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191.
Protandry, the earlier arrival of males than females to breeding areas, is widespread in birds, but its underlying mechanisms
are far from well understood. The two, not mutually exclusive most highly supported hypotheses to explain avian protandry
postulate that it has evolved from intrasexual male competition to acquire the best territories (“rank advantage” hypothesis)
and/or to maximize the number of mates (“mate opportunity” hypothesis). We studied for two consecutive years the relative
importance of both hypotheses in a population of pied flycatchers (Ficedula hypoleuca), a territorial songbird with a mixed mating strategy. We measured territory quality using a long-term dataset on nest occupation
and breeding output, and we used molecular techniques to assess male fitness across the range of social and genetic mating
options. Territory quality was unrelated to breeding date and had no influence on extra-pair paternity or social polygynous
events. However, males breeding early increased their chances of becoming socially polygynous and/or of attaining extra-pair
paternity and, as a consequence, increased their total reproductive success. These results support the “mate opportunity”
hypothesis, suggesting that sexual selection is the main mechanism driving protandry in this population. 相似文献
192.
In recent decades, dozens of studies have involved attempts to introduce native and desirable nonnative plant species into grasslands dominated by invasive weeds. The newly introduced plants have proved capable of establishing, but because they are rarely monitored for more than four years, it is unknown if they have a high likelihood of persisting and suppressing invaders for the long-term. Beyond invaded grasslands, this lack of long-term monitoring is a general problem plaguing efforts to reintroduce a range of taxa into a range of ecosystems. We introduced species from seed and then periodically measured plant abundances for nine years at one site and 15 years at a second site. To our knowledge, our 15-year data are the longest to date from a seeding experiment in invaded, never-cultivated grassland. At one site, three seeded grasses maintained high densities for three or more years, but then all or nearly all individuals died. At the second site, one grass performed similarly, but two other grasses proliferated and at least one greatly suppressed the dominant invader (Centaurea maculosa). In one study, our point estimate suggests that the seeded grass Thinopyrum intermedium reduced C. maculosa biomass by 93% 15 years after seeding. In some cases, data from three and fewer years after seeding falsely suggested that seeded species were capable of persisting within the invaded grassland. In other cases, data from as late as nine years after seeding falsely suggested seeded populations would not become large enough to suppress the invader. These results show that seeded species sometimes persist and suppress invaders for long periods, but short-term data cannot predict if, when, or where this will occur. Because short-term data are not predictive of long-term seeded species performances, additional long-term data are needed to identify effective practices, traits, and species for revegetating invaded grasslands. 相似文献
193.
194.
Tedford Edmund Halferdahl Geoff Pieters Roger Lawrence Gregory A. 《Environmental Fluid Mechanics》2019,19(2):457-473
Environmental Fluid Mechanics - We investigated temporal variations in turbidity in Base Mine Lake, an oil sands pit lake, located in northeast Alberta, Canada. The lake has a surface area of... 相似文献
195.
Sarah E. Crawford Catrina Brüll nee Cofalla Benedikt Aumeier Markus Brinkmann Elisa Classen Verena Esser Caroline Ganal Elena Kaip Roger Häussling Frank Lehmkuhl Peter Letmathe Anne-Katrin Müller Ilja Rabinovitch Klaus Reicherter Jan Schwarzbauer Marco Schmitt Georg Stauch Matthias Wessling Süleyman Yüce Markus Hecker Karen A. Kidd Rolf Altenburger Werner Brack Holger Schüttrumpf Henner Hollert 《Environmental Sciences Europe》2017,29(1):23
Protecting our water resources in terms of quality and quantity is considered one of the big challenges of the twenty-first century, which requires global and multidisciplinary solutions. A specific threat to water resources, in particular, is the increased occurrence and frequency of flood events due to climate change which has significant environmental and socioeconomic impacts. In addition to climate change, flooding (or subsequent erosion and run-off) may be exacerbated by, or result from, land use activities, obstruction of waterways, or urbanization of floodplains, as well as mining and other anthropogenic activities that alter natural flow regimes. Climate change and other anthropogenic induced flood events threaten the quantity of water as well as the quality of ecosystems and associated aquatic life. The quality of water can be significantly reduced through the unintentional distribution of pollutants, damage of infrastructure, and distribution of sediments and suspended materials during flood events. To understand and predict how flood events and associated distribution of pollutants may impact ecosystem and human health, as well as infrastructure, large-scale interdisciplinary collaborative efforts are required, which involve ecotoxicologists, hydrologists, chemists, geoscientists, water engineers, and socioeconomists. The research network “project house water” consists of a number of experts from a wide range of disciplines and was established to improve our current understanding of flood events and associated societal and environmental impacts. The concept of project house and similar seed fund and boost fund projects was established by the RWTH Aachen University within the framework of the German excellence initiative with support of the German research foundation (DFG) to promote and fund interdisciplinary research projects and provide a platform for scientists to collaborate on innovative, challenging research. Project house water consists of six proof-of-concept studies in very diverse and interdisciplinary areas of research (ecotoxicology, water, and chemical process engineering, geography, sociology, economy). The goal is to promote and foster high-quality research in the areas of water research and flood-risk assessments that combine and build off-laboratory experiments with modeling, monitoring, and surveys, as well as the use of applied methods and techniques across a variety of disciplines. 相似文献
196.
Roger B. Hammer Susan I. Stewart Todd J. Hawbaker Volker C. Radeloff 《Journal of environmental management》2009
Rural, forested areas throughout the United States are experiencing strong housing growth with potentially detrimental impacts on the environment. In this paper, we quantify housing growth in Northern Wisconsin over the last sixty years to determine if growth rates were higher near public lands, which may represent an important recreational amenity. We used data from the U.S. Census to produce decadal housing density estimates, “backcasts,” from 1940 to 2000 for northern Wisconsin to examine “rural sprawl” in northern Wisconsin and its relationship to forested areas and public lands. We integrated housing density estimates with the 1992/1993 National Land Cover Dataset to examine the relationship between rural sprawl and land cover, especially forests. Between 1940 and 2000, private land with <2 housing units/km2 decreased from 47% to 21% of the total landscape. Most importantly, housing growth was concentrated along the boundaries of public lands. In 14 of the 19 counties that we studied, housing growth rates within 1 km of a public land boundary exceeded growth rates in the remainder of the county, and three of the five counties that did not exhibit this pattern, were the ones with the least amount of public land. Future growth can be expected in areas with abundant natural amenities, highlighting the critical need for additional research and effective natural resource management and regional planning to address these challenges. 相似文献
197.
198.
C. Roger 《Marine Biology》1973,19(1):54-60
The predation of euphausiids by micronektonic migrant or deep-living fishes has been studied by examination of 1825 stomach contents selected from 282 samples collected with a 10-foot Isaacs-Kidd midwater trawl (IKMT) in the central equatorial Pacific Ocean. On the whole, euphausiids account for 8% of the total food ingested; this percentage rises to 21% when the genus Cyclothone is excepted. The species consumed belong to the genera Euphausia (45%), Stylocheiron (40%) and Nematoscelis (13%). 90% of the specimens are smaller than 18 mm and weigh less than 37 mg (wet weight); in most cases, there exists an almost linear relationship between predator size and the occurrence of euphausiids in the stomachs and also with the sizes of the preys. It is shown that the predation of euphausiids by micronektonic migrant and deep-living fishes is less during light hours and rises in the late afternoon and night time. Moreover, the species consumed are not the same at different times of the day; Euphausia spp. are ingested by night (in subsurface layers) as well as during the daytime (in deeper layers), small Stylocheiron mainly by night in subsurface layers, Nematoscelis spp. and Stylocheiron abbreviatum chiefly at the time of vertical migrations (sunset and sunrise). 相似文献
199.
Degradation of 1,1,1-trichloroethane in water by hydrolysis and dehydrochlorination may conceivably be a significant sink for this compound in the environment. The kinetics of these reactions have therefore been investigated over a wide range of temperature. The half-life at 20 °C is found to be 1.7 years. 相似文献
200.