排序方式: 共有46条查询结果,搜索用时 0 毫秒
1.
2.
K Ashley S Wilson JR Young HP Chan S Vitou S Suon PA Windsor RD Bush 《Tropical animal health and production》2018,50(1):63-73
Forage technology has been successfully introduced into smallholder cattle systems in Cambodia as an alternative feed source to the traditional rice straw and native pastures, improving animal nutrition and reducing labour requirements of feeding cattle. Previous research has highlighted the positive impacts of forage technology including improved growth rates of cattle and household time savings. However, further research is required to understand the drivers, challenges and opportunities of forage technology for smallholder cattle households in Cambodia to facilitate widespread adoption and identify areas for further improvement. A survey of forage-growing households (n = 40) in July–September 2016 examined forage technology adoption experiences, including reasons for forage establishment, use of inputs and labour requirements of forage plot maintenance and use of forages (feeding, fattening, sale of grass or seedlings and silage). Time savings was reported as the main driver of forage adoption with household members spending approximately 1 h per day maintaining forages and feeding it to cattle. Water availability was reported as the main challenge to this activity. A small number of households also reported lack of labour, lack of fencing, competition from natural grasses, cost of irrigation and lack of experience as challenges to forage growing. Cattle fattening and sale of cut forage grass and seedlings was not found to be a widespread activity by interviewed households, with 25 and 10% of households reporting use of forages for these activities, respectively. Currently, opportunities exist for these households to better utilise forages through expansion of forage plots and cattle activities, although assistance is required to support these households in addressing current constraints, particularly availability of water, if the sustainability of this feed technology for smallholder cattle household is to be established in Cambodia. 相似文献
3.
"Tubules-Within-a-Tubule" Hierarchical Order of Mesoporous Molecular Sieves in MCM-41 总被引:1,自引:0,他引:1
The recently discovered mesoporous aluminosilicate MCM-41 consists of hexagonal arrays of nanometer-sized cylindrical pores. It is shown that this material can be synthesized by cooperative condensation of silicate and cylindrical cationic micelles. Careful control of the surfactant-water content and the rate of condensation of silica at high alkalinity resulted in hollow tubules 0.3 to 3 micrometers in diameter. The wall of the tubules consisted of coaxial cylindrical pores, nanometers in size, that are characteristic of those of MCM-41. The formation of this higher order structure may take place through a liquid crystal phase transformation mechanism involving an anisotropic membrane-to-tubule phase change. The hierarchical organization of this "tubules-within-a-tubule" particle texture is similar to that of the frustules of marine diatoms. 相似文献
4.
5.
The rapid expansion of the world’s urban population is a major driver of contemporary landscape change and ecosystem modification.
Urbanisation destroys, degrades and fragments native ecosystems, replacing them with a heterogeneous matrix of urban development,
parks, roads, and isolated remnant fragments of varying size and quality. This presents a major challenge for biodiversity
conservation within urban areas. To make spatially explicit decisions about urban biodiversity conservation actions, urban
planners and managers need to be able to separate the relative influence of landscape composition and configuration from patch
and local (site)-scale variables for a range of fauna species. We address this problem using a hierarchical landscape approach
for native, terrestrial reptiles and small mammals living in a fragmented semi-urban landscape of Brisbane, Australia. Generalised
linear modelling and hierarchical partitioning analysis were applied to quantify the relative influence of landscape composition
and configuration, patch size and shape, and local habitat composition and structure on the species’ richness of mammal and
reptile assemblages. Landscape structure (composition and configuration) and local-scale habitat structure variables were
found to be most important for influencing reptile and mammal assemblages, although the relative importance of specific variables
differed between reptile and mammal assemblages. These findings highlight the importance of considering landscape composition
and configuration in addition to local habitat elements when planning and/or managing for the conservation of native, terrestrial
fauna diversity in urban landscapes. 相似文献
6.
William J.M. Probert Cindy E. Hauser Eve McDonald-Madden Michael C. Runge Peter W.J. Baxter Hugh P. Possingham 《Biological conservation》2011,(4):1237-1245
The quality of environmental decisions should be gauged according to managers’ objectives. Management objectives generally seek to maximize quantifiable measures of system benefit, for instance population growth rate. Reaching these goals often requires a certain degree of learning about the system. Learning can occur by using management action in combination with a monitoring system. Furthermore, actions can be chosen strategically to obtain specific kinds of information. Formal decision making tools can choose actions to favor such learning in two ways: implicitly via the optimization algorithm that is used when there is a management objective (for instance, when using adaptive management), or explicitly by quantifying knowledge and using it as the fundamental project objective, an approach new to conservation.This paper outlines three conservation project objectives – a pure management objective, a pure learning objective, and an objective that is a weighted mixture of these two. We use eight optimization algorithms to choose actions that meet project objectives and illustrate them in a simulated conservation project. The algorithms provide a taxonomy of decision making tools in conservation management when there is uncertainty surrounding competing models of system function. The algorithms build upon each other such that their differences are highlighted and practitioners may see where their decision making tools can be improved. 相似文献
7.
Madeleine C. Bottrill Jessica C. Walsh James E.M. Watson Liana N. Joseph Alejandro Ortega-Argueta Hugh P. Possingham 《Biological conservation》2011,(5):1595-1601
Recovery planning is a key component of government-funded initiatives to address declining populations of threatened species. To date, there has been limited retrospective evaluation on the impact of recovery plans, despite an increasing interest in evaluating recovery planning motivated by demands for greater accountability and a shift away from single-species focused strategies to multi-species, landscape and ecosystem-based plans. In the context of threatened species management in Australia, we aimed to investigate whether listed species with recovery plans are more likely to have improved their status compared to listed species without recovery plans. Since 1999, over 600 draft and approved recovery plans have been developed for more than 850 of 1663 species currently listed threatened species in Australia. We applied a novel econometric matching analysis to reduce biases associated with the non-random selection of species for listing and recovery planning. We found that the presence or absence of a recovery plan did not have a statistically significant effect on whether a species’ status was improving, stable or declining. The result suggests that recovery plans may not be useful in the short term and uncertainty persists about whether or not they make a long term contribution to species recovery. One major contributing factor is the lack of basic accounting of recovery planning efforts. This limits our ability to refute or confirm the impact of recovery planning on species status, and has the potential to reduce public confidence in government expenditures. Better systems for reporting and evaluation are therefore required to promote transparency, improve existing knowledge and facilitate efficient investments in future management actions. 相似文献
8.
9.
Organisms living in the marine rocky intertidal zone compete for space. This, together with predation, physical disruption, and differing species tolerances to physiological stress, explains the structure of the ecological communities at some sites. At other sites the supply of larvae is limiting, and events in the offshore waters, such as wind-driven upwelling, explain the composition of intertidal communities. Whether the community ecology at a site is governed by adult-adult interactions within the site, or by limitations to the supply of larvae reaching the site, is determined by the regional pattern of circulation in the coastal waters. Models combining larval circulation with adult interactions can potentially forecast population fluctuations. These findings illustrate how processes in different ecological habitats are coupled. 相似文献
10.