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371.
We examined the impact of single-tree selective logging and fuel reduction burns on the abundance of hollow-nesting bird species at a regional scale in southeastern Queensland, Australia. Data were collected on species abundance and habitat structure of dry sclerophyll production forest at 36 sites with known logging and fire histories. Sixteen bird species were recorded with most being resident, territorial, obligate hollow nesters that used hollows that were either small (<10 cm diameter) or very large (>18 cm diameter). Species densities were typically low, but combinations of two forest management and three habitat structural variables influenced the abundances of eight bird species in different and sometimes conflicting ways. The results suggest that habitat tree management for biodiversity in production forests cannot depend upon habitat structural characteristics alone. Management histories appear to have independent influence (on some bird species) that are distinguishable from their impacts on habitat structure per se. Rather than managing to maximize species abundances to maintain biodiversity, we may be better off managing to avoid extinctions of populations by identifying thresholds of acceptable fluctuations in populations of not only hollow-nesting birds but other forest dependent wildlife relative to scientifically valid forest management and habitat structural surrogates.  相似文献   
372.
We conducted field surveys and laboratory analyses to test the effects of soil characteristics in habitat mitigation sites and natural sites on the growth and condition of blue elderberry (Sambucus mexicana), which is the sole host plant for the federally threatened Valley elderberry longhorn beetle (Desmocerus californicus dimorphus). Thirty mitigation and 16 natural sites were selected throughout the range of the beetle. We found that although plant relative growth rates were comparable between mitigation sites and a natural site, mitigation sites contained substantially less soil nutrients than mitigation sites. Within mitigation sites, elderberry health and growth were positively correlated with the amount of total nitrogen in soils and less strongly with other soil nutrients and soil moisture. Analyses demonstrated reductions in the relative growth rate of elderberry as mitigation sites aged, and that soil nutrients and soil moisture became depleted over time. For mitigation sites, it took approximately seven years to develop basal stem diameters that have been linked to successful beetle colonization. Mitigation sites have smaller shrubs than natural sites and growth slows as mitigation sites age, thus delaying convergence of conditions between natural and mitigation sites. Analyses of soil particle size and whether sites were within the 100-year floodplain (as an indicator of riparian conditions) were inconclusive. We recommend investigating fertilizing and optimum planting densities for elderberry at restoration and mitigation sites, as well as increasing the duration of irrigation and monitoring.  相似文献   
373.
Analysis tools that combine large spatial and temporal scales are necessary for efficient management of wildlife species, such as the burrowing owl (Athene cunicularia). We assessed the ability of Ripley’s K-function analysis integrated into a geographic information system (GIS) to determine changes in burrowing owl nest clustering over two years at NASA Ames Research Center. Specifically, we used these tools to detect changes in spatial and temporal nest clustering before, during, and after conducting management by mowing to maintain low vegetation height at nest burrows. We found that the scale and timing of owl nest clustering matched the scale and timing of our conservation management actions over a short time frame. While this study could not determine a causal link between mowing and nest clustering, we did find that Ripley’s K and GIS were effective in detecting owl nest clustering and show promise for future conservation uses.  相似文献   
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375.
Anarchy, where honeybee workers produce males in the presence of a queen, is extremely rare in natural honeybee populations, suggesting that there are colony-level costs associated with being anarchistic. Yet, no significant costs have yet been identified. A possible reason for this may be that researchers have only focused on the behaviour of anarchistic workers, which have been shown to perform worker-tasks as do wild-type workers. Possibly, therefore, costs associated with anarchy should be sought in anarchistic queens and not workers. A potential cost could be a lower survival rate of eggs laid by anarchistic queens perhaps because their egg-marking signal is not as clear as that of a wild-type queen. In this paper, we determined the removal rate of eggs laid by anarchistic queens in standard worker-policing bioassays. Our results show that eggs laid by anarchistic queens are removed at a higher rate than eggs laid by wild-type queens. This does not seem to be due to differences in hydrocarbons found on the surface of eggs, as both egg types showed the same alkanes and alkenes in similar proportions. We postulate that higher removal rates of queen-laid eggs due to recognition errors may be one reason that anarchy is rare in natural honeybee populations.  相似文献   
376.
This paper investigates the structure, function and wealth distribution within the Pangasius hypophthalmus and Henicorhynchus spp./Labiobarbus spp. value chains in the Mekong Delta of Vietnam. The analysis is driven by key questions relating to the form and function of value chains, their contribution to the livelihoods of farmers and fishers, the effectiveness of government policy and the potential for value chain governance mechanisms, such as contracts and certification, to steer towards sustainable production. The results indicate that actors in the high value Pangasius hypopthalmus export chain have a higher potential income, but face considerably higher economic vulnerability from global markets. Alternatively, Henichorhychus/Labiobarbus spp. fishers are severely constrained in their ability to negotiate higher prices for their fish but appear to be less vulnerable to economic and environmental change. The paper concludes that for value chain governance to improve the livelihoods of fishers and farmers in both high and low value chains, new arrangements are needed that better accommodate customary institutions and informal market relations.  相似文献   
377.
Research into national innovation systems (NISs) has received extensive academic and policy attention, and is especially relevant with latecomer countries seeking to innovate in challenging industrial environments. In playing catch up with their early industrializing counterparts, methods of learning take on increased importance in determining industrial success for latecomers. The wind turbine technology innovation system is one that is highly dependent on both the extent of the national learning processes and the strength of the national social-institutional setting. This research investigates the case of Taiwan, a country which has embarked on a program to build its national innovative capacity in wind turbine technologies with specific emphasis on Taiwan’s social sector. Within this system, the spotlight will be on four types of learning processes that interplay during wind turbine development: learning by searching, learning by doing, learning by using, and learning by interacting. Through a case study of the emergence of Taiwan’s burgeoning large-scale wind power technology initiatives, the paper aims to add to the understanding on how methods of learning impact upon the success of innovation systems. The findings show that the industry’s future prospects are constrained because of the limited learning by interacting processes between turbine component producers, turbine owners, and researchers and because of weaknesses in the institutional framework. This research also recognizes the importance that culture has on dominant forms of learning.  相似文献   
378.
While the role Aboriginal people play in environmental governance programs are often underpinned by the Crown, Aboriginal peoples are ratifying negotiated agreements with mining proponents to ensure their issues and concerns are addressed. This paper examines Aboriginal participation in mine development to show how more inclusive social and environmental development models can support a more sustainable development. Through two complementary processes, negotiated agreements and environmental impact assessment, Aboriginal peoples are maximizing their benefits and minimizing the adverse impacts of a project to create a more sustainable resource development. Case study analysis of the Galore Creek Project in northwestern British Columbia, Canada, illustrates how environmental impact assessment and negotiated agreements can co-exist to positively contribute to a successful mineral development, and hence operationalize sustainability within this context.  相似文献   
379.
Developed countries are major markets for developing country fresh produce. Demand by developed country consumers for spotless produce has encouraged developing country consumers to rely increasingly on pesticides in producing fresh export vegetables. However developed country pesticide standards enacted in response to reports of increased farmer and farm worker pesticide poisoning and the food safety scandals of the 1980s and 1990s require changes in the way growers use pesticides. The EU has especially developed stringent food safety standards relating to, among other things, pesticide usage. Under EU pesticide standards (EU-PS) farmers are trained by their buyers on safe use of pesticides and then closely monitored under contract. This paper looks at the impact of these standards on developing country farmers’ use of alternative pest management practices, pesticide protective clothing and the actual usage of pesticides. It finds that compliance with EU-PS increases the use of alternative pest management practices and protective clothing. However, EU-PS has mixed effect on the quantity of pesticides used. The paper also finds that farmer’s education and access to information play an important role in the use of alternative pest management practices. The paper concludes that EU-PS encourage the use of alternative pest management practices and pesticide protective gear in production of fresh export vegetables. The findings imply that EU-PS promote environmentally-friendly methods of production of fresh export vegetables in developing countries.  相似文献   
380.
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