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排序方式: 共有58条查询结果,搜索用时 328 毫秒
31.
Jolanda M H Verspagen Jutta Passarge Klaus D J?hnk Petra M Visser Louis Peperzak Paul Boers Hendrikus J Laanbroek Jef Huisman 《Ecological applications》2006,16(1):313-327
To prevent flooding of the Dutch delta, former estuaries have been impounded by the building of dams and sluices. Some of these water bodies, however, experience major ecological problems. One of the problem areas is the former Volkerak estuary that was turned into a freshwater lake in 1987. From the early 1990s onward, toxic Microcystis blooms dominate the phytoplankton of the lake every summer. Two management strategies have been suggested to suppress these harmful algal blooms: flushing the lake with fresh water or reintroducing saline water into the lake. This study aims at an advance assessment of these strategies through the development of a mechanistic model of the population dynamics of Microcystis. To calibrate the model, we monitored the benthic and pelagic Microcystis populations in the lake during two years. Field samples of Microcystis were incubated in the laboratory to estimate growth and mortality rates as functions of light, temperature, and salinity. Recruitment and sedimentation rates were measured in the lake, using traps, to quantify benthic-pelagic coupling of the Microcystis populations. The model predicts that flushing with fresh water will suppress Microcystis blooms when the current flushing rate is sufficiently increased. Furthermore, the inlet of saline water will suppress Microcystis blooms for salinities exceeding 14 g/L. Both management options are technically feasible. Our study illustrates that quantitative ecological knowledge can be a helpful tool guiding large-scale water management. 相似文献
32.
Stefan H. Nessler Gabriele Uhl Jutta M. Schneider 《Behavioral ecology and sociobiology》2009,63(3):355-362
Sperm competition is a potent driving force in evolution leading to a remarkable variety of male adaptations that prevent
or reduce fertilization by rivals. An extraordinary defensive strategy against sperm competition has evolved in a number of
web spiders where males break off parts of their paired genitalia in order to obstruct the copulatory openings of females
(mating plug). A recent comparative analysis on the family level reports that genital damage is most frequent in species with
sexual cannibalism although, as yet, a functional association between sexual cannibalism and genital damage has not been found.
Using the moderately sexually cannibalistic orb-web spider Argiope lobata, we show for the first time that males cannibalized during their first copulation damaged their pedipalps with significantly
higher probability (74%) than males that escaped (15%). Of all males that damaged their genitalia, 44% were able to place
a genital fragment inside the copulatory opening of the female, resulting in a relatively low total plugging rate of 14%.
Successful obstruction of the female copulatory opening reduced the share of paternity of subsequent males (P
2 = 0.06%), thus, indicating that genital damage may have evolved as a response to sperm competition in this species as well.
However, the low incidence of successful plugging and the strong relationship between sexual cannibalism and genital damage
suggest that apart from paternity protection, the nature of genital damage in A. lobata is further shaped by sexual conflict or cryptic female choice. 相似文献
33.
Roland Weber Stefan Gonser Jutta Köhler Wolfgang Körner Christine Herold Roland Haag Margit Krapp Ludwig Peichl 《Environmental science and pollution research international》2018,25(17):16344-16354
In the 1980s, it was demonstrated that semi-volatile organic compounds (SVOCs) like polychlorinated biphenyls (PCBs) accumulate in plant leaves. Plants are at the base of the food chain, and therefore a starting point for transfer of PCBs to animals and related human exposure. For two decades, the Environment Agency of the German federal state of Bavaria (LfU) has been operating long-term monitoring stations to measure the impact of organic air pollutants. Standardized ryegrass, curly kale, and spruce needles are used as bioindicators for the atmospheric entries of PCBs into vegetation. From the end of 1990s to 2009, there was a marked decline in the concentrations of indicator PCBs (i-PCBs) and a minor decline in PCB-TEQ levels. After 2009, the concentrations leveled off. In rural areas, the median concentrations of Σ6 i-PCB in ryegrass and curly kale were about 3 and 4 μg/kg dm in 2000, and have been about 0.5 and 1 μg/kg dm since 2009, respectively. Concentrations in spruce needles fell from 0.9 to 0.4 μg/kg dm. Median PCB-TEQ concentrations in the bioindicator plants ranged from 0.05 to 0.23 ng/kg dm between 2002 and 2009 and from 0.15 to 0.05 ng/kg dm after 2009. Indicator PCB and PCB-TEQ concentrations were several times higher at the urban station in Munich than at the rural areas, reflecting the emissions from in-use PCB stocks in the building sector. The likely reason of the slower decrease of PCB-TEQ compared to i-PCBs is the formation of PCB-126 by dechlorination of industrial PCBs in open applications. 相似文献
34.
Jeffrey G. Holmquist Jutta Schmidt-Gengenbach Elizabeth A. Ballenger 《Environmental management》2014,53(6):1109-1118
Assessments of vertebrate disturbance to plant and animal assemblages often contrast grazed versus ungrazed meadows or other larger areas of usage, and this approach can be powerful. Random sampling of such habitats carries the potential, however, for smaller, more intensely affected patches to be missed and for other responses that are only revealed at smaller scales to also escape detection. We instead sampled arthropod assemblages and vegetation structure at the patch scale (400–900 m2 patches) within subalpine wet meadows of Yosemite National Park (USA), with the goal of determining if there were fine-scale differences in magnitude and directionality of response at three levels of grazing intensity. Effects were both stronger and more nuanced than effects evidenced by previous random sampling of paired grazed and ungrazed meadows: (a) greater negative effects on vegetation structure and fauna in heavily used patches, but (b) some positive effects on fauna in lightly grazed patches, suggested by trends for mean richness and total and population abundances. Although assessment of disturbance at either patch or landscape scales should be appropriate, depending on the management question at hand, our patch-scale work demonstrated that there can be strong local effects on the ecology of these wetlands that may not be detected by comparing larger scale habitats. 相似文献
35.
36.
Jutta Gutberlet 《Waste management (New York, N.Y.)》2010,30(2):171-173
37.
Assisting the genetic parents in the rearing of young, a widespread phenomenon in many birds and mammals, is usually regarded
as an altruistic or mutualistic behavior. Infant handling by females other than the mother is also common in many primates,
but due to high within- and between-species variation and limited knowledge about fitness consequences there is no consensus
about its evolutionary and functional significance. Analysis of female infant-handling patterns and its reproductive consequences
in three groups of semifree-ranging Barbary macaques revealed that nulliparous females significantly more often handled infants
than parous females, but infant handling experience did not affect survival of their own first live-born offspring. Females
interacted preferentially with closely related infants, but infant handling frequency improved neither infant survival nor
maternal fecundity. Reciprocation of infant handling by mothers was rare. Although “aunting to death” occurred in the population,
the hypothesis that infant handling serves to reduce the fitness of competitors was not supported. Limited evidence suggests
that females at least sometimes use infants as strategic tools in the course of alliance formation. In concert with this poor
evidence for a functional basis of the behavior, several lines of evidence support the hypothesis that infant handling evolved
as a non-adaptive by-product of a strong selection for mother-offspring bonding. (1) Rates of infant handling were highest
among females that experienced early infant loss. (2) Females caring for infants or yearlings of their own handled other infants
significantly less often than females without dependent offspring. (3) Infant handling by females was most prevalent during
the infants’ first month of life. (4) Both “aunting to death” and a successful adoption occurred irrespective of kinship relations.
Although the by-product hypothesis appears to be the only one able to explain all results of this study, the apparent rarity
of infant handling in non-female-bonded species suggest that kin selection is a possible alternative explanation for the evolution
of female infant-handling in primates.
Received: 30 December 1995/Accepted after revision: 10 May 1996 相似文献
38.
Jeffrey G. Holmquist Jutta Schmidt-Gengenbach Sylvia A. Haultain 《Environmental management》2013,52(6):1474-1486
Grazing management necessarily emphasizes the most spatially extensive vegetation assemblages, but landscapes are mosaics, often with more mesic vegetation types embedded within a matrix of drier vegetation. Our primary objective was to contrast effects of equine grazing on both subalpine vegetation structure and associated arthropods in a drier reed grass (Calamagrostis muiriana) dominated habitat versus a wetter, more productive sedge habitat (Carex utriculata). A second objective was to compare reed grass and sedge as habitats for fauna, irrespective of grazing. All work was done in Sequoia National Park (CA, USA), where detailed, long-term records of stock management were available. We sampled paired grazed and control wet meadows that contained both habitats. There were moderate negative effects of grazing on vegetation, and effects were greater in sedge than in reed grass. Conversely, negative grazing effects on arthropods, albeit limited, were greater in the drier reed grass, possibly due to microhabitat differences. The differing effects on plants and animals as a function of habitat emphasize the importance of considering both flora and fauna, as well as multiple habitat types, when making management decisions. Sedge supported twice the overall arthropod abundance of reed grass as well as greater diversity; hemipteran and dipteran taxa were particularly abundant in sedge. Given the greater grazing effects on sedge vegetation, greater habitat provision for terrestrial arthropods, and value as aquatic arthropod habitat, the wetter sedge assemblage is worthy of additional consideration by managers when planning for grazing and other aspects of land usage. 相似文献
39.
In a field study, soils of four conventional free-range and organic broiler runs were analyzed for N and P concentrations in the years 2000 and 2001. Zones of different use intensity by broilers were identified on the free runs and mean zonal nutrient contents were compared with each other. Intensity of use by birds and spatial distribution of soil nutrient concentrations were found to be related to each other. Fecal N input by broilers resulted in accumulation of soil mineral nitrogen (N(min)) contents down to a 90-cm sampling depth. In highly frequented "hot spots," plant requirement as defined by the German "N-Basis-Sollwert" (110 kg/ha N(min)) for grassland was exceeded in all four cases. This implies an increased environmental risk of ammonia volatilization and nitrate leaching. Fecal P input by broilers resulted in accumulation of plant-available and thus mobile soil P (phosphorus extracted with calcium-acetate-lactate [P(CAL)] and phosphorus extracted with water [P(w)]) in the most intensely used zones. In these areas, soil P contents exceeded 90 mg/kg P(CAL) (upper limit of soil test P defined in Germany for optimum plant yield) by as much as 217 mg/kg, which indicates an enhanced risk of P loss from the soil via runoff or leaching. The conclusion might be drawn that, with regard to nutrient loss from free-run soils, intensive indoor production in a closed system may be more environmentally neutral than conventional free-range or organic production. However, to put this into perspective, the scope of the environmental risk connected with spatially limited point accumulation of nutrients should be considered. Furthermore, an environmental evaluation must also account for the fate and environmental effects of the broiler litter produced inside the broiler house. 相似文献
40.