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1.
Hydroelectric development and the disruption of migration in caribou   总被引：1，自引：0，他引：1  
We investigated the effects of hydroelectric development on the movements and space-use of caribou (Rangifer tarandus caribou) in west-central Newfoundland, Canada. We compared patterns of range use, site fidelity, and timing of migration before, during, and after project construction. Coincidental with the first year of project construction, caribou were less likely to be found within 3 km of the site; this persisted at least 2 years after construction was completed. Relative timing of migration was individual-specific; the rank order of spring arrival on, and autumn departure from, the calving and summer grounds tended to be consistent year-to-year. This is the first report of such individual-specific consistency in migration for a non-avian species. This predictability disappeared during development: the year-to-year consistency of fall and spring migration among individuals was apparent before and after construction, but not during construction. Variation in calving site fidelity was correlated to year-to-year differences in snowfall. We conclude that the development caused a disruption of migrational timing during construction and longer-term diminished use of the range surrounding the project site. Long-term studies of individually marked animals can aid in environmental assessments for migratory animals.  相似文献   

2.
Unstressed and stress-induced plasma corticosterone levels in Galápagos marine iguanas (Amblyrhynchus cristatus) were compared in animals from a site heavily exposed to tourism to animals from a site undisturbed by humans. Initial corticosterone levels not only did not differ between the two groups, but they were 50% of levels in iguanas known to be chronically stressed. These data suggest that iguanas in tourist areas are not chronically stressed. Both groups of iguanas exhibited elevated corticosterone levels after 30 min of capture and restraint, indicating that they can physiologically respond to stressful stimuli. The stress response was lower, however, at the tourist site. This result indicates that iguanas are physiologically affected by tourism, although it is presently unknown whether these changes are ultimately beneficial or harmful.  相似文献   

3.
The distance at which animals flee an approaching predator is known as the ‘flight initiation distance’ (FID). Wildlife managers use FID to develop buffer zones to reduce human impacts on wildlife. Many variables have been demonstrated to influence FID leading one to question whether it can be viewed as a species-specific trait. We tested this critical assumption for developing buffer zones by experimentally approaching eight species of shorebirds found at six sites around Botany Bay, 15 km south of Sydney, Australia. Botany Bay encompasses a range of human impacted areas, from urban developments with high levels of human presence, through to National Parks and wildlife protection areas where human presence is significantly lower. We found that both species and site influenced the distance birds flew away from an approaching human. Importantly, however, there was no significant statistical interaction between site and species demonstrating that ‘flighty’ species were consistently flighty while more tolerant species were consistently tolerant. Taken together, these results suggest that FID can therefore be viewed as a species-specific trait for these shorebirds. The great variability in FID suggests that wildlife managers should be somewhat conservative in developing buffer zones, but they can use previously published FID data for a given species as guidelines for setting buffer zones.  相似文献   

4.
A multi-isotopic study of several components of milk has been carried out on commercial samples and on milk produced in feeding experiments involving different kinds of diets originating from C(3) or C(4) photosynthetic metabolisms and exhibiting a relatively wide range of isotope ratios. The dispersion of the carbon, hydrogen, and nitrogen isotope parameters of dried matter and of the lactose, protein, and lipid components has been estimated. In addition, the carbohydrates were represented by the site specific isotope ratios (SNIF-NMR) of ethanol resulting from standardized fermentation of lactose. The rates of response of the isotopic parameters to changes in the feeding materials is slower for the minor components, proteins, and lipids than for lactose and ethanol. For similar diets, the nonexchangeable sites of lactose and the methyl site of ethanol, in particular, are relatively enriched in deuterium in the case of polygastric animals, cow, goat, and ewe, as compared to the monogastric species, sow and mare, and woman. From an analytical point of view, the carbon and hydrogen parameters of ethanol provide efficient criteria for identifying a whey origin with respect to other agricultural and fossil sources.  相似文献   

5.
Depletion of moxidectin tissue residues in sheep   总被引：1，自引：0，他引：1  
The pattern of tissue depletion of moxidectin (MXD) subcutaneously administered to sheep was characterized in this study. MXD concentration profiles were determined in muscle, fat, and liver and at the site of injection following administration of a formulation combining MXD (0.5% w/v) with a standard 6 in 1 clostridial vaccine. Thirty-five (35) parasite-free Lincoln sheep were treated with the MXD injectable formulation at a dose rate of 0.2 mg of MXD/kg of live weight, administered subcutaneously on the inner surface of the thigh. Treated animals were sacrificed in randomly selected groups of six sheep weekly from day 21 until day 49 post-treatment. Three nontreated animals were sacrificed to obtain blank tissue samples to validate the analytical methodology. MXD concentration profiles were determined by a validated HPLC analytical method using fluorescence detection. MXD has an adequate pattern of absorption, based on the low residual concentrations found in the injection site area at all sampling intervals. Muscle samples showed the lowest MXD concentrations throughout the study period. The highest MXD concentrations at all sampling times were measured in the adipose tissue, indicating that fat is a target tissue for MXD. MXD concentrations in all of the tissues analyzed were below the accepted maximum limit of residue at 21 days post-treatment.  相似文献   

6.
Long-term overgrazing is known to influence soil microbiological properties and C sequestration in soil organic matter. However, much remains to be known concerning overgrazing impacts on soil microbial activity and litter turnover in heavily grazed rangelands of Central Iran. Aboveground litter decomposition of three dominant species (Agropyron intermedium, Hordeum bulbosum, and Juncus sp.) were studied using a litter bag experiment under field conditions in three range sites of Central Iran, a site with continuous grazing, a site ungrazed for 17 years with dominant woody species (80% cover), and a site ungrazed for 17 years with dominant pasture species (70% cover). Soil samples were taken from 0 to 30 cm depth and analyzed for their chemical and microbiological properties. Results demonstrate that soil organic C and total N contents and C/N ratios were similar for both ungrazed and grazed sites, while available P and K concentrations significantly decreased under grazed conditions. It was also evident that range grazing decreases soil respiration and microbial biomass C, suggesting a lower recent annual input of decomposable organic C. Nevertheless, grazing conditions had no significant effect on litter decomposition indicating soil microclimate is not affected by grazing animals in this ecosystem. It is concluded that overgrazing may presumably depress microbial activity through either reduced input of fresh plant residue into the surface soil or lack of living roots and exudates for stimulating microbial activity. This study also suggests that 17 years of livestock exclusion might be insufficient time for expected C accumulation in soil.  相似文献   

7.
We present evidence that Devil Facial Tumour Disease (DFTD) is an emerging disease that is now widespread and constitutes a serious threat to the Tasmanian devil Sarcophilus harrisii. This species, the world’s largest extant marsupial carnivore, is endemic to Tasmania. DFTD is a cancerous disease found exclusively in wild devil populations, and appears to be consistently fatal to afflicted individuals. We draw on data from a wide range of sources and locations across Tasmania, acquired through trapping, spotlighting and public observation, to assess the impact and distribution of this disease. The dramatic tumours characteristic of DFTD were first reported in 1996. There were no reports of these signs in any of more than 2020 individuals trapped previously. Since 1996, DFTD has been histologically confirmed in individuals from 41 separate sites, covering 32 930 km2 (51%) of mainland Tasmania. From the few sites for which timing of DFTD emergence can be estimated, there is evidence for geographical spread of the disease. Of 147 devils with DFTD-like signs, at least 140 were sexually mature. Proportion of animals displaying signs at any one site reached up to 83% (15/18) of trapped adults. Spotlighting surveys and trapping indicated a significant local association between population decline and date of first report of DFTD. In the region where the disease was first reported, mean spotlighting sightings declined by 80% from 1993-1995 to 2001-2003. On the basis of the threat posed by DFTD, the devil has been listed as a threatened species in Tasmania, and nominated for listing at national level.  相似文献   

8.
Calluna vulgaris-dominated heaths and moorlands are habitats of international conservation importance. Degradation has occurred throughout their range with Calluna typically being replaced by grass species. The cessation of grazing is often impractical and rarely results in the recovery of Calluna abundance when it is initially present at low cover. Thus the development of restoration methods is required; these should be practical at a large-scale, in remote areas and create suitable conditions for Calluna germination and establishment, whilst still allowing grazing to occur. A replicated field experiment was established on Nardus stricta and Molinia caerulea-dominated moorlands to test the efficacy of different grazing regimes and intervention techniques aimed at establishing Calluna. Disturbance (rotavation and trampling by animals) to create bare ground increased Calluna establishment. On the Nardus site, Calluna establishment was equally successful on rotavated and trampled plots, but rotavation was more successful on the Molinia site. Seeding with Calluna increased Calluna establishment irrespective of whether a seed-bank was present. At the Nardus site, 0.5 cow/ha for two months in summer led to Calluna establishment and growth similar to that of ungrazed plots and was more successful than a mixed grazing regime (1 ewe/ha plus 0.5 cow/ha for 2 months) or a sheep only regime (1.5 ewes/ha). The creation of small patches of bare ground, seed addition and low intensity grazing enabled the rapid establishment of Calluna on grass-dominated moorlands; such techniques may also be applicable in other habitats where restoration requires the addition of a single/few species and minimal intervention.  相似文献   

9.
Responses of decomposer animals to heavy-metal contamination were studied near a Cu–Ni smelter in Finland. Samples were taken 0.5, 2 and 8 km from the smelter. In addition, plots fertilised with lime were sampled. Decomposer community in coniferous forest soil appeared to be quite resistant to heavy-metals. Only in the vicinity (0.5 km) of the smelter, were numbers of soil animals clearly decreased and their community structure strongly altered as compared to the control site (8 km). At the 2-km site, the community structure was only slightly changed. Most of the collembolan species were still found at the 0.5-km site. High metal sorption capacity of the humus, and heterogeneous distribution of the metals obviously mitigated the effects of metals. Thus, a more diverse and more abundant decomposer community is able to exist in contaminated forest soil than can be expected. Liming affected the decomposer animal community only at the control site where its impact on soil pH was the highest.  相似文献   

10.
Barn swallows (Hirundo rustica) are arriving later in the spring than they did 30–40 years ago at numerous sites in Korea. In some cases their arrival times are later by more than 1 month. This result is perplexing as spring activities of plants and animals are generally getting earlier due to warming temperatures. The first arrival dates of swallows are not related to temperature, suggesting that another factor is involved. On the basis of a questionnaire, a large majority of long-term observers are confident that there has been a moderate to severe decline in swallow populations at their field site over the study period. The greatest delays in arrival times are associated with sites with more severe reported declines in population size. Simulations using trapping data of large migratory bird populations from the United States, consisting of hundreds of individuals, suggest that severe population declines of 99% can result in delays of 10–12 days in arrival times. In summary, our results suggest that the large delays in arrival time of Korean swallows are due, at least in part, to severe reductions of more than 99% in what were formerly very large populations. Significant delays in spring phenology over time during a period of climatic warming may indicate population decline, though alternative explanations, such as changes in range or migration path or changing number of broods per season, should also be investigated. Delays in first arrival data can provide a valuable new tool to conservation biologists by indicating declines in a population that would otherwise go unnoticed. This can, in turn, lead to efforts by researchers to verify the dynamics of a population and draw attention to the conservation needs of the species.  相似文献   

11.
Nitrous oxide emissions from grazed grassland   总被引：8，自引：0，他引：8  
Abstract. Grazing animals on managed pastures and rangelands have been identified recently as significant contributors to the global N2O budget. This paper summarizes relevant literature data on N2O emissions from dung, urine and grazed grassland, and provides an estimate of the contribution of grazing animals to the global N2O budget.
The effects of grazing animals on N2O emission are brought about by the concentration of herbage N in urine and dung patches, and by the compaction of the soil due to treading and trampling. The limited amount of experimental data indicates that 0.1 to 0.7% of the N in dung and 0.1 to 3.8% of the N in urine is emitted to the atmosphere as N2O. There are no pertinent data about the effects of compaction by treading cattle on N2O emission yet. Integral effects of grazing animals have been obtained by comparing grazed pastures with mown-only grassland. Grazing derived emissions, expressed as per cent of the amount of N excreted by grazing animals in dung and urine, range from 0.2 to 9.9%, with an overall mean of 2%. Using this emission factor and data statistics from FAO for numbers of animals, the global contribution of grazing animals was estimated at 1.55 Tg N2O-N per year. This is slightly more than 10% of the global budget.  相似文献   

12.
Investigations to determine stable or source-sink animal population dynamics are challenging and often infeasible for most species due to the time and expense of mark-recapture studies and the challenge of life histories attributes that result in low detectability and low recapture probabilities. Often, managers rely solely on occupancy or relative abundance patterns to assess a species’ sensitivity to environmental changes. Greater insight into population-level responses to environmental change can be gained by consideration of a combination of readily obtainable metrics, including occupancy, relative abundance, demographic structure and body condition. We examined how these metrics can improve our understanding of population-level responses to forest disturbance, using datasets for two exemplar species of terrestrial salamanders resident to the Pacific Northwestern USA. We compared population metrics for the Del Norte salamander (Plethodon elongatus) and the Siskiyou Mountains salamander (Plethodon stormi) across the seral continuum represented by four forest age classes: pre-canopy, young, mature, and old-growth. We compared these data with those collected from reference stands in mature (P. stormi) or old-growth (P. elongatus) forest containing robust populations. P. elongatus was twice as common as P. stormi. Both occupancy and salamander counts were lowest at pre-canopy sites for both species. Although there were numerous P. elongatus detections in young forests, higher proportions of these individuals were juveniles and sub-adults when compared to populations in late-seral forests. We found a negative relationship between the proportion of immature animals and total counts at a site, indicating that the high proportion of young animals in young forest stands is likely due to dispersal of young salamanders from nearby source populations and/or low survival of adult animals in young forests. We also found reduced body condition of P. stormi populations in young forests. Our results suggest that there are costs to populations occupying early seral forests, such as skewed age class structure and reduced body condition that are indicative of sink populations. Consideration of population-level metrics beyond occupancy and relative abundance can provide important insights when assessing a species’ sustainability in managed forest landscapes.  相似文献   

13.
Industrial development has increased fast in China the last decades. This has led to a range of environmental problems. Deposition of heavy metals to forest ecosystems via the atmosphere is one potential problem. In this paper we report results from a pilot study where the heavy metal levels in forest soils at four different sites have been measured. Three of the sites are located relatively close to the large cities Chongqing, Guiyang and Guangzhou; one site is located in a remote, mountainous area in Guizhou province. Total metal contents as well as fractions according to Tessier's scheme were determined. With a few exceptions, the metal concentrations can be characterized as low; i.e. in most cases within the range of what has been reported as typical background values in the literature. High content of arsenic (up to 100 ppm) was found in the samples from the site outside Guangzhou, most likely due to naturally high arsenic levels in the soil. Metals bound to organic matter and to iron- and manganese oxides were the dominant fractions. No clear differences in metal levels were found between topsoil and subsoil samples, indicating that the atmospheric deposition of heavy metals has been low.  相似文献   

14.
The term ”︁forest soil degradation” is frequently used in forest ecology. It is a highly integrated site property summarizing negative effects over a wide, yet undefined range of variables and a complex range of processes. In forest ecology, different, undefined, and idiosyncratic meanings of the term ’︁soil degradation’ are used. The evaluation for a particular soil is therefore not clear and may be inconsistent among experts. We integrated indicators of forest soil degradation into a fuzzy‐logic based model and predicted forest soil degradation for a set of sites by means of standard soil chemical data and easily accessible site characteristics. For validation we used expert judgements on selected sites. We also compared if the predicted soil degradation agrees with the results of a recent assessment of the ”︁naturalness” (hemeroby) of Austrian forests. The predicted results were consistent with our expectations: sites with a long history of nutrient exploitation were found to be degraded by the model. The fuzzy‐logic based model is open. Rules can be changed, additional rules can be included and others can be removed, if desired. We want to promote fuzzy‐logic based modeling as a means to support experts decisions in complex situations, where clarification can be added by crisply defining the pathway of the decision making process.  相似文献   

15.
The relationship between the strength of field soils, under grass ley and winter wheat, and soil moisture deficit has been monitored over an 18 month period. The soil types selected represent a range of agricultural soils commonly found in Europe. Strong correlations were found to exist between moisture deficit and penetration resistance. This relationship has been used to develop a technique for predicting the average number of days on which land at a given site can be trafficked or worked during a year.  相似文献   

16.
通过转基因动物乳腺表达系统生产重组药用蛋白比微生物发酵系统和动物细胞培养系统具有很多优势;同时,体细胞核移植技术为制备动物乳腺生物反应器开辟了一条新的途径。本实验旨在建立稳定整合人乳铁蛋白cDNA的山羊胎儿成纤维细胞系,为体细胞核移植法制备转基因动物提供可靠的供体细胞。本研究采用RT-PCR获得人乳铁蛋白cDNA,通过Long and Acute PCR扩增山羊β-酪蛋白5’ 端6.5 kb的调控序列,以pEGFP-C1为骨架构建乳腺特异性表达载体 p6.5hLF-EGFP。脂质体介导法转染山羊胎儿成纤维细胞,G418抗性筛选3-4周后,经PCR扩增和报告基因EGFP表达检测,得到稳定整合外源基因的转基因供体细胞系,为制备高效表达人乳铁蛋白的转基因山羊乳腺生物反应器提高可靠的核移植供体细胞。  相似文献   

17.
Prunus africana (Hook.f.) Kalkm. is a secondary forest canopy tree species that has been declining over much of its geographical range in sub-Saharan Africa during recent decades due to unsustainable harvesting of its bark for the international medicinal plant trade. One of the locations where the species is experiencing rapid mortality is Isecheno study site in the Kakamega Forest, Kenya where this study was conducted. Between 1997 and 2003, 21% of the P. africana (10 cm DBH) at Isecheno died and an additional 9% experienced 50% canopy dieback. However, scars from bark harvesting on P. africana were relatively small and scarred trees were not more likely to be dead or dying than unscarred trees, suggesting that bark exploitation is not causing P. africana mortality at Isecheno. Other possible causes that require further evaluation include disease, insect attack, nutrient deficiency, and/or climatic fluctuation. The poor regeneration of P. africana at Isecheno can likely be explained by the relative lack of recent disturbance coupled with the thick undergrowth layer at this site. P. africana mortality is of concern not only because the species is listed as Vulnerable by IUCN, but also because black and white colobus monkeys [Colobus guereza (Rüppell, 1835)] at Isecheno exploit it as their top food species and are particularly reliant on its leaves during times of ‘preferred' Moraceae fruit scarcity. The anticipated continued decline of P. africana may have adverse effects on C. guereza feeding habits, intergroup relations, and population density at Isecheno. Conservation of P. africana offers a formidable challenge since the species appears to require disturbance for regeneration, yet at sites where disturbance is occurring, P. africana is often a target of bark harvesters engaging in unsustainable levels of exploitation.  相似文献   

18.
Soil-Nitrate Determination with the NO3-sensitive Electrode A NO3-sensitive ion electrode (Orion, No. 92–07) was tested to determine the nitrate concentration in soil extracts. Some analytical problems are to be respected: 2. During a 2–8 week period of measurement the electrode gradually lost its potential (Figure 2). Therefore it is necessary to replace the sensitive elements (ion-exchanger, nitrate concentration and membran of electrode) at a certain level (in this 165 mV with 0.22 ppm NO,-N-solution). 3. Additional problems are from the heterogenity of thes oil(s = 0.10mg NO3-N/100g soil in this experiment). With 4 replications in sampling at given site or date, significant differences in the range of 20 kg NO,-N/ha have been obtained. Observing the before mentioned precautions the correlation between nitrate content 1. The optimal range for measurements can be calculated by application of the Peters-Nernst equation between 1 to 10 ppm NO3-N (Figure 1). This equation is influenced by the used electrode. Because this influence changed, it is necessary, to measure the standard solution before and after the series. determined by the nitrate electrode and conventional method (r = 0.92, Figure 3) was highly significant. The deviation of 0.28 ppm has no influence on the agronomy conclusions based on the nitrate determinations.  相似文献   

19.
Abstract. Native woodland restoration is a conservation priority within the UK and there is an increasing awareness that a long-term strategy is required to guide this process. A GIS-based modelling approach has been developed, which links site conditions as expressed in an integrated soil and land cover dataset with the site requirements for different woodland types. There are three important aspects to the model – the parameter weightings, the added value of the integrated dataset, and the woodland categories which are described and predicted. The initial quantitative and qualitative validation has been encouraging although more is required and planned. The results indicate that for broad strategic planning purposes, predictions of woodland potential are not improved significantly when climatic factors are incorporated. The concept that soil acts as an integrator of other environmental variables is discussed alongside the practical application of the model by a range of users.  相似文献   

20.
Precipitation that falls on compost sites picks up organic material from the windrows and the composting pad. The resulting runoff can contain high levels of nutrients, suspended solids, and organic matter, making it unsuitable for direct release into a receiving water body. Many jurisdictions require that the runoff from these sites be collected in a detention pond. Unfortunately, some of the recommended or required procedures for quantifying the volume of runoff from these sites are based on archaic or inappropriate hydrologic models. The development of better hydrologic models for open composting operations has been hampered by a lack of basic information regarding rainfall/runoff relationships at windrow composting sites. In this paper, a standard hydrologic model — the unit hydrograph method – is used to model the hydrology of a small, paved composting site. The model results compare well with field data collected at the site over a six month period. The volume of runoff predicted by the model was within 5% of the measured runoff volume for each of seventeen runoff events observed at the site over the study period. The results suggest that other industry standard hydrologic models can be adapted for use at open composting sites to account for the presence of large quantities of organic material on the site.  相似文献   

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