The influence of use,environmental and managerial factors on the width of recreational trails

This paper evaluates the relative influences of use, managerial and environmental factors on trail width, from a survey of all formal trails in Acadia National Park, Maine, USA. A Trimble GPS was used to navigate to and collect data at sample points spaced at a 152.4 m (500 ft) interval across all National Park Service trails on Mount Desert Island. Regression analyses focus on increasing understanding of factors that influence the width of formal hiking trails. ANOVA analyses demonstrate differences in trail width based on trail surface type (class), and the presence or absence of trail borders. A novel approach of comparing intended widths to actual widths enabled us to look specifically at the avoidable and undesirable impacts associated with having a trail that is wider than intended.     

Development of a combined isotopic and mass-balance approach to determine dissolved organic carbon sources in eutrophic reservoirs

A combined mass-balance and stable isotope approach was set up to identify and quantify dissolved organic carbon (DOC) sources in a DOC-rich (9 mg L⁻¹) eutrophic reservoir located in Western France and used for drinking water supply (so-called Rophemel reservoir). The mass-balance approach consisted in measuring the flux of allochthonous DOC on a daily basis, and in comparing it with the effective (measured) DOC concentration of the reservoir. The isotopic approach consisted, for its part, in measuring the carbon isotope ratios (δ¹³C values) of both allochthonous and autochthonous DOC sources, and comparing these values with the δ¹³C values of the reservoir DOC. Results from both approaches were consistent pointing out for a DOC of 100% allochthonous origin. In particular, the δ¹³C values of the DOC recovered in the reservoir (−28.5 ± 0.2‰; n = 22) during the algal bloom season (May-September) showed no trace of an autochthonous contribution (δ¹³C in algae = −30.1 ± 0.3‰; n = 2) being indistinguishable from the δ¹³C values of allochthonous DOC from inflowing rivers (−28.6 ± 0.1‰; n = 8). These results demonstrate that eutrophication is not responsible for the high DOC concentrations observed in the Rophemel reservoir and that limiting eutrophication of this reservoir will not reduce the potential formation of disinfection by-products during water treatment. The methodology developed in this study based on a complementary isotopic and mass-balance approach provides a powerful tool, suitable to identify and quantify DOC sources in eutrophic, DOC-contaminated reservoirs.     

Appreciating the biodiversity of remnant bushland: an ‘architectural’ approach

Tutor in the Department of Geography at the University of Western Australia. In response to the fragmentation and loss of indigenous vegetation caused by the expansion of metropolitan Perth, all levels of government in Western Australia have made some commitment to the preservation of biodiversity. A case for seeing and using vegetation structure as a possible surrogate for biodiversity is presented. The concept and a simple methodology which may be applied without any specialist ecological knowledge or expertise is outlined for the urban developer, engineer, planner, decision maker and educator. The notion that the degree of diversity of the vegetation structure of a banksia woodland remnant may indicate and give a substitute or preliminary measure of biodiversity assists the popular understanding of biodiversity. Such a non-technical yet objective appreciation and measure may prove satisfactory for some conservation purposes, until a detailed professional assessment is made of the plant and animal species in a remnant of native vegetation. It is currently being used by state planning staff in Western Australia for the preliminary assessment of native woodland in areas zoned for urban growth at the metropolitan fringe.     

Effects of smelter sulfur dioxide emissions: a spatiotemporal perspective using carbon isotopes in tree rings

We wanted to test the hypothesis that forest exposure to phytotoxic gases indirectly affects their carbon uptake. We estimated that the reduction of photosynthesis may have reached 20 to 30% at a site located 9 km (test site) from the Horne copper smelter in Rouyn-Noranda, which is a point source of SO2. Twenty-one spruce trees older than 100 yr were selected from seven sites at various distances from the smelter to evaluate conditions prior to and during the periods of smelter operation. The carbon isotope results obtained from spruce tree rings at our test site reveal an unprecedented and abrupt shift of +4/1000 after the onset of smelter operations. This large and permanent shift exceeds natural variations in regional pre-smelter series or in the series at a remote control site. All trees up to 116 km downwind from the smelter show delta13C positive shifts following the onset of operations. There is also a clear inverse relationship between the amplitude of the first-order trends and distance from the smelter. Those delta13C trends indicate that trees exposed to high levels of SO2 decrease their level of CO2 uptake through activation of stomatal closure. This is strongly supported by the significant departure of the Rouyn-Noranda trends from those measured for trees from non-industrialized areas of the Northern Hemisphere, or calculated using global atmospheric conditions. Considering the large number of SO2 point sources in North America, our results imply that CO2 uptake by the boreal forest in the vicinity of these sources may be lower than previously thought.     

Applicability of the Transient Storage Model to the hyporheic exchange of metals

Stream-subsurface exchange results from a complex ensemble of transport mechanisms that require different modeling approaches. Field and laboratory experiments show that advective exchange through the underlying sediments is an important mechanism of solutes transport and storage in riverine systems. Here, Transient Storage Model parameters are obtained for reactive solute exchange driven by bedform-induced advection. Consideration of exchange induced by this single mechanism allows specific relationships between model parameters and system properties like solute reactivity to be identified. This work shows that when a simplified model like the Transient Storage Model is applied to analyze metal storage in river sediments, particular attention must be devoted to the choice of modeling parameters.     

Experimental and natural changes in the peacock's (Pavo cristatus) train can affect mating success

Petrie et al. (1991) demonstrated a correlation between the degree of elaboration of peacocks' trains and their mating success, and also showed that this correlation occurred because females preferred to mate with the male that had the most elaborate train of those sampled on the lek. Although these data suggest that female choice is responsible for non-random mating in this species, they do not conclusively show that train morphology is the cue that females respond to, because they do not rule out the possible influence of another unidentified variable which is correlated with train elaboration. This paper presents an experimental test of the importance of the peacock's train in determining male mating success. If the number or arrangement of eye-spots in the peacock's train influences mating success, then changing the number of eye-spots should change mating success. This prediction was tested in an experiment where the trains of male peafowl (Pavo cristatus) were manipulated by removing a number of eye-spots between mating seasons. Peacocks with eye-spots removed showed a significant decline in mating success between seasons compared with a control group. This result, together with the observational data, supports the hypothesis that the peacock's train has evolved, at least in part, as a result of female choice.     

METRO集团对可持续发展负责:良好的实践范例

METRO集团,世界领军零售公司之一,已经在26个国家落户.集团的贸易战略目标设定在向一个可持续性的、赢利的公司发展.在它的第一份可持续性报告(发表于2002年春季)里,集团的许多可持续性发展的相关活动非常醒目.智能物流系统和广泛的废物管理行动扎根于集团的环境实力之中.强调食品安全的世界采购方针和措施,是满足消费者要求产品符合社会和环境标准的两种手段.只要消费者能获得全面的信息,只要员工的积极性被调动起来并经过适当的培训,那么METRO集团在其可持续性报告中所列出的所有的可持续性目标最终就一定能实现.