Response of gaseous carbon emissions to low-level salinity increase in tidal marsh ecosystem of the Min River estuary, southeastern China

Although estuarine tidal marshes are important contributors to the emission of greenhouse gases into the atmosphere, the relationship between carbon dioxide(CO_2), methane(CH_4)emission, and environmental factors, with respect to estuarine marshes, has not been clarified thoroughly. This study investigated the crucial factors controlling the emission of CO_2 and CH_4from a freshwater marsh and a brackish marsh located in a subtropical estuary in southeastern China, as well as their magnitude. The duration of the study period was November 2013 to October 2014. Relevant to both the field and incubation experiments, the CO_2 and CH_4emissions from the two marshes showed pronounced seasonal variations. The CO_2 and CH_4emissions from both marshes demonstrated significant positive correlations with the air/soil temperature(p 0.01), but negative correlations with the soil electrical conductivity and the pore water/tide water Cl-and SO_4~(2-)(p 0.01). The results indicate no significant difference in the CO_2 emissions between the freshwater and brackish marshes in the subtropical estuary, whereas there was a difference in the CH_4 emissions between the two sites(p 0.01). Although future sea-level rise and saltwater intrusion could reduce the CH_4 emissions from the estuarine freshwater marshes, these factors had little effect on the CO_2 emissions with respect to an increase in salinity of less than 5‰. The findings of this study could have important implications for estimating the global warming contributions of estuarine marshes along differing salinity gradients.     

Vertical diversity of sediment bacterial communities in two different trophic states of the eutrophic Lake Taihu, China

Vertical diversity of sediment bacterial communities in 2 different trophic states (macrophyte-dominated and algae-dominated) of the large shallow eutrophic Lake Taihu, China, were investigated using denaturing gradient gel electrophoresis (DGGE) and 16S rRNA sequence analysis. Clustering analysis of DGGE profiles showed that different clusters were recognized in different depths of sediment cores in the 2 lake trophic states. Analyses of the bacterial diversity, as estimated by the Shannon index (H'), showed that different sediment layers of the macrophyte-dominated state had higher diversity than the algae-dominated state. In addition, bacterial diversity of the sediment in the macrophyte-dominated state changed abruptly throughout the layers, but bacterial diversity of the algae-dominated state decreased gradually with sediment depth. Phylogenetic analysis showed that Proteobacteria was the most abundant phylum in the middle sediment of the 2 lake trophic states. In the macrophyte-dominated state, clone sequences related to Betaproteobacteria (50.0%) were the most abundant, followed by Epsilonproteobacteria (21.1%), Acidobacteria (7.9%), Deltaproteobacteria (7.9%), Chloroflexi (7.9%), and Bacteroidetes (5.3%); whereas in the algae-dominated state, sequences affiliated with Betaproteobacteria (84.4%) were predominant, followed by Deltaproteobacteria (12.5%) and Acidobacteria (3.1%). Canonical correspondence analysis showed that organic matter and pH play key roles in driving the vertical changes of bacterial community composition.     

Denaturing gradient gel electrophoresis fingerprinting of soil bacteria in the vicinity of the Chinese Great Wall Station, King George Island, Antarctica

Bacterial diversity was investigated in soil samples collected from 13 sites around the Great Wall Station, Fildes Peninsula, King George Island, Antarctica, using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes. The classes α-, β-, and γ-Proteobacteria, as well as the phylum Actinobacteria, were found to be the dominant bacteria in the soils around the Great Wall Station. Although the selected samples were not contaminated by oil, a relationship between soil parameters, microbial biodiversity, and human impact was still seen. Sample sites in human impacted areas showed lower bacterial biodiversity (average H′= 2.65) when compared to nonimpacted sites (average H′= 3.05). There was no statistically significant correlation between soil bacterial diversity and total organic carbon (TOC), total nitrogen, or total phosphorus contents of the soil. Canonical correlation analysis showed that TOC content was the most important factor determining bacterial community profiles among the measured soil parameters. In conclusion, microbial biodiversity and community characteristics within relatively small scales (1.5 km) were determined as a function of local environment parameters and anthropogenic impact.     

河水-地下水侧向交互带地球化学特征:以重庆市马鞍溪为例

河水-地下水交互带是河水与地下水相互交换和混合的区域,在河流、地下水生态和水质的保护方面具有重要作用.为了解河水-地下水侧向交互带地球化学特征,以重庆市马鞍溪为研究对象,对河水及交互带的水温、溶解氧(DO)、pH值、电导率(EC)进行自动监测,结合对水样离子浓度和交互带沉积物中元素含量的分析.结果表明,马鞍溪侧向交互带水化学类型为HCO_3-Ca·Mg型.监测期间交互带受河水入渗影响为主,交互带的缓冲作用使其温度、DO、pH值、EC等指标变异系数较河水低.随距河岸距离的增加,马鞍溪侧向交互带在物理、化学、生物综合作用下形成了迅速进入缺氧状态的氧化还原环境,以及pH值先降低后升高的酸碱环境.在其影响下,K~+、NH_4~+-N、NO_3~-、SO_4~(2-)呈下降趋势,全Mn、EC、Na~+、Ca~(2+)、Mg~(2+)、Sr~(2+)等先上升后下降,全Fe、Al~(3+)等呈上升趋势.受河水、地下水长期交互影响,在距河岸约30 cm处的交互带沉积物中元素含量较高,形成独特的水化学梯度.据此可推断出马鞍溪侧向交互带边界可能在距河岸30~50 cm处,其中浅层交互带的边界可能在距河岸10 cm左右的位置.在河水补给地下水过程中,河水-地下水侧向交互带对净化水质有重要作用.     

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)     

沉积物再悬浮对浮游细菌群落结构的影响

本研究通过小宇宙的模拟实验,设置3组处理,即无再悬浮的对照组(C)、强(SR)和弱(WR)2个不同再悬浮强度的处理组,采用末端限制性片段长度多态性(terminal restriction fragment length polymorphism,T-RFLP)和变性梯度凝胶电泳(denaturing gradient gel electrophoresis,DGGE)分析不同处理组中浮游细菌群落结构的变化.结果表明,再悬浮处理组浮游细菌的物种丰度高于对照组,并且弱再悬浮中浮游细菌物种丰度高于强再悬浮处理.弱再悬浮中细菌多样性也高于强再悬浮处理.浮游细菌与环境因子的典型对应分析(CCA)和冗余分析(RDA)结果表明,浮游动物枝角类(Cladocera)生物量和颗粒态磷(PP)浓度与浮游细菌群落结构动态变化均表现出显著的相关性(p0.05).由此可见,沉积物再悬浮对浅水湖泊浮游细菌的种类和多样性存在重要影响,其可能通过影响浮游动物群落结构以及水体中营养盐的形态和浓度对浮游细菌群落产生影响.     

巢湖水陆交错带生态服务价值梯度分析

基于巢湖水陆交错带1995、2000、2007和2013年4期遥感影像提取土地利用信息,参考前人的相关研究成果,测算研究区的生态服务价值。在综合研究区实际情况和相关研究基础上采用等距离缓冲带法,对研究区生态服务价值的梯度变化进行研究。结果表明:(1)各土地利用类型的梯度变化在不同时期有较为一致的变化趋势,在不同的缓冲带内都有1~2个贡献率较大的土地利用类型;(2)在研究期内各缓冲带生态服务价值处于基本平稳的状态,其中缓冲带1到缓冲带2的变化幅度较大;(3)从生态服务价值的空间分布来看,缓冲带1的生态服务价值始终最高,外层的缓冲带5和缓冲带6由低等级到中等级平稳过度,缓冲带3和缓冲带4则始终处在低水平;(4)林地和水域对生态服务价值的贡献率与距巢湖水陆边界的距离有显著的相关性,表明林地和水域对研究区生态服务价值的影响大。     

上海市城乡梯度上土壤重金属空间分布及其影响因素定量分析

提出了两种上海市城乡梯度上土壤重金属空间格局及影响因素的研究方法:缓冲区分析方法和滑动窗口分析方法.缓冲区分析的结果表明,人口变化指数及2~3 km范围内的建设用地比例能显著影响Cd和Cu的空间分布(p0.05),而3 km范围内的道路密度显著影响Pb的浓度.滑动窗口分析的结果表明,Cd和Cu主要受工业活动的影响,而Pb受交通流量,以及反映城市景观扩张过程的景观形状指数的影响.相关分析表明,两种方式揭示了较为相似的土壤重金属空间累积影响因素,即工业活动相关的城市化过程.研究对理解城市化的发生机制及其重金属环境风险的管理有重要意义.     

Investigation of physico-chemical properties and microbial community during poultry manure cocomposting process

Co-composting of poultry manure and rubber wood sawdust was performed with the ratio of 2:1 (V/V) for a period of 60 days. An investigation was carried out to study the extracellular enzymatic activities and structural degradation utilizing Fourier transform infrared spectroscopy (FT-IR), thermogravimetry and differential thermal analysis (TG/DTA) and scanning electron microscopy (SEM). The microbial succession was also determined by using denaturing gel gradient electrophoresis (DGGE). The compost was able to reach its highest temperature of 71 ℃ at day 3 and stabilized between 30 and 40 ℃ for 8 weeks. CMCase, FPase and β-glucosidase acted synergistically in order to degrade the cellulosic substrate. The xylanase activities increased gradually during the composting and reached the peak value of 11.637 U/g on day 35, followed by a sharp decline. Both LiP and MnP activities reached their peak values on day 35 with 0.431 and 0.132 U/g respectively. The FT-IR spectra revealed an increase in aromaticity and a decrease in aliphatic compounds such as carbohydrates as decomposition proceeded. TGA/DTG data exhibited significant changes in weight loss in compost samples, indicating degradation of organic matter. SEM micrographs showed higher amounts of parenchyma exposed on the surface of rubber wood sawdust at day 60, showing significant degradation. DGGE and 16S rDNA analyses showed that Burkholderia sp., Pandoraea sp., and Pseudomonas sp. were present throughout the composting process. Ornithinibacillus sp. and Castellaniella ginsengisoli were only found in the initial stage of the composting, while different strains of Burkholderia sp. also occurred in the later stage of composting.     

Batrachochytrium dendrobatidis and the Collapse of Anuran Species Richness and Abundance in the Upper Manu National Park,Southeastern Peru

Abstract: Amphibians are declining worldwide, but these declines have been particularly dramatic in tropical mountains, where high endemism and vulnerability to an introduced fungal pathogen, Batrachochytrium dendrobatidis (Bd), is associated with amphibian extinctions. We surveyed frogs in the Peruvian Andes in montane forests along a steep elevational gradient (1200–3700 m). We used visual encounter surveys to sample stream‐dwelling and arboreal species and leaf‐litter plots to sample terrestrial‐breeding species. We compared species richness and abundance among the wet seasons of 1999, 2008, and 2009. Despite similar sampling effort among years, the number of species (46 in 1999) declined by 47% between 1999 and 2008 and by 38% between 1999 and 2009. When we combined the number of species we found in 2008 and 2009, the decline from 1999 was 36%. Declines of stream‐dwelling and arboreal species (a reduction in species richness of 55%) were much greater than declines of terrestrial‐breeding species (reduction of 20% in 2008 and 24% in 2009). Similarly, abundances of stream‐dwelling and arboreal frogs were lower in the combined 2008–2009 period than in 1999, whereas densities of frogs in leaf‐litter plots did not differ among survey years. These declines may be associated with the infection of frogs with Bd. B. dendrobatidis prevalence correlated significantly with the proportion of species that were absent from the 2008 and 2009 surveys along the elevational gradient. Our results suggest Bd may have arrived at the site between 1999 and 2007, which is consistent with the hypothesis that this pathogen is spreading in epidemic waves along the Andean cordilleras. Our results also indicate a rapid decline of frog species richness and abundance in our study area, a national park that contains many endemic amphibian species and is high in amphibian species richness.