不同季节冬水田紫色土细菌群落的垂直分布规律

【背景】土壤细菌对环境变化非常敏感,是土壤环境质量检测的重要指标。【目的】为研究不同季节冬水田紫色土细菌的垂直分布规律,揭示土壤细菌群落结构和物种多样性与土壤环境因子的相互关系。【方法】以冬水田紫色土为研究对象,分别于2020年8月(夏季)和2021年 1月(冬季)采集不同深度土壤样品,对土壤细菌16S rRNA基因进行Illumina MiSeq高通量测序,分析在不同季节细菌群落组成和多样性的垂直分布规律。【结果】冬水田紫色土细菌ACE指数、Chao1指数和Shannon指数均呈现出夏季高于冬季,并且随土层深度增加呈现降低的趋势。冬水田紫色土优势菌门为变形菌门(Proteobacteria)、绿弯菌门(Chloroflexi)、酸杆菌门(Acidobacteria)、硝化螺旋菌门(Nitrospirae)、放线菌门(Actinobacteria)和浮霉菌门(Planctomycetes),优势菌属为Desulfobacca、Haliangium、Anaeromyxobacter、Candidatus_Omnitrophus和Defluviicoccus。Chloroflexi和Actinobacteria在夏季相对丰度较高,Proteobacteria和Nitrospirae在冬季相对丰度较高;Anaeromyxobacter和Candidatus_Omnitrophus在夏季相对丰度较高,Desulfobacca、Haliangium和Defluviicoccus在冬季相对丰度较高。冗余分析(redundancy analysis,RDA)和环境因子热图分析结果均表明,总氮(total nitrogen,TN)、土壤有机质(soil organic matter,SOM)和土壤氧化还原电位(soil redox potential,Eh)是显著影响紫色水稻土细菌群落的主要因子。【结论】本研究丰富了对冬水田紫色水稻土细菌群落组成和多样性的认识,证实了不同季节冬水田紫色土细菌群落组成和多样性存在差异。     

紫云英还田对黄泥田土壤理化和微生物特性及水稻产量的影响

为探明紫云英连年还田化肥减施单季稻田土壤性质及水稻产量的变化规律,依托位于福建省东部12年黄泥田紫云英-单季稻轮作定位试验,研究了不施肥（C₀）、单施化肥（C₁₀₀）、紫云英还田（M）、紫云英还田+全量化肥（MC₁₀₀）及紫云英还田+减量20%化肥（MC₈₀）处理的土壤理化性状、微生物群落结构和功能及稻谷产量的变化。结果表明：C₁₀₀、M、MC₁₀₀、MC₈₀处理土壤有机碳含量比C₀分别提高6.97%、15.05%、10.38%、11.15%,全氮分别提高9.52%、18.25%、15.87%、15.87%,硝态氮分别提高6.51%、69.52%、66.87%、78.19%（P < 0.05）。冗余分析表明,土壤有机碳、全氮、硝态氮含量对细菌和古菌群落结构和功能有显著的影响。与C₀相比,C₁₀₀、M、MC₁₀₀和MC₈₀处理土壤慢生根瘤菌属（Bradyrhizobium）丰度分别增加0.52%、24.30%、7.59%、11.93%,其中M处理增加达显著水平（P<0.05）;分枝杆菌属（Mycobacterium）分别增加5.51%、21.58%、10.00%、14.74%,其中M处理增加显著（P<0.05）;亚硝化杆菌属（Candidatus_Nitrosotalea）分别增加22.93%、17.21%、65.39%、89.89%,其中MC₁₀₀和MC₈₀处理增加均达显著水平（P<0.05）。相比C₀,M、MC₁₀₀和MC₈₀处理土壤链霉菌属（Streptomyces）分别增加6.76%、16.89%、12.16%,其中MC₁₀₀处理增加显著（P < 0.05）,而C₁₀₀却减少2.50%。物种贡献度分析发现,土壤碳代谢和氨基酸合成的主要功能微生物为细菌慢生根瘤菌属（Bradyrhizobium）、分枝杆菌属（Mycobacterium）、链霉菌属（Streptomyces）和古菌亚硝化杆菌属（Candidatus_Nitrosotalea）。M、MC₁₀₀、MC₈₀处理稻谷产量比C₀分别增加9.68%、19.16%、18.72%。阐明紫云英培肥处理能提升单季稻黄泥田土壤肥力水平,调节土壤微生物群落结构,促进土壤碳水化合物和氨基酸代谢。     

Host and environmental influences on the gut bacterial community of carabid beetles in distinct paddy fields

The relationship between the gut bacterial communities of carabid beetles and their habitats holds implications for understanding ecological dynamics. This study examined the gut bacterial communities of two carabid beetle species, Chlaenius pallipes and Pheropsophus jessoensis, in terraced and flat paddy fields. Differences in gut bacterial communities were evident at the species level and were based on habitat. Specifically, P. jessoensis had a greater presence of Firmicutes and Proteobacteria in terraced fields but more Actinobacteria in flatland fields. In comparison, C. pallipes consistently showed high levels of Firmicutes in both habitats. These differences were reflected at class and genus levels, emphasizing the role of host specificity in shaping gut microbiota. Alpha diversity metrics indicated that P. jessoensis hosted a more diverse bacterial community than C. pallipes. Terraced fields, however, showed slightly reduced diversity in P. jessoensis, suggesting environmental effects on microbial populations. Beta diversity analysis using Bray–Curtis distances differentiated the bacterial communities of the two beetles. Multivariate analysis of variance reinforced these findings. Insights from the Sloan neutral model indicate that environmental factors predominantly influence bacterial community assembly through stochastic processes. Functionally, metabolism was highlighted, indicating the role of gut bacteria in beetle metabolic processes. Notably, energy metabolism varied between field types, revealing environmental effects on gut bacterial functions. This study offers in-depth insights into interactions between host-specific and environmental factors influencing gut bacterial communities of carabid beetles, contributing to a broader understanding of microbial ecology and the roles of environment and host in microbiota dynamics.     

Influence of rice cultivar on methane emission from paddy fields

Influence of rice cultivars on CH₄ emissions from a paddy field was studied using four Japonica types, two Indica types, and two Japonica/Indica F₁ hybrids. In addition, the suppression of CH₄ emission by interrupting irrigation at the flowering stage was investigated. Patterns of seasonal variation in CH₄ emission rates were similar among the eight cultivars. Two of the Japonica types showed the maximum and minimum CH₄ emissions among the cultivars investigated. Neither the number of tillers, shoot length, shoot weight, and root weight correlated with the CH₄ emission rates at the tillering and reproductive growth stages. Following temporary interruption of irrigation at the flowering stage, CH₄ emission rates decreased drastically and remained at very low levels until the harvesting stage, indicating its great effectiveness for the suppression of CH₄ emission from rice paddies.     

Influence of soil temperature on methane emission from rice paddy fields

Methane emission rates from an Italian rice paddy field showed diel and seasonal variations. The seasonal variations were not closely related to soil temperatures. However, the dieL changes of CH₄ fluxes were significantly correlated with the diel changes of the temperature in a particular soil depth. The soil depths with the best correlations between CH4 flux and temperature were shallow (1–5cm) in May and June, deep (10–15cm) in June and July, and again shallow (1–5 cm) in August. Apparent activation energies (E_a) calculated from these correlations using the Arrhenius model were relatively low (50–150 kJ mol^–1) in May and June, but increased to higher values (80–450 kJ mol^–1) in August. In the laboratory, CH₄ emission from two rice cultures incubated at temperatures between 20 and 38°C showed E . values of 41 and 53 kJ mol^–1) Methane production in anoxic paddy soil suspensions incubated between 7 and 43°C showed E values between 53 and 132 kJ mol^–1 with an average value of 85 kJ mol^–1) and in pure cultures of hydrogenotrophic methanogenic bacteria E _a values between 77 and 173 (average 126) kJ mol^–1. It is suggested that diel changes of soil properties other than temperature affect CH₄ emission rates, e.g. diel changes in root exudation or in efficiency of CH⁴ oxidation in the rhizosphere.     

浙江天台山七子花种群结构与分布格局研究

浙江天台山七子花种群结构与分布格局研究金则新（台州师范专科学校,浙江临海３１７０００）ＡＳｔｕｄｙｏｆＰｏｐｕｌａｔｉｏｎＳｔｒｕｃｔｕｒｅａｎｄＤｉｓｔｒｉｂｕｔｉｏｎＰａｔｅｒｎｏｆＨｅｐｔａｃｏｄｉｕｍｍｉｃｏｎｉｏｉｄｅｓｉｎｔｈｅＴｉａｎｔ...     

Methane emissions from rice microcosms: The balance of production, accumulation and oxidation

In rice microcosms (Oryza sativa, var. Roma, type japonica),CH₄ emission, CH₄ production, CH₄oxidation and CH₄ accumulation were measured over an entirevegetation period. Diffusive CH₄ emission was measured inclosed chambers, CH₄ production was measured in soil samples,CH₄ oxidation was determined from the difference between oxicand anoxic emissions, and CH₄ accumulation was measured byanalysis of porewater and gas bubbles. The sum of diffusiveCH₄ emission, CH₄ oxidation, andCH₄ accumulation was only 60% of the cumulativeCH₄ production. The two values diverged during the first 50days (vegetative phase) and then again during the last 50 days (latereproductive phase and senescence) of the 150 day vegetation period. Duringthe period of day 50–100 (early reproductive phase/flowering), theprocesses were balanced. Most likely, gas bubbles and diffusion limitationare responsible for the divergence in the early and late phases. The effectof rice on CH₄ production rates and CH₄concentrations was studied by measuring these processes also in unplantedmicrocosms. Presence of rice plants lowered the CH₄concentrations, but had no net effect on the CH₄ productionrates.     

Feeding Fauna and Foraging Habits of Tiger Beetles Found in Agro‐ecosystems in Western Ghats,India1

Cicindela (Calochroa) whithilli (Hope) and Cicindela (Calochroa) flavomaculata Hope (Cicindelidae: Coleoptera) are seasonally dominant predatory insects in the cultivated, and irrigated rice paddy fields of the South Indian peninsula. While studying the feeding ecology of these tiger beetles in rice paddy agro‐ecosystems in Sringeri area of the central Western Ghats, we examined their potential as biocontrols on the major rice paddy pest populations available in this region. Earthworms and tadpoles were significant prey organisms during the early cultivation period, while other traditional prey organisms like ants and spiders (mainly wolf and jumping spiders) were more common as prey organisms toward the mid‐season. The results showed that the feeding fauna of tiger beetles can extend to prey items beyond arthropods, to include vertebrates. Cicindela (Calochroa) duponti Dejean is another common species that occurs abundantly in the Areca orchards and on the bunds that separate rice paddy fields from adjacent uncultivated lands. We performed laboratory tests to determine the feeding guild of these beetles, and to investigate their possible role as a predator of the rice paddy pests. Although preliminary in nature, the results suggest that both C. whithilli and C. flavomaculata are ineffective as biocontrol agents of rice paddy agro‐ecosystems. They appear to have only a marginal impact on the larvae of Leptocorisa acuta, a major insect pest of paddy rice, but further experimental and observational studies are needed to firmly establish the significance of this observation.     

Linking the Physicochemical Properties with the Abundance and Diversity of Rhizospheric Bacterial Population Inhabiting Paddy Soil Based on a Concerted Multivariate Analysis of PCR-DGGE and RISA

To unravel the existence of dominant bacterial population in the paddy fields of Eastern Uttar Pradesh, India and their relation to the prevailing soil physicochemistry using multivariate statistical analyses, a cumulative culture-independent 16S rRNA based Polymerase chain reaction-Denaturing gradient gel electrophoresis (PCR-DGGE) and a 16S-23S ribosomal intergenic spacer analysis (RISA) have been performed. Detrended correspondence analysis (DCA) and principal component analysis (PCA) biplot analyses were used to assess the relation between soil bacterial population and its physicochemistry. DCA analysis exhibited a strong dependence of bacterial existence on the soil physicochemical variables, such as organic matter, total nitrogen, inorganic nutrients, temperatures, and moisture status. Soil dehydrogenase activity (DHA) was assessed to check the metabolic activity of all soil samples which showed a range of 0.012–0.050 nmol TPF g^?1 min^?1 with significant variation (p < 0.01). Out of 96 bands excised, 45 different phylotypes were obtained using both techniques which elucidated the abundance of Cyanobacteria over other soil bacterial population. Scytonema sp., Leptolyngbya sp. and different uncultured cyanobacterial species were the major genera found. Profiling data obtained through PCR-DGGE and RISA were used in alpha diversity and rarefaction curve analysis suggested site 6 (Chandauli) as the most diversity rich site. Thus extensive dataset of weighted and unweighted variables generated through DGGE and RISA coupled with metabolic functioning of soil and multivariate analyses provided an excellent opportunity to map the soil microbial structure in paddy fields and their regulation with existing soil environment.