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41.
Pregitzer KS Zak DR Talhelm AF Burton AJ Eikenberry JR 《Ecology》2010,91(12):3456-62; discussion 3503-14
In order to better understand the nitrogen (N) cycle, a pulse of 15NO3- was applied in 1998 to a sugar maple (Acer saccharum) dominated northern hardwood forest receiving long-term (1994-2008) simulated atmospheric N deposition. Sugar maple leaf litter and live fine-root 15N were quantified for four years prior to labeling and for 11 subsequent years. Continuous sampling of 15N following addition of the tracer enabled calculation of leaf litter and fine-root N pool turnover utilizing an exponential decay function. Fine-root 15N recovery peaked at 3.7% +/- 1.7% the year the tracer was applied, while leaf litter 15N recovery peaked in the two years following tracer application at approximately 8%. These results suggest shoots are primarily constructed from N taken up in previous years, while fine roots are constructed from new N. The residence time of N was 6.5 years in leaf litter and 3.1 years in fine roots. The longer residence time and higher recovery rate are evidence that leaves were a stronger sink for labeled N than fine roots, but the relatively short residence time of tracer N in both pools suggests that there is not tight intra-ecosystem cycling of N in this mature forest. 相似文献
42.
43.
The Science of Adaptation: A Framework for Assessment 总被引:2,自引:0,他引:2
Smit B. Burton I. Klein R.J.T. Street R. 《Mitigation and Adaptation Strategies for Global Change》1999,4(3-4):199-213
Mitigation and Adaptation Strategies for Global Change - This paper outlines what is meant by "adaptation" to climate change, and how it might be addressed in the IPCC Assessments. Two... 相似文献
44.
Outreach nurseries are favored conservation and social forestry tools globally, but, as with many integrated conservation
and development programs (ICDPs), they do not always produce anticipated results. A synopsis of the experience of South African
practitioners is provided in this study of 65 outreach nurseries. South African outreach nurseries frequently include financial
objectives, creating additional challenges in simultaneously attaining conservation and socioeconomic goals. Progress was
hindered by biophysical problems (e.g., lack of water, poor soils, etc.) as well as the harsh socioeconomic conditions facing
most communities in which nurseries had been established. Attaining financial viability was challenging. Business management
skills were often restricted, and few viability studies included adequate market research. Costs to community participants
were usually high, and benefits were limited. Conservation objectives were frequently lost in the struggle to attain financial
viability. The management of social processes also proved challenging. Although small scale and relatively straightforward
compared with many ICDPs, nurseries usually require substantial institutional support, including a range of technical, business,
and development services. Project time frames need to be reconsidered, as practitioners estimate that it takes 5–10 years
for nurseries to start meeting objectives, and donors and implementing agencies often operate on 2–3-year project cycles.
Detailed viability studies are essential, incorporating a social probe and an assessment of potential impacts of projects
on community participants. Progress needs to be continuously evaluated to enable institutions and community participants to
adapt to changing conditions as well as ensure that the spectrum of objectives are being achieved. 相似文献
45.
Turner C Williams SM Burton CH Cumby TR Wilkinson PJ Farrent JW 《Journal of environmental science and health. Part. B》1999,34(6):989-1007
This paper describes a pilot scale treatment plant that has been designed and built for the thermal inactivation in pig slurry of two viruses that infect pigs--African swine fever virus (ASFV) and swine vesicular disease virus (SVDV). The plant treats pig slurry continuously at a rate of up to 100 litres/hour and functions by heating the slurry, maintaining at least 99.99% of the slurry at the required temperature for a minimum period of 5 minutes, and then recovering the heat to raise the temperature of the incoming slurry. Results obtained indicated that SVDV was inactivated in pig slurry to below detectable levels with an alkaline pH (pH 7.5 to 8, as is usually the case) at a temperature of between 50 and 55 degrees C. In acidified slurry (pH 6.4), inactivation occurred between 55 and 60 degrees C. The difference in inactivation temperatures was probably due to the presence of free ammonia in the unacidified slurry. ASFV was inactivated by operating the plant at a temperature of 53 degrees C at a pH of 8. 相似文献
46.
Jeffrey Burton Marliave Kim W. Conway Donna M. Gibbs Andy Lamb Charles Gibbs 《Marine Biology》2009,156(11):2247-2254
In the Strait of Georgia and Howe Sound, British Columbia, colonies of individual cloud sponges, growing on rock (known as
sponge gardens) receive resource subsidies from the high biodiversity of epifauna on adjacent rock habitats. Bioherms are
reefs of glass sponges living on layers of dead sponges. In the same area as the sponge gardens, newly discovered bioherms
in Howe Sound, BC (49.34.67 N, 123.16.26 W) at depths of 28- to 35-m are constructed exclusively by Aphrocallistes vastus, the cloud sponge. The sponge gardens had much higher taxon richness than the bioherms. The sponge garden had 106 species from 10 phyla, whereas
the bioherm had only 15 species from 5 phyla. For recruiting juvenile rockfish (quillback, Sebastes maliger), the food subsidy of sponge gardens appears to be missing on bioherms of cloud sponge, where biodiversity is relatively
low. While adult and subadult rockfishes (S. maliger, S. ruberrimus, S. proriger, and S. elongatus) were present on bioherms, no evidence for nursery recruitment of inshore rockfishes to bioherms was observed, whereas the
sponge gardens supported high densities of newly recruited S. maliger, perhaps owing to the combination of both refuge and feeding opportunities. These results indicate that sponge gardens form
a habitat for early stages of inshore S. maliger, whereas A. vastus bioherms are associated only with older juvenile and adult rockfishes. 相似文献
47.
The impact of disturbance from construction work around Cardiff Bay, south Wales, on the densities and feeding behavior of
seven waterbird species was studied over an 11-year period. Construction of a barrage across the mouth of the bay has subsequently
resulted in its impoundment; other major works included the construction of a bridge carrying a divided highway. Construction
work disturbance significantly reduced the densities of five species—green-winged teal (Anas crecca), Eurasian oystercatcher (Haematopus ostralegus), dunlin (Calidris alpina), Eurasian curlew (Numenius arquata), and common redshank (Tringa totanus)—on adjacent intertidal mudflats, and thus the overall carrying capacity of the bay. Construction work also reduced the feeding
activity of Eurasian oystercatcher, dunlin, and common redshank on these mudflats. The possible impact of the loss of birds
from these mudflats upon the populations that the bay supported is discussed. Evidence from other local studies suggests that
the displacement of common redshank from these mudflats did not contribute to a decline in this species. 相似文献
48.
49.
A denitrifying bacterium was isolated from activated sludge after enrichment on 4‐chlorophenol under anoxic, denitrifying conditions, and the microbial degradation of 4‐chlorophenol by this bacterium, with nitrate as the only electron acceptor, was investigated. The bacterium was capable of degrading up to 5 mM 4‐chlorophenol with stoichiometric release of chloride under denitrifying conditions. Anaerobic degradation of 4‐chlorophenol was dependent on nitrate as an electron acceptor. Nitrate (10 mM) severely inhibited the growth by the toxic effect of the accumulated nitrite. The optimum nitrate concentration for cell growth and chlorophenol degradation was 6 mM. 相似文献
50.
Genetic differentiation and reproductive incompatibility among Baja California populations of the copepod Tigriopus californicus 总被引:6,自引:0,他引:6
Populations of the harpacticoid copepod Tigriopus californicus were sampled from five sites from San Diego, California, to Playa Altamira, Baja California, Mexico. Allozyme analyses revealed that all the study populations are sharply differentiated genetically. At the extreme, two populations, Punta Baja and Playa Altamira, have no alleles in common at the seven allozyme loci studied. All pairwise interpopulation crosses successfully produced F2 hybrids except those involving the Playa Altamira population. All crosses using Playa Altamira females failed to produce F1 hybrids, while Playa Altamira males successfully produced F1 progeny with females from all other sites. These F1 offspring, however, were completely sterile (with San Diego and Punta Banda females) or only occasionally produced F2 offspring (with Punta Morro and Punta Baja females). These results suggest that allopatric differentiation among Baja populations has resulted in exceptionally high levels of genetic divergence and nearly complete reproductive isolation of the Playa Altamira population, which should now be recognized at the semispecies (or perhaps sibling species) level. 相似文献