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1.
ABSTRACT Lethal control alone has not proven entirely effective in reducing gray wolf (Canis lupus) depredations in chronic problem areas. Opponents of lethal control argue that more emphasis should be placed on integrating nonlethal strategies into current management. However, few evaluations have tested the effectiveness of nonlethal options. We compared behavior patterns in terms of frequency and duration of bait station visits for 5 wolves fitted with shock collars to 5 control animals inhabiting wolf pack territories in northern Wisconsin during summers of 2003 and 2004. Shock collared wolves spent less time and made fewer visits to bait station zones than did control animals. During and after shocking, wolves shifted 0.7 km away from the bait station zone. Although active shocking did restrict wolf access, which could be useful in controlling wolf depredations during a limited time period, conditioning was not clearly demonstrated once shocking ceased. The effect of shock collar design and operation on long-term conditioning and shock-conditioned wolves on pack behavior needs further study. If long-term conditioning is possible, shock collars could be used by wildlife managers as a nonlethal wolf management method in chronic problem areas where lethal control has proven ineffective.  相似文献   

2.
(1) The paper reports results of laboratory studies on growth rates at elevated temperatures of two diatoms (Chaetoceros wighami and Amphora coffeaeformis) isolated from the intake and outfall sites of a coastal power station on the east coast of India. (2) Temperature exposures consisted of acute and chronic treatments to simulate condenser transit and prolonged thermal plume entrainment. (3) The results showed that the various temperature zones presented by cooling water circuit of the power station would permit diatom growth, with growth rates that are marginally different form those at average ambient sea temperature. (4) Fundamental differences in the response of different diatom species to temperature stress result in the abundance of the more tolerant species such as A. coffeaeformis which dominate in an elevated temperature zone, such as that offered by the discharge canal of the power station.  相似文献   

3.
Laboratory sediment bioassays, both acute and chronic, were conducted on sediment elutriates from the River Eurajoki, SW Finland. The river is under impacts of industrial discharges, community effluents and agricultural run-offs. The water flea Daphnia magna Straus was used as a test organism. None of the elutriates tested were acutely toxic. In a long-term bioassay sediment elutriates had effects on survival, body growth and reproduction. Elutriates prepared from samples of a downstream station were characterized by low survival, small body size, reduced total offspring production, and delayed start of reproduction.  相似文献   

4.
Measurements were made of the fresh weight, dry weight, dry weight-fresh weight ratio, free and conjugated indole-3-acetic acid, and free and conjugated abscisic acid in seedlings of Zea mays grown in darkness in microgravity and on earth. Imbibition of the dry kernels was for 17 h prior to launch. Growth was for 5 d at ambient orbiter temperature and at a chronic accelerational force of the order of 3 × 10−5 times earth gravity. Weights and hormone content of the microgravity seedlings were, with minor exceptions, not statistically different from seedlings grown in normal gravity. The tissues of the shuttle-grown plants appeared normal and the seedlings differed only in the lack of orientation of roots and shoots. These findings, based upon 5 d of growth in microgravity, cannot be extrapolated to growth in microgravity for weeks, months, and years, as might occur on a space station. Nonetheless, it is encouraging, for prospects of bioregeneration of the atmosphere and food production in a space station, that no pronounced differences in the parameters measured were apparent during the 5 d of plant seedling growth in microgravity.  相似文献   

5.
Spatial and temporal variability of the phytoplankton community in the tropical coastal Imboassica lagoon, an environment naturally isolated from the ocean by a narrow sandbar, was analysed every two weeks for 19 months by sampling three sites. During this study, the lagoon received direct input of marine water three times, resulting in remarkable salinity, nutrient concentrations and phytoplankton biomass variations in both temporal and spatial aspects. The phytoplankton biomass presented relatively low values ranging, on average, from 0.54 mg x L(-1) in the station closest to the sea (station 1) to 1.34 mg x L(-1) in the station close to a macrophyte bank (station 3). Diatoms and cryptomonads dominated in stations 1 and 2 (located relatively close to station 1, yet receiving the runoff of domestic sewage), and euglenoids, cryptomonads and dinoflagellates at station 3. Stations 1 and 2 usually presented the same dominant species but station 2 presented a higher phytoplankton biomass. On the other hand, station 3 showed more similar results concerning phytoplankton biomass with station 2, however the dominant species were usually different. The high fluctuations of salinity and the reduced nutrient availability are pointed out as the main factors structuring the dynamics of the phytoplankton community at the Imboassica lagoon.  相似文献   

6.
A feeding station is the area of forage a grazing animal can reach without moving its forefeet. Grazing behavior can be divided into residence within feeding stations (with bites as benefits) and movement between feeding stations (with steps as costs). However, relatively little information has been reported on how grazing animals modify their feeding station behavior seasonally and interannually in response to varying environmental conditions. The feeding station behavior of beef cows (Japanese Black) stocked on a tropical grass pasture (bahiagrass dominant) was monitored for 4 years (2010 to 2013) in order to investigate the association of feeding station behavior with meteorological and sward conditions across the seasons and years. Mean air temperature during stocking often exceeded 30°C during summer months. A severe summer drought in 2013 decreased herbage mass and sward height of the pasture and increased nitrogen concentration of herbage from summer to autumn. A markedly high feeding station number per unit foraging time, low bite numbers per feeding station and a low bite rate were observed in summer 2013 compared with the other seasons and years. Bite number per feeding station was explained by a multiple regression equation, where sward height and dry matter digestibility of herbage had a positive effect, whereas air temperature during stocking had a negative effect (R2=0.658, P<0.01). Feeding station number per minute was negatively correlated with bite number per feeding station (r=–0.838, P<0.001). It was interpreted that cows modified bite number per feeding station in response to the sward and meteorological conditions, and this largely determined the number of feeding stations the animals visited per minute. The results indicate potential value of bite number per feeding station as an indicator of daily intake in grazing animals, and an opportunity for livestock and pasture managers to control feeding station behavior of animals through managements (e.g. fertilizer application, manipulation of stocking intensity and stocking time within the day).  相似文献   

7.
The abundance, growth, and grazing loss rates of picophytoplankton were investigated in August 2002 in Barguzin Bay, Lake Baikal. Water samples for incubation were taken once at a near-shore station and twice at an offshore station. Contributions of picophytoplankton to total phytoplankton were high (56.9–83.9%) at the offshore station and low (5.8–6.8%) at the near-shore station. The picophytoplankton community in the offshore station comprised mainly phycoerythrin (PE)-rich cyanobacteria, with eukaryotic picophytoplankton being less abundant. In contrast, as well as PE-rich cyanobacteria and eukaryotic picophytoplankton, phycocyanin (PC)-rich cyanobacteria were found in the near-shore station. At the offshore station, growth and grazing loss rates on 25 August were 0.56 and 0.43 day−1, respectively, and on 29 August, 0.69 and 0.83 day−1, respectively. At the near-shore station, growth and grazing loss rates were 1.61 and 0.70 day−1, respectively. These results show that there is a difference in the abundance, composition, and ecological role in the microbial food web of picophytoplankton between the near-shore and the offshore areas in Barguzin Bay.  相似文献   

8.
Density, age structure, and growth rates of wild brook trout (Salvelinus fontinalis)and brown trout (Salmo trutta)in Whetstone Brook in northcentral Massachusetts were monitored for 4 years before and 3 years during limestone treatment to mitigate acidic conditions. The population density of brook trout increased significantly during treatment. Liming did not have any significant effects on the growth rates of brook trout or brown trout. Actual survival rates of brook trout and brown trout were not calculated due to the low density of both species, but more older individuals of both species were captured during the treatment period. Fulton condition factors (an index of fish condition) increased significantly for both brook trout and brown trout during treatment. Seven-day in situ bioassays of brown trout and rainbow trout demonstrated that liming improved the chemical environment for fish in Whetstone Brook. During a pretreatment bioassay in 1987, 100% rainbow trout mortality was observed at both the control and treatment stations in Whetstone Brook. Brown trout mortality was 67% in the control station and 70% in the treatment station. The pH during the 1987 bioassay averaged 4.90 in the control station and 4.99 in the treated station. During a bioassay conducted in 1990 after treatment began, rainbow trout mortality was 100% in the control station and 0% in the treatment station. Brown trout mortality was 17% in the control station and 0% in the treatment station. The pH during the 1990 bioassay averaged 5.23 in the control station and 6.60 in the treatment station. Analysis of total aluminum in the gills of fish from the 1990 bioassay revealed higher levels in fish from the control station than in those from the treatment station.  相似文献   

9.
We studied downstream migration of 256 radio-tagged Atlantic salmon smolts passing a low-head power station where technical facilities have been improved to allow safe migration via several bypass routes. Extra mortality was 7 and 17% (two years) in the power station reservoir, and a minimum of 10 and 13% at the power station compared to in a control stretch. The majority of the smolts followed the main flow at the power station, towards the turbines. Sloped bar racks with 10 mm bar spacing hindered smolts from entering the turbines, hence there was no turbine mortality. Smolts used surface openings in the racks, which directed them to a bypass route outside the turbines. The extra mortality in the reservoir and at the power station was related to physical injuries in bypass routes and to predation. The mortality risk in the reservoir and at the power station decreased with increasing migration speed. Migration speeds increased with water discharge. Migration was slower when the smolts passed the power station than on other stretches. This study shows that hydropower regulation caused elevated mortality and delays for downstream migrating fish, even with improved technical facilities to reduce mortality.  相似文献   

10.
Statistically valid relations between radiation conditions in compartments of MIR station and the micromicete population (CFU number) on the surface of the equipment and the interior have been established. It was found that in conditions of a chronic exposure to space radiation the number of CFU increased in one thousand and more times with increasing of absorbed dose rate from 200 up to 1000 microGy/day. The results of land-based model experiments confirmed morphological changes in the "flight" strains of funguses under exposure to low doses of gamma (100-800 microGy/day) and neutron (0.2-2 neutron/cm2.s) radiation. It was found that the morphological changes in the control (museum) cultures of funguses of the same species, which were expressed in the weak increase of vegetative mycelium, were detected only after repeated gamma- and gamma + neutron irradiation.  相似文献   

11.
辽宁省城市热岛强度特征及等级划分   总被引:1,自引:0,他引:1  
根据气象站资料累积时间、资料连续性、站点位置、城郊站间距离、站点数量、迁站情况,对辽宁省61个气象站进行筛选,并利用选出的城郊代表站的月和年气温数据,分析了辽宁省热岛强度的变化范围及幅度,确定了热岛强度等级.结果表明:辽宁省铁岭站、大连站、鞍山站、朝阳站、丹东站、锦州站6个气象站可作为城市气温的代表站,台安站等18个气象站可作为郊区气温的代表站;1980-2009年,辽宁省6个代表城市的热岛强度年变化不同,除铁岭为微弱下降外,其他5市均表现为上升趋势,铁岭年热岛强度较强,大连年热岛强度较弱;6个代表城市的月热岛强度变化也不同,丹东、锦州、铁岭的月热岛强度呈明显的“U”型分布,6市最大热岛强度均出现在1月,最小热岛强度均出现在5-8月,具有冬季强、夏季弱的特点.6市热岛强度的年、月变化范围分别为0.57~2.15℃和-0.70~4.60℃,年和月热岛强度分别有97.8%和72.3%集中在0.5~2.0℃.辽宁省热岛强度可划分为无、弱、强和极强4个等级.  相似文献   

12.
Interest in the use of open barns on Swedish horse farms is increasing as an alternative to keeping horses in box stalls and as a 2007 law requires phasing out of tie stalls. To provide adequate forage to satisfy welfare requirements for nutrition, gut health and behavioural needs, the use of automated feeding is also increasing. Studies on forage intake rate report wide variation but provide little information on how to introduce horses to an automatic forage station and on how forage intake rate varies in individual horses fed using an automatic forage station. This study documented the process of training 22 horses to use a transponder-controlled automatic forage feeding station and measured forage intake rates. Observations on the learning period of horses for transponder-controlled automatic forage stations showed that after 4 days, 48% of the horses had reached the goal of 90% intake. After 8 days, learning was completed in 71% of horses and at 16 days in 95% of horses. Measurements of forage intake rate revealed significant differences between individual horses. Overall mean intake rate ± SD, based on 314 observations, was 22.4 ± 6.7 min/kg forage DM. Evaluation of the number of intake measurements required to set a representative average ration in the automatic station for an individual horse showed that the variation levelled off at four samples. In conclusion, horses quickly learned how to use an automatic forage station, with two-thirds of horses achieving this within 7 days. To ensure the correct ration in a timed transponder-controlled automatic forage station, each horse’s forage intake rate must be measured at least four times to obtain a representative average.  相似文献   

13.
In this work, the effect of antenna element loading on the localized specific absorption rate (SAR) has been analyzed for base station antennas. The analysis was conducted in order to determine whether localized SAR measurements of large multi-element base station antennas can be conducted using standardized procedures and commercially available equipment. More specifically, it was investigated if the antenna shifting measurement procedure, specified in the European base station exposure assessment standard EN 50383, will produce accurate localized SAR results for base station antennas larger than the specified measurement phantom. The obtained results show that SAR accuracy is affected by the presence of lossy material within distances of one wavelength from the tested antennas as a consequence of coupling and redistribution of transmitted power among the antenna elements. It was also found that the existing standardized phantom is not optimal for SAR measurements of large base station antennas. A new methodology is instead proposed based on a larger, box-shaped, whole-body phantom.  相似文献   

14.
The comparative study of cellular-tissue reactions in endocrine organs (thyroid and suprarenal glands, ovary) of rodents exposed to radiation in natural conditions (Radium station in Komi Republic and 30-km zone of Chernobyl APP) and experimental conditions modeling the chronic exposure has been conducted. There is evidence that chronic irradiation in low doses causes morphological disorders in different levels of structural organization (cellular-tissue, organism and population levels). The experimental results showed that observed variations in thyroid, suprarenal glands and ovary by morphometric parameters reflect the natural changes in their functional activity (within the physiological limits). These changes are directed at the homeostasis maintenance in changed conditions and have a compensatory and adaptation character. The effects of low dose radiation influence with combination of other agents may be amplified at the cellular-tissue reactions level. In comparison with experimental results, the natural conditions (high level of radioactivity with alpha- and beta-emitters, high natural radionuclides, toxic elements and extreme climatic factors) induce more expressed changes as a significant increasing of chromosomal and genes mutations in cells, destructive processes in organs of endocrine system and disorders of reproductive functions.  相似文献   

15.
Phytoplankton samples were collected on July 14 and 18, 1985from a station 460 km off the coast of northern Baja, California,near the eastern edge of the North Pacific central gyre. Thevertical distributions and species structures at this edge stationare compared with those observed over a 12 year period at astation 900 km north of Hawaii (central station). The edge station is somewhat colder and fresher than the centralstation but the chemical and general biological parameter aresimilar. At both locations, the phytoplankton are divided verticallyinto two assemblages, with a zone of transition near 100 m depth.Neither species composition nor dominance order within the shallowor deep zones at the edge station are significantly differentfrom those at the central station. The spatial differences ona scale of 3200 km are the same as those observed at the centralstation over temporal intervals of 4–5 and 12 years, respectively,in the shallow and deep assemblages.  相似文献   

16.
Abstract

A new station of Dianthus glacialis Haenke ssp. glacialis, on the Stelvio National Park in Cedech Valley (Valfurva-Lombardy). – The author refers to a new station of Dianthus glacialis Haenke ssp. glacialis on the Stelvio National Park in Cedech Valley, 2700 m. Many specimens collected have very short stems (f. reducta f. nova) in comparison with the forma normale which has the stems 1–5 (10) cm long. Examination of the soil characteristics of the station suggests the possibility that the plant grows in this station rich in limestone, since it is protected from the limestone by a certain stratum of organic matter.  相似文献   

17.
To understand the activity of marine viruses, experiments on viral production, viral decay and the percentage of lytic and lysogenic bacterial cells among the total number of bacterial cells were carried out seasonally at two stations in the Adriatic Sea with different trophic conditions. Additionally, we are providing an insight on the enrichment with dissolved and particulate organic matter by viral lysis in the studied area. Viral production was higher at the coastal station than at the open-sea station. Viral decay rates were also higher at the coastal sea station than at the open-sea station, and accounted for approximately 40% of viral production at both investigated stations. The percentage of lysogenic infection was lower than that of lytical infection, which indicates the prevalence of the lytic cycle at both stations. Viruses had a significant influence on bacterial mortality through high daily removal of the bacterial standing stock at the coastal and open-sea station. The viruses contributed to the restoration of dissolved organic carbon, nitrogen and phosphorus in the microbial loop by lysing the bacterial cells at the studied stations. All the above suggest that viruses are important in the microbial food web and an important factor in the control of bacterial populations within the study area.  相似文献   

18.
基于2009—2018年亚洲季风区7个大气本底站[印度尼西亚Bukit Kototabang(BKT)站、中国鹿林(LLN)站和瓦里关(WLG)站、日本Ryori(RYO)站和Yonagunijima(YON)站、韩国Tae-ahn Peninsula(TAP)站、蒙古Ulaan Uul(UUM)站]地面观测资料,利用谐波模型拟合和最大信息非参数探索方法,对亚洲季风区大气CH4浓度时空变化特征及影响因素进行分析。结果表明: 亚洲季风区大气CH4浓度范围在1853.04~1935.61 nmol·mol-1,高于同期美国夏威夷Mauna Loa(MLO)站观测值(1838.33 nmol·mol-1),总体呈现由北向南依次递减的纬向分布特征,两个高值中心为韩国TAP站(1935.61 nmol·mol-1)和日本RYO站(1907.19 nmol·mol-1)。大气CH4浓度平均季振幅最大为日本YON站(108.20 nmol·mol-1),最小为中国WLG站(29.48 nmol·mol-1),同时韩国TAP(4.49 nmol·mol-1·a-1)站表现出更高的季振幅变化速率;除中国WLG站和韩国TAP站外,其他本底站均呈现夏低冬高的季节循环特征;从长期变化上看,中国LLN站(7.68 nmol·mol-1·a-1)和WLG站(7.56 nmol·mol-1·a-1)大气CH4浓度增长趋势最明显。相对于风速而言,气温和降水量对亚洲季风区大气CH4浓度的影响程度更高,两个气象因子与大气CH4浓度之间均呈现显著负相关;局地排放对部分站点大气CH4浓度具有显著正向效应。  相似文献   

19.
In order to estimate the qualitative variation of sedimented mussel deposits, biochemical and microbial measurements were undertaken after a sediment enrichment with fresh faeces and pseudo-faeces collected in a mussel farming area (Carteau, Gulf of Fos).During two months, cores sampled were investigated at three stations: a first station enriched with mussel deposits, a second considered as a reference station without mussel deposits and occasionally a third corresponding to a continuously enriched sediment under a rope culture.Carbohydrate, organic carbon and nitrogen contents in the sediments gave evidence of a short term variation after sedimentation.Bacterial production increased rapidly at the enriched station and returned to its initial level 8 days later. At this station, exoglucosidasic activity of bacteria, low at the beginning, presented a maximum two weeks after enrichment whereas exoproteolytic activity, which was high in the biodeposits, decreased in the course of the first week. These exoenzymatic activities were significantly higher at the enriched station than at the reference stations. Carbohydrate measurements were in agreement with these results.Degradation rate of biodeposits is discussed on the basis of exoenzymatic activity, organic carbon, nitrogen and free amino acid content at the three stations.  相似文献   

20.
Mobile communication has become a ubiquitous part of today's life. The ongoing growth of this technology, however, involves the construction of new mobile phone base stations in order to assure network coverage. The selection of a new base station site often results in conflicts between providers and public authorities, on the one hand, and residents on the other. The aim of the present study was to examine public preferences regarding base station sites. A random sample of 503 persons from the German speaking part of Switzerland was interviewed face-to-face in their homes. Conjoint analysis was used to evaluate participants’ preferences for various attributes of base stations (appearance, location, building, decision process). The results show that location plays the most important role in participants’ acceptance of base stations. The findings also indicate that most people would prefer a covered or camouflaged base station to a freely visible one. By means of a cluster analysis, several segments were distinguished, showing that base station siting preferences were not homogeneous. Implications for risk communication are discussed.  相似文献   

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