Fluctuation in the zooplankton community in two solar salt ponds,Aveiro, Portugal

The zooplankton of two salt ponds at Aveiro was studied to evaluate its density and diversity. Samples were collected biweekly from the salt ponds Esmolas and Tanoeiras. Samples were first separated into Holoplankton (Copepoda, nauplii,Acartia, Ostracoda and Anostraca) and Meroplankton (Mollusca, Insecta, annelidan larvae and Ichthyoplankton). The Holoplankton was mainly composed of:Acartia tonsa, Acartia sp.,Eurytemora velox, Artemia sp., and harpacticoids and calanoids. In both salt ponds, species diversity was identical, but total zooplankton density was higher in the Tanoeiras salt pond, probably because its physical and chemical characteristics allowed the development of stable communities.     

Hydraulic and sedimentary controls on the availability and use of Atlantic salmon (Salmo salar) spawning habitat in the River Dee system, north-east Scotland

The hydraulic and sedimentary characteristics of the spawning habitat of Atlantic salmon (Salmo salar) in tributary and mainstem locations in a river system in north-east Scotland are described. Salmon used spawning sites with a relatively wide range in sediment characteristics, although measures of central tendency were all in the gravel (2–64 mm) size-class. The dominant factor differentiating the sediment characteristics of study sites was the level of fine sediment, which accounted for significant differences between tributary and mainstem samples. The ranges of depth and velocity in areas used for spawning by salmonids were found to be similar in all tributary study sites. However, due to the interdependence of depth and velocity, major differences were observed between tributary and mainstem study sites in that spawning in larger streams tended to be associated with deeper, faster flowing water. Spawning locations were shown to have similar Froude number, despite different sized streams and species of salmonid. Due to its dimensionless nature and significance in characterising flow hydraulics, the Froude number is proposed as a potentially useful variable for describing the habitat of aquatic organisms.     

Monitoring vegetation dynamics in semi-arid African rangelands: Use and limitations of Earth observation data to characterize vegetation structure

Vegetation community structure is a key indicator of long-term vegetation change in semi-arid ecosystems. This study uses ground-based spectral measurements and a canopy reflectance model to investigate the potential of Earth observation data to characterize variations in vegetation structure along a grazing gradient in the eastern Kalahari, Botswana. Despite differences in the bidirectional reflectances of soil, plant litter, bush and grass canopies towards the end of a dry season, it is unlikely that Earth observation data can be used to estimate vegetation structure at this time. This is due to an ambiguity in the relationship between spectral reflectance and vegetation structure caused primarily by the limited dimensionality of reflectance data. Variations in canopy architecture cause differences in the level of inter-canopy shadowing but the net effect—lower reflectance with an increase in bush cover—parallels the darkening effects of any vegetation cover on relatively bright sandy soils in semi-arid environments. These results highlight the continued need for long-term ground-based ecological monitoring in conjunction with satellite-based monitoring of changes in vegetation cover.     

BOOK REVIEWS

Book Reviewed in this article: Marine Resources of Kuwait: Their Role in the Development of Non-oil Resources . Fatimah H. Y. al -Abdul -Razzak Recollections of a Revolution: Geography as Spatial Science . Mark Billinge , Derek Gregory and Ron Martin Entre l'Eden et l'Utopie . Luc Bureau Developments in Political Geography . M. A. Busteed The Elements of Graphing Data . William S. Cleveland Rural Resource Management . Paul J. Cloke and Chris C. Park Third World Atlas . Ben Crow and Alan Thomas Exploitation, Conservation, Preservation: A Geographic Perspective on Natural Resource Use . Susan L. Cutter , Hilary Lambert Renwick, and William H. Renwick . Wine Regions of the Southern Hemisphere . Harm Jan de Blij Regional Development: Problems and Policies in Eastern and Western Europe . George Demko The Geographer at Work . Peter R. Gould Change in the Amazon Basin . John Hemming Geography Since the Second World War . R. J. Johnston and P. Claval Urbanization in China: Town and Countryside in a Developing Economy 1949–2000 A.D. , R. J. R. Kirkby Transport and Communications for Pacific Microstates: Issues in Organisation and Management . Christopher C. Kissling Fluvial Forms and Processes . David Knighton The Urban Millennium . Josef W. Konvitz Technological Transition in Cartography . Mark Stephen Monmonier Field Guide to Soils and the Environment: Applications of Soil Surveys . Gerald W. Olson Northern Australia: The Arenas of Life and Ecosystems on Half a Continent . Don Parkes A Killing Rain: The Global Threat of Acid Rain . Thomas Pawlick From the Family Farm to Agribusiness: The Irrigation Crusade in California and the West, 1850–1931 . Donald J. Pisani Hybrid Maize Diffusion in Kenya . Franz -Michael Rundquist Warning and Response to the Mount St. Helens Eruption . Thomas F. Saarinen and James L. Sell Coastal Geomorphology in Australia . B. G. Thom Tropical Rain Forests of the Far East , 2nd ed . T. C. Whitmore The Dark Side of the Earth . Robert Muir Wood Categorical Data Analysis for Geographers and Environmental Scientists , Neil Wrigley     

Characteristic and Geological Significance of Microbially Induced Sedimentary Structures(MISS) in Terrestrial P-T Boundary in Xingyang,Western He’nan Province

Microbially Induced Sedimentary Structures (MISS) are primary sedimentary structures that arise syndepositionally from microbial community activity. Especially valuable are MISS for the analysis of early Archean (and extraterrestrial) deposits. However, most reports of MISS have focused on the Precambrian and Phanerozoic mass extinction marine sediments, and only a few and terrestrial MISS have been studied. The MISS presented in this paper, which mainly consists of mat growth feature, mat destruction feature and mat decay feature, are well preserved in terrestrial clastic rocks around the P-T boundary in Xiyang area, western Henan. Large U ridges, oriented sand quartz, mica grains and thin clayey laminae arranged parallel to bedding plane are the main features visible under the microscope. Several lines of evidence indicate that the Xingyang MISS are of biogenic origin. Abundant MISS in Xingyang may indicate the degradation of terrestrial ecosystems and proliferation of microbial mats immediately after the severe Permian-Triassic mass extinction. Study aiming at MISS helps to analyze their space distribution in the globe and to probe into links between microbial proliferation and environmental stresses following the end-Permian mass extinction in terrestrial ecosystems.     

Herbaceous layer development during spring does not deplete soil nitrogen in the Portuguese montado

Nitrogen (N) content in the soil and in the herbaceous biomass were monitored during spring of 2004-2006 to determine how the herbaceous layer development influences soil N availability in the montado ecosystem of southern Portugal. Highest (246.6 ± 52.7 g m⁻²) and lowest (123.2 ± 89.5 g m⁻²) peak biomass occurred in 2006 and 2005 respectively. Total soil N within the top 20 cm soil profile ranged between 0.2 ± 0.1% in February and 0.41 ± 0.2% in May, while available soil N was lowest (5 ± 2 μg g⁻¹soil) in February but increased three-to-five fold in March and was >17.5 μg g⁻¹soil at senescence in May. Significant (p < 0.001) increase in total N in the aboveground pool occurred between February and May. There was however, no decay in soil N content. Instead, the herbaceous vegetation enhanced soil N input and N retention in the ecosystem. Most of the herbaceous plants were annuals with large reserves of organic N at senescence, which returned to the soil as detritus. The herbaceous vegetation is a critical component of the montado that contributes to N recharge and cycling within the ecosystem.     

不同生态系统CO2通量和浓度特征分析研究

本文利用1993～1994年日本国家农业环境研究所与中国科学院沙漠研究所合作在内蒙古奈曼地区实测的7种不同生态系统（沙丘、轻度放牧草原、中度放牧草原、重度放牧草原、无放牧草原、玉米田和大豆田）的净辐射、土壤热通量、两个高度的CO2浓度、温度、湿度和风速等资料，采用空气动力学方法，计算了CO2通量及其与环境和人为干扰因子的关系，并分析了不同下垫面的光合作用特征. 结果表明：各种下垫面CO2通量的共同特点是：在白天，CO2通量和梯度的输送方向是从大气向植被，在中午（11～13时）输送达到负的最大值； 在夜间，CO2通量和梯度输送方向与白天相反，是从植被向大气，在早晨（3～5时）达到正的最大值. 植被覆盖率及生物量不同的下垫面光合作用强度有明显差异，天气状况对光合作用也有一定影响.     

池塘养殖刺参安全度夏技术研究

文章概述夏季池塘养殖刺参死亡症状和灾情特点,分析刺参死亡原因主要包括池水盐度骤降、池水温度升高、池水pH值下降、池水分层、有机污染和刺参自身原因。在此基础上,提出池塘养殖刺参安全度夏的技术措施,主要包括科学合理选择养殖地址、规范池塘建设、做好度夏前准备工作、水质管理、及时清除水草和大型藻类、采取降温措施以及补充营养等,涉及大量具体操作方法,具有科学性和实用性。     

湖滨带芦苇恢复过程中沉积物氮赋存形态及含量变化:以巢湖为例

水生植被对于维持水生态系统结构和功能稳定性具有举足轻重的作用,而重建水生植物被认为是污染湖泊生态修复的重要手段.氮素是水生态系统重要的限制性元素之一,根着挺水植物生长发育无疑将深刻地影响着沉积物氮的迁移转化过程,但水生植物不同生长阶段对沉积物氮的需求和植物代谢强度均不同,目前对挺水植物完整生长过程中沉积物氮组分及含量变...     

富营养化湖泊围隔中重建水生植被及其生态效应

水体富营养化导致水生植被衰退、蓝藻水华暴发、水质恶化和水生生态系统崩溃.恢复水生植被被认为是改善受损水体水质和提高其生态系统稳定性的重要手段.本研究通过构建大型围隔,根据水生植物的耐污程度及其对水质和底质等条件的需求,选取几种适宜的水生植物在围隔内进行移栽与群落构建,并以不移栽水生植物的围隔和围隔外水体作为对照.实验期间(2011年4月至2012年6月),围隔内移栽的几种水生植物全部存活,并建立了相对稳定的群落.同时还跟踪监测了3个处理组的水质情况,结果显示,移栽水生植物的围隔内水质明显优于围隔外,与未移栽水生植物围隔相比,也有很大程度的改善,其中移栽水生植物围隔内水体的总氮、铵态氮、总磷、水下消光系数相比于围隔外水体分别低30.55%、44.09%、36.04%和42.13%,相比于未移栽水生植物围隔内水体分别低5.96%、13.40%、6.70%和7.60%,透明度分别比围隔外水体和未移栽水生植物围隔水体高74.59%和8.70%,浮游植物生物量也大大低于围隔外,而浮游动物生物量却明显高于后者.此外,实验后移栽水生植物围隔内沉积物氮、磷含量及其间隙水总氮、总磷、铵态氮浓度明显低于围隔外和未移栽水生植物围隔.研究表明,在富营养化浅水湖泊中通过建立围隔进行合理的群落配置,进而逐步恢复水生植物是完全可行的,而水生植物恢复后加强对其管理和维护至关重要.