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81.
A new, higher dam was installed at Kerkini Reservoir in 1982, causing habitat and landscape disruption. A decrease in the
area of grassland and shallow water areas, the rapid disappearance of reedbeds, the appearance of beds ofNymphaea, and the disappearance of half the forest area were all observed between 1982 and 1991. With the new hydrological regime,
a lacustrine system was created, with an extensive, rather deep (4–8 m), pelagic zone favorable for the development of coarse
fish species throughout the year. After 1982, an increase in fishing effort and a change in the relative abundance of fish
species in the catch, including the disappearance of eels and wels, were observed. The impact of the rise in the water level
of breeding aquatic birds led to a general decline in species typical of marshy habitats in favor of species preferring deeper
open water habitats. A decrease was recorded in bird species that feed largely on invertebrates and to a lesser extent fish
(e.g., glossy ibis) and that require extensive shallow feeding areas. There was a decline in geese, whose nests were regularly
flooded, and a major increase in piscivorous birds, particularly diving birds (e.g., cormorants), which prefer deeper open
water and benefitted directly from the large increase in coarse fish biomass. The disappearance of birds breeding in flooded
meadows (e.g., black-winged stilts) and of those restricted to reedbeds (e.g., marsh harrier) occurred from 1983. Over the
same period, the changes in populations of wintering birds at Kerkini were different from those occurring in other wetlands
in northern Greece. The changes recorded in the populations of wintering birds at Kerkini did not therefore result from overall
regional trends but from the major habitat modifications that occurred to this wetland. As for breeding birds, strictly piscivorous
species increased greatly as a result of the increased availability of fish, but also due to the appearance of many suitable
night roosting sites (flooded trees) and to the great increase in the area of open water greater than 2 m deep. Today, Kerkini
has become the most important breeding site in Greece for a majority of colonial waterbirds. In contrast, wintering shorebirds
practically disappeared. The many changes recorded in the status of breeding and wintering birds at Kerkini can mostly be
explained by the changes that occurred in the functioning of the ecosystem and in the habitat structure following the inauguration
of the new hydrological regime. These changes did not all occur at the same time: some were immediate and others required
a delay before they could be detected. 相似文献
82.
Effects of cattle grazing and haying on wildlife conservation at National Wildlife Refuges in the United States 总被引:1,自引:0,他引:1
Beverly I. Strassmann 《Environmental management》1987,11(1):35-44
The National Wildlife Refuge System is perhaps the most important system of federal lands for protecting wildlife in the United States. Only at refuges has wildlife conservation been legislated to have higher priority than either recreational or commercial activities. Presently, private ranchers and farmers graze cattle on 981,954 ha and harvest hay on 12,021 ha at 123 National Wildlife Refuges. US Fish and Wildlife Service policy is to permit these uses primarily when needed to benefit refuge wildlife. To evaluate the success of this policy, I surveyed grassland management practices at the 123 refuges. The survey results indicate that in fiscal year 1980 there were 374,849 animal unit months (AUMs) of cattle grazing, or 41% more than was reported by the Fish and Wildlife Service. According to managers' opinions, 86 species of wildlife are positively affected and 82 are negatively affected by refuge cattle grazing or haying. However, quantitative field studies of the effect of cattle grazing and haying on wildlife coupled with the survey data on how refuge programs are implemented suggest that these activities are impeding the goal of wildlife conservation. Particular management problems uncovered by the survey include overgrazing of riparian habitats, wildlife mortality due to collisions with cattle fences, and mowing of migratory bird habitat during the breeding season. Managers reported that they spend $919,740 administering cattle grazing and haying; thus refuge grazing and haying programs are also expensive. At any single refuge these uses occupy up to 50% of refuge funds and 55% of staff time. In light of these results, prescribed burning may be a better wildlife management option than is either cattle grazing or haying. 相似文献
83.
84.
Woo-Jung Choi Gwang-Hyun Han Sang-Mo Lee Goon-Taek Lee Kwang-Sik Yoon Soo-Myung Choi Hee-Myong Ro 《Agriculture, ecosystems & environment》2007,120(2-4):259-268
An understanding of the long-term changes in the nitrate contamination pattern of unconfined groundwater is critical to conservation of drinking water in rural areas supporting mixed land-use activities such as cropping, livestock farming, and residence. To examine the effect of different land-use activities on nitrate contamination, groundwater samples were collected monthly for 3 years (1997–1999) from 12 wells in rural areas with different land-use activities and analyzed for the concentrations and N isotopic ratios (δ15N) of nitrate. The characteristics of nitrate contamination clearly differed with land-use activities. The percentages of samples that had a nitrate concentration exceeding the national standard for drinking water (10 mg N L−1) were 0, 23, 43, and 67% for the uncontaminated natural area, cropping area, cropping-livestock farming complex area, and residential area, respectively. The range of δ15N values was between +1.4 and +4.5‰ for groundwater nitrate from the uncontaminated natural area. In the cropping area, the δ15N values were slightly different with the type of fertilizer applied to fields in the vicinity of the well, and the values ranged between +8.7 and +14.4‰ for the compost-applied area and between +4.5 and +8.5‰ for the area where urea was applied with compost. The δ15N values of the cropping-livestock farming complex area ranged from +1.0 to +17.7‰, probably resulting from mixed contamination sources (inorganic fertilizer and livestock manure). The well located closest to the livestock feedlot had relatively higher δ15N values, with a range between +8.7 and +17.6‰. In the residential area, a higher δ15N (most frequently above +10‰) of nitrate suggested that the major source of contamination was effluent from leaky septic tanks. Our data showed that unconfined groundwater is susceptible to land-use activities above the aquifers, and the impacts of the activities could be more precisely inferred from long-term data on the concentration and δ15N of nitrate. By determining the impacts, more effective (specific to contamination sources) measures for preventing groundwater quality could be implemented. 相似文献
85.
MARKKU T. KUITUNEN JOHANNA VILJANEN ESKO ROSSI ARTO STENROOS 《Environmental management》2003,31(1):0079-0085
The impact of dense traffic on the breeding success in pied flycatchers (Ficedula hypoleuca) was studied using roadside nest-boxes. Nest site selection and breeding success of flycatchers were observed in relation
to the distance from the road. The number of occupied territories was no higher closer to the road than it was deeper inside
the forest. The distance to the road had no effect on the laying date, clutch size, or brood size. However, nests closer to
the road were more likely to fail at the chick stage. The number of broods that were closer to roads and were lost completely
was significantly higher than those further away. As a consequence, the number of fledglings per breeding attempt decreased
closer to roads. The nestlings typically died as older chicks when the parent birds were providing them with maximum quantities
of food. A possible reason for the declining reproductive success was the traffic-related mortality of parent birds, as weather
conditions were not especially adverse for raising healthy offspring. 相似文献
86.
87.
This paper introduces a new portable intelligent electronic nose system developed especially for measuring and analysing livestock
and poultry farm odours. It can be used in both laboratory and field. The sensor array of the proposed electronic nose consists
of 14 gas sensors, a humidity sensor, and a temperature sensor. The gas sensors were especially selected for the main compounds
from the livestock farm odours. An expert system called “Odour Expert” was developed to support researchers’ and farmers’
decision making on odour control strategies for livestock and poultry operations. “Odour Expert” utilises several advanced
artificial intelligence technologies tailored to livestock and poultry farm odours. It can provide more advanced odour analysis
than existing commercially available products. In addition, a rank of odour generation factors is provided, which refines
the focus of odour control research. Field experiments were conducted downwind from the barns on 14 livestock and poultry
farms. Experimental results show that the predicted odour strengths by the electronic nose yield higher consistency in comparison
to the perceived odour intensity by human panel. The “Odour Expert” is a useful tool for assisting farmers’ odour management
practises.
Supported by Ontario Pork, Natural Sciences and Engineering Research Council (NSERC), and Ontario Ministry of Agriculture
and Food (OMAF) of Canada. 相似文献
88.
89.
岫玉产业是我国辽宁省岫岩满族自治县的特色产业和县域经济的支柱产业。由于岫玉产业生产原材料的稀缺性、独特性和不可再生性而成为国宝级的产业。近年来,岫玉产业的发展出现了过度开采、过度加工和无序竞争,导致岫玉产品贬值,盲目扩大产业规模带来了规模报酬递减。针对岫玉产业发展中的诸多问题,运用经济学的理论加以分析,提出岫玉产业可持续发展的政策性对策与建议。 相似文献
90.
V. K. Garg Y. K. Yadav Aleenjeet Sheoran Subhash Chand Priya Kaushik 《The Environmentalist》2006,26(4):269-276
In India, millions of tones of livestock excreta are produced. Our study explores the potential of an epigeic earthworm Eisenia foetida to compost different livestock excreta (cow, buffalo, horse, donkey, sheep, goat and camel) into value added product (vermicompost)
at the laboratory scale. Vermicomposting resulted in lowering of pH, electrical conductivity, potassium and C:N ratio and
increase in nitrogen and phosphorus contents. Total K was lower in the final cast than in the initial feed. C:N ratios of
the vermicomposts ranged from 16.2 ± 2.17 to 75.4 ± 6.84. Microbial activity measured as dehydrogenase activity in buffalo,
donkey and camel wastes increased with time up to day 90. But in sheep and goat wastes, maximum dehydrogenase activity was
recorded on day 60 and decreased thereafter. The cocoons and hatchlings production by Eisenia foetida in different excreta were also investigated. The greatest number and biomass of hatchlings was recorded in horse excreta
followed by cow, goat and sheep excreta. Thus, cow, horse, sheep and goat excreta show potential as good substrates in vermicomposting
using Eisenia foetida, although further research is required to explore the feasibility of use of buffalo, donkey and camel excreta in combination
with cow/sheep/goat excreta. 相似文献