Effects of Nitrogen Deposition on Bryophyte Species Composition of Calcareous Grasslands

Regular additions of NH₄NO₃ (35–140 kg N ha⁻¹ yr⁻¹) and (NH₄)₂SO₄ (140 kg N ha⁻¹ yr⁻¹) to a calcareous grassland in northern England over a period of 12 years have resulted in a decline in the frequency of the indigenous bryophyte species and the establishment of non-indigenous calcifuge species, with implications for the structure and composition of this calcareous bryophyte community. The lowest NH₄NO₃ additions of 35 kg N ha⁻¹ yr⁻¹ produced significant declines in frequency of Hypnum cupressiforme, Campylium chrysophyllum, and Calliergon cuspidatum. Significant reductions in frequency at higher NH₄NO₃ application rates were recorded for Pseudoscleropodium purum, Ctenidum molluscum, and Dicranum scoparium. The highest NH₄NO₃ and (NH₄)₂SO₄ additions provided conditions conducive for the establishment of two typical calcifuges – Polytrichum spp. and Campylopus introflexus, respectively. Substrate-surface pH measurements showed a dose-related reduction in pH with increasing NH₄NO₃ deposition rates of 1.6 pH units between the control and highest deposition rate, and a further significant fall in pH, of >1 pH unit, between the NH₄NO₃ and (NH₄)₂SO₄ treatments. These results suggest that indigenous bryophyte composition may be at risk from nitrogen deposition rates of 35 kg N ha⁻¹ yr⁻¹ or less. These effects are of particular concern for rare or endangered species of low frequency.     

A Comparison of Precipitation Sensors Used on the Wet-Only Collectors

The variability in performance of three precipitation sensor types, mounted on three identical wet-only collectors, has been compared for eight months at a single site. The catch efficiencies, determined from the sample volumes, are relatively high for these three apparatuses, since they exceed 89% on average. The recorded data of openings and closings of collector lids reveal that the highest losses of collection efficiency, observed for rainfalls of low intensity and low amount, are largely imputable to design and running characteristics of each sensor. Ionic compositions between the samples of these three collectors are relatively close, although significant differences are especially found for H⁺, Ca²⁺, Mg²⁺ and K⁺, suggesting that these apparatuses are differently exposed to the dry deposition of soil particles. The RS 85 sensor seems to be the most suitable one of the three, since it ensures a high catch efficiency for all rain types and tends to limit the exposures of funnel to the dry deposition.     

Dynamics of Bacterial Abundance,Biomass, Activity,and Community Composition in the Oligotrophic Traunsee and the Traun River (Austria)

The holomictic Traunsee is the deepest and second largest lakein Austria. The special characteristic of this ecosystem isthe fact that local salt and soda industries presumably alterthe lake by the discharge of waste materials. Since thebeginning of the 20th century salt and soda works areannually releasing up to 50,000 tons of solid wastes and up to150,000 tons of chloride into Traunsee. To assess potentialeffects of these anthropogenic impacts on the bacterioplanktonthree sampling sites, influenced as well as not influenced bythe industrial discharge, were chosen for comparison andsampled monthly from November 1997 to October 1998. Bacterialabundance ranged between 0.4 to 3.0 × 10⁶ cells ml^-1 with decreasing numbers along the depth profile. Theproportion of actively respiring bacteria, i.e. INT [2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyltetrazolium chloride]reducing cells, never exceeded 10% of DAPI (4',6'-diamidino-2-phenylindole) stained cells. Fluorescence in situ hybridization (FISH) was used to examine the seasonal and spatial distribution of dominant phylogenetic groups of thebacterioplankton. Up to 84% of bacteria detected with DAPIcould be detected via FISH applying the universal bacterialprobe EUB338. Percentages of alpha- and beta-Proteobacteriaand members of the Cytophaga-Flavobacterium cluster did notexceed 60% of DAPI-stained cells.Beta-Proteobacteriaappeared to be the most abundant group, not only in Traunsee butalso in two reference lakes, Attersee and Hallstättersee. No significant differences in any of the bacterial parameters couldbe detected between the three sampling sites and all measurementswere found in the range reported for oligotrophic lakes. The highdischarge of the Traun River, resulting in a lake water renewaltime of only one year, may diminish possible effects of industrial waste discharge in the pelagic zone.     

长江流域粮食资源及生产发展方向

论述长江流域发展粮食生产的重要性，分析粮食资源分布，生产状况，生产结构和地域差异，指出粮食合理布局的方向，提出以粮食集中产区为重点，建设长江流域粮食生产专业化地并以建设商品粮基地为建带突破口。     

Changes in the Biochemical Composition of Tetraselmis Suecia and Isochrysis Galbana During Growth and Decay

The variations of the biochemical composition of Tetraselmis suecica and Isochrysis galbana during growth and decay were determined. the content of chlorophyll a (Chl-a) of the cultures, as expected, slowly degraded into phaeopigments during decay, confirming that chlorophyll measurements do not always provide an accurate estimate of phytoplanktonic biomass and, consequently, may fail if used to measure the food availability of particulate matter for consumers. Measurements of total amounts of proteins, carbohydrates and lipids, related to the nutritional value of particles in terms of caloric content, are shown to provide information on the readily available food for consumers, particularly during the blooms. the protein/carbohydrate, C/N and POC/Chl-a ratios were used to evaluate the differences between these two species during the growth and the decomposition processes. A comparison between experimental and field conditions was undertaken to implement our understanding of the growth and degradation processes of particulate organic matter of phytoplanktonic origin in the sea and its role on natural systems, during and after phytoplankton blooms.     

关于建立资源与环境快速反应系统的探讨

本文阐述了国家快速反应系统的概念及其作用。以建立资源与环境快速反应系统为例,说明建立系统的必要性、系统的内容、组成及技术指示。     

系统聚类分析在农户生态系统类型划分中的应用

应用主成分分析法和系统聚类分析法，对湖北省京山县刘家岭村５０个农户进行了生态系统类型数值分类分析，结果表明，该村农户生态系统可分为农－牧业型、果－农－牧业型和渔－农－牧业型三类，与全村３３８个农户情况相符。     

Is Current Consumption Excessive? A General Framework and Some Indications for the United States

Abstract:  Many prior studies have explored the implications of human population growth and environmentally problematic technologies for biodiversity loss and other forms of environmental degradation. Relatively few, however, have examined the impacts of the level and composition of consumption. We offer a framework that shows how the level and composition of a society's total consumption relate to the uses of various forms of capital and to the sustainability of natural resources and human well-being. We relate the framework to two main approaches—top–down macro studies and bottom–up computer models—for measuring whether overall consumption in the United States satisfies a sustainability requirement. Existing top–down studies have shortcomings that bias their results toward optimism, and current computer simulation models, although strong on revealing biophysical outcomes, are limited in their ability to evaluate impacts on human well-being. Although some ambiguities arise in determining whether overall consumption in the United States is excessive, our conclusions regarding the composition of U.S. consumption are unambiguous. Distorted consumption patterns and associated production methods lead to excessively rapid natural resource depletion; greater conservation would yield gains to current and future generations that more than compensate for the sacrifices involved. Public policies that deal with the composition problem not only would help conserve natural resources and improve current welfare but also would reduce the costs of meeting the goal of sustainability.