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211.
James O. Luken Steven W. Beiting Scott K. Kareth Robyn L. Kumler Jun H. Liu Craig A. Seither 《Environmental management》1994,18(2):251-255
We tested two cutting regimens (cut/spray and cut/delay spray) and four radiarc-applied herbicides (Garlon + Tordon, Accord,
Accord + Escort, and Krenite) in an Ohio power-line corridor to determine which management combination best eliminated target
species (i.e., trees) and preserved nontarget species (i.e., low shrubs, vines, perennial herbs, and grasses).
When spraying was delayed after cutting, the herbicide with the least impact on nontarget species (Krenite) also was least
efficient at killing target trees. Spraying soon after cutting improved tree-killing efficiency of several herbicides, but
it also increased the negative impact on nontarget species. The herbicide with the most consistent tree-killing ability (Accord
+ Escort) had the most impact on nontarget species.
Because none of the herbicide/cutting treatments performed ideally, resource managers must decide the acceptable impact on
nontarget species when considering herbicide use. Future success of herbicides as part of an integrated succession management
approach requires more selective application methods and formulations so that target effects can be maximized and nontarget
effects can be minimized. 相似文献
212.
Craig P. Diamond 《环境质量管理》1995,5(2):9-23
Many anticipate that over the next decade, voluntary environmental management system (EMS) standards will take on the same importance in the marketplace as the ISO 9000 quality standards; the draft international EMS standard (ISO 14001) is on pace to be completed by mid-1996. In the United States, despite rapidly growing interest in EMS standards, most companies and regulatory agencies are uncertain about their potential benefits and about the process of developing an EMS. Case studies of EMS implementation, particularly in small and medium-sized companies, are needed to demonstrate the process and identify areas in which further EMS guidance is needed for environmental managers. This article presents seven case studies of EMS implementation in small, medium-sized, and large companies. Each company is participating in an EPA-sponsored Demonstration Project in which a variety of organizations are piloting the implementation of EMS standards (the project is being coordinated by NSF International, a not-for-profit company specializing in environmental and public health standards and certification). The case studies, written by the companies themselves, share experiences of EMS assessment, planning, and implementation, and discuss challenges that are special to particular industries. 相似文献
213.
Mitchell R. Peters Steven R. Abt Chester C. Watson Craig Fischenich John M. Nestler 《Journal of the American Water Resources Association》1995,31(4):745-752
ABSTRACT: The Riverine Community Habitat Assessment and Restoration Concept (RCHARC) was developed to integrate habitat enhancement into the stream restoration process. RCHARC assumes that aquatic habitat quality is closely related to hydraulic diversity based upon a “comparison standard” reach approach to stream restoration. A Beta test was performed by applying the RCHARC process to Rapid Creek in Rapid City, South Dakota. Standard and restored stream reaches were selected and data were collected. A comparison of field data and velocity-depth distributions indicated that the restored stream closely replicated the standard reach. The RCHARC methodology has the potential to assess habitat quality for planned comparison reaches and indicate the level of success resulting from restoration. 相似文献
214.
215.
Aspects of transboundary, water shortage, and fisheries issues are discussed in the context of the recently completed Global International Waters Assessment (GIWA) for the Pacific Islands. The region encompasses some 30 million km2 and approximately 12% of the world's ocean space, and features great geographic, demographic and developmental diversity. Global change, especially sea level rise and sea surface temperature increases, is the dominant transboundary concern as it impacts all aspects of life. Water shortage and unsustainable fishing issues are selected for discussion, as they will dominate the region into the foreseeable future, and they are illustrated with examples from Fiji, Kiribati, and Tonga. The environmental impacts are exacerbated by socioeconomic issues such as high population growth rates, urban drift, the breakdown of traditional life styles and the rapid adoption of the cash economy. Policy options that may assist in addressing these issues are proposed. 相似文献
216.
217.
Strongly interacting species often have pronounced direct and indirect effects on other species. Here we focus of the effects of pine squirrels (Tamiasciurus spp.), which are a dominant pre-dispersal seed predator of many conifers including limber pines (Pinus flexilis) and whitebark pines (P. albicaulis). Pine squirrels depress seed abundance by harvesting most limber and whitebark pine cones on their territories. Pine squirrels further reduce seed availability for Clark's Nutcrackers (Nucifraga columbiana), the primary seed disperser of these pines, because selection exerted by pine squirrels has reduced the number of seeds per cone and causes seeds to be less accessible. We predicted that, if fewer seeds were available for dispersal by nutcrackers, pine recruitment should be suppressed in areas with pine squirrels. In support of this prediction, stand densities were about two times greater in areas where pine squirrels are absent than in areas where they are present. Alternative explanations that we considered do not account for these differences; however, precipitation may limit stand densities in the absence of seed limitation by pine squirrels. In sum, pine squirrels apparently depress limber and whitebark pine stand densities, with the potential for ecosystem impacts because these pines are foundation species within Western subalpine ecosystems. 相似文献
218.
Heterogeneity in site quality can play an important role in patterns of abundance and population dynamics. Yet, estimating site quality in natural systems can be problematic because site quality can (1) vary through ontogeny for a focal organism, leading to shifts in site quality with age, (2) be confounded with (or masked by) variation in traits of individuals populating the sites, and (3) be correlated with local density. For example, if high-quality sites attract more individuals but vital rates are density dependent, then observed vital rates will be relatively homogeneous in space despite strong heterogeneity in site quality. Here, we operationally define site quality for a reef fish as the mean survival time of juveniles transplanted to sites at a common density and size structure, with random assignment of individuals to sites to remove potential confounding effects of local variation in individual quality and density. Our assays using juvenile age classes of the six-bar wrasse (Thalassoma hardwicke) showed that site quality varied in space (i.e., among patch reefs) but was constant through time. Site quality increased with availability of the branching coral Pocillopora (which is used as a refuge), but decreased with density of a predator, the arc-eye hawkfish, Paracirrhites arcatus (which also uses Pocillopora). We experimentally added colonies of Pocillopora to reefs and (1) increased site quality, (2) enhanced natural settlement rates of six-bar wrasse, but (3) attracted more hawkfish predators, and (4) did not increase survival of juvenile fish under ambient densities. Our results suggest that Pocillopora increases site quality, but attracts greater densities of settlers and predators, resulting in increased density dependence and predation, which mask the underlying effects of Pocillopora on site quality (supporting the hypothesis of "cryptic density dependence"). Variation in site quality and the possible confounding effects of density and individual traits warrant more experimental study. 相似文献
219.
Jackie D. Metheny Matina C. Kalcounis-Rueppell Craig K. R. Willis Kristen A. Kolar R. Mark Brigham 《Behavioral ecology and sociobiology》2008,62(7):1043-1051
Kin-based patterns of associations are often observed in group living mammals. Colonies of forest-living big brown bats (Eptesicus fuscus) exhibit fission–fusion roosting behavior and female philopatry. Within a roosting area of forest, adult females are distributed
into several subgroups roosting in different trees during the day. At night, adult females leave the roost subgroups to forage
and, upon return to the roosting area at dawn, both the individual composition and location of subgroups often change. Individuals
exhibit nonrandom roosting associations, and we hypothesized that genetic relationships would influence roosting associations.
We determined (1) whether the strength of roosting associations between pairs of bats (based on radiotelemetry) was correlated
with relatedness, (2) whether individuals that roosted together in roost subgroups were more related than by chance, and (3)
from roost subgroups, the pairs of bats that roosted nonrandomly and whether the proportion of related pairs was higher than
expected at random. Relatedness measures were based on microsatellite genotyping and mitochondrial DNA sequences. We found
from all analyses that roosting associations were not influenced by relatedness or matrilineal relationships. These results
provide clear evidence that, contrary to other mammals, kinship does not mediate roosting associations within forest living
big brown bats that exhibit fission–fusion roosting behavior. 相似文献
220.
The debate about the value of the allometric scaling exponent (b) relating metabolic rate to body mass (metabolic rate = a x mass(b)) is ongoing, with published evidence both for and against a 3/4-power scaling law continuing to accumulate. However, this debate often revolves around a dichotomous distinction between the 3/4-power exponent predicted by recent models of nutrient distribution networks and a 2/3 exponent predicted by Euclidean surface-area-to-volume considerations. Such an approach does not allow for the possibility that there is no single "true" exponent. In the present study, we conduct a meta-analysis of 127 interspecific allometric exponents to determine whether there is a universal metabolic allometry or if there are systematic differences between taxa or between metabolic states. This analysis shows that the effect size of mass on metabolic rate is significantly heterogeneous and that, on average, the effect of mass on metabolic rate is stronger for endotherms than for ectotherms. Significant differences between scaling exponents were also identified between ectotherms and endotherms, as well as between metabolic states (e.g., rest, field, and exercise), a result that applies to b values estimated by ordinary least squares, reduced major axis, and phylogenetically correct regression models. The lack of support for a single exponent model suggests that there is no universal metabolic allometry and represents a significant challenge to any model that predicts only a single value of b. 相似文献