Total PLFA biomass was significantly higher in the soil planted with cowpea line C1 inoculated with Bradyrhizobium than other treatments. Results suggest that root mucilage may contribute to the changes of the microbial biomass and composition in the rhizosphere, which in turn may positively impact PAH bioremediation.

Synergic degradation of diesel by Scirpus triqueter and its endophytic bacteria.

The endophytic bacterium isolated from Scirpus triqueter was proved to be an oil-degraded bacterium. A pot experiment was conducted to investigate the removal ratio of diesel under the combined effect of oil-degraded microorganism (Pseudomonas sp. J4AJ) and S. triqueter. The effect of diesel on plant growth parameters, soil enzymes and microbial community was assessed after 60 days. The results showed that the soils which were planted with S. triqueter and inoculated with J4AJ displayed the highest removal ratio (54.51 ± 0.15%) after 60-day experiment. However, the removal ratio of J4AJ-treated soils was 38.97 ± 0.55%. Diesel was toxic to S. triqueter, as evidenced by growth inhibition during the experimental period. However, the plant height and stem biomass in the soils inoculated with J4AJ significantly increased. The combined effect of S. triqueter and J4AJ improved the enzyme activities of the catalase and dehydrogenase in the contaminated soil. The diversity index in soils under the effect of S. triqueter combined with J4AJ was lower than that of the other soil samples. The principal analysis of phospholipid fatty acid signatures revealed that the combined effect of S. triqueter and J4AJ increased the differences of soil microbial community structure with the other treatments.

Effects of application of corn straw on soil microbial community structure during the maize growing season

This study investigated the influence of corn straw application on soil microbial communities and the relationship between such communities and soil properties in black soil. The crop used in this study was maize (Zea mays L.). The five treatments consisted of applying a gradient (50, 100, 150, and 200%) of shattered corn straw residue to the soil. Soil samples were taken from May through September during the 2012 maize growing season. The microbial community structure was determined using phospholipid fatty acid (PLFA) analysis. Our results revealed that the application of corn straw influenced the soil properties and increased the soil organic carbon and total nitrogen. Applying corn straw to fields also influenced the variation in soil microbial biomass and community composition, which is consistent with the variations found in soil total nitrogen (TN) and soil respiration (SR). However, the soil carbon-to-nitrogen ratio had no effect on soil microbial communities. The abundance of PLFAs, TN, and SR was higher in C1.5 than those in other treatments, suggesting that the soil properties and soil microbial community composition were affected positively by the application of corn straw to black soil. A Principal Component Analysis indicated that soil microbial communities were different in the straw decomposition processes. Moreover, the soil microbial communities from C1.5 were significantly different from those of CK (p < 0.05). We also found a high ratio of fungal-to-bacterial PLFAs in black soil and significant variations in the ratio of monounsaturated-to-branched fatty acids with different straw treatments that correlated with SR (p < 0.05). These results indicated that the application of corn straw positively influences soil properties and soil microbial communities and that these properties affect these communities. The individual PLFA signatures were sensitive indicators that reflected the changes in the soil environment condition.

罕山土壤微生物群落组成对植被类型的响应

选取分布在中国东北部地区的阔叶林-针叶林-亚高山草甸这一明显的植被垂直带谱来研究植被类型对土壤微生物群落组成的影响.选取5种植被类型-山杨(<em>Populus davidiana</em>)(1250-1300 m),山杨(<em>P. davidiana</em>)与白桦(<em>Betula platyphylla</em>)的混交林(1370-1550 m),白桦(<em>B. platyphylla</em>)(1550-1720 m),落叶松(<em>Larix principis-rupprechtii</em>)(1840-1890 m),亚高山草甸(1900-1951 m),采用磷脂脂肪酸(Phopholipid Fatty Acids, PLFAs)分析方法测定不同植被类型下的土壤微生物群落组成.分别采用主成分分析(Principal Components Analysis, PCA)以及冗余分析(Redundancy Analysis, RDA)来解释单种特征PLFAs的分异以及土壤理化指标与微生物PLFAs指标间的相关性.结果表明不同植被类型下土壤有机碳(SOC)对土壤微生物PLFAs总量,各类群(真菌(f)、细菌(b)、革兰氏阳性菌(G+)、革兰氏阴性菌(G-))生物量以及群落结构影响显著;土壤微生物PLFAs总量及各类群的生物量随土层加深总体上表现降低趋势,G+/G-和f/b分别随土层加深总体上表现升高趋势.不同植被类型下,阔叶混交林土壤PLFAs总量及各类群生物量总体上最高;针叶林比阔叶林下的f/b和G+/G-高;亚高山草甸下低的pH值对有机碳的可利用性有一定的抑制作用,导致f/b和G+/G-的值相对较高.总之,不同植被类型下SOC对土壤微生物群落组成的影响最为显著,而较低的pH对有机碳的可利用性有一定的抑制作用;真菌对植被类型的变化比细菌更敏感,而细菌更易受可利用性养分和pH变异的影响,这对预测不同林型下的土壤微生物群落组成有重要的启示作用.;There is no unifying conclusion among the considerable studies of soil microbial community composition under different vegetation types. We selected a distinct vertical vegetation distribution belt consisting of broad-leaved forests, coniferous forests, and subalpine meadows to study the effect of vegetation types on soil microbial community composition. Soil samples were collected at three different depths (0-5cm, 5-10cm, 10-20cm) from sites of five vegetation types. These sites were distinguished by their dominating vegetation: poplar (<em>Populus davidiana</em>) (1250-1300m), poplar (<em>P. davidiana</em>) mixed with birth (<em>Betula platyphylla</em>) (1370-1550m), birth (<em>B. platyphylla</em>) (1550-1720m), larch (<em>Larix principis-rupprechtii</em>) (1840-1890m) and subalpine meadow (1890-1951m). Soil microbial community compositions under the various vegetation types were determined by phospholipid fatty acid (PLFA) analysis. Ordination of individual PLFA signatures and correlations among soil properties and soil microbial PLFA indicators were analyzed by principal components analysis (PCA) and redundancy analysis (RDA), respectively. The results indicated that total PLFA contents of soil microbial community, biomasses of four main microbial taxa (fungi (f), bacteria (b), gram-positive bacteria (G+), gram-negative bacteria (G-)), and microbial community structure were significantly affected (<em>P</em> < 0.05) by soil organic carbon (SOC) under all vegetations; PLFA contents of total microbial community and main taxa generally decreased as soil depth increased, while G+/G-and f/b increased with soil depth. Among different vegetations, total PLFA contents and main taxa biomass under mixed broad-leaved forests were the highest; f/b and G+/G-under coniferous forests were higher than those under broad-leaved forests; the availability of SOC under subalpine meadows was constrained on some level by the low pH value, which led to a relatively high f/b and G+/G-. In conclusion, the effect of SOC on soil microbial community composition was the most significant of all soil parameters under all vegetation types, though the availability of SOC could be constrained by relatively low pH values on some level; fungi was more sensitive to the changes of vegetation types while bacteria was more sensitive to the variability of nutrient availability and pH. This conclusion could have a significant impact on forecasting soil microbial community composition under different vegetations.

Impact of Super Absorbent Polymer and Plants on Microbial Community and Petroleum Hydrocarbon Degradation in Contaminated Soil

A greenhouse pot test, in which wheat, cabbage, spinach were cultivated separately in petroleum contaminated soil with and without super absorbent polymer (SAP), was conducted to evaluated the effect of plants and SAP on soil microbiological properties. phospholipid fatty acids (PLFAs) profiles were analyzed to reveal the microbial communities. As a measure of the functional activity of soil microbial community, the ratio of degraded to total petroleum hydrocarbon (TPH) in soil was estimated. The results indicated that SAP had an important effect on the soil microbial community and its degrading TPH activities. First, the principal component analysis (PCA) of the PLFA signatures revealed marked changes between soil with SAP and without SAP. In addition, the total amount and the profile of PLFA were significantly different between the untreated and SAP-amended soils. Using PLFA patterns as a biomarker, it was found that gram-positive bacteria (G+) were more sensitive to SAP than gram-negative bacteria (G-), and the biomass of G+ was higher in soil with SAP than in that without SAP. Second, the crop could stimulate the growth of soil microorganisms; however, the differences depended clearly on the crop species. The G+ and G- biomass was increased in cabbage, spinach soil containing SAP, but was decreased in wheat soils. The population of fungi was increased in cabbage and spinach soils containing SAP, but was decreased in wheat soil with SAP. The population of actinomycetes was decreased in all soils with SAP. Third, the ratio of degraded to TPH was slightly increased in soil with SAP treatment, but a significant change depended on the crop species. In total, 12 different PLFAs were identified, including saturated, monounsaturated, branched, and polyunsaturated species. There was a clear difference in the PLFAs composition between soils with and without SAP.

Impact of Humics and Plants on Microbial Community and Petroleum Hydrocarbon Degradation in Contaminated Soil

A greenhouse pot experiment, in which 3 different crops (wheat, cabbage, spinach) were cultivated in soil with and without humics (HS), was conducted to evaluate the effect of HS on soil microbiological properties. Phospholipid fatty acid (PLFA) profiles were analyzed to reveal the microbial community structure. As a measure of the functional activity of soil microbial community, the ratio of degraded to total petroleum hydrocarbon in soil was estimated. The results indicated that HS had an important effect on the soil microbial community and its functional activities. First, the principal component analysis (PCA) of the PLFA signatures revealed marked changes between soil with HS and without HS. In addition, the total amount and the profile of PLFA were significantly different between the untreated and HS-amended soils. Using PLFA patterns as a biomarker, it was found that gram-positive bacteria (G+) were more sensitive to HS than gram-negative bacteria (G-), and the biomass of G+ was higher in soil with HS than in that without HS. Second, the crop could stimulate the growth of soil microorganisms; however, the differences depended clearly on the crop species. The G+ and G- biomass was increased in spinach soil containing HS, but was decreased in wheat and cabbage soils. The population of fungi was increased in wheat and spinach soils containing HS, but was decreased in cabbage soil. The population of actinomycetes was increased in cabbage soil, but was decreased in wheat and spinach soils containing HS. Third, the ratio of degraded to total petroleum hydrocarbon was also affected by the HS treatment. It was slightly increased in soil with HS treatment, but a significant change depended on the crop species. In general, fatty acids ranged from C13 to C19. In total, 25 different PLFAs were identified, including saturated (SAT), monounsaturated (MUFA), branched (BR), and polyunsaturated (PUFA) species. There was a clear difference in the PLFA composition between soils with and without HS.

Assessment of shifts in microbial community structure and catabolic diversity in response to Rehmannia glutinosa monoculture

Rehmannia glutinosa, a widely used Chinese medicinal herb, has been shown to suffer from serious consecutive monoculture problems that cause significant decline in both yield and quality. The objective of this study was to evaluate the response of the soil microbial community and the effect on catabolic diversity to consecutive monoculture regime using three different techniques: substrate-induced respiration (SIR), phospholipid fatty acid (PLFA) and community-level physiological profiles (CLPP) analyses. We found that basal soil respiration (BSR) was significantly higher in the control and newly planted soils than in the second and third year consecutive monoculture soils. However, no significant difference was observed in SIR among the newly planted, second and third year consecutive monoculture soils. The PLFA signatures indicated that the bacterial biomass was larger than the fungal biomass in all four treatments and both enhanced with the increasing years of monoculture and attained the peak in SM. The ratio of cyclopropyl PLFAs to their metabolic precursors (cy/pre), a measure of physiological stress in microbial communities, in the second and third year consecutive monoculture soils was significantly greater than that in the control and newly planted soils. Biolog analysis results revealed that the consumption of carboxylic acids, phenolic acids and amines, especially acid carbon substrates, in the consecutively monocultured soil was significantly greater than that in the newly planted soil. Both PLFA- and CLPP-based principal component analysis (PCA) and cluster analysis revealed the distinct separation between the control, newly planted plots and the second, third year consecutive monoculture plots. Through our PLFA-based and Biolog analysis, together with microbial respiration determination, we were able to reveal characteristic differences in the microbial community composition and activities in the rhizosphere following R. glutinosa monoculture.

Comparisons of Soil Microbial Communities Influenced by Soil Texture, Nitrogen Fertility, and Rotations

Two agricultural soil microbial communities were analyzed using phospholipid fatty acid (PLFA) analysis to identify coarse differences between community compositions after a 3-year nitrogen (N) rate study on cotton followed by a rotational cereal crop. The soils studied were a Wasco sandy loam and Panoche clay loam. The study compared the influence of soil type, soil N levels, and how rotation crops affected soil microbial biomass. Principal component analysis of the PLFA signatures indicated that microbial communities were significantly different between the two soil types after 3 years of similar management and cotton residue inputs. The Panoche soil showed a greater total microbial biomass than the Wasco soil. Phospholipid fatty acid biomarker results showed that the Panoche soil was characterized by a fungal population, and the Wasco soil showed evidence of a bacterial composition. The observed microbial response to different soil N levels was negligible, but crop yields were highly responsive to N treatments. Cereal rotations after 3 years of cotton produced a substantial increase in microbial biomass, but did not alter the community composition of either soil. Results suggested that microbial communities found in the two soils responded to changes in residue inputs from subsequent crop rotations by increasing total microbial biomass, but community composition was not influenced by changes in crop type or N additions. Based on the results of this study, soil texture had a more decisive role in soil microbial composition and consequent microbial activity than N fertilization or different rotational crops after 3 years of similar management.

Responses of Scirpus triqueter, soil enzymes and microbial community during phytoremediation of pyrene contaminated soil in simulated wetland

The aim of this study was to determine the enhancement of Scirpus triqueter in the dissipation of pyrene and the interaction of pyrene with plant, soil enzymes and microbial community. The results indicated that the dissipation ratios of pyrene in the rhizospheric and non-rhizospheric soil were 64.65 ± 3.86% and 54.49 ± 2.74%, respectively, and were higher than that in the unplanted soil (42.60 ± 0.71%) at 80d after planting S. triqueter. The pyrene was toxic to S. triqueter, as evidenced by growth inhibition in height, diameter, shoot number and biomass during the planting period. The activities of dehydrogenase decreased significantly at the presence of pyrene in soils, and increased remarkably with the introduction of S. triqueter. It was found that the pyrene addition increased the ratios of fungal/total fatty acids and gram-positive/gram-negative, but the presence of S. triqueter decreased the ratios of gram-positive/gram-negative. A larger stress level was found in the pyrene treated soils without S. triqueter. The ratio of aerobic/anaerobic bacteria decreased with increasing pyrene concentration, but increased when S. triqueter was planted. The principal analysis of phospholipid fatty acid signatures revealed that microbial community structures in the rhizospheric and non-rhizospheric soil were similar, but different from those in the unplanted and control soil.

Soil microbial community composition under Eucalyptus plantations of different age in subtropical China

Eucalyptus is one of the fastest growing woody plants in the world, but few studies have reported the soil microbial community composition in Eucalyptus ecosystems. This study investigated the soil microbial communities in plantations of 3-, 7-, 10- and 13-year-old Eucalyptus in subtropical China based on phospholipid fatty acids (PLFA) analysis. The variation in soil microbial biomass and community compositions were influenced by sampling site and season and the interaction of both, which were consistent with the variation in soil total nitrogen (TN), soil organic carbon (SOC) and soil moisture. The number and abundances of PLFAs, and the amount of soil TN and SOC were higher in plantation of 13-year-old Eucalyptus than those in other younger plantations, suggesting that the soil properties and the soil microbial community composition is not negatively affected by the planting of Eucalyptus. The ratio of monounsaturated-to-branched fatty acids, the proportional abundance (mol%) of bacterial PLFA and fungal PLFA varied significantly with Eucalyptus plantations of different age, suggesting that the individual PLFA signatures might be sensitive indicators of soil properties associated with forest plantations.