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1.
The Solent, a large estuarine system on the central south coast of England, is an important wintering ground for the dark-bellied brent goose Branta bernicla bernicla: peak winter counts there rose from 300 in 1951–1952 to 23 000 in 1979–1980. Until 1973–1974 the geese remained in the intertidal zone, where they fed on eelgrass Zostera and green algae Enteromorpha and Ulva lactuca. The increase in goose number coincided with the spread of these plants in parts of the Solent. The spread of algae has been linked with increased discharges of sewage. However, only part of the annual production of Zostera and algae is available to geese because of autumn and winter die-back, storm damage and other factors.From 1973 to 1974 geese fed on permanent pasture, playing fields and autumnsown cereals, the last being especially important in 1978–1979 and 1979–1980. The evidence suggests that in some estuaries terrestrial feeding is increasingly attractive even though the intertidal zone could still sustain most of the goose-days spent in the area. The habit appears to be stimulated by large numbers of first winter birds in the population.The geese have evoked great public interest and generated concern for estuarine conservation. However, terrestrial feeding conflicts with farming. Nature conservation organisations have encouraged a policy of scaring from valuable crops by proven methods, whilst seeking to provide alternative terrestrial refuges.  相似文献   

2.
This paper analyses data on movements and distribution of barnacle geese Branta leucopsis over a period of 15 years to examine the influence of the enlargement of a disturbance-free refuge at Caerlaverock on the Solway Firth on the numbers, distribution and feeding habits of the geese. The Solway barnacle geese form the whole of the discrete population breeding in the Svalbard (Spitsbergen) archipelago.The use of the refuge by geese increased markedly following its establishment, and a high proportion of the birds were accomodated there, especially in early winter. As the population increased, however, (from 3200 in 1970 to 10 500 in 1984), the geese dispersed in greater numbers to other habitats within the Caerlaverock area and elsewhere on the Solway. The creation of the new refuge has been, as was the declaration of the National Nature Reserve in 1957, responsible for the increase in numbers through reducing annual mortality rate, much of which was due to illegal shooting.The most significant change in distribution was the increase in the use of arable grassland in spring and this was attributed to the semi-natural saltmarsh at Rockcliffe, the traditional spring haunt, reaching capacity. The use of stubble grain also increased, but its availability is sporadic due to variation in late summer weather.The creation and management of the refuge achieved the objectives of redistributing the geese and allowing numbers to increase. It was also, at least partly, responsible for bringing about changes in feeding habits. This analysis has demonstrated that if the impacts of refuge establishment are to be fully understood, studies must be detailed and must include areas outside the refuge itself and its immediate environs.Detailed concurrent investigations on the dynamics of this population indicate that the slowing down of growth in numbers is due to some limitation on the breeding grounds. Continued monitoring and sensitive management over the whole of the winter range are essential not only to ensure the well-being of the population but also to minimise the conflict between the geese and farmers. Detailed investigations of possible changes in the saltmarsh habitat are also urgently needed.  相似文献   

3.
Connell's ‘intermediate disturbance hypothesis’ was tested using a relatively simple, species poor isopod community in grass heaths and in a coastal sand dune grassland. Variation in diversity resulted from disturbance both to the soil profile and sward structure due to grazing. Predictions from a spatial survey were tested using a 20 years time series. These changes were related to changes in rabbit activity, anthropogenic soil disturbance and on one site, deposition of blown sand. Changes in the soil profile resulted in diversity initially increasing due to decreases in the density of the commonest species, leading to an increase in equitability. Prolonged disturbance to the soil profile both due to sand blowing onto one site and rotavating on another, lead to a reduction in diversity due to one of the species being eliminated. The isopod community was most diverse when least disturbed by grazing, of intermediate diversity under intermediate grazing intensity and least diverse when most heavily grazed. In these simple communities, differences in diversity were mostly determined by differences in equitability rather than in species richness. We conclude that maximising heterogeneity of sward structure could have advantages for the conservation of both invertebrate biodiversity and vertebrates that feed on them.  相似文献   

4.
Declines of farmland birds have been pronounced in landscapes dominated by lowland livestock production and densities of seed-eating birds are particularly low in such areas. Modern livestock production often entails a simple cropping system dominated by ley grassland and maize grown for animal feed. These crops often lack invertebrate and seed resources for foraging birds and can be hostile nesting environments. Cereal-based wholecrop silages (CBWCS) offer potential benefits for farmland birds because they can be grown with minimal herbicide applications and can be spring-sown with following winter stubbles. We compared the biodiversity benefits and agronomic yields of winter-sown wheat and spring-sown barley as alternatives to grass and maize silage in intensive dairy livestock systems. Seed-eating birds foraged mainly in CBWCS fields during summer, and mainly on barley stubbles during winter and this reflected the higher densities of seed-bearing plants therein. Maize and grass fields lacked seed-bearing vegetation and were strongly avoided by most seed-eating birds. Production costs of CBWCS are similar to those of maize and lower than those of grass silage. Selective (rather than broad-spectrum) herbicide application on spring barley crops increased forb cover, reduced yields (by 11%) but caused only a small (<4%) increase in production costs. CBWCS grown with selective herbicide and with following winter stubbles offer a practical conservation measure for seed-eating farmland birds in landscapes dominated by intensively-managed grassland and maize. However, the relatively early harvesting of CBWCS could destroy a significant proportion of breeding attempts of late-nesting species like corn bunting (Emberiza calandra) or yellow wagtail (Motocilla flava). Where late-breeding species are likely to nest in CBWCS fields, harvesting should be delayed until most nesting attempts have been completed (e.g. until after 1st August in southern Britain).  相似文献   

5.
I examined the direct and indirect effects of human activity on birds at a coastal bay refuge along the Atlantic Coast. Over the year, human activity varied at different sample sites on the refuge, but people were present on part of the refuge every day, although activity was concentrated on designated paths around a freshwater pond and at a fishing pier. On the refuge (exclusive of the ponds) people were present at the sample sites 17% of the time, birds were present 42% of the time when people were present, but birds were present 72% of the time when people were absent. Human activities, such as jogging or grass mowing, which involved rapud movement or close proximity to roosting birds, usually caused them to flush. Slow-walking bird watchers and clammers did not usually cause birds to flush. Gulls and terns were least affected as they usually relanded where they had been, ducks usually flushed and flew to the centre of the pond, and herons, egrets and shorebirds were most disturbed and flushed to distant marshes. These results suggest that if management objectives include providing roosting areas for migrating shorebirds then some areas must be protected from close and fast-moving human activities.  相似文献   

6.
Herbage growth and nitrogen (N) use efficiency in grazed or mown grasslands are generally low, associated mostly with poor response to fertilizer N. The aim of the present investigation was to examine the short-term response of grass to fertilizer N with respect to herbage yield and nitrogen use efficiency (NUE) in order to provide a better basis for improving the efficient use of fertilizer N in grassland ecosystems. Both NO3 ? and NH4 + sources of N were applied to an established grass sward with three moisture levels, i.e., natural conditions (63% water-filled pore space, WFPS), near field capacity level (71% WFPS), and slightly wetter than field capacity (84% WFPS). Herbage yield, i.e., dry matter (DM), N uptake, N recovery efficiency, yield efficiency, and physiological efficiency were determined over a 7–28 d period. Addition of N fertilizers significantly increased the herbage yield and N uptake of grass sward over that of the control. In the plots where NO3 ??N was added as the N source, DM yield was between 1760–1870 kg ha?1, N recovery efficiency was between 24%–43%, and yield and physiological efficiency were in the range of 2.1–3.2 and 6.4–8.8 kg DM kg? 1 N, respectively. In NH4 +?N added plots, the DM yield was between 3190–3700 kg ha? 1, N recovery efficiency was between 39%–48% while yield and physiological efficiency were in the range of 3.5–5.6 and 9.0–11.6 kg DM kg? 1 N, respectively. Results indicated that total DM yield, N uptake, and NUE depend on the source of N and the level of moisture in the field. Assimilation of N is also affected by the stage of plant development after N fertilization. About 50%–54% of applied N was recovered in the initial 14 and 21 d after fertilizer application and thereafter translocation of N slowed. A fall in herbage production and minimal response to N fertilizer has been observed at 84% WFPS, while the maximum herbage yield and N recovery efficiency was recorded in soil near or below field capacity. The grass sward with added NH4 +?N produced a larger yield and had higher NUE relative to the sward with NO3 ??N. Results confirm that applied N was not utilized efficiently by grass sward and a decrease in N uptake and its utilization seem to be the key factors responsible for the poor herbage productivity often observed in pastoral agriculture. These results suggest that both moisture and N source have a substantial effect on herbage yield and N utilization by plants and therefore should be considered for efficient management of N fertilization and recommendations for grass sward.  相似文献   

7.
Abstract. Formulation of nitrogen balances on farms requires accurate information on all inputs of the nutrient. N2-fixation by legumes, particularly forage legumes, is an important input which is difficult to measure. Simple regression models have been established from the literature for predicting N2-fixation by grass–white clover ( Trifolium repens ) mixtures using dry matter yields.
Linear relationships were obtained between the N2- fixation (Nfix) and the extra dry matter production of mixed swards (Md) compared with pure grass swards. Nitrogen fixation was given by Nfix= A + 0.067Md where A is the intercept having a value of 6.8 for cut swards and -168.1 for grazed swards. A common slope was adopted because the F statistics showed that slopes fitted separately were not significantly different. The value of the negative intercept represents the supply of N to the grazed sward from soil and excreta-derived N. The regression equation for the cut sward gave reasonable predictions (r2= 0.953) of values of N2-fixed for experimental data not used in establishing the relationship. For grazed grass, the approach over-estimated the N2- fixation by an average of 15%.  相似文献   

8.
As most species of geese have increased their numbers in the past 15 years, additional refuges are not needed at present to conserve goose stocks. During this period there have been increasingly frequent claims of agricultural damage and various methods are used and proposed for alleviating the conflict between farmers and geese. Most traditional methods are relatively ineffective in the long term or are prohibitively expensive. It is suggested that the creation of a network of refuges to accommodate geese potentially in conflict with agriculture is the best long-term solution.Examination of existing refuges shows that good management can result in doubling of the ‘carrying capacity’ of pasture, and that the birds can be successfully lured from surrounding farmland. It is calculated that about 7500 ha of well managed refuge would be required to accommodate the 140,000 geese which cause agricultural problems, over the critical period.  相似文献   

9.
Dramatic declines in the endangered Columbia Basin pygmy rabbit, a genetically unique population of small, burrowing rabbits in Northwestern United States, are likely the combined results of habitat degradation and fragmentation, disease, and predation. A critical component of pygmy rabbit habitat includes big sagebrush (Artemisia tridentata), which constitutes 82-99% of their winter diet and 10-50% of their summer diet. Sagebrush also forms the bulk of hiding cover around burrow sites. Across the range of pygmy rabbits, sagebrush habitat is grazed extensively by cattle. However, grazing has unknown effects on pygmy rabbits inhabiting the remaining, fragmented shrub-steppe habitat. We evaluated the effects of four grazing treatments on the distribution of pygmy rabbit burrows, diets of pygmy rabbits, and quality and quantity of vegetation at Sagebrush Flat in central Washington. Ungrazed areas contained significantly more burrows per unit area than did grazed areas. Vegetation composition and structure differed little among treatments in early summer before annual grazing by cattle. However, cattle grazing in late summer through winter removed about 50% of the grass cover, and reduced the nutritional quality (e.g., increased fiber and decreased protein) of the remaining grass. Although pygmy rabbits ate <2% grasses in winter, grasses and forbs comprised 53% of late summer diets. Because these endangered rabbits avoided grazed areas, removing cattle grazing from key habitat locations may benefit efforts to restore this rabbit in Washington.  相似文献   

10.
Habitat remnants on urban green-space areas (i.e. parks, gardens and golf courses) sometimes provide refuge to urban-avoiding wildlife, leading some to suggest these areas may play a role in wildlife conservation if they are appropriately designed and managed. The high densities observed on some green-space areas may however be attributed to external influences. Localised efforts to enhance the habitat value of urban green-space areas may therefore have little more than a cosmetic effect. This study investigated environmental factors influencing bird, reptile, mammal and amphibian diversity on Australian golf courses to assess the efficacy of small-scale conservation efforts. Abundance and species richness did not simply reflect local habitat qualities but were instead, partly determined by the nature of the surrounding landscape (i.e. the area of adjacent built land, native vegetation and the number of connecting streams). Vertebrate abundance and species richness were however, also associated with on-site habitat characteristics, increasing with the area of native vegetation (all vertebrates), foliage height diversity and native grass cover (birds), tree density, native grass cover and the number of hollows (mammals), woody debris, patch width and canopy cover (reptiles), waterbody heterogeneity and aquatic vegetation complexity (frogs). Localised conservation efforts on small land types can benefit urban-avoiding wildlife. Urban green-space areas can provide refuge to urban-avoiding vertebrates provided combined efforts are made at patch (management), local (design) and landscape (planning) scales.  相似文献   

11.
A method was developed using high-performance liquid chromatography to assay 4,4'-dinitrocarbanilide (DNC), the active ingredient in Nicarbazin, in eggshells collected from Canada geese fed a formulated feed fortified with Nicarbazin at doses of 0, 125, 250, and 500 microg/g. The method was developed using chicken eggshells fortified with DNC. The method was used to quantify DNC in both the shell-associated membranes and the calcified shell extracellular matrix. These values were compared to those obtained for a composite sample consisting of both the membranes and the calcified shell extracellular matrix. The validated method was used to quantify DNC in eggshells from geese fed fortified feed to ascertain the effect of Nicarbazin feed concentration on shell DNC concentration. DNC levels in the eggshells were highly correlated with feed dose.  相似文献   

12.
本试验选用216只1日龄东北肉鹅,采用四因素三水平L9(34)正交试验设计,探讨0-28日龄东北肉鹅日粮代谢能、粗蛋白、钙和非植酸磷水平对东北肉鹅生长性能、部分血液生化指标及激素水平的影响。结果表明：日粮代谢能水平极显著影响肉鹅的日增重、采食量及料肉比( P < 0.01),粗蛋白显著影响料肉比( P < 0.05)。能量水平对高密度脂蛋白(HDL)、低密度脂蛋白(LDL)和胆固醇(CHO)含量影响显著( P < 0.05),对尿酸的影响极显著( P < 0.01);肉鹅日增重与T3呈较强的正相关,能量水平显著影响血清生长激素(GH)、胰岛素样生长因子-1(IGF-1)的含量( P < 0.05),并且日增重与血清中GH和IGF-1的含量、GH与IGF-1的含量呈显著的正相关。  相似文献   

13.
[目的]探究锡林郭勒草地在景观尺度上土壤容重空间分布规律及其与风蚀的关系,为有效进行草原风蚀防治提供理论参考。[方法]对锡林郭勒草原不同地形和土地利用条件下土壤容重的空间变异性进行调查分析,主要采用环刀法、吸管法、TOC法测定土壤容重、机械组成和有机碳含量。[结果]锡林郭勒草原土壤容重呈现中等空间变异性;容重随地形变化在轻牧区表现为:迎风坡背风坡平地,而在中牧和重牧区的变化与之相反,且海拔与容重呈负相关性;在同样地形条件下,不同土地利用容重变化规律为:重牧区耕地中牧区轻牧区禁牧区。[结论]研究区土地利用类型是影响容重最主要的因素。容重与风蚀速率呈现明显的负相关性,容重可作为评估本区域风蚀发生与影响强度的一个重要参考指标。  相似文献   

14.
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15.
This project aimed to investigate the release of mineral N following the ploughing of clover-rich and grass-dominated swards, previously subject either to cutting or grazing regimes. The hypotheses tested were firstly that N mineralisation and losses following incorporation of grass-clover swards are greater than from grass swards, and secondly that N mineralisation and losses following incorporation of previously grazed swards are greater than from previously cut swards. Following ploughing of previously grazed swards in 1992 and swards that had been subjected to an unfertilised, ungrazed regime in 1993, N uptake, N leaching losses (measured by soil solution samplers with drainage estimation from a nearby experiment) and N2O losses (measured by the closed chamber method) were determined on both resown and fallow plots. Results showed: (1) higher N release after ploughing from the grass-fallow treatment (449 kg N ha-1) than from the grass-clover fallow treatment (244 kg N ha-1) over 18 months; (2) the net release of N after ploughing and reseeding, compared with a continued unfertilised sward, was about 85 kg ha-1 for the grass-clover plots and 140 kg ha-1 for the grass-only plots, over the following 18 months. Of this, the net releases in the second cropping season after incorporation were 19 and 25 kg N ha-1 on the resown grass-clover and grass-only plots, respectively; (3) the net release of mineral N after ploughing in 1993/1994, when swards had not been grazed for over a year, was only about 40 kg ha-1 and no effect of the previous sward was evident; (4) in the 7 weeks after the 1992 ploughing, there was a considerable short-term input of N2O to the atmosphere (1.5-3.7 kg N ha-1), due to the supply of readily available C. Leaving swards ungrazed and unfertilised over winter before ploughing in spring has the potential to reduce such emissions considerably. We conclude that N release following cultivation of grazed swards is more a function of grazing intensity and history prior to ploughing rather than of sward composition.  相似文献   

16.
Increasing grazing intensities of sheep and goats can lead to an increasing degradation of grasslands. We investigated four plots of different grazing intensities (heavily grazed, winter‐grazed, ungrazed since 1999, and ungrazed since 1979) in Inner Mongolia, PR China, in order to study the effects of trampling‐induced mechanical stresses on soil hydraulic properties. Soil water transport and effective evapotranspiration under “heavily grazed” and “ungrazed since 1979” were modeled using the HYDRUS‐1D model. Model calibration was conducted using data collected from field studies. The field data indicate that grazing decreases soil C content and hydrophobicity. Pore volume is reduced, and water‐retention characteristics are modified, the saturated hydraulic conductivity decreases, and its anisotropy (vertical vs. horizontal conductivity) is influenced. Modeling results revealed higher evapotranspiration on the ungrazed site (ungrazed since 1979) compared to the grazed site (heavily grazed) due to wetter soil conditions, more dense vegetation, litter cover, and decreased runoff and drainage, respectively. Grazing modified the partitioning of evapotranspiration with lower transpiration and higher evaporation at the grazed site owing to reduced root water uptake due to reduced evaporation and a patchy soil cover.  相似文献   

17.
A key point in designing grass‐arable rotations is to find the right balance between the number of cultivations and the length of the grass phase. In a field experiment, we investigated the effect of cropping history (grazed unfertilized grass–clover and fertilized [300 kg N per hectare] ryegrass, proportion of grassland and previous fertilizer use) on crop growth and nitrate leaching for 2 years following grassland cultivation. In the final year, the effect of perennial ryegrass as a catch crop was investigated. The nitrogen fertilizer replacement value (NFRV) of grassland cultivation was higher at 132 kg N per hectare in the rotation with 75% grassland compared with on average 111 kg N per hectare in rotations with 25 and 38% grassland and the NFRV of ryegrass in the rotation was higher than that of grass–clover. Nitrate leaching following cultivation was not affected by the proportion of grassland in the crop rotation or sward type. However, there was a considerable effect of having a ryegrass catch crop following the final barley crop as nitrate leaching was reduced from 60 to 9 kg N per hectare. When summarizing results from the crop rotations over a longer period (1997–2005), management strategy adopted in both the grassland and arable phases appeared to be the primary instrument in avoiding nutrient losses from mixed crop rotations, irrespective of grass proportion. In the arable phase, the huge potential of catch crops has been demonstrated, but it is also important to realize that all parts of the grass‐arable crop rotations must be considered potentially leaky.  相似文献   

18.
The objective of this study was to assess the extent of lead pellet ingestion by British wildfowl, particularly ducks and geese, and to examine regional variations. The gizzard contents of 2445 shot and 238 found-dead birds were examined, and lead concentrations were determined for 1620 liver and 1841 wing bone samples. In addition, X-ray photographs and blood samples were taken from live-caught birds. Ingested lead pellets were found in 3·2% of the birds examined. For a range of species, including pink-footed goose, white-fronted goose, barnacle goose, wigeon, teal, pintail, shoveler, scaup and moorhen, recorded incidences were either very low or zero. Relatively high incidences were noted for swans, greylag goose (7·1% of shot birds), gadwall (11·8%), mallard (4·2%), pochard (10·9%), tufted duck (11·7%) and goldeneye (6·7%). Most ingested pellets originated from shotguns, though anglers' split shot were found in one pochard and four mute swans. A marked seasonal variation in the extent of pellet ingestion was noted for mallard, with a peak in September, and evidence of high levels immediately before and after the shooting season. Pellet ingestion by mallard was found to be of widespread occurrence, though with considerable variation in recorded incidence from place to place. Inland areas tended to be worse, with the highest incidences recorded for birds shot at flight ponds and other freshwater bodies. Six per cent of mallard shot at inland sites contained ingested pellets, compared with 2·6% of those collected from coastal areas. The observed extent of pellet ingestion in British mallard is calculated directly to cause the death of at least 8000 each winter. Some measures that could be taken to alleviate the lead-poisoning problem in Britain are discussed, and progress of the USA's non-toxic pellet programme is examined.  相似文献   

19.
黄土旱塬塬面生态系统土壤硝酸盐累积分布特征   总被引：9，自引：5，他引：9  
研究了渭北旱塬塬面不同土地利用方式下土壤剖面硝酸盐含量与分布特征,并与长期田间定位试验结果进行对比分析。结果表明,地表有植物生长与氮肥投入显著影响土壤剖面硝态氮含量与分布。土壤0-400.cm硝态氮累积含量顺序是:苹果园高产粮田裸地刺槐林地荒草地人工草地。苹果园土壤剖面硝态氮在深层累积严重,累积层在80-160.cm,最高含量达201.9.mg／kg。高产农田也发生了硝态氮的淋溶累积,累积峰出现在120-140cm土层,最高含量为44.1.mg/kg。林草地因为没有氮肥投入,剖面硝态氮含量处于很低水平。由于塬面土地大部分为高产农田与苹果园,土壤中累积的大量硝态氮既浪费了资源又可能对环境造成潜在的威胁,建议降低氮肥用量,特别是果园,并建议对大量施用化肥对区域生态环境与苹果品质的影响进行研究。  相似文献   

20.
Raptors that consume game species may ingest lead fragments or shot embedded in their prey’s flesh. Threatened Spanish imperial eagles Aquila adalberti feed on greylag geese in southern Spain in winter, and often ingest lead shot. We analysed bone and feather samples from 65 Spanish imperial eagle museum specimens collected between 1980 and 1999, to investigate the prevalence of elevated lead concentrations. Four of 34 birds (12%) had very elevated bone lead concentrations. All four birds were young and the concentrations were outliers to the distribution, suggesting probable exposure to lead gunshot. Excluding these elevated lead outliers, bone lead concentrations were correlated with the bird’s age at death. Three of 41 feathers (7%) had elevated lead concentrations, indicative of high exposure during feather formation. When these outliers were omitted, feather lead concentration was correlated with the age of museum specimens, suggesting that a high proportion of feather lead was exogenous, deposited after specimen collection. Therefore, careful interpretation of feather lead concentrations is required to separate endogenous and exogenous lead. We discuss the potential significance of lead poisoning in Spanish imperial eagles and other raptors, and recommend measures for its reduction.  相似文献   

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