Modern pollen assemblages of the forest communities and their relationships with vegetation and climate in northern China

53 pollen traps and surface samples were collected in order to detect the characteristics of pollen assemblages and their relationships with vegetation and climate in 16 forest communities located in 10 mountains in northern China. The results show that 72% of the pollen taxa (80 taxa) are the same between the traps and the surface samples. The dominant taxa in the plant communities are consistent with the main pollen taxa in the pollen assemblages at the same sites. In Pinus plant communities, both Pinus pollen influx and concentration are higher, indicating the high pollen productivity and good pollen preservation ability of Pinus. In Picea and Abies plant communities, Picea and Abies have lower pollen influxes but higher concentrations, suggesting their low pollen productivities but better pollen preservation abilities. In Betula and Quercus plant communities, Betula and Quercus have higher pollen influxes but lower concentrations, revealing their high pollen productivities but poor pollen preservation abilities. The study of relationships between pollen and vegetation with discriminant analysis shows that pollen assemblages from both trap and surface samples can reflect the characteristics of different communities and distinguish different ecological areas, but surface samples can reflect the dominant components of communities much better than the traps. The study on correlations between pollen assemblages and climate with DCCA reveals that significant correlations exist between pollen assemblages and mean temperature of the coldest month (r = 0.84 for trap samples, r = 0.72 for surface samples), and then annual mean precipitation (r = 0.73 for trap samples, r = 0.71 for surface samples).     

Mapping benthic faunal communities in the shallow and deep sediments of Las Perlas Archipelago, Pacific Panama

Las Perlas Archipelago (LPA) is located off the Pacific Coast of Panama and was designated as a marine protected area (MPA) in 2007. This baseline study of the shallow and deeper sedimentary habitats of the islands partly informed the MPA designation. Ninety-two grab stations and twenty trawl stations were sampled. Sediment grab sample results were interpolated to produce a map that showed the area to be dominated by mud (1246 km², 40%) and sand/shell sediments (780 km², 25%). A total of 201 taxa were recorded and over 5800 individual specimens were processed, revealing that the sediments hold varying community compositions, with annelids being the dominant group (73%) followed by crustaceans (14%). Relationships were evident between community, feeding guilds, and sediment types, which give an indication of communities that can be expected in similar sediments in other areas of the Tropical Eastern Pacific. A study of this scale and level of detail is rare for this biogeographic region and provides a valuable, comprehensive appreciation of the LPA’s benthos.     

上海苏州河鱼类群落的初步研究

苏州河是一条流经上海市区的过境河流.本研究试图以鱼类群落状况来评估该河的环境质量.将2001年采集到的鱼类标本与20世纪60年代上海科技馆(旧名上海自然博物馆)的收藏标本进行对比.1960年代,鱼类物种数有62种,2001年为44种,前后减少18种;其中鲤科鱼类中营底柄生活、食无脊椎动物的鮈亚科鱼类变化明显,减少6种.鱼类的食性结构也发生了明显的变化.食鱼性鱼类的物种比例由1960年代的27.4%下降到2001年的22.7%;食无脊椎动物鱼类的比例由1960年代的24.2%下降到2001年的11.4%,而杂食性鱼类的物种比例则由1960年代的25.8%上升到2001年的38.6%.杂食性鱼类在个体数也占据优势.沿程分布显示上游的物种多样性明显高于下游.以上结果表明苏州河的鱼类群落变得简单.食物网复杂度降低,生物完整性下降,推测其主要原因可能在于作为水生生物柄息地主要构成的底质状况发生了改变.     

新的组合激活函数BP网络模型研究

作者提出了一种新的 BP神经网络模型 ,其隐层激活函数采用中心参数可调的 Gaussian函数 ,输出层采用斜度可调的 Sigmoid函数 ,从而神经元具有了更强的信息存储、处理能力。由于采用组合函数 ,将 Gaussian函数良好的局部性和 Sigmoid函数良好的全局性相结合 ,提高了神经网络的收敛速度。几个典型实验的结果表明 ,与传统 BP网络模型相比 ,新网络模型在学习能力和泛化推广能力方面都有明显提高     

Metagenomic Analysis of Bacterial Communities from a Nitrification–Denitrification Treatment of Landfill Leachates

The efficiency of the biological removal of carbon and nitrogen from leachates is determined by the activity of microbial populations present in biological reactors. In this work, a complete characterization of bacterial communities revealed by personal genome machine sequencing (PGM) has been carried out from different points of a nitrification–denitrification process operated in an urban landfill. The leachate fed to the treatment is a mixture of young leachate, old leachate, and effluent from an anaerobic digestion process, in a volume ratio of 1:0.9:0.12, respectively. The anoxic and oxic reactors are followed by an ultrafiltration step. Samples are taken from different points of the process. Results reveal the microbial diversity of the samples, which include detection of minority populations that are difficult to explore by other methods. Bacteria belonging to Bacteroidetes and Proteobacteria are dominant in all the samples analyzed. Proteobacteria represents more than 50% of the total population in all cases. Samples taken after the biological treatment show a significant reduction in the relative abundance of Firmicutes, Tenericutes, and Lentisphaerae phyla in comparation with the initial leachate. The relative abundance of the classes is also studied and the most abundant in the samples are β‐Proteobacteria and Flavobacteria.     

Comparison of Phytoplankton Communities Between Melt Ponds and Open Water in the Central Arctic Ocean

Climate warming has a significant impact on the sea ice and ecosystem of the Arctic Ocean.Under the increasing numbers of melt ponds in Arctic sea ice,the phytoplankton communities associated with the ice system are changing.During the 7th Chinese National Arctic Research Expedition cruise in summer 2016,photosynthesis pigments and nutrients were analyzed,revealing differences in phytoplankton communities between melt ponds and open water in the central Arctic.Photosynthetic pigment analysis suggested that Fuco(5-91μg m^-3)and Diadino(4-21μg m^-3)were the main pigments in the open water.However,the melt ponds had high concentrations of Viola(7-30μg m^-3),Lut(4-59μg m^-3)and Chl b(11-38μg m^-3),suggesting that green algae dominated phytoplankton communities in the melt ponds.The significant differences in phytoplankton communities between melt ponds and open water might be due to the salinity difference.Moreover,green algae may play a more important role in Arctic sea ice ecosystems with the expected growing number of melt ponds in the central Arctic Ocean.     

Diurnal changes in bacterial communities in oxic surface and hypoxic middle seawater layers of the Changjiang River Estuary

The Changjiang River Estuary(CRE) in the East China Sea suffers from seasonal hypoxia in summer. The vertical distributions and seasonal changes of microbial communities in the CRE were well documented. However, little is known about the diurnal changes of bacterial communities in the hypoxic zone of the CRE. Here, 16 S rRNA gene analysis was used to explore the changes of bacterial communities in the oxic surface and hypoxic middle seawater layers during 24 h in the CRE. Significant differences between the hypoxic and oxic layers were observed:the phyla Cyanobacteria, Bacteroidetes and Acidimicrobiia were enriched in the oxic layer, whereas the phylum SAR406 and the class Deltaproteobacteria were more abundant in the hypoxic layer. In addition, some subtle diurnal variations of the bacterial relative abundance were found in both two layers. The relative abundance of Synechococcus increased at night, and this change was more obvious in the hypoxic layer. The similar trend was also found in some phototrophic and several heterotrophic bacteria, such as Rhodobacteraceae, OM60 and Flavobacteriaceae. Their relative abundances peaked at 16:00 in the oxic layer, while the relative abundances peaked at around 7:00 and decreased until 13:00 in the hypoxic layer. Together, the results of the present study suggest that some photosynthetic bacteria and several heterotrophic bacteria have similar diurnal variations implying the light and physicochemical heterogeneity in the course of a day are important for bacterial diurnal changes in the CRE.     

Fischökologische Leitbilder fünf ausgewählter Salzkammergutseen

Ecological base line states for fish communities are necessary for the evaluation of ecological integrity. In Austria the fish communities of all the larger lakes are strongly influenced by human activities, like commercial fisheries, fish stocking, eutrophication or shore line degradation, and therefore these baseline states can not be developed by comparison with a natural, undisturbed lake. We developed ecological baseline states for the fish communities of the lakes Hallstättersee, Traunsee, Mondsee, Irrsee and Wallersee by reconstructing the native fish communities of these lakes from historical documents (from between 1500 to 1940). Then we classified the potential fish species of these lakes according to their ecological requirements. Finally we developed the base line states with 16 different ecological factors similar to the factors used for the ecological integrity assessment procedure for streams.

The process of reconstructing the fish communities and some advantages and disadvantages of the base line states for fish communities are discussed.     

多道震电非周期信号测试仪的研制

震电效应研究已成为当今地球物理学界最热门的研究课题之一。与该课题相配套的测试仪器对研究工作的进展起关键作用。仪器的研制本着智能化、高精度、低噪声的设计思想 ,采用单片微型计算机作控制单元 ,以菜单设置各种采集命令 ,操作简便。具有电位和梯度两种采集方式 ,电极距为 10 0m ,测线长度为 10 0 0m。仪器启动后 ,各通道间的切换、放大、A/D、存储都是自动完成的 ,可连续采样 15h。野外测量完成后 ,可对计算机进行数据回放。在结构设计上 ,针对野外作业的特点 ,使仪器轻便化、抗震、防潮、可靠耐用 ,适应各种恶劣的野外环境。该仪器经过油田上的现场试验 ,初步证明能满足震电效应研究的技术要求。     

试论图们江陆桥枢纽共同体成长特点,模式及其演进展望

本文从世界经济贸易地理理论出发,总结与回顾了图们江地区国际合作研究和开发实践的三个阶段,概括出复杂性、长期性、突变性和政治经济互动性等四个特点;在总结以往模式基础上,指出图们江地区开发必须采取多国合作方式,按着以建立东北亚新大陆桥东端枢纽为核心的经济共同体的成长模式发展,并对未来３０年的开发进程进行了初步预测。