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411.
Preety M. Bhandari Suruchi Bhadwal Ulka Kelkar 《Mitigation and Adaptation Strategies for Global Change》2007,12(5):919-933
India occupies 2.4% of the world’s geographical area with a large percentage of its land under agriculture. About 228 Million
hectares (Mha) of its geographical area (nearly 69%) fall within the dryland (arid, semi-arid and dry sub-humid) region. Of
the total cultivated area of 142 Mha, major part of agriculture in the country is rainfed, extending to over 97 Mha and constituting
nearly 68% of the net cultivated area, therefore making the agricultural sector vulnerable and exposed to the vagaries of
weather conditions. Climate change adds to this dimension of stress. A strong need is felt for targeting programmes in these
areas that address issues related to employing suitable soil and water conservation measures. In this context this paper seeks
to examine the case for watershed development as an adaptive strategy. An examination of the possibility of fortifying the
existing programme with a view to adapting to expected changes in climate in future is undertaken. Also, the possibility of
watershed development integrating into a suitable mitigation strategy for the country is assessed.
相似文献
Preety M. BhandariEmail: |
412.
U. Martin Persson Christian Azar 《Mitigation and Adaptation Strategies for Global Change》2007,12(7):1277-1304
The possibility of adopting national targets for carbon dioxide (CO2) emissions from tropical deforestation in a future international climate treaty has received increasing attention recently.
This attention has been prompted by proposals to this end and more intensified talks on possible commitments for developing
countries beyond the United Nations Framework Convention on Climate Change Kyoto Protocol. We analyze four main scientific
and political challenges associated with national targets for emissions from tropical deforestation: (1) reducing the uncertainties
in emission inventories, (2) preserving the environmental integrity of the treaty, (3) promoting political acceptance and
participation in the regime, and (4) providing economic incentives for reduced deforestation. We draw the following conclusions.
(1) Although there are large uncertainties in carbon flux from deforestation, these are in the same range as for other emissions
included in the current Kyoto protocol (i.e., non-CO2 GHGs), and they can be reduced. However, for forest degradation processes the uncertainties are larger. A large challenge
lies in building competence and institutions for monitoring the full spectrum of land use changes in developing countries.
(2 and 3) Setting targets for deforestation is difficult, and uncertainties in future emissions imply a risk of creating ‘tropical
hot air’. However, there are proposals that may sufficiently deal with this, and these proposals may also have the advantage
of making the targets more attractive, politically speaking. Moreover, we conclude that while a full carbon accounting system
will likely be politically unacceptable for tropical countries, the current carbon accounting system should be broadened to
include forest degradation in order to safeguard environmental integrity. (4) Doubts can be cast over the possible effect
a climate regime alone will have on deforestation rates, though little thorough analysis of this issue has been made.
相似文献
U. Martin PerssonEmail: |
413.
从一起爆炸事故的原因--没有办理设备检修许可证,分析了使用作业安全票证(单)存在的问题,提出了加强作业安全票证(单)管理措施. 相似文献
414.
红枫湖钻孔沉积物中滴滴涕的沉积记录 总被引:1,自引:0,他引:1
采用GC/MS方法分析了红枫湖钻孔沉积物中滴滴涕的垂直分布状况,并对其来源和生态风险进行了分析和评估.红枫湖钻孔沉积物中滴滴涕的含量介于7.6~23.7ng/g之间,且从底层至表层基本上呈下降的趋势.其中,1981~1983年间有一个急剧下降的过程,随后基本上呈缓慢下降的趋势.沉积物中滴滴涕的组成以p,p′-DDTs(p,p′-DDT、p,p′-DDE和p,p′-DDD的总和)为主,p,p′-DDTs与o,p′-DDTs(o,p′-DDT、o,p′-DDE和o,p′-DDD总和)的比值在5.1~8.4之间,说明沉积物中的滴滴涕主要来源于农药滴滴涕的残留.又因为沉积物中残留的滴滴涕是以它的代谢产物为主,DDT/(DDD+DDE)的比值为0.31~0.84,所以沉积物中的滴滴涕主要源于历史的残留.此外,DDT/(DDD+DDE)和DDE/DDD比值的垂直变化特征显示,尽管我国1983年就禁止了滴滴涕在农业上的使用,但直至1990年前后,红枫湖流域内仍存在滴滴涕使用的可能.风险评价的结果显示,红枫湖表层沉积物中DDE、DDD、DDT和DDTs的含量均介于ERL和ERM值之间,可能造成潜在的生态风险,因此红枫湖沉积物中滴滴涕的污染仍值得密切关注. 相似文献
415.
Communication is shaped and constrained by the signaling environment. In aquatic habitats, turbidity can reduce both the quantity
and quality of ambient light and has been implicated in the breakdown of visual signaling. Here, we examined the relationship
between turbidity (quantified with long-term data) and the expression of carotenoid-based nuptial coloration in the red shiner
(Cyprinella lutrensis), a small-bodied cyprinid. Males in more turbid habitats displayed redder fins, and an experimental manipulation of adult
diet suggested that carotenoid intake alone did not explain among-population color differences. These results run counter
to similar studies where signal expression decreased in turbid conditions, and may be explained by the non-territorial red
shiner mating system, interactions between the mechanism of coloration and the signaling environment, or reduced cost of color
expression in turbid habitats (e.g., reduced predation risk). Our results highlight how the behavioral and ecological contexts
in which signals function can shape evolutionary responses to the environment. 相似文献
416.
Sperm competition is thought to be an important selective pressure shaping sperm form and function. However, few studies have
moved beyond gross examinations of sperm morphology. Sperm length is subject to sexual selection via sperm competition in
the scarab beetle Onthophagus taurus. Here, the structure and ultrastructure of spermatozoa in this species were investigated using light and electron microscopy.
Spermatozoa were found to be filiform, measuring about 1,200 mm in length. The sperm head consists of a three-layered acrosome
and a nuclear region bearing the anterior extension of the centriole adjunct. Acrosome and nuclear regions are bilaterally
symmetric, with their axes of symmetry being orthogonal to each other. Head and flagellar structures are connected by a well-developed
centriole adjunct. The sperm heads are asymmetrically surrounded by accessory material and embedded into the cytoplasm of
the spermatocyst cell. The accessory material is produced inside the spermatids and then transferred to the outside due to
a new membrane formed around the sperm’s organelles. The old spermatid membrane separates the accessory material from the
cyst cell. The flagellum contains a 9+9+2 axoneme, two accessory bodies, and two mitochondrial derivatives of unequal size.
The major mitochondrial derivative is significantly larger than the minor one. The axoneme is arranged in a sinusoidal manner
parallel along the major mitochondrial derivative. The spermatozoa show no progressive motility when released in buffer solution
which is likely to be the result of the flagellar arrangement and the structure of the major mitochondrial derivative. The
cross-sectional area of the minor and the major mitochondrial derivatives show different patterns of genetic variation. The
data provide the first estimates of genetic variation in sperm ultrastructure for any species, and give evidence for the persistence
of genetic variation in ultrastructure required for the rapid and divergent evolution that characterizes spermatozoa generally. 相似文献
417.
In this study, landmark-based methods of geometric morphometrics are used for investigating the main aspects of cranial shape transformation in the evolution of the giant panda, Ailuropoda melanoleuca. Specifically, we explore if the highly derived cranial adaptations for bamboo feeding of the living panda were developed early in the panda's lineage. Results obtained show that the overall cranial morphologies of the oldest known panda, the "pygmy" Ailuropoda microta, and the late Pleistocene Ailuropoda baconi are both very similar to that of their closest living relative, A. melanoleuca, which agrees with a previous proposal based on qualitative criteria. However, we also describe several differences between the crania of A. microta, A. baconi, and A. melanoleuca, including the development of the postorbital process, the orientation of the occipital region, and the expansion of the braincase. As a result, the cranial morphology of A. microta shows a less specialized morphology toward a fibrous and durophagous diet compared to the giant panda. These results are confirmed by a comparative analysis of the dimensions of the upper teeth in bears, which has revealed differences in relative tooth size between A. microta and A. melanoleuca, most probably as a result of mosaic evolution. Therefore, we conclude that cranial shape did not remain essentially uniform in the Ailuropoda lineage, as previously thought, but underwent a number of changes during more than 2?Myr. 相似文献
418.
Leclaire S Merkling T Raynaud C Giacinti G Bessière JM Hatch SA Danchin E 《Die Naturwissenschaften》2011,98(7):615-624
The importance of olfaction in birds’ social behavior has long been denied. Avian chemical signaling has thus been relatively
unexplored. The black-legged kittiwake provides a particularly appropriate model for investigating this topic. Kittiwakes
preferentially mate with genetically dissimilar individuals, but the cues used to assess genetic characteristics remain unknown.
As in other vertebrates, their body odors may carry individual and sexual signatures thus potentially reliably signaling individual
genetic makeup. Here, we test whether body odors in preen gland secretion and preen down feathers in kittiwakes may provide
a sex and an individual signature. Using gas chromatography and mass spectrometry, we found that male and female odors differ
quantitatively, suggesting that scent may be one of the multiple cues used by birds to discriminate between sexes. We further
detected an individual signature in the volatile and nonvolatile fractions of preen secretion and preen down feathers. These
results suggest that kittiwake body odor may function as a signal associated with mate recognition. It further suggests that
preen odor might broadcast the genetic makeup of individuals, and could be used in mate choice to assess the genetic compatibility
of potential mates. 相似文献
419.
Lu Y Beeman RW Campbell JF Park Y Aikins MJ Mori K Akasaka K Tamogami S Phillips TW 《Die Naturwissenschaften》2011,98(9):755-761
We report that the abdominal epidermis and associated tissues are the predominant sources of male-produced pheromones in the
red flour beetle, Tribolium castaneum and, for the first time, describe the stereoisomeric composition of the natural blend of isomers of the aggregation pheromone
4,8-dimethyldecanal (DMD) in this important pest species. Quantitative analyses via gas chromatography–mass spectrometry showed
that the average amount of DMD released daily by single feeding males of T. castaneum was 878 ± 72 ng (SE). Analysis of different body parts identified the abdominal epidermis as the major source of aggregation
pheromone; the thorax was a minor source, while no DMD was detectable in the head. No internal organs or obvious male-specific
glands were associated with pheromone deposition. Complete separation of all four stereoisomers of DMD was achieved following
oxidation to the corresponding acid, derivatization with (1R, 2R)- and (1S, 2S)-2-(anthracene-2,3-dicarboximido)cyclohexanol to diastereomeric esters, and their separation on reversed-phase high-performance
liquid chromatography at −54°C. Analysis of the hexane eluate from Porapak-Q-collected volatiles from feeding males revealed
the presence of all four isomers (4R,8R)/(4R,8S)/(4S,8R)/(4S,8S) at a ratio of approximately 4:4:1:1. A walking orientation bioassay in a wind tunnel with various blends of the four synthetic
isomers further indicated that the attractive potency of the reconstituted natural blend of 4:4:1:1 was equivalent to that
of the natural pheromone and greater than that of the 1:1 blend of (4R,8R)/(4R,8S) used in commercial lures. 相似文献
420.
The sympatric neotropical termites Nasutitermes corniger and Nasutitermes ephratae are clearly distinguishable based on morphology, nest architecture, defensive secretion composition, and molecular markers.
However, given the extensive ecological, geographical, and behavioral overlap of these closely related species, the potential
for interbreeding may exist. To explore this possibility, heterospecific pairs were formed experimentally to examine courtship
and colony-establishment behaviors, and reproductive potential. Courtship and nest construction behavior occurred in heterospecific
pairs in a similar manner to that of conspecific pairs. Survival of pairs depended upon the species of the female partner.
N. ephratae females paired with N. corniger males produced as many offspring as conspecific pairs. N. corniger females mated to N. ephratae males, however, produced significantly fewer offspring at 60 days post-establishment than the reciprocal cross or conspecific
N. ephratae or N. corniger pairs. This was also the only pairing in which any aggression was observed. Heterospecific pairs and groups formed in mate
choice mesocosms, suggesting that species recognition between these two termites is not an important aspect of mate choice.
Overall, species mismatch tolerance and hybrid offspring viability are high. The present data, together with previous evidence
from defensive secretions and isozyme analysis, suggest that hybridization may periodically occur in nature, and that reproductive
barriers between these two species may be incomplete. Hybridization could provide a rare but important source of genetic diversity
and may ensure mating opportunities for the more abundant sex of alates in each species. 相似文献