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Upper Zone (upper + zone)
Selected AbstractsNutritional quality of semi-arid grassland in western Spain over a 10-year period: changes in chemical composition of grasses, legumes and forbsGRASS & FORAGE SCIENCE, Issue 3 2000Vázquez-de-Aldana From 1987 to 1996, the nutritional quality of the main botanical components (grasses, legumes and forbs) in semi-arid grasslands in the dehesa ecosystem in western Spain was analysed. Herbage samples were collected at the end of spring, in 30 locations, at two different topographic positions (upper and lower slope zones). Herbage mass over 2 cm and proportion of botanical components were estimated and samples were analysed for crude protein, neutral-detergent fibre (NDF), hemicellulose, cellulose, lignin and in vitro dry matter digestibility (DMD). Analysis of variance revealed a significant effect of sampling year on the herbage mass, proportion of botanical components and their nutritional quality. The three botanical groups, grasses, legumes and forbs, followed similar year-to-year trends in their crude protein, cellulose and lignin contents and in vitro DMD. Herbage mass was not significantly related to any meteorological variables, suggesting that interannual variation in biomass production of botanically complex pastures cannot be explained by a single factor. However, annual precipitation was significantly related to the proportion of the botanical group that was dominant at each slope zone: grasses in the lower zone and forbs in the upper zone. In the upper zone, spring precipitation explained part of the interannual variation in the NDF, cellulose, lignin contents and in vitro DMD of the botanical components. [source] PATTERNS OF INTERSPECIFIC INTERACTIONS IN THE ULVA -DOMINATED INTERTIDAL COMMUNITY IN A SOUTHERN COAST OF KOREAJOURNAL OF PHYCOLOGY, Issue 2000Y.J. Bhang In the southern coast of Korea, rocky intertidal zones where green tide commonly occurs are dominated by Ulva pertusa, red algal turf (a mixed stand of Gigartina intermedia and Gigartina teedii) and species of Enteromorpha with highly opportunistic occurrence. To investigate their interspecific interactions, a field experiment was carried out using press effect of one species removal from permanent plots (20 x 20cm) set up on two different tidal heights. Mechanisms of interaction were also attempted using artificial plants to test the possible effects of shading, scouring, allelopathy of U. pertusa on the turf algae. The turf-forming red algae lowered the abundance of U. pertusa presumably by inhibiting the recruitment of U. pertusa; this effect was consistent along the tidal height. However, the greater abundance of Enteromorpha was observed in the presence of turf in the upper zone, indicating a positive effect of turf on Enteromorpha. Once U. pertusa was successfully recruited and grown to the adult plant, it inhibited the growth of turf by shading, which was effective both in winter and summer regardless of desiccation stress. No scouring and allelopathic effects of U. pertusa on the turf were detected. When an open substrate was provided, Enteromorpha colonized the space faster than any other species in the upper zone, but the turf was the fastest one followed by U. pertusa and Enteromorpha in the lower zone. Results indicated that patterns of interaction represented a complex network with no ultimate winner and the outcomes of interaction varied over time and space. [source] Sedimentation History of Neogene Lacustrine Sediments of Su,eo,ka Bela Stena Based on Geochemical Parameters (Valjevo-Mionica Basin, Serbia)ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 6 2008AJNOVI, Aleksandra Abstract: Sediments of the western part of the Valjevo-Mionica basin (Serbia) were examined both geochemically and mineralogically to explain, on the basis of their sedimentological characteristics, the causes of changes in their qualitative and quantitative composition. A total of 62 samples obtained from the drillhole at depths up to 400 m was investigated. Using correlation of the obtained data, six geochemical zones were defined, two of which being specially distinguished by their mineralogical, geochemical and sedimentological characteristics. The first one, upper zone A, consists of banded marlstones interbedded with clay and oil shales and is characterized by presence of analcite and searlesite. These minerals and very high contents of Na2O indicate sedimentation in alkaline conditions with increased salinity in arid climate. That provided pronounced water stratification, as well as higher bioproductivity in the basin and sedimentary organic matter preservation. Therefore, the zone A sediments are characterized by high organic matter contents of the type which provides good potential for production of liquid hydrocarbons. Another specific zone, zone F, contains sediments with very high MgO, K2O and Li concentrations. Their geochemical correlation, as well as almost complete absence of illite in this zone, indicates the presence of interstratified clay mineral type illite-saponite (lithium-bearing Mg-smectite). [source] Natural 15N abundance of epiphytes depends on the position within the forest canopy: source signals and isotope fractionationPLANT CELL & ENVIRONMENT, Issue 4 2002R. Wania Abstract The natural 15N abundance (,15N) of epiphytes and its N sources were studied in the canopy of a lowland rainforest in Costa Rica. Vascular and non-vascular epiphytes and canopy soils were collected from four canopy zones and analysed for N contents and ,15N signals. In addition, the N concentrations and ,15N signatures of bulk precipitation, throughfall and stemflow were measured during the wet and the dry season. The ,15N values of epiphyte leaves decreased significantly from the lower zones (means of ,3ˇ9 and ,4ˇ3,) to the upper zones (means of ,5ˇ4 and ,6ˇ1,) of the canopy. In contrast, ,15N signatures of canopy soils (average ,0ˇ3,) differed little between the zones. Bulk deposition was enriched in 15N (+4ˇ3,) compared to all other potential N sources and was higher than throughfall and stemflow (+0ˇ5 to ,1ˇ3,). ,15N values of atmospheric deposition were inversely related to those of the epiphyte leaves, whereas N isotopic composition of canopy soils did not vary significantly. Consequently, it is concluded that the variations in foliar N isotope composition of epiphytes were not simply caused by utilization of isotopically different N sources, but by different 15N discrimination during N acquisition. [source] | |||||||||||||