Protected‐Area Boundaries as Filters of Plant Invasions

Abstract: Human land uses surrounding protected areas provide propagules for colonization of these areas by non‐native species, and corridors between protected‐area networks and drainage systems of rivers provide pathways for long‐distance dispersal of non‐native species. Nevertheless, the influence of protected‐area boundaries on colonization of protected areas by invasive non‐native species is unknown. We drew on a spatially explicit data set of more than 27,000 non‐native plant presence records for South Africa's Kruger National Park to examine the role of boundaries in preventing colonization of protected areas by non‐native species. The number of records of non‐native invasive plants declined rapidly beyond 1500 m inside the park; thus, we believe that the park boundary limited the spread of non‐native plants. The number of non‐native invasive plants inside the park was a function of the amount of water runoff, density of major roads, and the presence of natural vegetation outside the park. Of the types of human‐induced disturbance, only the density of major roads outside the protected area significantly increased the number of non‐native plant records. Our findings suggest that the probability of incursion of invasive plants into protected areas can be quantified reliably.     

A Small‐Scale Land‐Sparing Approach to Conserving Biological Diversity in Tropical Agricultural Landscapes

Two contrasting strategies have been proposed for conserving biological diversity while meeting the increasing demand for agricultural products: land sparing and land sharing production systems. Land sparing involves increasing yield to reduce the amount of land needed for agriculture, whereas land‐sharing agricultural practices incorporate elements of native ecosystems into the production system itself. Although the conservation value of these systems has been extensively debated, empirical studies are lacking. We compared bird communities in shade coffee, a widely practiced land‐sharing system in which shade trees are maintained within the coffee plantation, with bird communities in a novel, small‐scale, land‐sparing coffee‐production system (integrated open canopy or IOC coffee) in which farmers obtain higher yields under little or no shade while conserving an area of forest equal to the area under cultivation. Species richness and diversity of forest‐dependent birds were higher in the IOC coffee farms than in the shade coffee farms, and community composition was more similar between IOC coffee and primary forest than between shade coffee and primary forest. Our study represents the first empirical comparison of well‐defined land sparing and land sharing production systems. Because IOC coffee farms can be established by allowing forest to regenerate on degraded land, widespread adoption of this system could lead to substantial increases in forest cover and carbon sequestration without compromising agricultural yield or threatening the livelihoods of traditional small farmers. However, we studied small farms (<5 ha); thus, our results may not generalize to large‐scale land‐sharing systems. Furthermore, rather than concluding that land sparing is generally superior to land sharing, we suggest that the optimal approach depends on the crop, local climate, and existing land‐use patterns. Un Método para Reservar Tierras a Pequeña Escala para Conservar la Biodiversidad en Paisajes Agrícolas Tropicales     

PM2.5 and volatile organic compounds (VOCs) in ambient air: a focus on the effect of meteorology

PM(2.5) and VOCs (benzene, toluene, m-p-o-xylenes) concentrations were measured in an urban and a suburban site in Athens, Greece, during the period between April and November 2004. This period, which is considered to be the warmer period in Greece, is characterized by the development of sea-breeze over the Attica Basin. Additionally strong Northern, North-eastern winds called "The Etesians", predominate during the summer months (July-August), acting positively to the dispersion of pollutants. In this campaign, 24 days with sea-breeze development were observed, 15 days with northern winds, 6 days with southern winds while the rest of the days presented no specific wind profile. Maximum concentrations of PM(2.5), VOCs and nitrogen oxides, were detected during the days with sea-breeze, while minimum concentrations during the days with northern winds. Ozone was the only pollutant that appeared to have higher concentrations in the background site and not in the city centre, where benzene presented strong negative correlation with ozone, indicating the photochemical reaction of hydrocarbons that lead to the ozone formation. The BTX ratios were similar for both sites and wind profiles, indicating common sources for those pollutants. T/B ratio ranged in low levels, between 3-5 for site A and 2-5 for site B, suggesting vehicles emissions as the main sources of volatile compounds. Finally, the strong correlations of PM(2.5) and benzene concentrations, between the two sampling sites, indicate that both the city centre and the background site, are affected by the same sources, under common meteorological conditions (sea-breeze, northern winds).     

Diel Cycling of Zinc in a Stream Impacted by Acid Rock Drainage: Initial Results from a New in situ Zn Analyzer

Recent work has demonstrated that many trace metals undergo dramatic diel (24-h) cycles in near neutral pH streams with metal concentrations reproducibly changing up to 500% during the diel period (Nimick et al., 2003). To examine diel zinc cycles in streams affected by acid rock drainage, we have developed a novel instrument, the Zn-DigiScan, to continuously monitor in situ zinc concentrations in near real-time. Initial results from a 3-day deployment at Fisher Creek, Montana have demonstrated the ability of the Zn-DigiScan to record diel Zn cycling at levels below 100 μg/l. Longer deployments of this instrument could be used to examine the effects of episodic events such as rainstorms and snowmelt pulses on zinc loading in streams affected by acid rock drainage.     

LEGAL ASPECTS OF MINING DEVELOPMENT IN DEVELOPING COUNTRIES

This article discusses the legal criteria of a mining investment decision - the legal status of investments, fiscal regime and mining legislation. The importance of the security of tenure of mining titles and of the stability of the terms and conditions, as stated from the inception, is emphasized, and the concepts of state sovereignty, state ownership of mineral deposits and state participation in mining ventures are considered. The preference for legalistic solutions rather than ad hoc contracts is stated, and a brief review of the various types of mining agreements is given. Cet article analyse les critères juridiques de la decision concernant l'investissement minier: statut juridique des investissements, régime fiscal et legislation minière. L'importance de la sécurité de la concession minière et la garantie des clauses de contrats est mise en evidence. L'article considère également les concepts de souveraíneté de l'Etat, la propriété étatique des dépôts minéraux et la participation de l'Etat dans la recherche minérale. L'auteur indique sa préférence pour des solutions juridiques plutôt que des contrats particuliers et passe brièvement en revue les différents types d'accords miniers. Este artículo analiza los criterios legates empleados en la toma de decisiones sobre inversión minera: estado legal de la inversión, régimen fiscal y legislación minera. Se da énfasis a la importancia de la seguridad de posesión de los títulos mineros, la estabilidad de las condiciones iniciales de contrato y se consideran también los conceptos de soveranía del estado, propiedad estatal de los depósitos mineros y la participación del estado en la actividad minera. Se indica la preferencia por las soluciones a través de leyes en vez de contratos ad hoc y se revisan brevemente varios tipos de acuerdos mineros.     

40.5kV真空灭弧室内部电场强度分布的仿真分析

40.5 kV/2.5 kA/63 kA真空灭弧室作为363 kV/5 kA/63 kA快速断路器串联模块的子单元,研究其内部电场强度分布以确保其绝缘性能,对于整套快速断路器装置的安全可靠运行尤为重要。根据实际参数搭建了40.5 kV真空灭弧室的基本模型,利用Ansoft 有限元计算仿真软件搭建了40.5 kV真空灭弧室的仿真模型,进行了电场强度分布的仿真计算,得到了灭弧室中的动触头台阶倒角区域、动触头倒角区域、静触头台阶倒角区域、静触头倒角区域的电场强度最大,最有可能发生击穿的结论。提出了通过改变台阶倒角和触头倒角以改善电场分布进行优化设计的建议,并利用Ansoft 仿真软件进行改变台阶倒角值和触头倒角值后的仿真计算,得到了触头台阶处倒角取值2mm、动静触头倒角2mm或3mm的设计较优,只设置1个触头片时触头倒角取值3 mm设计较优。     

山西关帝山神尾沟植物群落物种多样性与环境关系的研究I．丰富度、均匀度和物种多样性指数

以89个植物群落调查样地数据为基础，运用8个多样性指数对山西关帝山神尾沟物种多样性与环境之间的关系进行了分析.（1）群落总的表现为多样性和均匀度随海拔升高而下降，丰富度从1700m下降到2400m后开始升高；（2）群落不同层次表现为乔木层和灌木层多样性、丰富度和均匀度随海拔升高而下降，草本多样性和均匀度表现为上升趋势，丰富度下降到1900m后开始上升；（3）乔灌草三者多样性和丰富度指数值以及变化幅度都表现为草本层>灌木层>乔木层，三者均匀度相差不大；（4）群落不同坡向表现为阳坡多样性和丰富度都大于阴坡，均匀度相差不大.图6参7     

Planting History and Propagule Pressure as Predictors of Invasion by Woody Species in a Temperate Region

Abstract:  We studied 28 alien tree species currently planted for forestry purposes in the Czech Republic to determine the probability of their escape from cultivation and naturalization. Indicators of propagule pressure (number of administrative units in which a species is planted and total planting area) and time of introduction into cultivation were used as explanatory variables in multiple regression models. Fourteen species escaped from cultivation, and 39% of the variance was explained by the number of planting units and the time of introduction, the latter being more important. Species introduced early had a higher probability of escape than those introduced later, with more than 95% probability of escape for those introduced before 1801 and <5% for those introduced after 1892. Probability of naturalization was more difficult to predict, and eight species were misclassified. A model omitting two species with the largest influence on the model yielded similar predictors of naturalization as did the probability of escape. Both phases of invasion therefore appear to be driven by planting and introduction history in a similar way. Our results demonstrate the importance of forestry for recruitment of invasive trees. Six alien forestry trees, classified as invasive in the Czech Republic, are currently reported in nature reserves. In addition, forestry authorities want to increase the diversity of alien species and planting area in the country.