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901.
推导了用滤膜法测定环境空气中放射性(气土)子体(ThB、ThC)浓度的计算公式及其潜能公式,为放射性环境空气质量监测提供了一种方便简捷的方法。 相似文献
902.
903.
指出了生物技术作为当前的6大高新技术之一,具有许多优点,也存在不少缺点,环境生物技术是解决现存环境问题中的具体应用,本质上仍是一种末端治理技术。而由生态学与生物技术交叉而产生的生态生物过程工程则符合整体,协调,再生,循环的原理,其目的是研究开发出清洁生产技术,可使生产持续发展,已被当作21世纪的新科学与范例。 相似文献
904.
905.
The US Department of Defense (DOD) manages over 10.1 million ha of land, much of which is used for training military personnel.
However, vast sections receive little or no use, and military lands have become refuges for many species. At Fort McCoy, Wisconsin,
USA, populations of the endangered Karner blue butterfly (Lycaeides melissa samuelis) are found in oak and pine barren communities where wild lupine (Lupinus perennis), a perennial forb required by Karner blue butterfly larvae, still occurs. Oak and pine barren communities are disturbance-dependent,
and the barrens ecosystems in the Midwest have declined in extent by 98% because of fire suppression, succession, and habitat
fragmentation. We studied the effects of disturbance by military manuever training on the density of lupine and Karner blue
butterfly at Fort McCoy. We also wanted to determine whether military training activity could enhance Karner blue butterfly
habitat.
At locations where tracked vehicles had driven through lupine patches, the abundance of lupine and nectar-producing plants
was greater in the median strip between vehicle ruts than in vehicle ruts or 5 m outside the vehicle ruts. The proportion
of lupine stems with Karner blue butterfly larvae feeding sign (the ratio of stems fed upon to stems examined) was greater
in areas where military vehicles had traveled than where they had not. The proportion of lupine stems with feeding sign and
lupine stem density was also positively related to the occurrence of prior bivouacs and fires caused by military munitions.
Shrub and forest canopy abundance were lower in areas traveled by tracked vehicles. At the scale of the lupine patch, lupine
abundance and the proportion of lupine stems with feeding sign were positively correlated with military training activities,
suggesting that maintenance of lupine habitat can be achieved in concert with military training. 相似文献
906.
Lance R. Williams Christopher M. Taylor Melvin L. Warren Jr. J. Alan Clingenpeel 《Environmental management》2002,29(1):76-87
Using Basin Area Stream Survey (BASS) data from the United States Forest Service, we evaluated how timber harvesting influenced
patterns of variation in physical stream features and regional fish and macroinvertebrate assemblages. Data were collected
for three years (1990–1992) from six hydrologically variable streams in the Ouachita Mountains, Arkansas, USA that were paired
by management regime within three drainage basins. Specifically, we used multivariate techniques to partition variability
in assemblage structure (taxonomic and trophic) that could be explained by timber harvesting, drainage basin differences,
year-to-year variability, and their shared variance components. Most of the variation in fish assemblages was explained by
drainage basin differences, and both basin and year-of-sampling influenced macroinvertebrate assemblages. All three factors
modeled, including interactions between drainage basins and timber harvesting, influenced variability in physical stream features.
Interactions between timber harvesting and drainage basins indicated that differences in physical stream features were important
in determining the effects of logging within a basin. The lack of a logging effect on the biota contradicts predictions for
these small, hydrologically variable streams. We believe this pattern is related to the large scale of this study and the
high levels of natural variability in the streams. Alternatively, there may be time-specific effects we were unable to detect
with our sampling design and analyses. 相似文献
907.
A Multiscale Conceptual Framework for Integrated Ecogeomorphological Research to Support Stream Naturalization in the Agricultural Midwest 总被引:1,自引:0,他引:1
The complexity of fluvial systems necessitates interdisciplinary research in fluvial geomorphology and aquatic ecology to
develop a fundamental understanding of interconnections among biotic and abiotic aspects of these systems. Integrated knowledge
of this type is vital for environmental management of streams in human-dominated environments. A conceptual framework is presented
for integrating geomorphological and ecological research on streams in East Central Illinois, USA, a glaciated low-relief
agricultural landscape. The framework embodies a multiscale perspective in which a geomorphological conception of the fluvial
system is used to define a hierarchy of characteristic spatial scales for exploring important linkages between stream geomorphology
and aquatic ecology. The focus ecologically is on fish, because a rich body of historical information exists on fisheries
in East Central Illinois and because past work has suggested that availability of physical habitat is a major factor influencing
the community characteristics of fish in this human-altered environment. The hierarchy embodied in the framework includes
the network, link, planform, bar unit, bar element, and bedform/grain scales. Background knowledge from past research is drawn
upon to identify potential linkages between geomorphological and ecological conditions at each of these scales.
The conceptual framework is useful for guiding integrated ecogeomorphological research at specific scales and across different
scales. It also is helpful for illustrating how widespread human modification of streams has catastrophically altered the
scalar structure of fluvial systems in East Central Illinois. Knowledge emerging from the integrated research provides a basis
for environmental-management schemes directed toward stream naturalization. 相似文献
908.
G. Darrel Jenerette Jay Lee David W. Waller Robert E. Carlson 《Environmental management》2002,29(1):67-75
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
909.
综放采空区防灭火注氮数值模拟与参数确定 总被引:7,自引:2,他引:7
李宗翔 《中国安全科学学报》2003,13(5):53-57
用有限元数值方法 ,求解了综放开采采空区注氮情况下的漏风渗流方程和氧浓度渗流耗散方程 ;结合计算机图形技术 ,直观展示了注氮前后采空区流场、流态和氧浓度分布动态变化 ;模拟了在不同注氮量下注氮控制区边界的变化过程 ,得到控制区边界位置与注氮流量呈负指数关系 ;重点探讨了用数值模拟方法确定合理注氮参数 (注氮流量、注氮位置和注氮时间 )的新方法。 相似文献
910.
VIRGINIA GALLEGOS PÉRULA RAFAEL M. NAVARRO CERRILLO PILAR FERNÁNDEZ REBOLLOo GEMADEL VALLE MURILLO 《Environmental management》2003,31(1):0086-0099
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