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Cation Content (cation + content)
Selected AbstractsEdaphic niche differentiation among Polybotrya ferns in western Amazonia: implications for coexistence and speciationECOGRAPHY, Issue 3 2006Hanna TuomistoArticle first published online: 22 FEB 200 To study the degree of edaphic specialization in Amazonian plants, the distribution patterns of seven species of Polybotrya ferns were studied in 109 sites in a climatically uniform area of northwestern Amazonia (Colombia, Ecuador and northern Peru). The two most abundant species of Polybotrya were found in about two-thirds of the sites with almost 7000 individuals each, the rarest species occurred in just one site with 40 individuals. Each of the seven species appeared to have a unique realised niche, when niche dimensions were defined by gradients in soil texture, soil cation content, and inundation. The species also differed in how broadly or narrowly they were distributed along each gradient. Some species were practically never found in the same sites, whereas others co-occurred with a high frequency, in spite of showing clearly different abundance patterns among sites. A single site only contains a small part of the edaphic variation present in the landscape, and a small proportion of any species' niche space, so broad-scale studies are needed to adequately describe and compare species' niches and to assess to what degree niche differences promote species coexistence. The distribution patterns in Polybotrya are consistent with, but do not prove, that ecological speciation may have been important in the radiation of the genus. If such a pattern is found to be common in other Amazonian plants, this would indicate that each evolutionary lineage has adapted to the available habitats largely independently of the others. [source] Zeolite synthesis employing alkaline waste effluents from the aluminum industryENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2002A. La Iglesia Zeolites 4A, 13X, Y, and HZSM5 have been synthesized from alkaline residues from aluminum finishing plants. These residues could contain concentrations of sodium aluminate and sodium hydroxide between 200 and 300 Kg/m3, and small concentrations of heavy metal cations (Cd, Co, Cr, Cu, Mn, and Zn). These contaminants make handling and disposal of these residues difficult. However, the physicochemical properties of the synthesized zeolites (cation exchange capacity of 3 mmol g,1, specific surface area between 600,900 m2g,1, particle size distribution between 0.5,2 ,m and whiteness of 97%) make them useful as detergents and catalysts. Analysis of the chemical composition of the raw materials and the reaction products demonstrates that the heavy metal cation content in the synthesized zeolites is low enough to allow their industrial use (lower than that of the original residues). Therefore, the production of various types of zeolites for industrial use could be used for the elimination of these residues from the aluminum industry. [source] Increases in pH and soluble salts influence the effect that additions of organic residues have on concentrations of exchangeable and soil solution aluminiumEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2002M. S. Mokolobate Summary It has been suggested that additions of organic residues to acid soils can ameliorate Al toxicity. For this reason the effects of additions of four organic residues to an acid soil on pH and exchangeable and soil solution Al were investigated. The residues were grass, household compost, filter cake (a waste product from sugar mills) and poultry manure, and they were added at rates equivalent to 10 and 20 t ha,1. Additions of residues increased soil pH measured in KCl (pH(KCl)) and decreased exchangeable Al3+ in the order poultry manure > filter cake > household compost > grass. The mechanism responsible for the increase in pH differed for the different residues. Poultry manure treatment resulted in lower soil pH measured in water (pH(water)) and larger concentrations of total (AlT) and monomeric (Almono) Al in soil solution than did filter cake. This was attributed to a soluble salt effect, originating from the large cation content of poultry manure, displacing exchangeable Al3+ and H+ back into soil solution. The considerably larger concentrations of soluble C in soil solution originating from the poultry manure may also have maintained greater concentrations of Al in soluble complexed form. There was a significant negative correlation (r = ,0.94) between pH(KCl) and exchangeable Al. Concentrations of AlT and Almono in soil solution were not closely related with pH or exchangeable Al. The results suggest that although additions of organic residues can increase soil pH and decrease Al solubility, increases in soluble salt and soluble C concentrations in soil solution can substantially modify these effects. [source] Importance of soils, topography and geographic distance in structuring central Amazonian tree communitiesJOURNAL OF VEGETATION SCIENCE, Issue 6 2008Stephanie A. Bohlman Abstract Question: What is the relative contribution of geographic distance, soil and topographic variables in determining the community floristic patterns and individual tree species abundances in the nutrient-poor soils of central Amazonia? Location: Central Amazonia near Manaus, Brazil. Methods: Our analysis was based on data for 1105 tree species (, 10 cm dbh) within 40 1-ha plots over a ca. 1000-km2 area. Slope and 26 soil-surface parameters were measured for each plot. A main soil-fertility gradient (encompassing soil texture, cation content, nitrogen and carbon) and five other uncorrelated soil and topographic variables were used as potential predictors of plant-community composition. Mantel tests and multiple regressions on distance matrices were used to detect relationships at the community level, and ordinary least square (OLS) and conditional autoregressive (CAR) models were used to detect relationships for individual species abundances. Results: Floristic similarity declined rapidly with distance over small spatial scales (0,5 km), but remained constant (ca. 44%) over distances of 5 to 30 km, which indicates lower beta diversity than in western Amazonian forests. Distance explained 1/3 to 1/2 more variance in floristics measures than environmental variables. Community composition was most strongly related to the main soil-fertility gradient and C:N ratio. The main fertility gradient and pH had the greatest impact of species abundances. About 30% of individual tree species were significantly related to one or more soil/topographic parameters. Conclusions: Geographic distance and the main fertility gradient are the best predictors of community floristic composition, but other soil variables, particularly C:N ratio, pH, and slope, have strong relationships with a significant portion of the tree community. [source] Mesoscale Gradients of Herb Richness and Abundance in Central Amazonia,BIOTROPICA, Issue 6 2006Flávia R. C. Costa ABSTRACT There are few hypotheses to explain local understory diversity patterns. There is a consensus that climate and soil fertility affect understory density and diversity at large scales, but few studies addressed the mechanisms controlling density and diversity locally. Here, I examine patterns of abundance and diversity of three understory herb groups along gradients of soil nutrients and topography at the mesoscale (64 km2) in a wet tropical forest, and possible factors causing them. Herb richness, diversity, density, and cover were measured in fifty-nine 250 × 2 m plots systematically distributed over Reserva Ducke, Manaus. Herb groups responded differently to environmental gradients. Whereas density and cover of pteridophytes increased with altitude and slope, Marantaceae density and cover decreased. Density of sedges increased with altitude, but did not vary with slope. Density and cover of Marantaceae and sedges but not pteridophytes increased with the soil cation content. Pteridophyte richness increased with slope whereas Marantaceae richness decreased, richness of both groups increased with cation content. Diversity increased with altitude for Marantaceae and decreased for pteridophytes. Some of these patterns agree with what is expected from herbs, such as the greater abundance of Marantaceae and sedges in flat and low altitude plots, where water availability is higher and probably also light, and the greater richness of Marantaceae and pteridophytes in higher nutrient plots. The unexpected results of higher abundance and richness of pteridophytes in slopes, instead of in bottomlands, suggest that biotic or litter-mediated controls may be important to set these patterns. RESUMO Existem poucas hipóteses para explicar os padrões locais de diversidade do sub-bosque. Existe consenso de que clima e fertilidade do solo afetam a densidade e diversidade do sub-bosque em macro-escala, mas poucos estudos procuraram os mecanismos que controlam a densidade e diversidade em escala local. Neste estudo, eu examino os padrões de abundância e diversidade de 3 grupos de ervas de sub-bosque ao longo de gradients de nutrientes e topografia em uma floresta tropical úmida, e os possíveis fatores causais. A riqueza, diversidade, cobertura e densidade das ervas foram medidas em 59 parcelas de 250 × 2 m, distribuídas sobre 64 km2 na Reserva Ducke, Manaus. Os grupos de ervas responderam de forma diferente aos gradientes ambientais. Enquanto a densidade e cobertura das samambaias aumentaram com a altitude e a inclinação do terreno, a densidade e cobertura de Marantaceae diminuíram. A densidade de capins aumentou coma altitude, mas não variou com a inclinação. A densidade e cobertura de Marantaceae e capins aumentou com o conteúdo de nutrientes do solo, mas não para as pteridófitas. A riqueza de samambaias aumentou com a inclinação do terreno enquanto a riqueza de Marantaceae decresceu, e a riqueza dos dois grupos aumentou com o conteúdo de nutrientes. A diversidade aumentou com a altitude para Marantaceae e diminuiu para as samambaias. Alguns destes padrões concordam com o esperado para ervas, tais como a maior abundância de Marantaceae e capins nas parcelas planas e baixas, onde a disponibilidade de água e provavelmente de luz são maiores. Entretanto, os resultados inesperados de maior abundância e riqueza de pteridófitas nos terrenos mais inclinados, ao invés de nos baixios, sugerem que controles bióticos ou mediados pela liteira podem ser mais importantes para o estabelecimento destes padrões. [source] The cyclic nucleotide-gated channel, AtCNGC10, influences salt tolerance in ArabidopsisPHYSIOLOGIA PLANTARUM, Issue 3 2008Kun-Mei Guo Cyclic nucleotide-gated channels (CNGCs) in the plasma membrane transport K+ and other cations; however, their roles in the response and adaptation of plants to environmental salinity are unclear. Growth, cation contents, salt tolerance and K+ fluxes were assessed in wild-type and two AtCNGC10 antisense lines (A2 and A3) of Arabidopsis thaliana (L.) Heynh. Compared with the wild-type, mature plants of both antisense lines had altered K+ and Na+ concentrations in shoots and were more sensitive to salt stress, as assessed by biomass and Chl fluorescence. The shoots of A2 and A3 plants contained higher Na+ concentrations and significantly higher Na+/K+ ratios compared with wild-type, whereas roots contained higher K+ concentrations and lower Na+/K+ ratios. Four-day-old seedlings of both antisense lines exposed to salt stress had smaller Na+/K+ ratios and longer roots than the wild-type. Under sudden salt treatment, the Na+ efflux was higher and the K+ efflux was smaller in the antisense lines, indicating that AtCNGC10 might function as a channel providing Na+ influx and K+ efflux at the root/soil interface. We conclude that the AtCNGC10 channel is involved in Na+ and K+ transport during cation uptake in roots and in long-distance transport, such as phloem loading and/or xylem retrieval. Mature A2 and A3 plants became more salt sensitive than wild-type plants because of impaired photosynthesis induced by a higher Na+ concentration in the leaves. [source] | |||||||||||||