首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   10篇
  免费   1篇
  2篇
综合类   1篇
水产渔业   1篇
畜牧兽医   6篇
植物保护   1篇
  2022年   1篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2013年   2篇
  2011年   1篇
  2009年   1篇
  2006年   1篇
  2004年   1篇
  1962年   1篇
排序方式: 共有11条查询结果,搜索用时 328 毫秒
1.
2.
3.
4.
5.
6.
Abstract  It is possible to use an ecosystem-based management approach to incorporate knowledge of climate regime impacts on ecosystem productivity to manage fishery resources. To do so, it requires the development of a coherent framework that can be built using existing stock assessment and management activities: ecosystem assessment, risk analyses, adaptive management and reference points. This paper builds such a framework and uses two population simulations to illustrate the benefits and tradeoffs of variable regime-specific harvest rates. The framework does not require prediction of regime shifts, but assumes that detection can occur soon after one has happened. As such, decisions do not need to be coincident to regime shifts, but can be delayed by an appropriate period of time that is linked to a species' life history, i.e. age of maturity or recruitment. Fisheries scientists should provide harvest recommendations that reflect a range of levels of risk to the stock under different assumptions of productivity. Coupling ecosystem assessment with ecosystem-based management would allow managers to select appropriate regime-specific harvest rates.  相似文献   
7.
We quantified livestock (cattle, shoats, horses and donkeys) losses to lions (Panthera leo) and attitudes to lions, livestock losses and tourism among livestock owners, village residents and tourism workers around Makgadikgadi Pans National Park in Botswana. Losses were not correlated with the size or structure of livestock enclosures, numbers of dogs or herders. Rather losses increased with the amount of livestock owned. Most were stray animals preyed upon at night. Attitudes to wildlife, conservation and lions were also not consistently distributed within the society we studied. Negative attitudes to lions were almost ubiquitous among cattleposts but less widespread among people living in the more urbanized society of villages or among people working in tourism.Although four tourist camps were operating in the area, benefits from these operations were largely limited to employees. Despite considerable sums of money being paid to Botswana by local tourist facilities few respondents viewed tourism as valuable and most felt that the government and not they or their community was the main beneficiary of tourism. Tourism employees made up a small sub-section of the adult population drawn predominately from larger villages while the costs of livestock losses were spread among cattleposts near the park boundary. These same cattlepost respondents were not prepared to improve stock care to protect livestock, but indicated a willingness to kill lions instead. If tourism is to play a role in reducing human–wildlife conflict, communities must not be regarded as homogenous entities into which to distribute benefits evenly. Benefits might usefully be distributed in relation to the costs of coexisting with wildlife or used as incentives to better protect livestock or other human resources.  相似文献   
8.
This study was the first to analyze the polymorphic characteristics of a wide range of genetic markers in three Lithuanian horse breeds. Genetic variation at seven red blood cell alloantigen (blood group) loci, 10 biochemical genetic loci and 16 microsatellites was examinated in 31 Zemaitukai, 30 large-type Zemaitukai and 24 Lithuanian Heavy Draught horse and compared to that of other domestic horse breeds. Genetic variability of the Zemaitukai breeds based upon blood groups and biochemical loci was higher than average for domestic horse breeds. For microsatellite loci, the variability of the large-type Zemaitukai and the Heavy Draught breeds also was high compared to the mean variation for domestic breeds; however, for the Zemaitukai breed, variation levels were very near the average for horses.  相似文献   
9.
In recent years there has been a veritable explosion in the use of genome editors to create site-specific changes, both in vitro and in vivo, to the genomes of a multitude of species for both basic research and biotechnology. Livestock, which form a vital component of most societies, are no exception. While selective breeding has been hugely successful at enhancing some production traits, the rate of progress is often slow and is limited to variants that exist within the breeding population. Genome editing provides the potential to move traits between breeds, in a single generation, with no impact on existing productivity or to develop de novo phenotypes that tackle intractable issues such as disease. As such, genome editors provide huge potential for ongoing livestock development programs in light of increased demand and disease challenge. This review will highlight some of the more notable agricultural applications of this technology in livestock.  相似文献   
10.
The influence of landscapes and vegetation types on soil aggregate stability was studied at 55 sites in rangeland and 18 sites in cropland in northeastern Syria. For the measurement of soil aggregate stability, the wet-sieving test was applied to air-dried and prewetted aggregates. As soil properties, pH, EC, organic carbon content, inorganic carbon content, sand content were determined. Slope gradients at all the sites and soil surface coverage at the sites in the rangeland were also determined. Due to the slaking process, the stability of air-dried aggregates with a mean value of 47.5 × 10-2 kg kg-1 was lower than that of prewetted ones with a mean value of 89.8 × 10-2 kg kg-1. The absence of a significant relationship between the soil aggregate stability and soil chemical properties in the cropland suggested the influence of tillage. Principal component analysis and stepwise multiple regression analysis for the sites in the rangeland indicated that the air-dried aggregate stability could be described by a coverage factor and slope factor (r=0.76). The contribution of the coverage factor suggested that the increase of the soil organic matter content through the addition of plant materials and protection of the soil surface from the raindrop impact could enhance the soil aggregate stability. The positive contribution of the slope factor implied that unstable aggregates on steeper slopes had already been translocated, while stable aggregates remained. Thus, for the preservation of the soil aggregate stability, the soil surface coverage should be improved especially on gentler slopes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号