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991.
Choosing Indicators of Natural Resource Condition: A Case Study in Arches National Park, Utah, USA 总被引:2,自引:0,他引:2
Jayne Belnap 《Environmental management》1998,22(4):635-642
/ Heavy visitor use in many areas of the world have necessitated development of ways to assess visitation impacts. Arches National Park recently completed a Visitor Experience and Resource Protection (VERP) plan. Integral to this plan was developing a method to identify biological indicators that would both measure visitor impacts and response to management actions. The process used in Arches for indicator selection is outlined here as a model applicableto many areas facing similar challenges. The steps were: (1) Vegetation types most used by visitors were identified. Impacted and unimpacted areas in these types were sampled, comparing vegetation and soil factors. (2) Variables found to differ significantly between compared sites were used as potential indicators. (3) Site-specific criteria for indicators were developed, and potential indicators evaluated using these criteria. (4) Chosen indicators were further researched for ecological relevancy. (5) Final indicators were chosen, field tested, and monitoring sites designated. In Arches, indicators were chosen for monitoring annually (soil crust index, soil compaction, number of used social trails and soil aggregate stability) and every five years (vegetation cover and frequency; ground cover; soil chemistry; and plant tissue chemistry).KEY WORDS: Biological indicators; Recreation impacts; Recreation management; Desert soils; Trampling 相似文献
992.
Steven G. Paulsen Robert M. Hughes David P. Larsen 《Journal of the American Water Resources Association》1998,34(5):995-1005
ABSTRACT: Despite spending $115 billion per year on environmental actions in the United States, we have only a limited ability to describe the effectiveness of these expenditures. Moreover, after decades of such investments, we cannot accurately describe status and trends in the nation's aquatic ecosystems or even those in specific regions. Why? This situation has arisen in part because we have excluded the fundamental principles of probability designs that are widely used in other fields and we have often ignored direct measures of biota, the subjects of greatest concern. To demonstrate the results of ignoring these powerful statistical and biological tools, we present four case studies. These studies compare estimates of aquatic resource status derived from using (1) a probability-based study design, often with biological measures of condition; and (2) a nonstatistical study design, often using chemical surrogates. In three of the four cases, the results derived from the nonstatistical perspective underestimate the degree of biological degradation. 相似文献
993.
对传统财务业绩评价体系及其所提供的会汁信息质量进行了分析,认为财务分析应以现金流量力核心,通过现金流量指标分析企业的获利能力和支付能力更具可行性.笔者认为,以现金流量为核心,将现金流量分析指标溶于其他财务分析中,能够对企业当前存在的报表粉饰,利润操纵等现象进行充分的揭示,有助于重新构建出一套更为科学、合理的财务分析评价体系。 相似文献
994.
Of the three species of hirundine that breed sympatrically across the U.K., one, the barn swallow, has outer tail feathers
elongated into streamers, whereas the other two species, the house martin and the sand martin, do not. The tail streamer of
the barn swallow is regarded as a classic example of a sexually selected trait. Recent evidence, however, has suggested that
streamers may have evolved largely through natural selection for enhanced flight performance and increased maneuverability.
We tested the hypotheses that small streamers (1) increase performance in turning flight, but (2) decrease performance in
flight variables related to velocity. We manipulated the lengths of house martin outer tail feathers and measured changes
in their free-flight performance, using stereo-video to reconstruct the birds" three-dimensional flight paths. Five flight
variables were found to best describe individual variation in flight performance. Of these five, the three variables determining
maneuverability predicted that flight performance would be optimized by a 6- to 10-mm increase in the length of the outer
tail feathers. In contrast, for mean velocity and mean acceleration, extension of the outer tail feathers appears to have
a detrimental effect on flight performance. We suggest that the initial selection pressure for streamers in ancestral short-tailed
"barn swallows" was via natural selection for increased maneuverability. In addition, we propose that the benefits of increased
maneuverability have differed between hirundines in the past, such that the cost of increasing the length of the outer tail
feather has, to date, outweighed the benefits of doing so in streamerless hirundines.
Received: 14 February 2000 / Revised: 2 July 2000 / Accepted 18 July 2000 相似文献
995.
Improvement in collective performance with experience in ants 总被引:3,自引:4,他引:3
Elizabeth?A.?Langridge Nigel?R.?FranksEmail author Ana?B.?Sendova-Franks 《Behavioral ecology and sociobiology》2004,56(6):523-529
We show that entire ant colonies can improve their collective performance progressively when they repeat the same process. Colonies of Leptothorax albipennis can reduce their total emigration times over successive emigrations. We show that this improvement is based on experience and some memory-like process, rather than a coincidental developmental change or an increased general level of arousal. We demonstrate that the benefits of experience can be lost (i.e. forgotten) if the interval between successive emigrations is too long. We also show that the benefits of experience are more likely to be retained over a longer period if the collective performance has been repeated several times. This is a new demonstration of a process akin to learning in ants and we briefly discuss how it may involve not only improvements in individual performance but also improvements in the ways in which the ants interact with one another.Communicated by L. Sundström 相似文献
996.
The importance of spatial autocorrelation,extent and resolution in predicting forest bird occurrence 总被引:3,自引:0,他引:3
Concerns about declines in forest biodiversity underscore the need for accurate estimates of the distribution and abundance of organisms at large scales and at resolutions that are fine enough to be appropriate for management. This paper addresses three major objectives: (i) to determine whether the resolution of typical air photo-derived forest inventory is sufficient for the accurate prediction of site occupancy by forest birds. We compared prediction success of habitat models using air photo variables to models with variables derived from finer resolution, ground-sampled vegetation plots. (ii) To test whether incorporating spatial autocorrelation into habitat models via autologistic regression increases prediction success. (iii) To determine whether landscape structure is an important factor in predicting bird distribution in forest-dominated landscapes. Models were tested locally (Greater Fundy Ecosystem [GFE]) using cross-validation, and regionally using an independent data set from an area located ca. 250 km to the northwest (Riley Brook [RB]). We found significant positive spatial autocorrelation in the residuals of at least one habitat model for 76% (16/21) of species examined. In these cases, the logistic regression assumption of spatially independent errors was violated. Logistic models that ignored spatial autocorrelation tended to overestimate habitat effects. Though overall prediction success was higher for autologistic models than logistic models in the GFE, the difference was only significantly improved for one species. Further, the inclusion of spatial covariates did little to improve model performance in the geographically discrete study area. For 62% (13/21) of species examined, landscape variables were significant predictors of forest bird occurrence even after statistically controlling for stand-level variability. However, broad spatial extents explained less variation than local factors. In the GFE, 76% (16/21) of air photo and 81% (17/21) of ground plot models were accurate enough to be of practical utility (AUC > 0.7). When applied to RB, both model types performed effectively for 55% (11/20) of the species examined. We did not detect an overall difference in prediction success between air photo and ground plot models in either study area. We conclude that air photo data are as effective as fine resolution vegetation data for predicting site occupancy for the majority of species in this study. These models will be of use to forest managers who are interested in mapping species distributions under various timber harvest scenarios, and to protected areas planners attempting to optimize reserve function. 相似文献
997.
Spider webs as environmental indicators 总被引:1,自引:0,他引:1
Analysis of spider webs from limestone arches in New South Wales, Australia showed levels of lead and zinc to be several times higher at Jenolan Caves than reference sites at Abercrombie and Wombeyan Caves. The high concentrations at Jenolan were attributed to emissions from motor vehicles that travel through the arch. Analysis of water-soluble ions in webs from Jenolan and Abercrombie Caves showed large differences between the sites, which could be explained by differences in the geology and biology of the cave environments. Spider webs proved useful indicators of environmental chemistry and undoubtedly have applications beyond the cave environments studied here. 相似文献
998.
高效液相色谱法分析水中痕量多环芳烃 总被引:14,自引:3,他引:14
本文利用高效液相色谱法测定水中痕量多环芳烃(PAHs)。以二氯甲烷作溶剂,超声提取水中痕量PAHs;甲醇、水作流动相,梯度淋洗,用程序可变波长荧光检测器测定。PHAs浓度为0.007=0.6μg·ml^-1范围时,线性相关系数均在0.9999以上;峰高、峰面积的相对标准偏差(n=10)分别为1.01-1.85%,2.00-3.94%;检测限(S/N=2)为3.1-23.0pg;实际水样的加标回收率 相似文献
999.
1000.
Background Different types of indicators have been developed to describe the impact of chemicals on society and environment. Due to
the high number of substances and their different types of use, most of these indicators are directed to specific areas of
interest – regarding workplace safety, environmental health or consumer health. They address a specific subset of chemicals
and can be used for monitoring enterprise-specific, national or international management measures.
Main Features A survey of existing indicators for chemicals has shown that indicators already exist for a remarkable number of problem
fields. As soon as the release and the environmental fate of chemicals are taken into account, the complexity of the approaches
increases considerably. The distinction between indicators for drivers, pressures, state, impacts and responses, as proposed
by the European Environmental Agency, supports the identification of proper indicators for a specific type of problem.
Discussion and Conclusions. No single indicator exists which is able to cover the whole range of chemicals and their applications. Several
indicator approaches cover at least a subset of the most relevant substances. If they are intended to be used for European
monitoring, robust data must be provided by EU Member States.
Chemicals in enterprises (ancillary inputs as well as process chemicals) are an important element of in-plant material flow
management – in terms of occupational safety and health as well as environmental protection. Existing indicators for hazardous
chemicals can be a valuable tool for process and product refinement regarding hazardous chemicals, especially for enterprises.
Outlook Indicators for production and impact of chemicals, as well as policy performance indicators, are essential elements in order
to monitor the management of chemicals. They have to be established for the national and for the EU level. 相似文献