Short-Term Influence of Tank Tracks on Vegetation and Microphytic Crusts in Shrubsteppe Habitat

Artemisia tridentata Nutt.) habitat within the Idaho Army National Guard Orchard Training Area in southwestern Idaho. The purpose of this study was to determine the short-term (1–2 years) influence of tank tracks on vegetation and microphytic crusts in shrubsteppe habitat. The two types of tank tracks studied were divots (area where one track has been stopped or slowed to make a sharp turn) and straight-line tracks. Divots generally had a stronger influence on vegetation and microphytic crusts than did straight-line tracks. Tank tracks increased cover of bare ground, litter, and exotic annuals, and reduced cover of vegetation, perennial native grasses, sagebrush, and microphytic crusts. Increased bare ground and reduced cover of vegetation and microphytic crusts caused by tank tracks increase the potential for soil erosion and may reduce ecosystem productivity. Reduced sagebrush cover caused by tank tracks may reduce habitat quality for rodents. Tank tracks may also facilitate the invasion of exotic annuals into sagebrush habitat, increasing the potential for wildfire and subsequent habitat degradation. Thus, creation of divots and movement through sagebrush habitat by tanks should be minimized.     

Potential re-colonisation by cladocerans of an acidic tropical pond

To predict how re-colonisation of acidified lakes will proceed, at least two approaches are possible: (i) to compare the life history traits of candidate species and determine which one has the highest fitness, and (ii) to simulate a more realistic scenario carrying out experiments with the grouping of the candidate species, so that the intrinsic rate of natural increase of each species is integrated with its sensitivity to low pH and its ability to compete with the other candidate populations. The objective of the present study was to investigate the future re-colonisation of such acidified systems, taking as case-study a tropical pond (Lagoa das Dunas, Camaçari, BA, Brazil) and four species of cladocerans occurring in nearby water bodies (Ceriodaphniacornuta, Ceriodaphniasilvestrii, Latonopsisaustralis and Macrothrix elegans), by comparing the two above mentioned approaches. The second approach included two sets of in situ microcosms experiments, one simulating the re-colonisation by immigrating ephippia, thus using neonates of each species as colonisers, and another simulating the immigration of adults. Both these simulations followed nearly the same trends. The integration of the effects of a higher temperature, a different photoperiod and species competition determined differences in the species densities ranking between the two approaches: life history versus microcosms. The densities of C.cornuta in the microcosms matched the biphasic concentration/response hormetic model, in the simultaneous presence of two increasingly intense stressors (interspecific competition and acidity), with a low-dose stimulation and a high-dose inhibition. The present study provided, thus, a further support to the acceptance of hormesis in ecotoxicology, also at the population level in multispecies experiments.     

Fluctuating sexual dimorphism and differential hibernation by sex in a primate, the gray mouse lemur (Microcebus murinus)

The aim of this study was to investigate reproductive strategies and their consequences in gray mouse lemurs (Microcebus murinus), small solitary nocturnal primates endemic to Madagascar. Previous reports of sexual dimorphism in favor of males and females, respectively, a high potential for sperm competition and pheromonal suppression of mating activity among captive males, led us to investigate mechanisms of intrasexual competition in a wild population. Based on 3 years of mark-recapture data, we demonstrate that sexual dimorphism in this species fluctuated annually as a result of independent changes in male and female body mass. Male body mass increased significantly prior to the short annual mating season. Because their testes increased by 100% in the same period and because their canines are not larger than those of females, we suggest that large male size may be advantageous in searching for estrous females and in enabling them to sustain periods of short-term torpor. In contrast to reports from captive colonies, we found no evidence for two morphologically distinct classes of males. Finally, we also show that most adult males are active throughout the cool dry season that precedes the mating season, whereas most adult females hibernate for several months. This is in contrast to other solitary hibernating mammals, where males typically emerge 1–2 weeks before females. Thus, this first extended field study of M.␣murinus clarified previous conflicting reports on sexual dimorphism and male reproductive strategies in this primitive primate by showing that their apparent deviation from predictions of sexual selection theory is brought about by specific environmental conditions which result in sex-specific life history tactics not previously described for mammals. A general conclusion is that sexual selection can operate more strongly on males without resulting in sexual dimorphism because of independent selection on the same traits in females. Received: 6 July 1997 / Accepted after revision: 28 March 1998     

中国环评制度的发展历程及展望

环评制度作为中国知名度最高的环境管理手段之一,在环保工作中发挥了重要作用,但近年来也暴露出众多问题,广为社会关注。特别是十八大以来,关于环评改革的呼声日益高涨。本文系统回顾了环境影响评价制度在中国的发展历程,以环评重大事件为分水岭,首次将环评发展历程划分为成长期、发展期、壮大期和问题高发期。以此为基础,总结了当前环评制度的主要问题,并剖析了其深层次原因,包括制度设计失当、体系运行失效、公众意识觉醒等,最后针对这些问题为环评制度的优化与发展提出了建议。     

粘滞阻尼支撑框架结构弹塑性时程分析

对阻尼支撑框架结构的弹塑性时程分析方法进行了探讨,给出了阻尼支撑的力学计算模型;对地震动的选用进行了分析,给出了地震动选取的初步建议。建立了两个三层的单榀粘滞阻尼支撑框架结构,利用IDARC 2D非线性分析软件进行了弹塑性时程分析,对框架弹塑性阶段的地震响应、塑性铰分布及结构损伤进行了对比研究,提出了阻尼支撑框架结构的设计要点,为实际工程提供设计依据。     

Trade-offs between time, predation risk and life history, and their implications for biogeography: A systems modelling approach with a primate case study

Group sizes are often considered to be the result of a trade-off between predation risk and the costs of feeding competition. We develop a model to explore the interaction between different ecological constraints on group sizes, using a primate (baboons) case study. The model uses climatic correlates of time budgets to predict maximum ecologically tolerable group size, and climatic predictors of predation risk (reflected mainly in predator density and female body mass) to predict minimum tolerable group size for any given habitat. As well as defining the range of sustainable group sizes for a given habitat, the model also allows us to reliably predict our exemplar taxon's biogeographical distribution across Africa. We also explore the life history implications of the model to ask whether baboons form group sizes which maximise survival or fecundity in the classic trade off between these two key life history variables. Our results indicate that, within the range of study sites in our sample, baboons prefer to maximise fecundity. However, the data indicate that in higher predation risk habitats they would switch to maximising survival at the expense of fecundity. We argue that this is due to the fact that interbirth interval and developmental rates have a ceiling that cannot be breached. Thus, while females can shorten interbirth intervals to compensate for increased predation risk, there is a limit to how much these life history variables can be altered, and when this is reached the best strategy is to maximise survivorship.     

Entangling the Complexity of Protected Area Management: The Case of Wolong Biosphere Reserve,Southwestern China

Protected Area (PA) management is a complex issue that requires the consideration of many factors and relationships. A conceptual framework for the analysis of biodiversity change, local human communities, and PA management was put forward, accordingly. Under the framework, we investigated the economic status, livelihood activities, biodiversity use and perceptions of local communities, and the land use history in Wolong Biosphere Reserve, southwestern China through household survey and document review in order to gain a better understanding of the complexity of PA management. According to the land use history, the preservation of agro-biodiversity, and the raising of productivity, ecological rehabilitation and the regulation of the human pressures are indispensable in the management of the reserve. Livelihood activities and the perceptions of local communities were largely determined by the socioeconomic background, which has important implications in solving the conflicts or incompatibilities in the reserve. In Wolong Biosphere Reserve, it is beneficial to support local farmers in solving their socioeconomic problems such as the overabundance of labor force and the lack of livelihood alternatives. Without this, there will be scarcely any effective biodiversity conservation and successful reserve management in the long term.     

DECLINING INTENSITY OF ACID MINE DRAINAGE IN THE NORTHERN APPALACHIAN BITUMINOUS COAL FIELDS: MAJOR ALLEGHENY RIVER TRIBUTARIES1

ABSTRACT: For more than 30 years, a program of continuous monitoring of pH, acidity, alkalinity, and other parameters has been maintained on a network of large streams degraded by acid mine drainage in the northern Appalachian high sulfur coal region. Continuous records since 1952 are available at a number of stations, and at several stations, acidity records date back to 1930. Comparable analysis techniques were maintained over the period of record, assuring the long term continuity of the database. This monitoring program has captured integrated long term trends within large and complex watersheds with numerous and varied types of mine discharges. The focus of this paper is a historical trend analysis of lightly to severely acid degraded major tributaries of the Allegheny River. Over the past three decades, all of the Allegheny River drainage basin stations have demonstrated steady and substantial declines in acidity and associated increases in pH and alkalinity. The average recorded decline in total acidity at four stations monitored since the 1950s was 94 percent. Since the 1970s, acidity declined by an average of 63 percent at 10 stations. Oxidative exhaustion of pyritic minerals exposed by mining is proposed as a major factor influencing these trends.     

Deconstructing a gender difference: driving cessation and personal driving history of older women

PROBLEM: The purpose of this study is to understand the reasons behind older women's driving cessation by comparing the driving histories of Finnish women who either gave up or renewed their drivers license at the age of 70. METHOD: A mail survey was sent to all Finnish women born in 1927 who gave up their license in 1997 (N=1,476) and to a corresponding random sample of women who renewed their license (N=1,494). The total response rate was 42.1%. RESULTS: The length and level of activity of personal driving history were strongly associated with driving cessation and continuation. Ex-drivers tended to have an inactive driving career behind them, whereas drivers had a more active personal driving history. In addition, those women with an active, "male-like" driving history who had decided to stop driving gave reasons for driving cessation that were similar to what is known about older men's reasons to give up driving. The results suggest that the decision to stop driving is related to driving habits rather than gender.     

Monitoring the Environment: Taking a Historical Perspective

This paper introduces the five papers that follow, all of which were originally presented at a workshop titled Monitoring the Environment: Scales, Methods, and Systems in Historical Perspective. The workshop, sponsored by the Society for the History of Technology and the American Society for Environmental History, examined past efforts to develop tools, methods, and systems for measuring or monitoring some aspect of the physical environment. Four of the papers included here focus on various aspects of air quality monitoring; the fifth has to do with monitoring the earth from space. Despite differences in time period and approach, each article examines how specific tools and methods – and the motivations for developing those tools and methods – evolved. Among other things, these papers make clear that systems for monitoring various aspects of the physical environment are shaped by a variety of stakeholders and suggest that efforts to construct such systems should not be viewed as a purely technical task.