Chemistry and Mineralogy of Soils cultivated with Eucalyptus (Eucalyptus sp.)

Chemical and mineral analyses were performed with the objective of evaluating the content and availability of nutrients for Eucalyptus growth in forests of Rio Grande do Sul state, Brazil. The Quartzarenic Neosol presented a very simple mineralogy, with an extremely poor nutrient content. The Melanie Gleisol, Haplic Planosol and Red-Yellow Argisol revealed a low Ca and Mg content, while the Haplic Cambisol, Litholic Neosol and Red Argisol presented higher amounts of these nutrients. The data of the annual average increment (AAI) of seven-year old Eucalyptus permitted the distinction of three soil groups according to their differential attributes: the first group formed by well drained soils (AAI >= 46 m(3)/ha/year), the second group formed by waterlogged soils (AAI approximate to 40 m(3)/ha/year) and the third group formed by very sandy soils (AAI of 38 m(3)/ha/year).388864565

Spatial distribution and secondary production of Copepoda in a tropical reservoir: Barra Bonita, SP, Brazil

The present paper aims to describe the spatial distribution of zooplankton copepods, their biomass and instantaneous secondary production, in Barra Bonita, a large eutrophic, polymitic reservoir (22° 29' S and 48° 34' W) on the Tietê River, of the Paraná basin. Sampling was carried out during two seasons: dry winter and rainy summer. Species composition, age structure and numerical density of each copepod species population were analyzed at 25 sampling stations. Secondary production was calculated for Copepoda, the dominant group in zooplankton communities, taking Calanoida and Cyclopoida separately. Copepoda represented the largest portion of the total zooplankton biomass, the dominant species being Notodiaptomus iheringi among the Calanoida and Mesocyclops ogunnus and Thermocyclops decipiens among the Cyclopoida. The production of Copepoda was higher during the rainy summer (23.61 mgDW.m-3.d-1 in January 1995) than during the dry winter season (14 mgDW.m-3.d-1 in August 1995), following the general pattern of abundance for the whole zooplankton community. Among the copepods, Cyclopoida production was higher than that of Calanoida, a pattern commonly observed for tropical lakes and reservoirs. Barra Bonita copepods are very productive, but there was a great degree of spatial heterogeneity, related to the physical and chemical conditions, particularly the level of nutrients and also to phytoplankton biomass