Managing for biodiversity from the electric utilities' perspective

The quality and sustainability of the natural environment is a matter of inestimable value and is critical to public health and welfare. All species have a purpose, and they exist for the betterment of other species. It is, therefore, incumbent on all humans to do their part in the preservation of this vast, diverse ecosystem called Earth. All humans are the beneficiaries, the ultimate customers, of a sound environment—water that is safe to drink, air that can be breathed, and soil that will sustain crops. There must be a commitment to leaving a clean and healthy planet for generations to follow, an earth which is enhanced, not diminished, by humans' presence.     

Herbaceous Covers to Control Tree Invasion in Rights-of-Way: Ecological Concepts and Applications

In northeastern America, thousands of kilometers of utility rights-of-way (ROWs) have to be managed to prevent the establishment of a tall vegetation cover that does not comply with safety and maintenance regulations. Recent decades have seen the emergence of ecologically based vegetation control strategies to reduce environmental impacts as well as maintenance costs. One such strategy is to take advantage of competitive herbaceous covers to limit tree invasion. This approach, however, as well as its fundamental underlying principles, has been little scrutinized. In this article, (1) we present the main ecological concepts supporting the use of a herbaceous cover to limit tree invasion, emphasizing naturally forested ecosystems of northeastern America. They include reported evidence of stable plant communities and an overview of potential underlying mechanisms of inhibition. (2) We then review field applications, specifically testing the ability of seeded herbaceous covers to control tree invasion in ROWs. (3) We discuss unresolved issues relevant to management and research. The available evidence suggests that seeding herbaceous covers in ROWs can help control tree invasion, but many issues still limit broad-scale applications. The various interactions that govern plant community dynamics are far from being fully understood, so selecting species still largely depends on an empirical approach. Patterns of resistance to tree invasion must be investigated over a wide range of spatial, historical, and environmental contexts to determine effective management and seeding practices that will lead to broad-scale applications. We suggest establishing communities rather than single dominant species and using as much as possible native species to limit risks of invasion.Published online     

Establishment and Growth of Experimental Grass Species Mixtures on Coal Mine Sites Reclaimed with Municipal Biosolids

The Surface Mining Control and Reclamation Act of 1977 requires that coal mine sites in the United States be reclaimed to establish vegetative cover that is diverse, native, and capable of plant succession. However, there is a question as to whether vegetation established on coal mine sites reclaimed with biosolids is diverse and capable of plant succession. The influx of nutrients with the addition of biosolids leads to long-term dominance by early-successional species, most notably grasses, and consequently, a low establishment of woody and volunteer species. Additionally, many grass species commonly planted in reclamation have aggressive growth habits that lead to their dominance in coal mine plant communities. The establishment and growth of selected grass mixes was evaluated to determine whether alternative grass mixes would be less competitive with woody and volunteer species as compared to commonly used grass mixes. Percent vegetative cover, species richness, and the survival of direct-seeded woody species were assessed for each treatment grass mixture. It was found that Poa compressa and a mixture of P. compressa, Panicum virgatum, and Trifolium repens provided adequate coverage while still allowing the highest species richness and survival of woody species. Use of these species mixtures in coal mine reclamation with biosolids in the eastern United States would likely lead to establishment of a more species-rich plant community with a greater woody species component while still providing erosion control and site protection.     

Assessment of Cs and Sr accumulation in two epiphytic species of Tillandsia (Bromeliaceae) in vitro

Multiple nuclides commonly occur together and exert toxicity simultaneously, but the difference between single and combined effects of the nuclides is rarely investigated. Epiphytic Tillandsia species are efficient air pollution biomonitors, but rarely used to monitor nuclide contamination. Two Tillandsia species, that is, T. brachycaulos and T. stricta, were chosen to test their capacity to accumulate Cs and Sr. Most plants were able to endure Cs and Sr stress for a long period, which suggested these species could resist toxic elements physiologically and metabolically. With the increasing Cs or Sr concentrations, nuclide contents in both species increased significantly, indicating the potential of Tillandsia species in monitoring nuclide pollutants. However, when the plants were treated with combined nuclides, the content of each ion decreased distinctly compared to those treated with single ion, which suggested Cs and Sr influenced and inhibited each other. In addition, T. brachycaulos seemed more efficient in the uptake of Sr, while T. stricta was more efficient for Cs. Both species accumulated more Sr than Cs at low concentrations, while more Cs than Sr at high concentrations. These results indicated that the uptake of Cs and Sr was related to both the concentrations of the nuclides and the plant species exposed.     

Effects of ozone on inter- and intra-species competition and photosynthesis in mesocosms of Lolium perenne and Trifolium repens

Trifolium repens and Lolium perenne were exposed as both monocultures and two-species mixtures to an episodic rural ozone regime in large, well-watered containers within solardomes for 12 weeks. There were reductions in biomass for T. repens, but not L. perenne, and the proportion of T. repens decreased in ozone-exposed mixtures compared to the control. In addition, leaf biomass of T. repens was maintained at the expense of biomass partitioning to the stolons. The decreased growth corresponded with decreased photosynthetic capacity for T. repens, however, by the end of the exposure there was also decreased photosynthetic capacity of L. perenne, a species previously considered insensitive to ozone. The observed decreases in photosynthetic efficiency and capacity in elevated ozone indicate that the ability of such ubiquitous vegetation to act as a sink for atmospheric carbon may be reduced in future climates.     

Spermatophore characteristics in bushcrickets vary with parasitism and remating interval

Male bushcrickets provide females with a nuptial gift, a spermatophore, which is transferred to females at mating. The spermatophore consists of a gelatinous mass, the spermatophylax, and the sperm-containing ampulla. Male spermatophore size is positively correlated with insemination rate and female refractory period and therefore with male reproductive success. In this study, we examined spermatophylax weight, ampulla weight and sperm number in males of Poecilimon mariannae parasitized by the acoustically orienting fly Therobia leonidei. We show that in parasitized males, spermatophylax weight decreases with the level of parasitism. In line with the hypothesis that parasitism is a cost to reproduction, we found that spermatophylax weight was reduced at remating. In contrast, the replenishment of the spermatophylax in unparasitized males was complete after 2 days and was increased no further after 3 days. Both sperm number and ampulla weight showed an increase over time since last mating and sperm production was estimated at a constant rate of 500,000 per day in all individuals, regardless of parasitism. The allocation of investment in components of the spermatophore varies greatly with parasitism and remating. Both factors had rather independent effects on spermatophore constitution, revealing functional constraints acting on spermatophore characteristics in bushcrickets, which are important for understanding the selection pressures working on its components. Received: 13 September 1999 / Received in revised form: 4 February 2000 / Accepted: 13 March 2000     

氮磷对微囊藻和栅藻生长及竞争的影响

为了揭示不同营养条件下,藻类优势种的形成规律,选取了3种具有代表性水体的营养盐浓度,对于蓝藻水华的常见种铜绿微囊藻和绿藻水华的常见种四尾栅藻进行了竞争实验.通过竞争抑制参数对相互间的竞争关系进行了分析.结果表明,在贫营养水平下,栅藻的存在能够刺激微囊藻的生长,N/P值越小,刺激作用越明显,微囊藻也能刺激栅藻的生长;富营养水平下,竞争抑制作用与N/P有关;超富营养水平下,栅藻对微囊藻的抑制能力约为微囊藻对栅藻的抑制能力的3倍,N/P值的变化对竞争抑制作用的影响不明显.在较低氮磷浓度的水体中,微囊藻容易成为优势种,而在较高的氮磷浓度的水体中,四尾栅藻更容易成为优势种.     

安全成本与国际贸易竞争力关系的经济学分析

分析了职业安全卫生标准一体化和劳工标准对国际贸易产生的现实影响,运用经济学的基本理论对安全保护成本与国际贸易竞争力之间的关系进行深入探讨;推理得出国际贸易中小国的安全保护成本对其国际贸易竞争力影响较大,而大国的影响则较小,如果大国某一出口产品需求价格弹性小于1,其增加安全成本总收入反而增加的结论,因此,大国有增加安全投资的积极性。笔者提出发展中国家应从自身经济、政治利益实际出发,反对不切实际的提高劳工标准,并提出中国的出口企业应该适应目标市场绿色安全生产的发展趋势,实现本质安全型生产。     

旅游规划中的目的地竞合分析——以芜湖市为例

经过多年旅游开发实践的驱动，我国旅游规划工作有了长足发展，但目前仍存在旅游规划模式化，忽视规划区的“地方性”，缺乏规划区的区际与区内旅游空间竞争与合作关系研究等，使规划区功能、产品、市场等定位不准，策划的项目与周边区域雷同等问题突出。在旅游规划中加强目的地竞合分析是寻求目的地特色、准确定位、优化线路、创新产品体系等的前提和重要、有效的技术手段。阐述了旅游目的地竞合分析的内容和方法，并以芜湖市为例，对芜湖市的区内和区际旅游空间竞合进行分析，提出了芜湖市旅游功能定位、战略目标与空间布局。     

Competition of the active roots of Cassia siamea Lam. and Zea mays L.(cv.Katumani Composite B) in an alley cropping trial in semi arid Kenya

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