排序方式: 共有25条查询结果,搜索用时 15 毫秒
1.
2.
3.
Joseph L. Ebersole William J. Liss Christopher A. Frissell 《Journal of the American Water Resources Association》2003,39(2):355-368
ABSTRACT: Discrete cold water patches within the surface waters of summer warm streams afford potential thermal refuge for cold water fishes during periods of heat stress. This analysis focused on reach scale heterogeneity in water temperatures as influenced by local influx of cooler subsurface waters. Using field thermal probes and recording thermistors, we identified and characterized cold water patches (at least 3°C colder than ambient streamflow temperatures) potentially serving as thermal refugia for cold water fishes. Among 37 study sites within alluvial valleys of the Grande Ronde basin in northeastern Oregon, we identified cold water patches associated with side channels, alcoves, lateral seeps, and floodplain spring brooks. These types differed with regard to within floodplain position, area, spatial thermal range, substrate, and availability of cover for fish. Experimental shading cooled daily maximum temperatures of surface waters within cold water patches 2 to 4°C, indicating a strong influence of riparian vegetation on the expression of cold water patch thermal characteristics. Strong vertical temperature gradients associated with heating of surface layers of cold water patches exposed to solar radiation, superimposed upon vertical gradients in dissolved oxygen, can partially restrict suitable refuge volumes for stream salmonids within cold water patches. 相似文献
4.
5.
6.
Parental care is a costly part of reproduction. Hence, natural selection should favor males which avoid caring for unrelated
young. However, the decision to abandon or reduce care requires cues which are evaluated to give information on potential
reproductive value of the offspring. The prediction that male sand gobies, Pomatoschistus minutus, care for foreign eggs as long as they were spawned in their own nest and at least some of such cues are fulfilled was tested.
Egg-guarding males that had recently taken part in a spawning event were given a clutch of eggs that was sired either by themselves
or another male, in either their own or another male’s aquarium. Males that had not taken part in a spawning event were used
as controls and were given eggs sired by another male. We measured the amount of filial cannibalism and nest building. Control
group males did not care for eggs and ate them all before rebuilding the nest. In the other treatments, there were no significant
effects of paternity, though males moved to another male’s aquarium increased their clutch area threshold and completely consumed
larger clutches than males that were not moved. There was no intermediate response in any treatment in the form of increased
partial filial cannibalism or less well-constructed nests. Our results suggest that egg-guarding males cannot distinguish
between eggs sired by themselves and those sired by other males but are able to react to cues indicating paternity state.
Males do not adopt eggs to attract females in P. minutus. 相似文献
7.
Arthropod communities in pear are conceptualized as hierarchically organized systems in which several levels of organization
or subsystems can be recognized between the population level and the community as a whole. An individual pear tree is taken
to be the community habitat with arthropod subcommunities developing on leaf, fruit, and wood subcommunity habitats. Each
subcommunity is composed of trophically organized systems of populations. Each system of populations is comprised of a functional
group or guild of phytophagous arthropods that use the habitat primarily for feeding but also for overwintering or egg deposition,
and associated groups of specialized predators, parasitoids, and hyperparasitoids. Several species move from one subcommunity
to another during the course of community development and thus integrate community subsystems.
Community development or change in organization through time is conceptualized as being jointly determined by the development
of the habitat and the organization of the species pool. The influence of habitat development on community development within
a species pool is emphasized in this research. Seasonal habitat development is expressed as change in the kinds and biomasses
of developmental states of wood, leaf, and fruit subcommunity habitats. These changes are accompanied by changes in the kinds,
biomasses, and distributions of associated community subsystems. 相似文献
8.
Russell LM Rasch PJ Mace GM Jackson RB Shepherd J Liss P Leinen M Schimel D Vaughan NE Janetos AC Boyd PW Norby RJ Caldeira K Merikanto J Artaxo P Melillo J Morgan MG 《Ambio》2012,41(4):350-369
Geoengineering methods are intended to reduce climate change, which is already having demonstrable effects on ecosystem structure and functioning in some regions. Two types of geoengineering activities that have been proposed are: carbon dioxide (CO(2)) removal (CDR), which removes CO(2) from the atmosphere, and solar radiation management (SRM, or sunlight reflection methods), which reflects a small percentage of sunlight back into space to offset warming from greenhouse gases (GHGs). Current research suggests that SRM or CDR might diminish the impacts of climate change on ecosystems by reducing changes in temperature and precipitation. However, sudden cessation of SRM would exacerbate the climate effects on ecosystems, and some CDR might interfere with oceanic and terrestrial ecosystem processes. The many risks and uncertainties associated with these new kinds of purposeful perturbations to the Earth system are not well understood and require cautious and comprehensive research. 相似文献
9.
10.