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Are invasive species most successful in habitats of low native species richness across European brackish water seas? 总被引：5，自引：0，他引：5
Marjo Paavola Sergej Olenin Erkki Leppkoski 《Estuarine, Coastal and Shelf Science》2005,64(4):738-750
European brackish water seas (Baltic Sea, Black Sea and Sea of Azov, Caspian Sea) are subject to intense invasion of non-indigenous species (NIS). In these seas, salinity is the most important range limiting factor and native species seem to reach a minimum species richness at intermediate salinities. This trend, revealed by Remane in 1934 and later on confirmed by many other scientists, was compared to the salinity range of already established NIS in the European brackish water seas. It turned out that most NIS are well adapted to the salinities holding lowest native species richness, already in their native area, and that NIS richness maximum in brackish water seas occurs in the salinity intervals of native species richness minimum. A predictable pattern in the salinity range of NIS can be used as a tool in initial risk assessment of future invasions in brackish water seas, especially when mapping highly potential donor and recipient areas. A product of empty niches, suitable environmental conditions, and availability of proper vectors might be the most effective predictor for the invasibility of brackish water areas. 相似文献
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Several cores were compared to elucidate the grade of mercury retention in sediments of the Baltic Sea near Oulu, Finland. The known history of the mercury discharge to waste water from a chlor-alkali plant, the primary pollution source, was compared to that in the sedimentary record. One core was dated by lead-210 and varve counts. During the past thirty years, the rate of sedimentation was up to 10 mm per year corresponding to a dry matter accumulation rate of about 3 kg m–2a–1. Under these conditions, most of the mercury reaching the sediment was retained. Correspondingly, the mercury levels in fish were considerably lower, with a delay of some five years.The present mercury content of the upper layers is some 1/4 or 1/5 that of the late 1970's, but it is still some twentyfold compared to levels at the beginning of the century. The extent to which the present mercury level in the sediment represents the various phases of industrial emission remains unsolved due to the origin of mercury in this sea area from several other sources and due to difficulties in exact core correlations from different years. 相似文献
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Bertaux Jean-Loup QuÉmerais Eric Lallement Rosine KyrÖlÄ Erkki Summanen Tuula 《Solar physics》1997,170(2):365-370
In a recently published paper, Scherer and Fahr (1995) claimed that the departures of sky L emission measured by Prognoz 5 and 6 from an optically thin model can be attributed entirely to deficiencies of the optically thin approximation, and are not due to variations of solar wind ionization rate with latitude, as advocated since many years by our research group. They base their claim on the result of their new sophisticated model of L radiation transport.It is shown here that their new model, in the simple case of isotropic solar wind, predicts a distribution of intensity in a simple geometry which is completely contradicted by the observations: they find a minimum of intensity near the upwind direction, where a maximum has been observed consistently by all L instruments. Therefore, their conclusion based on an erroneous model must be rejected. 相似文献
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Population, income and ecological conditions as determinants of forest area variation in the tropics 总被引：1，自引：0，他引：1
The underlying causes of forest area variation were studied by using data from the original forest assessments between 1970 and 1991 of FAO FORIS database representing 477 subnational geographical units in 67 tropical countries. Multiple regression modelling was applied to measure the effects. Five ecological variables were used to control the varying ecological conditions in the subnational units. Three variables were used to control the varying reliability of forest inventory data. Population and income variables were found to be significant factors explaining forest area variation after controlling for ecological variation. In particular population density and income per capita turned out to be significant underlying factors of deforestation. The overall conclusion is that determining the factors behind forest area variation helps explaining the causes of deforestation. 相似文献
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Tomas KOHOUT Lauri J. PESONEN Alexander DEUTSCH Kai WÜNNEMANN Daniela NOWKA Ulrich HORNEMANN Erkki HEIKINHEIMO 《Meteoritics & planetary science》2012,47(10):1671-1680
Abstract– Physical properties of multidomain magnetite‐bearing porous pellets shocked up to 45 GPa were measured. The results show general magnetic softening as a result of shock. However, a relative magnetic hardening trend and slight magnetic susceptibility decrease is observed with increasing pressure among shocked samples. Initially, the shock also seems to cause a slight decrease in porosity, but at higher shock pressures macroscopic porosity increases progressively in our pellets. The microscopic porosity remains almost unchanged. Since our samples have distinctly higher initial porosity compared with samples used in previous studies, our results may be representative for impacts into highly porous magnetite‐bearing sedimentary or volcanic rocks and are relevant to impacts into such target rocks on Earth and Mars. 相似文献
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Erkki Kivinen 《International Journal of Earth Sciences》1942,32(4-5):644-646
Zusammenfassung In Finnland hat man im Auftrage der Geologischen Kommission rein geologische Bodenkartierungen ausgeführt.Kartierungen und Untersuchungen, durch die man die Eignung und Eigenschaften der Bodenarten in erster Linie mit Rücksicht auf ihre landwirtschaftliche Ausnutzung gekennzeichnet hat, sind seit 1910 durch das Institut, das unter den Namen Agrogeologische Abteilung der Geologischen Kommission, Staatliches bodenkundliches Institut gearbeitet hat und gegenwärtig Bodenkundliche Abteilung der Landwirtschaftlichen Versuchsanstalt heißt, angestellt worden. Die veröffentlichten bodenkundlichen Karten umfassen etwa 3 Mill. ha, aber unveröffentlichtes Material liegt in reichlichem Maße vor.Insbesondere mit Rücksicht auf die wirtschaftliche Ausnutzung der Moore hat der Finnische Moorkulturverein schon seit 1897 in verschiedenen Teilen des Reiches Mooruntersuchungen angestellt, deren gesamte Ausdehnung fast 1 Mill. ha ausmacht. Nur ein Teil der Ergebnisse ist veröffentlicht worden. 相似文献
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