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251.
252.
Vertical distributions of (36)Cl and (99)Tc are presented from deep and shallow lysimeters above artificially controlled water tables for a 4-yr experiment from 1990 to 1993. Activity concentration profiles were all measured in late summer when a winter wheat (Triticum aestivum L. cv. Pastiche) crop was harvested. After harvest, activity concentrations in different organs of the crop were determined and crop uptake quantified as both an inventory ratio (IR) and a transfer factor (TF(w)), weighted to account for differential root and radionuclide distributions within the soil profile. Vertical distributions of radionuclides, crop roots within the soil, and IR and TF(w) values were each subjected to analysis of variance to estimate the individual and combined effects of soil depth and the year of the experiment on the results obtained. Chlorine-36 and (99)Tc exhibited highly significant variations in activity concentrations with soil depth and from year to year, indicating considerable physical mobility of both radionuclides. Soil-to-plant transfer was also high for both radionuclides compared with data obtained for gamma-emitting radionuclides. The IR values indicated that up to 40% of (36)Cl was incorporated in the crop's tissues at harvest, compared with a maximum of less than 1% for the less mobile gamma-emitting radionuclides. On the basis of the TF(w) values determined, (36)Cl uptake by winter wheat exceeded (99)Tc uptake, indicating that (36)Cl is highly bioavailable. Factors controlling the migration and bioavailability of both (36)Cl and (99)Tc in soils are discussed. 相似文献
253.
254.
David Shaw 《Journal of Environmental Planning and Management》1996,39(3):403-418
Faced with a crisis in the mid 1980s, farmers were encouraged by policy makers to diversify their activities in order to survive. Evidence has suggested that this response was not as widely adopted as anticipated. This paper argues that farmers may have adopted a different adjustment strategy whereby they sought to capitalize their assets which often brought them into play with the planning system. This paper explores the extent to which farmers appear to be adopting this strategy and the response of planners in two rural districts of South Shropshire and the Malvern Hills. Furthermore it goes on to suggest that if there is a desire to truly diversify the rural economy as opposed to merely farming, planners may have to adopt a mre relaxed approach to non residential development proposals from farmers. 相似文献
255.
256.
The Aquatic Macrophyte Community Index (AMCI) is a multipurpose tool developed to assess the biological quality of aquatic
plant communities in lakes. It can be used to specifically analyze aquatic plant communities or as part of a multimetric system
to assess overall lake quality for regulatory, planning, management, educational, or research purposes. The components of
the index are maximum depth of plant growth; percentage of the littoral zone vegetated; Simpson's diversity index; the relative
frequencies of submersed, sensitive, and exotic species; and taxa number. Each parameter was scaled based on data distributions
from a statewide database, and scaled values were totaled for the AMCI value. AMCI values were grouped and tested by ecoregion
and lake type (natural lakes and impoundments) to define quality on a regional basis. This analysis suggested that aquatic
plant communities are divided into four groups: (1) Northern Lakes and Forests lakes and impoundments, (2) North-Central Hardwood
Forests lakes and impoundments, (3) Southeastern Wisconsin Till Plains lakes, and (4) Southeastern Wisconsin Till Plains impoundments,
Driftless Area Lakes, and Mississippi River Backwater lakes. AMCI values decline from group 1 to group 4 and reflect general
water quality and human use trends in Wisconsin. The upper quartile of AMCI values in any region are the highest quality or
benchmark plant communities. The interquartile range consists of normally impacted communities for the region and the lower
quartile contains severely impacted or degraded plant communities. When AMCI values were applied to case studies, the values
reflected known impacts to the lakes. However, quality criteria cannot be used uncritically, especially in lakes that initially
have low nutrient levels. 相似文献
257.
Environment, Development and Sustainability - Sustainability has emerged as a dominating paradigm across global institutions as a critical component for their prospects. Organisations all across... 相似文献
258.
Shimpei Iwasaki Bam Haja Nirina Razafindrabe Rajib Shaw 《Mitigation and Adaptation Strategies for Global Change》2009,14(4):339-355
Climate change combined with human activities poses significant risks to people’s livelihood especially in developing countries.
Adaptation at the community level is of crucial importance in enabling them to respond to the direct and indirect effects
of changes in climate. In a case study of fishing communities in Chilika lagoon, India, the focus is made on understanding
climate change adaptation at the community level and scaling it up into the policy perspective through application of Sustainable
Livelihood Approach. This article challenges the research and policy community to encourage the identification of locally
negative constraints and positive strengths toward climate resilient communities in rural areas.
相似文献
Rajib ShawEmail: |
259.
Recent assessments of global climate/environmental change are reaching a consensus that global climate change is occurring but there is significant uncertainty over the likely magnitude of this change and its impacts. There is little doubt that all aspects of the natural environment will be impacted to some degree. Soil-to-plant transfer of radionuclides has long been a significant topic in radioecology, both for the protection of humans and the environment from the effects of ionising radiation. Even after five decades of research considerable uncertainty exists as to the interplay of key environmental processes in controlling soil-plant transfer. As many of these processes are, to a lesser or greater extent, climate-dependent, it can be argued that climate/environmental change will impact soil-to-plant transfer of radionuclides and subsequent transfers in specific environments. This discussion attempts to highlight the possible role of climatic and climate-dependent variables in soil-to-plant transfer processes within the overall predictions of climate/environmental change. The work is speculative, and intended to stimulate debate on a theme that radioecology has either ignored or avoided in recent years. 相似文献
260.
Evolution of the mate recognition system (MRS) can play a central role in animal speciation. One dramatic consequence of changes
in the MRS is the failure of individuals from divergent lineages to successfully court and mate, thereby reducing gene flow
between these groups. Here, we test the role of an acoustic mating signal on mate choice in a Hawaiian cricket genus (Gryllidae:
Laupala). Speciation in Laupala is proceeding at an extremely rapid rate, apparently driven by divergence in aspects of the mate recognition system, most
conspicuously the pulse rate of male calling song. Previous studies demonstrate that females prefer the pulse rate of a conspecific
male’s song when perceived at long range, in laboratory phonotaxis trials. In this study, we examined mate choice in two species
that differ dramatically in pulse rate: Laupala paranigra and Laupala kohalensis. We tested the female’s preference in both species for pulse rates at close range, by providing females an opportunity to
mate with hybrid males producing a range of intermediate pulse rates. Results of our study demonstrate that while strong behavioral
barriers exist between these two species, variation in the pulse rate of male calling song did not predict female mate choice
at close range. These results suggest a more complex architecture to mate recognition in Laupala than previously hypothesized. 相似文献