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451.
An attempt has been made to make a comprehensive assessment of biological factors in the ecology of humus formation in forest-steppe
and steppe chernozem soils of the Cisural region. Certain regional features in the effect of vegetation structure and composition
and soil microbial and enzymatic activities on the humus state of zonal chernozem subtypes in virgin and plowed landscapes
have been revealed. 相似文献
452.
The remote effect of the nuclear polyhedrosis virus on the gypsy moth was studied for the first time under natural conditions.
In the generation that developed from infected eggs, the weight of pupae was reduced, sex ratio was altered, and female fecundity
and egg fertility were lower than in control individuals. The F1 progeny of these moths were characterized by an increased rate of latent virus carriage and high mortality caused by the
combined effect of polyhedrosis and insect parasites. 相似文献
453.
454.
455.
V. V. Tuzhilkina 《Russian Journal of Ecology》2009,40(4):227-232
To estimate the response of conifers to long-term industrial air pollution at the pigment system level, the dynamics of photosynthetic pigments have been studied in needles of Scots pine (Pinus sylvestris L.) and Siberian spruce (Picea obovata Ledeb.) growing at different distances from the emission source (a pulp and paper mill). It has been shown that the pigment apparatus of spruce. The results show that in spruce, unlike in pine, the pigment apparatus remains unchanged under the effect of weak pollution. Long-term exposure at high levels of industrial emission results in suppression of chlorophyll and carotenoid syntheses in pine but stimulates pigment production in spruce. An increase in the contents of pigments in the needles of conifers growing in the impact zone of the pulp and paper mill reflects a compensatory mechanism of adaptation of their pigment system to long-term stress exposure. 相似文献
456.
V. E. Zverev 《Russian Journal of Ecology》2009,40(4):254-260
Long-term monitoring of mountain birch populations (1992–2006) was performed in 14 test plots located at distances of 1 to 63 km from the copper-nickel smelter in Monchegorsk (Murmansk oblast) and differing in the degree of disturbance. In the period from 1999 to 2006, atmospheric emissions of sulfur dioxide and heavy metals amounted to only one-third of those between 1992 and 1998, but birch mortality in heavily polluted areas (with nickel concentrations in leaves exceeding 160 mg/kg) remained at the same level, being absent (as previously) in less polluted areas. Throughout the observation period, birch recruitment was observed only in areas where nickel concentrations in the leaves were below 160 mg/kg; i.e., this concentration proved to be the threshold with respect to both mortality and recruitment of mountain birch. The course of demographic processes in its populations has remained unchanged after the reduction of emissions, confirming the hypothesis of the “inertial“ effect of industrial emissions on ecosystems. In some areas of industrial barrens, mountain birch may perish completely within the next decade. 相似文献
457.
Landscape-geochemical features providing for manifestation of gigantism in herbaceous plants have been revealed in natural habitats in the south of Sakhalin and Kunashir islands. Tall herb assemblages have proved to be associated with geochemical landscapes characterized by reducing (gley or hydrogen sulfide) conditions and increased contents of petroleum hydrocarbons and some trace elements (total and movable forms). A hypothesis is put forward that gigantism in herbaceous plants is manifested in zones of active faults, which serve as a kind of conduits supplying endogenous heat, matter, and water to the root systems. 相似文献
458.
K. Rajakumar V. Sarasvathy A. Thamarai Chelvan R. Chitra C. T. Vijayakumar 《Journal of Polymers and the Environment》2009,17(3):191-202
Polypropylene (PP) has achieved a dominating position and hence, their consumption increases thereby littering, which lead
to environmental pollution. Photodegradation seems to be a better choice because of naturally available sunlight as energy
source for degradation. The present work involves the study of the variation of degradation behavior of PP film during tropical
summer and winter seasons. The photodegradation is followed by Fourier transform infrared (FTIR) spectroscopic technique.
Various indices like hydroxyl, carbonyl, vinylidene, lactones, ester, carboxylic acid and crystallinity are calculated and
these values increased after a brief induction period. The variation in the mechanical properties like tensile strength and
elongation at break percentages are determined. The scanning electron microscopic (SEM) images of weathered PP showed surface
cracks when carbonyl index value increases sharply and the mechanical properties show a sudden decrease. Attempted life time
prediction using mathematical models showed that the carbonyl growth is more affected by ultraviolet (UV) and cumulative total
solar radiation for PP weathered during summer. The loss in tensile strength of PP weathered during summer is more dependent
on the average temperature and the UV portion of the total solar radiation whereas, intensity of UV radiation has profound
effect on the tensile strength of PP weathered during winter. 相似文献
459.
Mario C.R. Vidal Paulo V.R. Carvalho Marcello S. Santos Isaac J.L. dos Santos 《Journal of Loss Prevention in the Process Industries》2009,22(4):516-527
This article aims to describe the characteristics of collective working situations in complex systems – especially those in nuclear power plants – related to common forms of cooperation, in order to improve systems resilience. In addition, we will try to detail some aspects of collective working situations, emphasizing the differences between various forms of control. The similarities between work activities (multi-addressed messages, linkage to regulation, central and peripheral information) are nonetheless exposed. We conclude by proposing a contribution to support systems design, thus facilitating cooperation in teamwork activities. 相似文献
460.