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131.
Summary In four fruit-eating bats sniff-rate analysis revealed the threshold value for natural banana odour to be 1 × 10–4 vol% of head-space while the threshold values for its major components were found to be 3–6 orders of magnitude higher; even the total of molecules present at the threshold dilution of banana odour was 2 orders of magnitude below the lowest threshold values obtained for single components. Thus, the responsiveness of the bats to threshold concentration of natural banana odour is discussed as an example of synergism of stimuli. 相似文献
132.
Variation in the endospermal protein patterns of seeds amongst and between inland and coastal populations of the dune building
grassLeymus arenarius was examined in Iceland. Seeds were collected from six coastal populations and five inland populations in Iceland. Endospermal
proteins (prolamins) of seeds were extracted with Tris-buffered 2-propanol (50%) and β-mercaptoethanol (0.5% v/v). We used
8% and 12% sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) to separate the prolamin protein bands, which
were stained with Coomassie Brilliant Blue R. Coastal populations were differentiated from inland populations on the basis
of high frequency of high molar weight (HMW) (110–150 kg mol−1) prolamins. Coastal populations had significantly higher proportions of their seed with more than two HMW prolamins, than
those of inland populations. Subtle differences were found among the HMW prolamins of coastal and inland populations indicating
limited intrapopulation variation. The dynamic environment of sand dunes probably influences the genetic composition of these
populations. The results suggest that seeds of the inland and coastal populations should be treated separately in sand dune
reclamation and restoration works 相似文献
133.
In 1990, the Government and Parliament of the Netherlands decided on a new national policy for coastal defence. To ensure
the enduring safety of the low-lying polders as well as the sustainable preservation of the coastal dunes, it was decided
to maintain the coastline in its 1990 position.
The main method for coastline preservation in the Netherlands is beach nourishment. Since 1991, approximately 7 million m3 of sand is added to the Dutch beaches annually. From an evaluation study of sand nourishment projects it is concluded that
nourishment is an effective and efficient method to preserve the coastline. The evaluation study also proves that nourishment
projects should be ‘tailor-made’, taking the local morphological and hydraulic conditions into account. The first results
of an experimental shoreface nourishment are discussed.
The choice for nourishment as the principal method to combat erosion is well in line with the intention to restore the natural
dynamics of the dune-coast in the Netherlands. The key probably is a less strict policy with regard to the maintenance of
the foredunes. Plans for the development of typical coastal features such as slufters*, wash-overs, blow-outs and mobile dunes are currently under discussion.
A slufter is a breakthrough in the first dune-ridge whereby the sea invades former dune slacks or beach plains situated behind
the duneridge. In this way a tidal marsh is formed within the dune zone. 相似文献
134.
Coastal zones in Portugal, as interface areas between land and sea, have problems related to the growing human pressure in
terms of changes in land use associated with urban and industrial occupation, new accessibility (ports, motorways) and traffic
flows, intensification of recreational use (beaches, water sports) and excessive fishing. Impacts include deterioration of
water quality and sediments; alteration and degradation of natural habitats; new hydrodynamic situations; major landscape
changes: and rapid changes in habits and way of life of the local populations and increased exposure of populations and assets
to natural and induced risks (storms, accidents, spills, explosions).
Plans for the Management of the Coastal Zone (POOC) have been developed and seven of them have been approved, while two similar
plans are at a final stage of preparation. Together they cover the entire coast of Portugal. Their implementation and assessment
could be a first step towards an integrated management of the Portuguese coastal zones. River Basin Management Plans (PBH)
have been concluded and recently approved for the whole country. However, these plans do not consider estuarine systems and
some other issues related to coastal systems. The National Water Plan (PNA) is under public presentation and discussion. Several
‘key messages’ are presented in this paper as a contribution for assessment of the proposals of this plan on issues related
with coastal waters. 相似文献
135.
生物有机无机复合肥对土壤微生物活性的影响 总被引:3,自引:0,他引:3
进行了化肥、有机肥、生物堆肥、有机无机复合肥和生物有机无机复合肥的田间比较试验。结果表明 :生物有机无机复合肥显著提高土壤微生物活性。与不施肥处理比较 ,土壤细菌增加了 1 6 5 .3 8% ,真菌增加了1 89.4 7% ,放线菌增加了 4 8.72 % ,总量增加了 1 0 4 .0 7% ,其增加量高于其他处理。土壤蔗糖酶、脲酶、磷酸酶活性也都有明显提高 ,促进了土壤有机质的分解转化和速效养分的释放。 相似文献
136.
Frode Skarstein Ivar Folstad Ståle Liljedal Mats Grahn 《Behavioral ecology and sociobiology》2005,57(4):374-380
Genes of the major histocompatibility complex (MHC) are remarkably polymorphic. Several selection mechanisms have been invoked to account for this diversity, including disassortative mating preferences. In addition, eggs may discriminate between sperm based on MHC. To investigate the effects of MHC-genotype on fertilization success, we obtained mature gametes from ripe Arctic charr (Salvelinus alpinus) males and females captured on spawning grounds. The eggs of each female were divided into two batches, and by letting each of 2 males fertilize 1 of the batches, we obtained a total of 36 half-sibling batch-pairs. The semen was diluted to ensure that the two males in each half-sibling batch-pair contributed with the same number of sperm cells. We found that MHC-heterozygous males had significantly higher fertilization success than MHC-homozygous males and neither initial spermatocrit, sperm motility nor swimming velocity co-varied with difference in fertilization success. There was no effect of female genotype or female-male MHC-similarity on fertilization success. However, one MHC-allele was associated with increased fertilization success. It seems plausible that the difference in fertilization success between homo- and heterozygous males may be due to MHC-dependent sperm selection by the ovum.Communicated by M. Abrahams 相似文献
137.
Paul Harvey 《Disasters》1998,22(3):200-217
The paper examines the challenge of rehabilitation from complex political emergencies (CPEs) and identifies a strategy that is characterised as a civil society rebuilding approach. It focuses on Somalia and a case study of a CARE project that aims to build the capacity of local NGOs. The paper argues that civil society in CPEs is simultaneously being undermined and contested by warring parties and emerging after state collapse. The scope of the paper is limited to one case study and that case study examines only a single aspect of civil society: national and international NGOs. The paper therefore presents tentative and preliminary results based on limited research. However, in reviewing the literature and presenting a way of approaching the subject, it aims to suggest a starting-point for developing a theoretical framework for such research. The paper finds that international agencies have tended to focus on civil society institutions simply as conduits for aid money and that this has tended to create organisations which lack downward accountability, are dependent on donors and are not addressing the wider roles for civil society envisaged in the approach. Rebuilding civil society does hold out the promise of giving non-military interests a stronger voice and starting a process of changing the aid delivery culture. Achieving these objectives, however, will be a slow and largely indigenous process and there is a need for lowered expectations about what outside assistance can achieve 相似文献
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