Influence of Woody Debris on Channel Structure in Old Growth and Managed Forest Streams in Central Sweden

Anecdotal information suggests that woody debris have had an important channel-forming role in Swedish streams and rivers, but there are few data to support this view. We identified 10 streams within near-natural and 10 streams within managed forest landscapes in central Sweden, and quantified their channel characteristics and content of woody debris. All pieces of woody debris greater than 0.5 m in length and greater than 0.05 m in base diameter were included. The near-natural forests were situated in reserves protected from forest cutting, whereas the managed forests had previously faced intensive logging in the area adjacent to the stream. The two sets of streams did not differ in general abiotic characteristics such as width, slope, or boulder cover, but the number of wood pieces was twice as high and the wood volume almost four times as high in the near-natural streams. This difference resulted in a higher frequency of debris dams in the near-natural streams. Although the total pool area did not differ between the two sets of streams, the wood-formed pools were larger and deeper, and potentially ecologically more important than other pools. In contrast to what has been believed so far, woody debris can be a channel-forming agent also in steeper streams with boulder beds. In a stepwise multiple regression analysis, pool area was positively and most strongly related to the quantity of woody debris, whereas channel gradient and wood volume were negatively related. The frequency of debris dams increased with the number of pieces of woody debris, but was not affected by other variables. The management implications of this study are that the wood quantity in streams in managed forests would need to be increased if management of streams will target more pristine conditions.     

Effects of Fireplace Use on Forest Vegetation and Amount of Woody Debris in Suburban Forests in Northwestern Switzerland

Urban forests are popular recreation areas in Europe. Several of these temperate broad-leaved forests also have a high conservation value due to sustainable management over many centuries. Recreational activities, particularly the use of fireplaces, can cause extensive damage to soil, ground vegetation, shrubs, and trees. Firewood collection depletes woody debris, leading to a loss of habitat for specialized organisms. We examined the effects of fireplace use on forest vegetation and the amount of woody debris by comparing disturbed and control plots in suburban forests in northwestern Switzerland. At frequently used fireplaces, we found reduced species densities in the ground vegetation and shrub layer and changes in plant species composition due to human trampling within an area of 150–200 m². Picnicking and grilling also reduced the height and changed the age structure of shrubs and young trees. The amount of woody debris was lower in disturbed plots than in control plots. Pieces of wood with a diameter of 0.6–7.6 cm were preferentially collected by fireplace users. The reduction in woody debris volume extended up to a distance of 16 m from the fire ring, covering an area of 800 m² at each picnic site. In order to preserve the ecological integrity of urban forests and to maintain their attractiveness as important recreation areas, we suggest depositing logging residues to be used as firewood and to restrict visitor movements near picnic sites.     

云南木本食用油料资源及其开发

食用油料木本化对我国具有重要的战略意义。云南具有丰富多彩的木本食用油料树种,本文记述了云南具有重要开发价值的３２ 科８４ 种食用油料树种,并提出了它的三个开发利用的方向。     

珠江三角洲的耕地及其持续利用

耕地的持续利用是农业持续发展的前提和基础,是人类经济社会持续发展的根本保证。本文论述了珠江三角洲耕地的现状和经济快速增长所引发的耕地问题,并指出耕地的持续利用需要全社会的共同努力。     

庐山野生木本观赏植物资源及其开发利用

庐山植物资源丰富.记述了庐山野生木本观赏植物的5个主要类别和4个观赏特性,充分认识和合理利用这些各具特色的野生木本观赏植物资源,在庐山生态旅游及城市建设中具有重要意义.     

Woody Vegetation Composition and Structure in Peri-urban Chongming Island, China

Chongming, the world’s largest alluvial island, is located within the municipality of Shanghai, China. Recent projects have now linked peri-urban Chongming to Shanghai’s urban core and as a result will soon undergo substantial changes from urbanization. We quantitatively analyzed the structure and composition of woody vegetation across subtropical, peri-urban Chongming as a basis for sustainable management of these rapidly urbanizing subtropical ecosystems elsewhere. We used 178 permanent, random plots to statistically and spatially analyze woody plant composition and tree structure across the 1,041 km² of Chongming. A total of 2,251 woody plants were measured comprising 42 species in 37 genera. We statistically and geospatially analyzed field data according to land uses and modeled air pollution removal by trees. Average tree diameter at breast height, total height, and crown widths on transportation land uses were greater than other land uses. These same values were lowest on forest land use and greater tree cover was associated with areas of increased anthropogenic activity. Less than 20 % of the woody vegetation was exotic and a species richness index was significantly different between land uses due to legacy effects. Composition of agriculture and forest land uses were similar to residential and transportation. Tree cover across Chongming was also estimated to annually remove 1,400 tons of air pollutants. We propose that this integrated and quantitative method can be used in other subtropical, peri-urban areas in developing countries to establish baseline trends for future sustainability objectives and to monitor the effects of urbanization and climate change.     

休宁县野生木质藤本植物种质资源及园林用途研究

野外考察和文献调查分析表明,安徽省休宁县野生木质藤本植物资源丰富、种类繁多,累计有25科48属132种(含种以下等级),其中主要有葡萄科、蔷薇科、猕猴桃科、毛茛科、卫矛科、豆科等6个科.对藤本植物的观赏特性及园林用途进行了较详细的阐述.     

丽江地区中低产耕地及其开发利用

本义探讨了丽江地区中低产耕地的特征,并从自然因素和人文因素分析了低产的原因,进而提出合理改良利用低产耕地的对策。     

Method to Partition Between Attached and Unattached E. coli in Runoff From Agricultural Lands1

Abstract: Remediation of waters impaired by bacterial indicators is usually dictated by total maximum daily load plans, which are heavily dependent on fate and transport modeling of bacterial indicators. Nonpoint source pollution models are most frequently used to assess bacterial transport to surface waters and most models typically simulate bacterial transport as a dissolved pollutant. Previous studies have found that cells preferentially attach to sediments; however, a variety of techniques have been used to assess attachment including filtration, fractional filtration, and centrifugation. In addition, a variety of chemical and physical dispersion techniques are used to release attached and bioflocculated cells from particulates. Here we developed and validated an easy‐to‐replicate laboratory procedure for separation of unattached from attached E. coli which will also identify particle sizes to which E. coli preferentially attach. Physical and chemical dispersion techniques were evaluated and a combined hand shaker treatment for 10 min followed by dilutions in 1,000 mg/l of Tween 85 significantly increased total E. coli concentrations by 31% when compared with a control. In order to separate unattached from attached fractions, two commonly used techniques, fractional filtration, and centrifugation were combined. The filtration and centrifugation treatments did not reduce E. coli concentrations when compared with a control (p > 0.05), indicating that damage was not inflicted upon the E. coli cells during the separation procedure.     

Multiple Determinants of Anuran Richness and Occurrence in an Agricultural Region in South-Eastern Brazil

In agricultural landscapes, studies that identify factors driving species richness and occupancy are important because they can guide farmers to use conservation practices that minimize species loss. In this context, anurans are threatened by habitat loss because they depend on the characteristics of both local water bodies and adjacent landscapes. We used a model selection approach to evaluate the influence of local and landscape variables in determining anuran species richness and occurrence in 40 freshwater bodies in a heavily deforested region of semideciduous Atlantic Forest in southeastern Brazil. Our aim was to develop recommendations for conservation of anuran communities in rural areas. Pond hydroperiod and area were the most important variables for explaining anuran species richness and occupancy, with greatest species richness being found in water bodies with intermediate hydroperiod and area. Other important variables that reflected individual species occupancies were the number of vegetation types and pond isolation. In addition, recent studies evidenced that water bodies near forest fragments have higher anuran abundance or diversity. In conclusion, we suggest the maintenance of semi-permanent ponds, isolated from large rivers or reservoirs and near forest fragments, as an effective strategy to conserve anuran fauna in agricultural landscapes of southeastern Brazil. Brazilian government requires the maintenance of forests as legal reserve in each farm, and farmers need to maintain ponds as drinking water for cattle or crop irrigation. For this reason, the guidelines suggested in the present study can be easily adopted, without additional costs to rural productivity.     

论农资产品的使用对新疆农业生态环境的影响

从农业生产、农业生态及环境保护等角度,对农药、化肥和农膜三大农资产品在农业生产中的作用及负面效应进行了分析。认为在现代农业生产中的农药、化肥和农膜具有不可替代的作用。在相当长的一段时间内、这些农资产品的应用是不可能摈弃的。但其负面效应也是不可忽视的。尤其是对农业生态环境的影响。应采取一切行之有效的措施消除或消弱其不利影响。     

东南亚珠芽魔芋多苗接力生长特性及应用前景

以珠芽魔芋人工诱导开花进行规模化无性育种,可将魔芋繁殖系数从1位数提高约330倍;采用催苗技术让种子及叶面球茎提早出苗,可显著延长魔芋生长周期,使魔芋种植周期由3年缩短为1年;魔芋种子1年生长最高膨大率超过5000倍,当年即形成1180g球茎;魔芋叶面球茎最大膨大率超过100倍,两者种植一季魔芋即可用于加工.突破了魔芋繁殖系数低、膨大率低导致种植周期长的双重困局,显著降低了病害风险,大幅度缩短了魔芋种植周期,从而突破魔芋传统种植区域的地理限制,使魔芋总产量超常规增长.     

污水灌溉对我国农业生态系统的影响及其对策

本文运用生态学原理,分析了污灌区农业生态系统的特点,指出了污灌在农业生态系统中既起着水源和肥源,又起着污染源的三重作用。同时,从正反两方面阐述了污灌对我国农业生态系统的影响,提出了污灌条件下建立农业生态系统良性循环的途径,即(1)尽量控制污水中的污染物质进入农业生态系统;(2)减少污染物质在农田生态系统的累积;(3)改变污染物在农业生态系统中的迁移途径。     

中国矿产地战略储备的运行管理模式研究

矿产地储备是矿产资源战略储备的重要形式之一.政府是实施矿产地战略储备的主体,储备地建立的途径包括规划、国家直接出资勘查和回购矿业权三种形式.随着国内外政治、经济、资源、市场、技术等因素的变化,需要对储备的矿产地实行梯次动态轮换.矿产地储备的启动资金由国家财政负担,在轮换和动用时用矿业权转让价款弥补储备期间的成本.中国应实行大储备的管理体制,统筹协调矿产品储备、石油储备和矿产地储备.现阶段矿产地战略储备管理体制应由决策层、执行层和操作层组成.矿产地战略储备要协调国家与地方经济利益,建立补偿机制促进矿产地战略储备的顺利进行.     

海南热带农产品绿色营销的现状分析及对策探讨

绿色营销是一项系统工程,它需要政府、企业、消费者、社会公众等各方面的共同努力.21世纪是绿色食品产业迅速发展的时代,海南热带农产品的可持续发展必须顺应这一潮流,抓住机遇,实施绿色营销.阐述了当前海南热带农产品的绿色营销现状,针对其存在问题进行了分析,提出了海南热带农产品的绿色营销对策.     

Reflections on the Growing Influence of Good Agricultural Practices in the Global South

EurepGAP is a pioneering field level food safety protocol called ‘good agricultural practices’ currently exercising influence over the global food quality assurance system. Developed by a consortium of major European retailers, this private standard enforces codes of conduct that address issues of health and safety for producers and consumers, as well as working conditions and environmental management on the farmland. Despite various merits and benefits that the standard is premised to offer, the institutional design gives a financial edge to powerful large farms and exporters while diminishing opportunities for smaller growers and exporters to remain in the profitable agricultural export sector of the Global South. This paper explores the institutional origin and evolution of EurepGAP, discusses entry barriers and risks that EurepGAP imposes on the global value chain stakeholders, as well as the ethical implications from broader theoretical perspectives. Subsequently, it examines the evolving nature of a new trend in the fresh fruit and vegetable sector, i.e., the rise of public GAP standards. Promoted by some governments in the Global South, these GAP standards emphasize support for horizontal partnerships among value chain stakeholders, farmer participation, and less capital-intensive agricultural innovations. The paper argues that, within certain limitations, these GAP standards have the potential to be the major alternative GAP approach by encouraging a much broader inclusion of small-scale producers towards the attainment of various social, economic, and environmental benefits.     

Influence of Riparian Seepage Zones on Nitrate Variability in Two Agricultural Headwater Streams

Riparian seeps have been recognized for their contributions to stream flow in headwater catchments, but there is limited data on how seeps affect stream water quality. The objective of this study was to examine the effect of seeps on the variability of stream NO₃‐N concentrations in FD36 and RS, two agricultural catchments in Pennsylvania. Stream samples were collected at 10‐m intervals over reaches of 550 (FD36) and 490 m (RS) on 21 occasions between April 2009 and January 2012. Semi‐variogram analysis was used to quantify longitudinal patterns in stream NO₃‐N concentration. Seep water was collected at 14 sites in FD36 and 7 in RS, but the number of flowing seeps depended on antecedent conditions. Seep NO₃‐N concentrations were variable (0.1‐29.5 mg/l) and were often greater downslope of cropped fields compared to other land uses. During base flow, longitudinal variability in stream NO₃‐N concentrations increased as the number of flowing seeps increased. The influence of seeps on the variability of stream NO₃‐N concentrations was less during storm flow compared to the variability of base flow NO₃‐N concentrations. However, 24 h after a storm in FD36, an increase in the number of flowing seeps and decreasing streamflow resulted in the greatest longitudinal variability in stream NO₃‐N concentrations recorded. Results indicate seeps are important areas of NO₃‐N delivery to streams where targeted adoption of mitigation measures may substantially improve stream water quality.     

Changes in Soil Particulate Organic Matter, Microbial Biomass, and Activity Following Afforestation of Marginal Agricultural Lands in a Semi-Arid Area of Northeast China

Afforestation of agricultural lands has been one of the major land use changes in China in recent decades. To better understand the effect of such land use change on soil quality, we investigated selected soil physical, chemical and microbial properties (0–15 cm depth) in marginal agricultural land and a chronosequence of poplar (Populus euramericana cv. ‘N3016’) plantations (5-, 10-, 15- and 20-years old) in a semi-arid area of Northeast China. Soil bulk density significantly declined after conversion of agricultural lands to poplar plantations. Soil total organic carbon (TOC) and nitrogen (TN) concentrations, microbial biomass C (MBC) and potential N mineralization rate (PNM) decreased initially following afforestation of agricultural lands, and then increased with stand development. However, soil metabolic quotient (qCO₂) exhibited a reverse trend. In addition, soil particulate organic matter C (POM-C) and N (POM-N) concentrations showed no significant changes in the first 10 years following afforestation, and then increased with stand age. These findings demonstrated that soil quality declined initially following afforestation of agricultural lands in semi-arid regions, and then recovered with stand development. Following 15 years of afforestation, many soil quality parameters recovered to the values found in agricultural land. We propose that change in soil quality with stand age should be considered in determining optimum rotation length of plantations and best management practices for afforestation programs.     

平安县农业环境污染现状及防治对策

文章分析了平安县农业环境的主导因素—土壤受废水、农药、化肥、地膜、畜禽粪便污染的现状,探讨了防治对策。