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991.
Luiza Galbarczyk-Gąsiorowska Michał Gąsiorowski Krystyna Szeroczyńska 《Hydrobiologia》2009,631(1):173-183
Short sediment cores from two small oxbow lakes located in the Vistula valley near Warsaw (Poland) were analysed for chemical
composition and zooplankton (Cladocera) remains. The results of these analyses were evaluated using ordination techniques
and the results were used to reconstruct the history of human impact of the lakes. The cores were dated using the 210Pb method. These analyses show that the collected sediments (60 cm- and 67 cm-long-cores) were deposited during the last 150–200 years.
Cladocera assemblages were different in the two lakes; however, Bosmina longirostris was dominant among subfossil Cladocera species in both lakes. The presence of this species indicates the high trophic state
of the lakes. Changes in Cladocera species composition suggest that a significant increase in the lakes’ trophic levels has
occurred since the 1920s. The change could be related to the construction of flood dikes along the river Vistula, the isolation
of the studied lakes from the river, changes in land use, or some combination of these factors. The chemical composition of
sediments, particularly the increase in phosphorus and sulphur concentrations, confirms that the construction of dikes against
flood was the major factor inducing eutrophication of the oxbow lakes. This study shows that the Warsaw small water bodies
are especially sensitive to local disturbances caused by human activity, mainly water management, land use changes and agriculture.
Guest editors: K. Buczkó, J. Korponai, J. Padisák & S. W. Starratt
Palaeolimnological Proxies as Tools of Environmental Reconstruction in Fresh Water 相似文献
992.
Annika?C.?DahlbergEmail author Sophie?B.?Trygger 《Human ecology: an interdisciplinary journal》2009,37(1):79-94
Indigenous medicine is important to rural livelihoods, but lay knowledge and use of medicinal plants has not been extensively
studied. Research in KwaZulu-Natal, South Africa, showed that medicinal plants were frequently used by villagers and contributed
to their ability to cope with health problems. Knowledge of plants and household remedies was extensive and varied in that
households often held different knowledge. Villagers mainly relied on common species, and were generally aware of alternative
species for a certain ailment. People were flexible in their use of indigenous and western health care, which were both perceived
as beneficial. Improved cooperation between health care systems could improve health standards. Extraction of medicinal plants
has been described as unsustainable in the region—a situation not found in the study area. It is argued that conservation
policies aimed to restrict access should be differential and potentially not include local consumption, since this may be
ecologically unnecessary and entail local hardships. 相似文献
993.
We tested the mode of action of Cd on photosynthesis and activities of ATP-sulfurylase (ATP-S), catalase (CAT), superoxide
dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), and on contents of phytochelatins (PCs) and glutathione
(GSH) in two cultivars of wheat (Triticum aestivum L.) PBW-343 and WH-542 differing in yield potential. Cd treatment increased Cd content and photosynthetic activity in PBW-343
more than in WH-542. The activities of APX, GR, ATP-S, and synthesis of PCs and GSH were also increased by Cd, but the CAT
and SOD activities were inhibited in both the cultivars. The efficient functioning of antioxidative enzymes, production of
PCs and GSH, helped in counteracting the effects of Cd namely in PBW-343, protected photosynthetic ability, and increased
the tolerance to Cd. 相似文献
994.
Historical (1947–1950) and present day (1998–2000) aerial photograph data of aquatic vegetation were combined with soil, land use and habitat morphology variables in two lakes, oligotrophic L. Näsijärvi (256 km2) and eutrophic L. Pyhäjärvi (122 km2), with regulated water levels in southern Finland. Multivariate GLM analyses were used to examine the determining factors of occurrence and horizontal extension of vegetation, occurrence of common reed (Phragmites australis) and water horsetail (Equisetum fluviatile) and the vegetation change in 474 sites. Despite differences in geography and water level regulation between the lakes, congruent trends were identified. The vegetation occurrence in both lakes had a positive response to clay soils and incoming nutrients and a negative response to housing and shore slope. Moraine soils, housing and shore slope had a negative effect on horizontal extension of vegetation in both lakes. The occurrence of P. australis was controlled by a negative response to moraine and the occurrence of E. fluviatile to slope in both lakes. The vegetation change in both lakes was characterized by a negative response to housing and slope. 相似文献
995.
FACE-ing the global change: Opportunities for improvement in photosynthetic radiation use efficiency and crop yield 总被引:1,自引:0,他引:1
The earth is rapidly changing through processes such as rising [CO2], [O3], and increased food demand. By 2050 the projected atmospheric [CO2] and ground level [O3] will be 50% and 20% higher than today. To meet future agricultural demand, amplified by an increasing population and economic progress in developing countries, crop yields will have to increase by at least 50% by the middle of the century. FACE (Free Air Concentration Enrichment) experiments have been conducted for more than 20 years in various parts of world to estimate, under the most realistic agricultural conditions possible, the impact of the CO2 levels projected for the middle of this century on crops. The stimulations of crop seed yields by the projected CO2 levels across FACE studies are about 18% on average and up to 30% for the hybrid rice varieties and vary among crops, cultivars, nitrogen levels and soil moisture. The observed increase in crop yields under the projected CO2 levels fall short of what would be required to meet the projected future food demand, even with the most responsive varieties. Crop biomass production and seed yield is the product of photosynthetic solar energy conversion. Improvement in photosynthetic radiation use efficiency stands as the most promising opportunity allowing for major increases in crop yield in a future that portends major changes in climate and crop growing environments. Our advanced understanding of the photosynthetic process along with rapidly advancing capabilities in functional genomics, genetic transformation and synthetic biology promises new opportunities for crop improvement by greater photosynthesis and crop yield. Traits and genes that show promise for improving photosynthesis are briefly reviewed, including enhancing leaf photosynthesis capacity and reducing photorespiration loss, manipulating plant hormones’ responses for better ideotypes, extending duration of photosynthesis, and increasing carbon partitioning to the sink to alleviate feedback inhibition of photosynthesis. 相似文献
996.
Mary Jane West-Eberhard has suggested that plasticity may be of primary importance in promoting evolutionary innovation and
diversification. Here, we explore the possibility that the diversification of phytophagous insects may have occurred through
such a process, using examples from nymphalid butterflies. We discuss the ways in which host plant range is connected to plasticity
and present our interpretation of how West-Eberhard’s scenario may result in speciation driven by plasticity in host utilization.
We then review some of the evidence that diversity of plant utilization has driven the diversification of phytophagous insects
and finally discuss whether this suggests a role for plasticity-driven speciation. We find a close conceptual connection between
our theory that the diversification of phytophagous insects has been driven by oscillations in host range, and our personal
interpretation of the most efficient way in which West-Eberhard’s theory could account for plasticity-driven speciation. A
major unresolved issue is the extent to which a wide host plant range is due to adaptive plasticity with dedicated modules
of genetic machinery for utilizing different plants. 相似文献
997.
998.
999.
UWE LANGNER TORSTEN JAKOB KATJA STEHFEST & CHRISTIAN WILHELM 《Plant, cell & environment》2009,32(3):250-258
Chlamydomonas is one of the most well-studied photosynthetic organisms that had important biotechnological potential for future bioproductions of biofuels. However, an energy balance from incident photons to the energy stored in the new biomass is still lacking. In this study, we applied a recently developed system to measure the energy balance for steady state growth of Chlamydomonas reinhardtii grown at pH 6.5, and C. acidophila that was grown at pH 6.5 and 2.6. Energy use efficiency was quantified on the basis of light absorption, photosynthetic quantum yield, photosynthetic and respiratory quotient, and electron partitioning into proteins, carbohydrates and lipids. The results showed that lower growth rates of C. acidophila under both pH conditions were not caused by the differences in the photosynthetic quantum yield or in alternative electron cycling, but rather by differences in the efficiency of light absorption and increased dark respiration. Analysis of the macromolecular composition of the cells during the light phase showed that C. acidophila uses biosynthetic electrons preferentially for carbohydrate synthesis but not for synthesis of lipids. This led to a strong diurnal cycle of the C/N ratio and could explain the higher dark respiration of C. acidophila compared with C. reinhardtii . 相似文献
1000.
Tanguy De Bock Baptiste Kervyn de Meerendré Tim Hess Anne-Christine Gouder de Beauregard 《African Journal of Ecology》2009,47(3):289-298
The following research describes through an ecohydrological approach, the first assessment of the ecology of Lake Solai, with a particular emphasis on the vegetation. Lake Solai is located 50 km north of Nakuru in the Rift Valley in Kenya at E36°80'–36°84' to N00°05'–00°08'. It is a shallow lake that follows a very peculiar seasonal water regime, and that faces conflicts between agriculture and conservation water users. In the upper catchment, an overview of the agricultural practices was implemented and river water uses were identified to assess river flows. Crops/grassland and woodland/shrubland were the major land uses, covering c. 65% of the catchment. Closer to the lake, vegetation samples were collected around the lake together with samples of environmental factors such as soil and water quality. Thirteen vegetation communities were identified within four main zonations: forest, grassland, river inlet and rocky outcrop. These communities showed abundance, distribution and diversity determined mostly by the human pressures, the flooding periods and the salinity. Cynodon , Cyperus and Sporobolus genera were the most abundant. 相似文献