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991.
In einem komplexen Feldversuch auf einem sandigen Standort wurde über einen Zeitraum von 5 Jahren in verschiedenen Fruchtfolgen die Wirkung unterschiedlicher Bodenbearbeitung und Mineral‐N‐Düngung auf die Nitratkonzentration in Bodenlösungen mit Hilfe einer Saugkerzenanlage untersucht. Die Nitratkonzentrationen in Bodenlösungen (60 cm Tiefe) wurden untersucht und die potentielle N‐Fracht auf der Grundlage der Nitratkonzentration im Bodenwasser und der klimatischen Wasserbilanz kalkuliert. Die Nitratkonzentrationen in Bodenlösungen folgten einer ausgeprägten jahreszeitlichen Dynamik, mit Maxima in der Hauptsickerperiode und Minima in der Vegetationszeit, wobei die Wirkung der Prüffaktoren in folgender Reihenfolge abnahm: Mineral‐N‐Düngung > Fruchtfolge > Bodenbearbeitung. In der Hauptsickerperiode wurde > 50% der jährlichen Sickerwassermenge und 36 . . . 94% der N‐Fracht ermittelt. Auf dem Untersuchungsstandort betrugen die maximalen N‐Frachten ca. 100 kg ha?1a?1. Die N‐Frachten wurden durch die N‐Entzüge der verschiedenen Fruchtarten beeinflusst. Durch mineralische N‐Düngung stiegen die N‐Entzüge von Wintergetreide um 42 . . . 85% und von Silomais um 32 . . . 53%. 相似文献
992.
Michael Baumecker Frank Ellmer Frank-Michael Chmielewski 《Archives of Agronomy and Soil Science》2013,59(5):533-542
The Static Nutient Deficiency Experiment at the location of Thyrow/Germany exists since 1937 and remained unchanged in its management during the whole period of experimentation. From the beginning of the 60th soil samples were collected every year in the autumn and the organic carbon content was determined constantly using the same method. For the period 1965-2000 a decrease of carbon content could be found in an order of 15% (average of all variants in the experiment). The air and soil temperatures showed rising tendencies. Since 1965 the average air temperature annually increased by 0.03°C and the soil temperature in the depth 0.1-0.2m by 0.02°C, respectively. According to the rising temperatures in this period the number of days with a soil temperature higher than 6°C increased by 3.8 days per decade of years. The evaluation of data by regression analysis revealed that in average the organic carbon content is reduced by 1.5mg per 100g soil each day which shows a higher soil temperature than 6°C. 相似文献
993.
Background
The excessive use of inorganic P (Pi) in soils is alarming as it is causing numerous environmental problems and may lead to the depletion of rock phosphate reserves earlier than expected. Hence, to limit the over-dependence on Pi, there is the need to investigate organic phosphorus (Po), which is the dominant P form of soil P pool, as an alternate P source for plant growth.Aim
The present study seeks to investigate organic P use efficiency of eight varieties of faba bean grown symbiotically.Methods
The plants were grown in pots (6 kg soil) under greenhouse condition with three P source, namely, phytic acid (organic P, Po), KH2PO4 (inorganic P, Pi), and no-P. The P was applied at the rate of 1.79 g kg−1 soil.Results
The plants grown with Po and Pi produced similar amounts of root, shoot, and total dry matters. Despite producing statistically similar dry matters, P uptake by Pi-fertilized plants was twofold higher than by Po-fertilized plants. Meanwhile, Pi differed significantly from Po in terms of nodulation characteristics such as nodule dry biomass and individual nodule dry biomass. However, Po varied significantly from Pi in P utilization and acquisition efficiencies. Principal component analysis of Pi and Po revealed no significant variation and close association, confirming the nonsignificant differences between the two P treatments. Among the varieties tested, Tiffany tended to accumulate more dry matter, coupled with highest organic P utilization efficiency (0.48 g mg−1) as well as the highest organic P beneficiary factor (80%).Conclusion
These results provide a solid basis for further comparisons at physiological, biochemical, and molecular levels between Tiffany (Po-efficient) and Fuego (Po-inefficient) varieties, offering deep insights into and making it easier to understand the mechanisms that allow soil Po to be utilized under symbiotic conditions. 相似文献994.
The effects of freshwater regulation and diversion on the adult and larval stages of fish and invertebrates in coastal marine waters are reviewed. Potential impacts of river modification are highlighted based on our present understanding of the role of fresh water on the physical, chemical and biological processes on the marine environment. These include effects on migration patterns, spawning habitat, species diversity, water quality and distribution and production of lower trophic levels. The effect of dams on anadromous and catadromous fish are also presented. We discuss in detail the marine response to specific river regulation projects on the Nile, Indus and rivers flowing into the Black Sea, San Francisco Bay and James Bay in Canada. A decline in some coastal fisheries with an overall negative impact on the biota is generally associated with reductions in freshwater flow. Extensive ecological considerations are needed during the planning stage of large-scale freshwater modification projects to minimize potential impacts. 相似文献
995.
Effect of yellow loess on clearance rate in seven species of benthic, filter-feeding invertebrates 总被引:1,自引:0,他引:1
Sandra E Shumway Dana M Frank Lisa M Ewart & J Evan ward 《Aquaculture Research》2003,34(15):1391-1402
Attempts have been made, especially in Asia, to displace harmful algal blooms (HABs) by spraying ‘china clay’ and ‘loess’ over affected coastal waters. The impact of this technique on benthic communities and processes is not known. We examined the effects of yellow loess on clearance rates of the benthic, filter‐feeding invertebrates, Crassostrea virginica (Gmelin 1791), C. gigas (Thunberg 1793), Mytilus edulis (Linnaeus 1758), M. trossulus (Gould 1850), Argopecten irradians (Lamarck 1819), and Crepidula fornicata (Linnaeus 1758). An Obelia species of hydroid was also studied and the percent time open was analysed. Depletion rates were measured using a range of loess concentrations suspended in culture with unicellular algae (Rhodomonas lens) in 0.45 μm filtered seawater. The effects of loess on clearance rates and behaviour were species‐specific. C. virginica was not impacted until clay concentrations reached 1.0 g L?1, while A. irradians showed a significant decrease at 0.01 g L?1. M. edulis showed a significant decrease in clearance rates at the 1 and 10 g L?1 concentrations. For hydroids, the percent time open was significantly lower than the control at 0.01, 0.1, and 10 g L?1. We clearly demonstrate that loess has a significant negative impact on filter‐feeding invertebrates. The use of clay as a strategy for mitigation of HABs should be approached with extreme caution. While the control of active blooms may eventually be possible, it may not necessarily be an environmentally advisable or responsible approach to dealing with HABs. 相似文献
996.
Nyanasengeran Movin Tatjana Gamova Sergei G.Surmach Jonathan C.Slaght A.A.Kisleiko James A.Eaton Frank E.Rheindt 《中国鸟类》2022,(1):17-24
Although Blakiston's Fish Owl(Bubo blakistoni)is widely treated as a single species,marked differences in the structure of pair duets between continental and in... 相似文献
997.
Coale KH Johnson KS Chavez FP Buesseler KO Barber RT Brzezinski MA Cochlan WP Millero FJ Falkowski PG Bauer JE Wanninkhof RH Kudela RM Altabet MA Hales BE Takahashi T Landry MR Bidigare RR Wang X Chase Z Strutton PG Friederich GE Gorbunov MY Lance VP Hilting AK Hiscock MR Demarest M Hiscock WT Sullivan KF Tanner SJ Gordon RM Hunter CN Elrod VA Fitzwater SE Jones JL Tozzi S Koblizek M Roberts AE Herndon J Brewster J Ladizinsky N Smith G Cooper D Timothy D Brown SL Selph KE Sheridan CC Twining BS 《Science (New York, N.Y.)》2004,304(5669):408-414
The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and abundant nitrate, yet iron-enhanced growth of phytoplankton may be differentially expressed between waters with high silicic acid in the south and low silicic acid in the north, where diatom growth may be limited by both silicic acid and iron. Two mesoscale experiments, designed to investigate the effects of iron enrichment in regions with high and low concentrations of silicic acid, were performed in the Southern Ocean. These experiments demonstrate iron's pivotal role in controlling carbon uptake and regulating atmospheric partial pressure of carbon dioxide. 相似文献
998.
Zuber MT Phillips RJ Andrews-Hanna JC Asmar SW Konopliv AS Lemoine FG Plaut JJ Smith DE Smrekar SE 《Science (New York, N.Y.)》2007,317(5845):1718-1719
Both poles of Mars are hidden beneath caps of layered ice. We calculated the density of the south polar layered deposits by combining the gravity field obtained from initial results of radio tracking of the Mars Reconnaissance Orbiter with existing surface topography from the Mars Orbiter Laser Altimeter on the Mars Global Surveyor spacecraft and basal topography from the Mars Advanced Radar for Subsurface and Ionospheric Sounding on the Mars Express spacecraft. The results indicate a best-fit density of 1220 kilograms per cubic meter, which is consistent with water ice that has approximately 15% admixed dust. The results demonstrate that the deposits are probably composed of relatively clean water ice and also refine the martian surface-water inventory. 相似文献
999.
Zimmermann R Strauss JG Haemmerle G Schoiswohl G Birner-Gruenberger R Riederer M Lass A Neuberger G Eisenhaber F Hermetter A Zechner R 《Science (New York, N.Y.)》2004,306(5700):1383-1386
Mobilization of fatty acids from triglyceride stores in adipose tissue requires lipolytic enzymes. Dysfunctional lipolysis affects energy homeostasis and may contribute to the pathogenesis of obesity and insulin resistance. Until now, hormone-sensitive lipase (HSL) was the only enzyme known to hydrolyze triglycerides in mammalian adipose tissue. Here, we report that a second enzyme, adipose triglyceride lipase (ATGL), catalyzes the initial step in triglyceride hydrolysis. It is interesting that ATGL contains a "patatin domain" common to plant acyl-hydrolases. ATGL is highly expressed in adipose tissue of mice and humans. It exhibits high substrate specificity for triacylglycerol and is associated with lipid droplets. Inhibition of ATGL markedly decreases total adipose acyl-hydrolase activity. Thus, ATGL and HSL coordinately catabolize stored triglycerides in adipose tissue of mammals. 相似文献
1000.
We have developed a method to separate metallic from semiconducting single-walled carbon nanotubes from suspension using alternating current dielectrophoresis. Our method takes advantage of the difference of the relative dielectric constants of the two species with respect to the solvent, resulting in an opposite movement of metallic and semiconducting tubes along the electric field gradient. Metallic tubes are attracted toward a microelectrode array, leaving semiconducting tubes in the solvent. Proof of the effectiveness of separation is given by a comparative Raman spectroscopy study on the dielectrophoretically deposited tubes and on a reference sample. 相似文献