Interspecific association among main plant species in the unstable slope with high-frequency debris flow北大核心CSCD

To determine the characteristics of vegetation community structure and the relationship between species in the frequent watersheds of debris flow in fragile ecological environments, based on sample survey and 2 × 2 joint table techniques, we used analysis of variance test, χ2 test, Jaccard index, Pearson correlation coefficient, and Spearman's rank correlation coefficient test to study the main plant species correlations in the stable zone, instable zone, and deposit zone of the unstable slope. The analysis of variance test showed that all 45 species pairs had a significant negative correlation in the stable zone and instable zone, whereas there was no significant negative correlation in the deposit zone, which showed that the species had an independent distribution trend. The results from the different tests showed that there were 1 pair, 4 pairs, and 4 pairs from the stable zone, instable zone, and deposit zone, respectively, which had significant interspecific association under the χ2 test and the ratios of positive correlation pairs to negative correlation pairs were 0.55, 0.67, and 0.67 in the stable zone, instable zone, and deposit zone, respectively. There were 8 pairs, 5 pairs, and 5 pairs from the stable zone, instable zone, and deposit zone, respectively, which had significant interspecific association from the Pearson correlation analysis test, and the ratios of positive correlation pairs to negative correlation pairs were 0.36, 0.45, and 0.45 in the stable zone, instable zone, and deposit zone, respectively. There were 10 pairs, 6 pairs, and 9 pairs from the stable zone, instable zone, and deposit zone, respectively, which had significant interspecific association from the Spearman's rank correlation analysis test and the ratios of positive correlation pairs to negative correlation pairs were 0.5, 0.55, and 0.6 in the stable zone, instable zone, and deposit zone, respectively. The three test results showed general similarities but there were some differences. Most species pairs did not reach a significant level in the three zones and the number of negatively related species was more than the number of positively related species. In brief, this loose interspecific relationship indicates that the entire plant community was not stable, and the interspecific relationships among species are susceptible to environmental interference in the ecologically fragile areas of the debris flow basin. Therefore, rational selection and configuration of species should be applied to promote community structure development and ecological environmental improvement in vegetation restoration process areas with high-frequency debris flow. © 2018 Science Press. All rights reserved.     

Characteristics of bacterial community in Poyang Lake sandy land under different vegetation restoration conditions北大核心CSCD

为掌握不同植被恢复措施下鄱阳湖沙地土壤细菌群落变化特征,以湿地松、香根草、单叶蔓荆、狗牙根等植物恢复措施的沙地土壤为研究对象,采用高通量测序技术,分析植物恢复前后细菌群落变化.结果显示,相较对照组,土壤细菌多样性均有提升,在门水平上,绿弯菌门丰度大幅降低,而变形菌门、放线菌门和厚壁菌门丰度增加.在属水平上,副伯克霍尔德氏菌属、慢生根瘤菌属、芽孢杆菌属、分枝杆菌属等丰度提升,而假单胞菌属丰度大幅下降.植被恢复后,不同植被固氮功能细菌丰度提升,而香根草、狗牙根土壤磷细菌丰度下降,湿地松土壤固氮、解磷功能优势细菌提升幅度为76.11%、51.12%,单叶蔓荆为65.04%、23.17%.土壤容重、有机质、全磷、有效氮是影响功能细菌变化的重要因素,其中有效氮与芽孢杆菌属、分枝杆菌属呈显著水平以上相关性.本研究表明鄱阳湖沙地植被恢复措施提升了固氮细菌的丰富度,但不同植被土壤解磷细菌群落变化差异大;研究结果可为沙地治理提供科学依据.(图6表3参34)     

Microorganisms and physico-chemical properties of soils with different slope-protecting vegetation in Daguang Highway北大核心CSCD

In order to investigate the effect of different slope-protecting vegetation on soil restoration in the highways, we collected soils at depths of 0-10 cm, 10-20 cm, and 20-30 cm from areas planted with Amorpha fruticosa, Periploca sepium, and Paederia scandens for 6-7 years in the Daming road section of the Daguang Highway, in October 2016. The physico-chemical properties and microbial community of the soils were then analyzed. The soil microbial community was analyzed by terminal restriction fragment length polymorphism (T-RFLP). The correlation between the microbial community and the physico-chemical properties of the soils was determined by redundancy analysis (RDA). The results showed that (1) the physico-chemical properties were the best for soils with Paederia scandens; the nutrient content, water holding capacity, and porosity of the soils with the three types of slope-protecting vegetation were better in the 0-10 cm layer than in the other layers; (2) the contents of soil aggregates (diameter > 5 mm) were the highest in the 0-10 cm and 10-20 cm layers for the soil with Paederia scandens; (3) the dominant bacteria in the 0-10 cm layer and dominant fungi in the 0-10 cm, 10-20 cm, and 20-30 cm layers were higher in the soils with Pe. sepium and Pa. scandens than in the soil with A. fruticosa; and (4) results of RDA showed that the physical properties of the soils were the main factors that influenced the soil microbial community. The physical properties of the soils were sensitive to the change of soil quality. Soil quality can be improved by appropriate management measures, such as burying litter, which can subsequently improve the ecological environment of soils in sloping regions. © 2018 Science Press. All rights reserved.     

Characteristics of soil fauna community in the decomposition of Deyeuxia arundinacea litters北大核心CSCD

This study aimed to understand the soil fauna characteristics during the litter decomposition process of perennial herb Deyeuxia arundinacea. The litters were put in 6-, 30-, and 260-mesh litterbags to investigate their mass loss and the dynamics of soil faunal community during Aug. 2013 to Jul. 2014. Faster decomposition rate of Deyeuxia arundinacea in different meshes was found in the early period than in mid- and end-periods. Among different mesh sizes, 6-mesh had the fastest decomposition rate, followed by 30-mesh and 260-mesh. A total of 2218 individuals of soil fauna were obtained in different meshes, with 958, 737 and 523 individuals in 30-, 260- and 6-mesh respectively. Oribatida and Poduridae were the dominant groups, accounting for 73.22% of total individuals. The soil animal individual and group densities shared a very similar trend among the decomposition bags of three aperture sizes, all with obvious characteristics of seasonal dynamic distribution. During the 12 months of decomposition, the density of soil animal groups did not show significant difference between the 6 mesh and 260 mesh decomposition bags except for May. Correlation analysis showed that the group density was highly significantly correlated with average monthly temperature and rainfall, and the individual density significantly correlated with the average monthly temperature. The results indicated that the structure and diversity of soil fauna community of Deyeuxia arundinacea are influenced by hydrothermal conditions. The findings help in understanding the effect of soil fauna to perennial herb litter decomposition.     

Seasonal and interannual variation of soil respiration in four vegetation types in the loess hilly region北大核心CSCD

Soit carbon (C) stock is the largest C pool in terrestrial ecosystems, and the emission of CO2 through soil respiration contributes to the majority of soil C expenditure and atmospheric C. Soil respiration is also one of the major processes controlling the C budget of terrestrial ecosystems. A slight change in soil CO2 emission might cause drastic variations in global C balance. Therefore, it is of great significance to investigate the characteristics of soil respiration of soils growing different types of vegetation over a long period, and determine its relationship with variables such as soil temperature and moisture. The rate of soil respiration was measured each month in the growing seasons (from April to October) of 2011, 2013, and 2014 using the Li-8100 CO2 flux measurement system in the central Loess Plateau. Four types of vegetation (Quercus liaotungensis, Platycladus orientalis, Robinia pseudoacacia, and a natural shrub) were chosen for the periodical measurements. A permanent sample plot was established for each type of vegetation, and five polyvinyl chloride (PVC) collars were placed in each plot for the measurements. The temperature and water content of the soil in the upper 12 cm near the collar were measured using a digital soil temperature probe and a TDR 200 soil moisture meter at the same time when the soil respiration was measured. The soil respiration rates were fitted to the soil temperature and moisture with an exponential function, power function, linear function, and an equation combining the two variables. The results showed that: (1) the seasonal variation in the rates of soil respiration in the soils growing the four types of vegetation were almost the same, and were lower in the earlier period and then increased to high levels in the middle and later periods; (2) the rates of soil respiration in the same month varied with the type of vegetation grown, and were in the descending order: Q. liaotungensis > P. orientalis > shrub > R. pseudoacacia; (3) the average values of the rates of soil respiration in 2011, 2013, and 2014 were 2.77, 3.48, and 5.08 μmol m-2 s-1, respectively. The variation in soil respiration was higher across the three years than the variation for the types of vegetation grown; and (4) the rate of soil respiration was positively correlated to soil temperature and moisture for all the types of vegetation. A better fit was obtained by using the equation that included both the variables, soil temperature and moisture, than by an equation that included a single factor. Our results suggested that both seasonal and inter-annual variations of soil respiration occurred in the soils growing the four types of vegetation in the region. The temperature and water content of soils are the major regulating factors, and soil respiration in the Loess Plateau is more greatly affected by environment factors than by the type of vegetation. © 2018 Science Press. All rights reserved.     

Comparison of zooplankton community of different areas in Changjiang River estuary北大核心CSCD

To compare the zooplankton communities in the South Branch, North Branch, North Channel and offshore of the Changjiang (Yangtze River) estuary, two cruises were carried out in the autumn of 2009 and the spring of 2010. A total of 27 species of zooplankton were identified in the spring, including 17 in the offshore, 11 in the south branch, 9 in the north branch, and only 5 in the North Channel. In autumn, altogether 71 species were collected, including 6 in the south branch, 11 in the north branch, 8 species in the North Channel area and 63 in the offshore. Either in the spring or autumn, the average species numbers of the offshore were the highest. Additionally, species numbers of the offshore were significantly higher than that in other areas (P < 0.05) for both seasons. There were no significant differences between the species number of the South Branch and the North Branch (P > 0.05). The species number and diversity index of the inner area were lower than that of the offshore. The average diversity index of offshore area was still the highest in both spring (1.69) and autumn (3.73). In spring, the diversity index of the North Channel was the lowest among four areas, while in autumn, that of the South Branch was the lowest (0.49). In spring, Sinocalanus sinensis was the dominant species of the South Branch, North'Branch and North Channel (> 50% of the total collection by number). The dominant species of offshore area were Tortanus vermiculus and Labidocera euchaeta. While in autumn, the dominant species were different for each area. In the South Branch, the most important species was S. dorrii (93.55% of the total collection by number). The main species was S. dorrii in the South Branch area, S. stenellus and T. vermiculusin in the North Branch and Subeucalanus subcrassus in the offshore (< 30% of the total collection by number). Numbers of species and diversity index seemed to vary among different areas of Changjiang estuary. The underline mechanisms of the regional variation in species number were mainly the salinity and suspended sediment concentrations. Generally speaking, zooplankton was more abundant in the polyhaline water. Diversity index was largely affected by both species number and abundance percentage. The zooplankton community was mainly influenced by the Changjiang diluted water and offshore water mass through affecting the salinity. In autumn, the Kuroshio flowed northward carrying polyhaline water, and brought subtropical species to the offshore of the Changjiang estuary. Since the North Channel is located in the estuarine turbidity zone, suspended sediment concentration of that area is higher than the other areas, which might limit the distribution of some species. To sum up, salinity is the most important factor causing the difference of zooplankton community among different areas in the Changjiang estuary. Besides, water masses and estuarine turbidity also influence the zooplankton community.     

Comparison of macroinvertebrate community structure in urban (Shenzhen City) streams with typical habitat characteristics北大核心CSCD

2020年12月在深圳市城市区域典型生境特征溪流——城市山区源头溪流金龟河、国家地质公园保护区入海溪流杨梅坑河与黑臭水体治理后溪流石溪河,开展底栖动物多样性与生境质量状况取样,通过多元统计分析探明各溪流底栖动物群落结构差异及其主要环境影响因子.结果表明:(1)金龟河底质异质性(SI)最高;杨梅坑河水质最好且流态异质性(Fr)最优,石溪河水质最差且底质异质性(Fr)最低.(2)共采集鉴定大型底栖动物118个分类单元,隶属于3门6纲14目87科.水生昆虫均占绝对优势,其中金龟河67属(81.7%),杨梅坑河62属(95.4%),石溪河12属(52.2%).金龟河中底栖动物Shannon-Wiener多样性指数、改进的Shannon-Wiener多样性指数、Pielou均匀度均高于杨梅坑河与石溪河.(3)金龟河的主要功能摄食类群是滤食者(45.5%),杨梅坑河(38.3%)与石溪河(58.7%)的主要功能摄食类群均为收集者.(4)冗余分析(RDA)结果显示,氨氮、海拔、湿宽、水温、溶氧、底质异质性(SI)、电导率和流态异质性(Fr)为影响深圳市溪流的大型底栖动物群落结构的主要环境因子.研究表明:(1)深圳市的山区溪流可作为深圳市生物多样性保护的重点区域.(2)在城市溪流生态系统中,水环境化学因子并非为主要影响因子,生境多样性发挥了重要作用.(图6表3参43)     

Relationship between herbaceous community distribution and soil environmental factors in the riparian zone of the Baiyangdian River Basin北大核心CSCD

Riparian zone vegetation is an important part of the riparian ecosystem and plays an important role in the riparian zone functioning. Herbs, which are one of the main types of riparian vegetation, are extremely sensitive to environmental changes and human activities and have become a hot spot of riparian vegetation research. In this study, the herbaceous communities of four representative rivers (Xiaoyi, Baohe, Fuhe, and Baigouyin River) entering Baiyangdian Lake in China were researched. The herbaceous species in their riparian zones were systematically investigated using the sample plot method. The Shannon-Wiener diversity (H’), Pielou evenness (J), and Patrick richness (R) indices were estimated to examine the species composition and diversity of the herb communities, following which redundancy analysis (RDA) was conducted. The relationship between species diversity, distribution patterns of herbaceous plant communities, and soil environmental factors in the riparian zone of the four rivers is discussed. (1) Eighty-three species of herbaceous plants belonging to 66 genera and 27 families in the riparian zone entering Baiyangdian Lake. Most herbaceous plants, including Poaceae, Compositae, and Chenopodiaceae, were weeds or associated plants. Riparian vegetation was greatly affected by human disturbance. (2) All the three estimated indices of the Xiaoyi, Baigouyin, and Fuhe rivers were better than those of the Baohe River. (3) The vegetation coverage and species diversity of riparian herbaceous communities were positively correlated with soil organic matter and water content but negatively correlated with pH, total nitrogen, and total phosphorus. Therefore, these communities are conducive to the restoration of vegetation and the stability of biodiversity in the riparian core area to reduce the disturbance of human activities and increase humidity. © 2022 Science Press. All rights reserved.     

Soil bacterial community characteristics of rice-rice-rape crop rotation北大核心CSCD

To investigate the characteristic changes in soil bacterial community under rice-rice-rape rotation in southern China, soil samples from a 30-year crop rotation and continuous cropping system were collected. Clone library and gene sequence analysis were adopted. The PCR amplification was carried out using universal primers of the 16S rDNA gene. The amplified fragments were then used to construct a clone library. The subclones were sequenced and analyzed. The experimental analysis showed that, in July 2015, and October and April 2016, the Shannon Wiener index and richness index of bacteria from the rotation treatment soils were higher than those of the continuous cropping treatment soil. The soil bacterial diversity of the rotation treatment was higher than that of the continuous cropping treatment. The results of BLAST analysis in the GenBank showed that Proteobacteria accounted 55% of total bacteria in the rotation treatment soil, whereas it accounted for 45% of total bacteria in continuous cropping treatment soil. Gemmatimonadetes accounted for 13% of the total bacteria in rotation treatment and 10% in the continuous cropping treatment. The proportion of Acidobacteria, Firmicutes, and Planctomycetes in rotation soil was less than those in the continuous cropping soil. Proteobacteria and Gemmatimonadetes were the dominant flora in soil. The changes in the predominant bacteria affected the diversity of soil bacteria in rotation and continuous cropping. The sequence analysis showed that the dominant bacteria in the soil were Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria, which higher than those in the rice-rice continuous cropping treatment. The sequences similar to Chloroflexi were observed in the rice-rice-rape rotation soils, but not in the continuous cropping soils. The results showed that the soil microbial population is conducted by agricultural tillage, and rice-rice-rape rotation increased the soil bacterial abundance compared with that of the rice-rice continuous treatment. © 2018 Science Press. All rights reserved.     

Bacterial community structure in waterlogged bamboo slips excavated from the Laoguanshan Han Dynasty Tomb of Chengdu北大核心CSCD

To investigate the bacterial community structure features of soak solutions used to preserve bamboo slips that were excavated from Han dynasty tomb located in Laoguanshan of Chengdu and to reveal the diversity of bacteria in these soak solutions, PCR-DGGE was employed. Subsequently, the major DGGE bands were excised and sequenced to analyze the phylogeny of bacteria. The richness (S), Shannon-Wiener index (H), and Simpson index (D) of deionized water (0#) without the soaked bamboo slips were higher than those of the other samples. Among the bamboo slip soak solution samples, there were significant differences in these indicators; the bacterial genetic diversity of sample 121# was the highest and that of sample 1# was the lowest. Principal Component Analysis (PCA) showed that there were comparatively large differences among the samples, and the similarity between sample 1# and others was the lowest. Based on the sequence analysis, the major community of bacteria in soak solution were belonged to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria, including Cupriavidus, Aquabacterium, Comamonas, Albidiferax, Hyphomicrobiaceae, Azospirillum, Nevskia, Streptococcus, Staphylococcus, Sediminibacterium, and Propionibacterium, among which Cupriavidus of the β-Proteobacteria class was detected in all samples. The bacterial community structure of the soak solutions that were collected from different bamboo slips was quite complex and significantly different. The analysis of the main bacterial community revealed the potential bacteria species that may trigger the damage in bamboo slips; the result provided a reference to prevent waterlogged bamboo slips from microbial diseases in the future. © 2018 Science Press. All rights reserved.     

Spatial variability in soil water and salinity in Tamarix community in a semiarid saline region of the upper Yellow River北大核心CSCD

Tamarix is widely distributed in semiarid saline regions of the upper Yellow River. The community of Tamarix affects the spatial distribution of soil water and salinity. It is important to explore the dynamic response relationship of Tamarix community and spatial distribution of soil water and salinity in order to evaluate the effects of vegetation community construction and ecological restoration in this region. The natural Tamarix community in the secondary saline-alkali land of the Ningxia Yellow River Irrigation Area was investigated in July 2016. Classical statistics and geostatistics were used to analyze the spatial distribution characteristics of soil water and salinity. The results showed that the soil water content was relatively low (1.98%-7.55%), whereas the soil salinity was high (average conductivity 10.28-25.38 mS/cm) in the study area. The variability coefficient range of soil water and salinity was 36.1%-83.7%, both with moderate variations. Furthermore, the variation degree of soil salinity decreased with the increase in soil depth. The soil water and salinity had obvious spatial structure characteristics, which was mainly affected by structural factors or structural factors associated with stochastic factors. The coefficients of nugget were 0.04%-49.88%, indicating the strong spatial correlation. The spatial distribution of soil water and salinity in Tamarix community showed a patchy pattern; the soil water and salinity distribution in the areas with high Tamarix growing density were considerably high. The correlation analysis showed that there was a positive correlation between soil water and salinity in the study area. In conclusion, soil water and salinity restrict the distribution and growth of Tamarix. Furthermore, the distribution and growth of Tamarix enhanced the spatial variability of soil water and salinity. Keywords. © 2018 Science Press. All rights reserved.     

Diversity and community composition of phosphorus accumulating organisms (PAOs) in the sediments of the Sanshiliujiao Lake reservoir北大核心CSCD

The diversity and community composition of phosphorus accumulating organisms (PAOs) in the sediments of the Sanshiliujiao Lake reservoir in Pingtan island, Fujian Province, were investigated by terminal restriction fragment length polymorphism (T-RFLP) methods combined with the construction of clone libraries. The diversity of PAOs in summer samples was significantly higher than that in winter. The dominant terminal restriction fragments (T-RFs) of PAOs were in the range of 200 to 300 bp in summer, while they were in the range of 150 to 200 bp in winter. Cloning sequencing and phylogenetic analysis showed that the main phyla of PAOs in the sediment of the Sanshiliujiao Lake reservoir were Proteobacteria, Actinobacteria, and Acidobacteria. Anaeromyxobacter, Azospirillum, Microlunatus phosphovorus, and Burkholderia were the dominant genera in the summer samples. Anaeromyxobacter, Methylobacterium, Solibacter, Azospirillum, and Microlunatus phosphovorus were the dominant genera in sediment samples in winter. The results of this study demonstrated that the diversity and community composition of PAOs in the sediments of the Sanshiliujiao Lake reservoir had specific seasonal characteristics. Various forms of phosphorus also showed their influence on the diversity of PAOs, especially Fe/Al-P. Our findings lays a scientific foundation for the future disclosure of microbial mechanisms involved in the phosphorus metabolic cycle in the sediments of reservoirs. © 2018 Science Press. All rights reserved.     

Population structure and community characteristics of Acer catalpifolium Rehd北大核心CSCD

Acer catalpifolium Rehd., a critically endangered tree species with an extremely limited range of distribution, is one of the 120 plant species with extremely small populations, as approved by the state forestry administration of the People's Republic of China and requires urgent rescue action. In order to comprehensively understand the population status and the future developmental trend of A. catalpifolium, the plant communities were investigated from 5 sites, including Caishenmiao (CSM), Banruosi (BRS), Zhangshancun (ZSC), Fuhusi (FHS), and Baoguosi (BGS). The population structure of A. catalpifolium as well as the species composition and community characteristics of its habitat were investigated. The results showed that A. catalpifolium is mainly distributed in the evergreen broad-leaved and deciduous broad-leaved mixed forests, in different community layers, namely, the tree layer, shrub layer, and herb layer, and is accompanied by 52, 74, and 52 plant species, respectively. Analyses of the distribution of population abundance revealed that BRS had the largest distribution of A. catalpifolium, accounting for 26.04% of the total population, followed by FHS, ZSC, BGS, and CSM, in that order. Analyses of the community characteristics revealed that the species diversity indices in FHS, BRS, BGS, and CSM were greater than that in ZSC. Analyses of the population age structure of A. catalpifolium revealed the gap in the distribution of the levels of seedlings and young trees. There were serious obstacles to the regeneration of the natural population. We concluded that the obstacle to the regeneration of the population of A. catalpifolium might be caused by the high competitive pressure from the dominant species and the micro-environment in the forest. Understanding the community characteristics and the population structure of A. catalpifolium could provide a theoretical foundation for its reintroduction and recovery. © 2018 Science Press. All rights reserved.     

Diversity and structural characteristics of nitrogen-fixing bacterial community in tobacco-growing soils at different elevations in Panzhihua北大核心CSCD

固氮细菌在土壤氮素转换过程中发挥重要作用.为深入认识攀枝花地区农田土壤固氮细菌群落特征及其与土壤理化性质的关联性,以攀枝花米易县不同海拔高度(1 600 m、1 800 m、2 000 m)植烟土壤为研究对象,采用高通量测序技术(high-throughput sequencing)对nifH基因进行测序,分析固氮细菌群落结构特征和多样性.结果显示,固氮酶活性随海拔升高而逐渐降低,并与土壤有机碳及全氮呈极显著正相关(P <0.01);固氮细菌群落多样性指数在海拔1 800 m处达到最大值.3个海拔土壤共获得高质量序列1 159 980条,所检测到的固氮细菌分属于4个门、11个纲、19个目、29个科、40个属.基于门分类水平分析结果,变形菌门(Proteobacteria)在所有海拔土壤中均为优势固氮菌群,相对丰度达64.69%-78.36%;而蓝细菌门(Cyanobacteria)仅在海拔高度2 000 m时为优势类群.在属水平上,伯克霍尔德菌属(Burkholderia)、克雷伯氏菌属(Klebsiella)相对丰度分别为海拔高度1 800 m与2 000 m土壤优势菌属,而类伯克霍尔德氏菌属(Paraburkholderia)是所有海拔土壤中的主要菌属.采用随机森林分析评估和筛选标志物种,确认Azohydromonas对固氮细菌群落结构差异存在重要影响.结合Pearson相关性分析与冗余分析结果,土壤含水量、硝态氮、碱解氮与有效磷是造成不同海拔土壤固氮细菌群落特征差异的主要环境因子.本研究表明海拔梯度及响应其变化的土壤理化因子,对调控固氮细菌群落结构与多样性有较大影响.(图8表3参41)     

Quantitative analysis of riparian herbaceous community in Liaohe River Conservation Area and its tributaries北大核心CSCD

Research on community characteristics of riparian herbs is an important scientific basis of riparian vegetation rehabilitation. This study aimed to investigate the species diversity and quantitative characteristics of riparian herbs in Liaohe River Conservation Area and its tributaries. Herbaceous communities were investigated by sample line method. Group average clustering analysis and detrended correspondence analysis (DCA) were used to find the major environmental factors affecting the distribution pattern of riparian herbaceous communities. The result showed altogether 154 herbaceous species, belonging to 40 families and 96 genera. The riparian herbaceous species diversity was found to be correlated to river slope, sinuosity and stream order, being lower in rivers of mountain area than in rivers of plain area, and higher in tributaries than in Liaohe River Conservation Area. Clustering analysis classified the herbaceous communities into 23 types, being dominated by hygrophytes including communities of Echinochloa crusgalli, Oenanthe javanica, Polygonum hydropiper, Murdannia keisak, Artemisia selengensis, Scirpus triqueter, Heleocharis soloniensis, Pycreus sanguinolentus, Cyperus fuscus, Phragmites australis, Polygonum amphibium, Carex diandra + Artemisia selengensis and Carex diandra + Rorippa islandica. Correlation analysis between DCA ordination axes and environmental factors showed that the altitude, river slope, sinuosity and stream level were the major environmental factors affecting the distribution pattern of herbaceous communities in the riparian zone of Liaohe River Conservation Area and its tributaries. The results of CCA showed that the contribution ratio of stream level was the highest, followed by altitude and slope, with sinuosity the last. The results suggested that riparian herbaceous characteristics are affected by the comprehensive force of altitude, river slope, sinuosity and stream order, and that Calamagrostis epigeios, Triarrhena sacchariflora and Phragmites australis are suitable species for riparian vegetation rehabilitation.     

Phase transition behavior of elastin-like polypeptides oligomerized with the Foldon domain北大核心CSCD

To investigate the underlying mechanism of the unique phase transition behavior of SpyCatcher-ELPs40 (C-E) and the influence of the oligomerization domain on the phase transition of C-E, we constructed a non-covalent three-armed star oligomerization of C-E-F and E-F by fusing the Foldon (F) domain with SpyCatcher-ELPs40 (C-E) and ELPs40 (E). Results showed that the phase transition temperature of ELPs40 fused with Foldon was higher than that of ELPs120, whereas it was lower than those of ELPs40 and the SpyTag/SpyCatcher-mediated covalent three-armed elastin-like polypeptides (ELPs). This proved that the topology of ELPs could affect their phase transition behaviors. The phase transition temperature of C-E-F was 28.8 ℃ and 35.6 ℃ higher than those of C-E and ELPs40, respectively, although C-E-F had a similar sequence with C-E and ELPs40. When the concentration of NaCl was 0.8 mol/L, the differences in the phase transition temperatures were 41.2 ℃ and 47.1, respectively. We could only observe the phase transition of C-E-F in the Na2CO3 solution with high concentration (≥ 0.7 mol/ L); however, the phase transition could be clearly detected in the Na2SO4 solution, even when the concentration of Na2SO4 was very low. This result was obviously inconsistent with the Hofmeister series. This is the first report of non-linear ELPs that has shown this unique phase transition behavior. The possible reason was related to the charges distributed on the solvent accessible surface and the oligomeric state of C-E-F triggered by the Foldon domain. © 2018 Science Press. All rights reserved.     

Screening of the marine actinomycetes with anti-complement activity and isolation of the active fractions北大核心CSCD

Studies on anti-complement agents are essential for the development of drugs to treat various diseases caused by excessive or abnormal activation of the complement system. However, studies on microbial-derived anti-complement agents are still very limited. The anti-complement activities of 42 marine-derived actinomycete strains isolated from the sediment samples collected from Xinghai Bay in Dalian were studied using the hemolysis method. In addition, the active fractions of the strain Streptomyces sp. DUT11 were separated by C18 and Sephadex LH-20 column chromatography, and the active compounds with anti-complement activity were identified. Streptomyces strains S187, M5, S088, M8, S063, DUT11 and MD16 showed good anti-complement activities upon being cultured in TSB medium, with the strain DUT11 showing the best anti-complement activity among these strains. When different fermentation media were tested, the highest anti-complement activity of DUT11 was observed in M33 fermentation medium. The anti-complement activity was 56.5% for the extract of supernatant and 60.8% for the extract of mycelia, respectively. Furthermore, three compounds with anti-complement activity were obtained from the active components, which were identified as 3-indolecarboxylic acid (1), p-hydroxy benzoic acid (2) and 2-pyrrolecarboxylic acid (3). These results demonstrated that marine-derived streptomycetes can be employed to produce active compounds with anti-complement activity. This study presents a new alternative for the utilization of marine actinomycetes and provides a basis for the exploration of new anti-complement agents. © 2018 Science Press. All rights reserved.     

Bacterial community structure of Tricholoma matsutake stipe soil by high-throughput sequencing北大核心CSCD

In order to understand the interaction between microorganisms in soil attached to the stipes of Tricholoma matsutake, we utilized high-throughput sequencing technology using an Illumina HiSeq 2500 System (San Diego, CA, USA) to explore the bacterial community structure in such soils and analyzed the effects of microorganisms on the formation and growth of T. matsutake. A total of 6 730 sequences were obtained from the samples, and these sequences were clustered into 928 operational taxonomic units (OTUs) at a 97% similarity level. In addition, these OTUs were grouped into 22 bacterial phyla (including 62 classes, 90 orders, 162 families, and 275 genera) and 2 archaeal phyla (including 4 classes, 6 orders, 7 families, and 8 genera). Proteobacteria was the dominant phylum present in all the samples, and these bacteria were significantly more abundant in soils attached to stipe of T. matsutake than they were in the control samples. Similarly, Beta-proteobacteria were the dominant class, and bacteria in this class were less abundant than they were in the control samples. Moreover, the genus Burkholderia within the Proteobacteria was more abundant in the control samples than in the T. matsutake soil samples. Generally, Proteobacteria, especially the genus Burkholderia, played an important role in the growth of T. matsutake, whereas other bacteria, such as Unknown-Ellin 60, would probably inhibit the growth of T. matsutake. This study showed that bacteria might be involved in the growth of T. matsutake and the formation of its fruiting bodies, but they had no positive relationship with bacterial abundance, which may provide theoretical guidance for the cultivation of T. matsutake. © 2018 Science Press. All rights reserved.     

Differences in the quality of steamed hull-less barley and wheat cakes北大核心CSCD

In this study, three different hull-less barley varieties were used to prepare steamed cakes, and their nutritional value, sensory qualities, textural properties, and in vitro starch hydrolysis were evaluated. The results showed that the contents of total dietary fiber (4.50%-5.12%), β-glucan (2.96%-3.96%), total flavonoids (12.56-38.73 mg/100 g), and γ-aminobutyric acid (5.08-9.53 mg/100 g) in the steamed hull-less barley cakes were significantly higher than that in the steamed wheat cake, which were 0.65%, 0.23%, 3.93 mg/(100 g), and 2.63 mg/(100 g), respectively. The sensory properties of steamed ordinary hull-less barley and wheat cakes were not significantly different, but the steamed 08-1127 (waxy hull-less barley) cake was softer and out of shape. The springiness, resilience, cohesiveness, gumminess, and adhesiveness of steamed ordinary hull-less barley cakes were similar to those of steamed wheat cake, while those of steamed 08-1127 cakes were significantly lower than those of steamed ordinary hull-less barley cakes. Steamed hull-less barley cake also showed a maximum starch hydrolysis rate (38.76%-42.74%) that was lower than that of steamed wheat cake (49.92%), and the contents of rapidly (11.58%-13.16%) and slowly digested starch (5.34%-7.56%) were lower than that of steamed wheat cake (17.21% and 15.97%, respectively). In addition, the glycemic (59.37-61.67) and hydrolysis indexes (35.82-40.00) were lower than those of steamed wheat cake (76.66 and 67.30, respectively), and the contents of resistant starch (2.74%-3.55%) were higher than those of wheat steamed cake (1.68%). Therefore, the steamed cakes of ordinary hull-less barley had a higher content of nutritional components than the steamed cake of wheat, and the in vitro starch hydrolysis parameters were better than those of steamed wheat cake. When it is necessary to consider both nutritional and sensory qualities, ordinary hull-less barley can be selected as the raw material for steamed cakes, but waxy hull-less barley is not suitable for making steamed cakes. © 2022 Science Press. All rights reserved.     

Distribution and habitat characteristics of fishes in the Pearl River Estuary北大核心CSCD

To explore the current situation and distribution of fish in the eight major estuaries of the Pearl River Estuary in China, acoustic detection and water quality monitoring were conducted in 2018. The results showed that almost living in eight major estuaries were juvenile, the proportion of strong echo was higher in winter, and Jiaomen and Modaomen Estuary were relatively rich in adult fish. In winter, the Humen, Jiaomen, and Yamen Estuary had a high density relatively, for 46.05 (± 50.30), 33.12 (± 93), and 32 (± 78) ind/103 m3, respectively. However, the fish densities of the Hengmen, Modaomen, and Hutiaomen estuaries were higher in summer at 55.72 (± 83.23), 37.52 (± 55) and 36 (± 99) ind/103 m3, respectively. Thus, fish are mainly concentrated in the flood tidal estuary in winter and in the ebb tidal estuary in summer. In addition, fish density was higher in flood tide than in ebb tide, and the strong echo proportion was lower. In winter, the key water quality factors affecting the biodiversity of estuary fish Shannon were chlorophyll a (P < 0.05), while what affected the fish density were turbidity and salinity (P < 0.05). This study showed that the Pearl River estuary was still the main habitat for juvenile fish. However, habitat variability is obvious; hence, it is important to flexibly carry out the delimitation of estuarine fish reserves and ecological restoration. © 2022 Authors. All rights reserved.