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511.
Abdelli I. S. Asnoune M. Arab Z. Abdelmalek F. Addou A. 《Journal of Material Cycles and Waste Management》2017,19(1):265-281
Journal of Material Cycles and Waste Management - The management of solid waste in Mostaganem district was limited to collection and transportation to open dumpsites. By the end of 2010, the... 相似文献
512.
I. V. Petrova S. N. Sannikov F. I. Tembotova N. S. Sannikova V. S. Farzaliev M. Z. Mollaeva E. V. Egorov 《Russian Journal of Ecology》2017,48(6):524-531
Allozyme analysis of 18 Pinus sylvestris L. populations from seven landscape-geographic groups has been performed in the Greater Caucasus, Crimea, and Russian Plain. The results show that populations of the Mt. Elbrus region (isolated by high mountain ridges) are characterized by lower polymorphism and most distinct differentiation (at the level of geographic race) from other populations, which are differentiated from each other at the level of geographic groups. Genetic gradients (boundaries) between populations reach a maximum on transects across the Greater Caucasus Range, and Transcaucasian populations are more similar to populations of the Russian Plain, compared to North Caucasian populations, which confirms the hypothesis of ancestral connections between their gene pools. 相似文献
513.
The critical paths for radionuclides and the critical foods in Asian countries differ from those in Western countries because agricultural products and diets are different. Consequently, safety assessments for Asian countries must consider rice as a critical food. As most rice is produced under flooded conditions, the uptake of radionuclides by rice is affected by soil conditions. In this report, we summarize radionuclide and stable element soil-to-plant transfer factors (TFs) for rice. Field observation results for fallout 137Cs and stable Cs TFs indicated that while fallout 137Cs had higher TF than stable Cs over several decades, the GM (geometric mean) values were similar with the GM of TF value for 137Cs being 3.6 × 10−3 and that for stable Cs being 2.5 × 10−3. Although there are some limitations to the use of TF for stable elements under some circumstances, these values can be used to evaluate long-term transfer of long-lived radionuclides in the environment. The compiled data showed that TF values were higher in brown rice than in white rice because distribution patterns for elements were different in the bran and white parts of rice grains. 相似文献
514.
E. Z. Baisheva S. N. Zhigunova V. B. Martynenko P. S. Shirokikh 《Russian Journal of Ecology》2009,40(3):180-186
The composition of bryophytes in forests of the Ufa Plateau has been studied. The results obtained by ordination methods show that the coverage of epigeic mosses decreases with an increase in tree stand density and proportion of broadleaf tree species as well as in the coverage and average height of herbaceous layer. The main factors determining the distribution of epigeic mosses are illumination level, soil fertility, and the degree of soil development. 相似文献
515.
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517.
The production dynamics and carbon balance of Thalassia testudinum in the lower Laguna Madre, Texas, USA, were examined during the 1995 summer period based on in situ photosynthesis vs irradiance
(PI) measurements and continuous measurements of underwater photon-flux density (PFD). The validity of applying the H
sat model, used to calculate production for Zostera marina as the product of the maximum rate of photosynthesis (P
max) and daily hours of saturating irradiance (H
sat) was assessed for T. testudinum by comparison with integrated production estimates derived through numerical integration. Gross integrated production values
were combined with dark-respiration measurements of photosynthetic (PS) and non-photosynthetic (NPS) tissues and areal biomass
to generate daily whole-plant carbon balance. Production and whole-plant carbon balance are discussed in relation to surface
and underwater PFD measurements, biomass and other physical and chemical parameters collected during a 1 yr period from January
to December 1995. The H
sat model significantly underestimated production during all summer months, averaging 70% of integrated production over the entire
study period. Gross integrated production ranged between 11.5 mg C g−1 leaf dry wt d−1 in June (during a period of unseasonably low PFDs caused by a drift-alga mat covering the seagrass bed) to 26.7 mg C g−1 leaf dry wt d−1 in July. Modeled net carbon gain was highest in July at 454 mg C m−2 d−1 (1.4 g dry wt m−2 d−1), sufficient to account for measured rates of leaf production in the study area and representative of T. testudinum populations of low productivity. During part of the summer period, however, the population was in negative carbon balance.
The relatively low productivity of this population and the periods of negative carbon balance are attributed to low net photosynthesis:dark
respiration (P
net:R
d) ratios, sporadic low-light periods, the small fraction of PS tissue relative to whole-plant biomass (5 to 13%) and nutrient
limitation. Production models are sensitive to both light availability and the proportion of PS tissue supporting NPS biomass
as reflected in whole-plant P
net:R
d ratios.
Received: 13 August 1997 / Accepted: 6 March 1998 相似文献
518.
E. Z. Cameron W. L. Linklater K. J. Stafford E. O. Minot 《Behavioral ecology and sociobiology》2000,47(4):243-249
In many mammalian species, female success in raising offspring improves as they age. The residual reproductive value hypothesis
predicts that each individual offspring will be more valuable to the mother as she ages because there is less conflict between
the current and potential future offspring. Therefore, as mothers age, their investment into individual offspring should increase.
Empirical evidence for an influence of declining residual reproductive value on maternal investment is unconvincing. Older
mothers may not invest more, but may be more successful due to greater experience, allowing them to target their investment
more appropriately (targeted reproductive effort hypothesis). Most studies do not preclude either hypothesis. Mare age significantly
influenced maternal investment in feral horses living on the North Island of New Zealand. Older mares, that were more successful
at raising foals, were more protective for the first 20 days of life, but less diligent thereafter. Total maternal input by
older mothers did not seem to be any greater, but was better targeted at the most critical period for foal survival and a
similar pattern was observed in mares that had lost a foal in the previous year. In addition, older mothers were more likely
to foal in consecutive years, supporting the hypothesis that they are investing less than younger mares in individual offspring.
Therefore, older mothers seem to become more successful by targeting their investment better due to experience, not by investing
more in their offspring.
Received: 22 September 1999 / Received in revised form: 30 October 1999 / Accepted: 6 November 1999 相似文献
519.
Photometry, laser photometry, liquid scintillation (LSC), gamma spectrometry and alpha spectrometry were used for estimating waterborne uranium concentration. The chemical procedures applied were pre-concentration, liquid extraction, chromatographic resin extraction and precipitation. Our results show that laser photometry is an easy and accurate method capable of estimating low uranium concentrations, parts of micrograms per litre. It is not applicable for higher concentrations, difficult water matrixes and isotope determination. The classical photometry is complementary, resolving the problem related to high concentrations, practically up to 10 mg/l. Alpha and gamma spectrometry resolve the problem of precise isotope determination, but with the disadvantage of hard chemical preparation and long measurement times. An intermediate method is LSC, with the problem of isotope estimation, due to poor energy resolution. 相似文献
520.
Selenium geochemistry of paddy soils in Yangtze River Delta 总被引:12,自引:0,他引:12
Selenium (Se) content both in total and bioavailable forms were very low (25-35 and 9.5 micrograms/kg, respectively) in waterlogged paddy soils in the central Yangtze River Delta. This was due to changes in geochemistry and the inherent properties of the parent materials of these lowland paddy soils. The very low Se content (23 micrograms/kg) in the parent material resulted in low total Se content in the soil. The main chemical changes under long-term waterlogged conditions are depletion of molecular oxygen, decrease of redox potential, and reduction of Fe (III) to Fe (II) and SeO3(2-) to Se0. This led to low availability of Se in soils, and subsequently low Se content (29 micrograms/kg) in brown rice grain produced in this region. It has been suspected that low Se content in staple food might be one of the major reasons for a high infection rate of the intestine and stomach cancers and the higher death rate caused by these diseases in the region. Foliage spray of Na2SeO3 at early heading stage of rice plant growth improved the Se content of brown rice grain, hull, and straw, and would improve human and animal health. 相似文献