The ecoregion concept is a popular method of understanding the spatial distribution of the environment', however, it has yet
to be adequately demonstrated that the environment is distributed in accordance with these bounded units. In this paper, we
generated a testable hypothesis based on the current usage of ecoregions: the ecoregion classification will allow for discrimination
between lakes of different water quality. The ecoregion classification should also be more effective better than a comparably
scaled classification based on political boundaries, land-use class, or random grouping. To test this hypothesis we used the
Environmental Monitoring and Assessment Program (EMAP) lake water chemistry data from the northeast United States. The water
chemistry data were reduced to four components using principal component analysis. For comparison to an optimal grouping of
these data we used K-means cluster analysis to define the extent at which these lakes could be segregated into distinct classes.
Jackknifed discriminant analysis was used to determine the classification rate of ecoregions, the three alternative spatial
classification methods, and the clustering algorithm. The classification based on ecoregions was successful for 35% of the
lakes included in this study, in comparison to the clustered groups accuracy of 98%. These results suggest that the large
scale spatial distribution of ecosystem types is more complicated than that suggested by the present ecoregion boundaries.
Further tests of ecoregion delineations are needed and alternative large-scale management strategies should be investigated. 相似文献
The objective of this study was to examine postfire regeneration of tree, shrub, and dwarf shrub species, in relation to levels
of damage in four planted pine forests (Pinus pinea, Pinus pinaster) in Andalusia. A prefire vegetation map was used for detailing species composition, vertical structure, and density and another
for detailing the extent and intensity of fire damage. Between 3 and 7 years after the fires, an inventory was made of the
vegetation in each area, using the step-point method. The information thus obtained was used to determine the amount of cover
in the dwarf/shrub and tree layers, the frequency of species in each of the layers, floristic richness, and diversity (Shannon
index). The botanical composition of the dwarf and shrub layer was analyzed using TWINSPAN. Variables were poorly correlated
with level of fire damage, which suggests that the forests in this study followed the autosuccession model. Because of the
artificial origin or seminatural condition, regeneration of the dominant tree species is poor, and it seems unlikely that
forests will recover to their prefire state. Therefore action is recommended to restore these ecosystems. 相似文献
Managing the activities of commercial wildlife viewing tends to involve either restricting the number of industry participants
and/or regulating the activities or industry participants. We report on operator compliance with regulations regarding humans
swimming with free-ranging bottlenose dolphins (Tursiops sp.) in Port Phillip Bay, Victoria, Australia. A total of 128 commercial dolphin-swim trips was studied between September
1998 and April 2000. Four permit conditions were investigated: approach type, swim time, time in proximity of dolphins, and
presence of “fetal fold” calves. Results demonstrate noncompliance by operators to all of the four permit conditions studied.
Compliance with temporal conditions was poorer than with other conditions. When conducting studies on the extent to which
tourism affects cetaceans, investigators should consider whether tourist operations comply with existing regulations or guidelines. 相似文献
The impact of dense traffic on the breeding success in pied flycatchers (Ficedula hypoleuca) was studied using roadside nest-boxes. Nest site selection and breeding success of flycatchers were observed in relation
to the distance from the road. The number of occupied territories was no higher closer to the road than it was deeper inside
the forest. The distance to the road had no effect on the laying date, clutch size, or brood size. However, nests closer to
the road were more likely to fail at the chick stage. The number of broods that were closer to roads and were lost completely
was significantly higher than those further away. As a consequence, the number of fledglings per breeding attempt decreased
closer to roads. The nestlings typically died as older chicks when the parent birds were providing them with maximum quantities
of food. A possible reason for the declining reproductive success was the traffic-related mortality of parent birds, as weather
conditions were not especially adverse for raising healthy offspring. 相似文献
Objective: The objective of this study was to investigate whether the 5-point harness or the impact shield child restraint system (CRS) or both have the potential to cause chest injuries to children. This is determined by examining whether the loading to the chest reaches the internal organ injury threshold for children.
Method: The chest injury risk to a child occupant in a CRS was investigated using Q3 dummy tests, finite element (FE) simulations (Q3 dummy and human models), and animal tests. The investigation was done for 2 types of CRSs (i.e., the impact shield CRS and 5-point harness CRS) based on the UN R44 dynamic test specifications.
Results: The tests using a Q3 dummy indicated that although the chest deflection of the dummy in the impact shield CRS was large, it was less than the injury threshold (40 mm). Computational biomechanics simulations (using finite element FE analysis) showed that the Q3 dummy's chest is loaded by the shield and deforms substantially under this load. To clarify whether chest injuries due to chest compression can occur with an impact shield or with the 5-point harness CRS, 7 experiments were performed using Tibetan miniature pigs with weights ranging from 9.7 to 13 kg. Severe chest and abdominal injuries (lung contusion, coronary artery laceration, liver laceration) were found in the tests using the impact shield CRS. No chest injuries were present when using the 5-point harness CRS.
Conclusion: When using the impact shield CRS, the chest deformed substantially in dummy tests and FE simulations, and chest and abdominal injuries were observed in pig tests. It is possible that these chest injuries could also occur to child occupants sitting in the impact shield CRS. 相似文献