Considering river structure and stability in the light of evolution: feedbacks between riparian vegetation and hydrogeomorphology          下载免费PDF全文

Dov Corenblit  Neil S. Davies  Johannes Steiger  Martin R. Gibling  Gudrun Bornette 《地球表面变化过程与地形》2015,40(2):189-207

River ecological functioning can be conceptualized according to a four‐dimensional framework, based on the responses of aquatic and riparian communities to hydrogeomorphic constraints along the longitudinal, transverse, vertical and temporal dimensions of rivers. Contemporary riparian vegetation responds to river dynamics at ecological timescales, but riparian vegetation, in one form or another, has existed on Earth since at least the Middle Ordovician (c. 450 Ma) and has been a significant controlling factor on river geomorphology since the Late Silurian (c. 420 Ma). On such evolutionary timescales, plant adaptations to the fluvial environment and the subsequent effects of these adaptations on fluvial sediment and landform dynamics resulted in the emergence, from the Silurian to the Carboniferous, of a variety of contrasted fluvial biogeomorphic types where water flow, morphodynamics and vegetation interacted to different degrees. Here we identify several of these types and describe the consequences for biogeomorphic structure and stability (i.e. resistance and resilience), along the four river dimensions, of feedbacks between riparian plants and hydrogeomorphic processes on contrasting ecological and evolutionary timescales. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

基于功能区的行政区划调整研究——以绍兴城市群为例   总被引：6，自引：3，他引：3  

顾朝林  王颖  邵园  顾江 《地理学报》2015,70(8):1187-1201

本文构建了基于功能区的行政区划调整研究框架。首先,运用功能区思想,以大城市地区的街道或乡镇为空间单元,采集相关的自然、历史、文化、产业、客流和信息流数据,进行要素功能区的分析,准确获取不同层次相互依赖的功能空间单元,使城市在空间上充分适应和支撑多变的社会经济环境,为城市的多样性提供充分的弹性空间依据。其次,在城市基层单元的要素功能区的基础上,进一步采用因子分析和聚类分析方法,进行城市功能区的划分,可以为行政区划调整提供基于城市功能区有机的空间组织科学依据。在上述行政区划调整研究框架的基础上,以绍兴市为例进行了案例研究,结果表明,绍兴市域内自然、文化功能区清晰,块状经济特征明显,基层区之间的经济、文化、通勤和信息联系已经突破现在的市县行政区边界,按照综合功能区的思想进行行政区划调整。总体上说,基于功能区的行政区划调整,对大城市地区或城市群地区,保证其物质环境和社会空间的快速和谐发展,有效利用资源,具有重要的科学意义和实用价值。  相似文献   

Genesis of Dolomite from Ma55–Ma510 Sub-members of the Ordovician Majiagou Formation in the Jingxi Area in the Ordos Basin     

LIU Jingdong  JIANG Youlu  LIU Xinshe  YANG Zhiwei  HOU Xiangdong  ZHU Rongwei  WEN Caixi  WANG Feiyan 《《地质学报》英文版》2017,91(4):1363-1379

We clarified three stages of dolomitization and secondary changes by studying the petrology and geochemistry characteristics of dolomite from the Ma55–Ma510 sub-members of the Ordovician Majiagou Formation in the Jingxi area in the Ordos Basin: (1) Syngenetic microbial dolomitization is characterized by formation of dolomite with a mainly micrite structure and horse tooth-shape dolomite cements. (2) Seepage reflux dolomitization during the penecontemporaneous period superposed adjustment functions such as recrystallization and stabilization in the middle-deep burial stage, forming dolomites mainly consisting of micro crystal and powder crystal structure. (3) Powder dolomite, fine dolomite, and medium-coarse crystalline dolomite formed in pores and fractures in the middle-deep burial stage. The secondary concussive transgression-regression under a regressive background is an important condition for the occurrence of many stages of dolomitization in the study area. The basin was an occlusive epicontinental sea environment in the Ma5 member of the Ordovician Majiagou Formation sedimentary period. In the sediments, sulfate content was high, which is conducive to the preservation of microbial activity and microbial dolomitization. Micritic dolomite formed by microbial dolomitization provides good migration pathways for seepage reflux dolomitization. Affected by evaporation seawater with increased Mg/Ca ratio, seepage reflux dolomitization was widely developed and formed large-scale dolomite, and underwater uplifts and slopes are favorable areas for dolomite. In the middle-deep burial stage, dolomitizing fluid in the stratum recrystallized or stabilized the previous dolomite and formed a small amount of euhedral dolomite in the pores and fractures.  相似文献   

Temporal and environmental significance of microbial lamination: Insights from Recent fluvial stromatolites in the River Piedra,Spain          下载免费PDF全文

Concha Arenas  Brian Jones 《Sedimentology》2017,64(6):1597-1629

Despite extensive research, the environmental and temporal significance of microbial lamination is still ambiguous because of the complexity of the parameters that control its development. A 13 year monitored record of modern fast‐accreting calcite stromatolites (mean 14 mm year^?1) from artificial substrates installed in rapid flow in the River Piedra (north‐east Spain) allows comparison of the sedimentological attributes of successive six‐month depositional packages with the known climatic, hydrophysical and hydrochemical parameters of the depositional system. The stromatolites are formed of dense, porous and macrocrystalline composite laminae. The dense and porous composite laminae, which are composed of two to eight laminae consisting largely of calcified cyanobacteria, are characterized by: (i) dense composite laminae, up to 15 mm thick, mostly with successive dense laminae and minor alternating dense and porous laminae; and (ii) porous composite laminae, up to 12 mm thick, consisting mainly of porous laminae alternating with thinner dense laminae. Most of the dense composite laminae formed during the warm periods (April to September), whereas most of the porous composite laminae developed in the cool periods (October to March). Each dense and porous composite lamina represents up to or slightly longer than six months. The alternation of these two types of composite laminae parallels seasonal changes in temperature. The dense and porous laminae result from shorter (for example, intraseasonal) variations in temperature, insolation and hydrological conditions. The macrocrystalline laminae, with crystals >100 μm long, occur isolated and grouped into composite laminae up to 1·7 mm thick. Their occurrence suggests the absence or poor development of microbial mats over periods of weeks to several months. Thus, stromatolite lamination can record different‐order, periodic and non‐periodic changes in the magnitude of environmental parameters over a single year. These results hold important implications for the temporal and environmental interpretation of lamination in microbial structures.  相似文献   

冻融循环条件下生境基材中三种功能微生物数量变化规律研究   总被引：1，自引：1，他引：0  

张琳瑶  刘大翔  许文年  童标 《冰川冻土》2017,39(5):1122-1129

为揭示高寒地区典型生境基材中功能微生物数量变化的规律,以黄棕壤土为试验土样,在两种初始含水率条件下,分别制备客土、植被混凝土以及加菌植被混凝土三种不同类型的生境基材进行冻融循环模拟试验,探讨生境基材类型、初始含水率和冻融循环次数对基材中功能微生物数量的影响。试验结果显示：三种基材中功能微生物数量均受冻融循环影响显著,且随冻融循环次数增加总体呈"下降~上升~下降"趋势;冻融循环过程中,三种基材中功能微生物总量存在显著性差异,排序为：加菌植被混凝土 > 植被混凝土 > 客土,且固氮、解钾微生物数量显著低于解磷微生物;含水率为22%的基材中功能微生物总量普遍高于含水率为18%的基材。研究结果表明,加菌植被混凝土的肥力、抗冻性相比客土和植被混凝土有一定程度提升,但仍需对现有功能菌剂配方加以改进,以适应高寒地区冻融环境。  相似文献   

缢蛏(Sinonovacula constricta)生物扰动对养殖废水处理系统中沉积物磷赋存形态垂直分布的影响     

郑余琦  郑忠明  秦文娟 《海洋与湖沼》2017,48(1):161-170

为研究缢蛏(Sinonovacula constricta)生物扰动在养殖废水生态处理系统中对沉积物不同垂直分层的各种磷形态迁移转化的影响,于2016年5—7月在养殖废水处理池的贝藻处理区采集不同缢蛏养殖密度下的实验围隔箱内的底泥,测定不同垂直方向上的磷形态、微生物活性(FDA)以及碱性磷酸酶活性(APA)。结果表明,在底栖动物缢蛏生物扰动作用下,改变了沉积物内部的微环境,促进了微生物的生长,增大了沉积物中总微生物活性以及碱性磷酸酶活性。而沉积物中有机磷(OP)含量显著减少(P0.05);非磷灰石态无机磷(NAIP)、磷灰石态无机磷(AP)和无机磷(IP)含量显著增加(P0.05),这表明在缢蛏的生物扰动下OP可能转变成为AP、NAIP等无机磷成分;总磷含量呈降低趋势。本试验结果表明,缢蛏生物扰动下对于养殖废水生态处理系统沉积物垂直方向上的磷赋存形态具有显著的影响,且高密度组的生物扰动作用对沉积物中磷形态迁移转化的影响强于低密度组。  相似文献   

热带西太平洋Y3和M2海山微食物网主要类群生态分布与比较   总被引：2，自引：0，他引：2  

赵丽  赵燕楚  王超锋  张武昌  孙晓霞  李学刚  赵苑  肖天 《海洋与湖沼》2017,48(6):1446-1455

2014年12月和2016年3月分别对热带西太平洋Y3海山(中层海山)和M2海山(浅海山)微食物网主要类群(包括聚球藻、原绿球藻、微微型真核浮游生物、异养细菌和浮游纤毛虫)丰度和生物量垂直分布进行了研究。结果表明,Y3和M2海山水文环境比较相似但略有区别,叶绿素最大值层(DCM)分别在75—100m和110m水层,微食物网各主要类群在垂直尺度上的分布与叶绿素a浓度紧密相关。其中浮游纤毛虫呈现"双峰型"模式,即丰度高值出现在表层和DCM层;原绿球藻和微微型真核浮游生物呈现"单峰型"模式,丰度高值出现在DCM层;聚球藻和异养细菌峰型相对不显著,DCM层以浅丰度较高,DCM层以深丰度明显降低。分析其原因,可能是受到温度、光照和营养盐的共同影响。Y3和M2海山微食物网结构的垂直变化不完全一致。其中,Y3海山30m以浅和150m以深异养细菌生物量占绝对优势,75—100m水层自养型生物(原绿球藻和微微型真核浮游生物)占绝对优势;M2海山75m以浅和200m以深异养细菌占绝对优势,110—150m自养型生物占绝对优势。M2海山自养型生物占优势的水层要明显深于Y3海山,可能与它们的海山类型和采样季节不同有关。  相似文献   

Size scaling patterns of species richness and carbon biomass for marine phytoplankton functional groups          下载免费PDF全文

Lydia Ignatiades 《Marine Ecology》2017,38(5)

Phytoplankton assemblages were clustered into associations according to functional taxonomic (diatoms, dinoflagellates and coccolithophores) and “ataxonomic” unimodal (nanoplankton, microplankton and macroplankton) size‐based criteria. Scaling relations of species richness‐cell size were performed in terms of histogram and log‐transformed data analyses for both taxonomic and ataxonomic groups. Frequency distribution histograms were fitted to a negative power function, which was strongly unimodal and right skewed and invariant across taxonomic and ataxonomic units. Regression analyses of the log‐transformed data were fitted to negative linear curves, which had common patterns and they were independent of taxonomic or ataxonomic affiliation. Species carbon biomass–cell size spectra produced by log transformation of the relevant data yielded positive slopes for both taxonomic and ataxonomic groups. In contrast, comparisons of the relative cell abundance, cell volume and carbon biomass levels showed large differences among these variables across taxonomic and ataxonomic groups. This work demonstrates that phytoplankton taxonomic and ataxonomic functional group relationships should be considered when developing future models of phytoplankton community structure.  相似文献   

利用限制性最大似然方法和贝叶斯方法估计大菱鲆生长性状的遗传参数。   总被引：1，自引：0，他引：1  

官健涛  王伟继  胡玉龙  王陌桑  田涛  孔杰 《海洋学报(英文版)》2017,36(6):47-51

Bayesian and restricted maximum likelihood(REML) approaches were used to estimate the genetic parameters in a cultured turbot Scophthalmus maximus stock. The data set consisted of harvest body weight from 2 462progenies(17 months old) from 28 families that were produced through artificial insemination using 39 parent fish. An animal model was applied to partition each weight value into a fixed effect, an additive genetic effect, and a residual effect. The average body weight of each family, which was measured at 110 days post-hatching, was considered as a covariate. For Bayesian analysis, heritability and breeding values were estimated using both the posterior mean and mode from the joint posterior conditional distribution. The results revealed that for additive genetic variance, the posterior mean estimate( δ_a~2=9 320) was highest but with the smallest residual variance,REML estimates( δ_a~2=8 088) came second and the posterior mode estimate( δ_a~2=7 849) was lowest. The corresponding three heritability estimates followed the same trend as additive genetic variance and they were all high. The Pearson correlations between each pair of the three estimates of breeding values were all high,particularly that between the posterior mean and REML estimates(0.996 9). These results reveal that the differences between Bayesian and REML methods in terms of estimation of heritability and breeding values were small. This study provides another feasible method of genetic parameter estimation in selective breeding programs of turbot.  相似文献   

Organic carbon and microbial biomass in a raised beach deposit under terrestrial vegetation in the High Arctic, Ny-Ålesund, Svalbard     

Takayuki Nakatsubo  Shinpei Yoshitake  Masaki Uchida  Masao Uchida  Yasuyuki Shibata  & Hiroshi Koizumi 《Polar research》2008,27(1):23-27

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