0000000000498100
AUTHOR
Carlos Clemente Cerri
Characterization of organic matter in topsoils under rain forest and pasture in the eastern Brazilian Amazon basin
In topsoils under forest and 7-, 12- and 17-year-old pastures, organic matter was characterized by analysing C and N distribution in particle-size fractions, the C decomposition rates of soil and particle-size fractions and by employing density-fractionation of macro-organic matter (>150 μm). The C and N associated with clay fractions increased with increasing age of pasture. The weight (%) of macro-organic matter and its heavy fractions (>1.37 g cm–3) also increased with increasing age of pasture. However, in a long-term incubation (100 days), these changes seemed to involve an increase in the C decomposition rate in the topsoil of the oldest pasture. Using the C decomposition rates of par…
Organic matter dynamics and aggregation in soils under rain forest and pastures of increasing age in the eastern Amazon Basin
Abstract In the eastern Amazon basin, four neighbouring clayey Oxisols with similar particle-size distributions were selected, one under rain forest and three under pasture for 7, 12 and 17 years, respectively. These soils were sampled at depth intervals of 0.1 m down to 1 m. Although no clear effect of pasture establishment on aggregate stability was assessed, significant negative effects of cattle trampling on porosity and water retention and of vegetation change on clay water-dispersion were observed in the organic-rich horizons (0–0.40 m layers). Indirect evidence of a great change of the nature of organic materials was also suggested, particularly with (i) an increase in both negative …
Carbon decomposition of the topsoils and soil fractions under forest and pasture in the western Brazilian Amazon basin, Rondonia
The topsoils of two sites, comprising natural forest and 4- and 20-year-old pastures, respectively, were selected in Rondonia to evaluate the changes of soil organic matter due to pasture establishment. These changes were evaluated by measuring the proportions of the C and N associated with clay and silt fractions, and by the C decomposition (CD) rate of the whole topsoils and their size fractions. The topsoils studied had large proportions of C and N associated with fine fractions, especially with clay fractions. The CD rate of the silt fractions was higher than that of the clay fractions under the two forest topsoils and under the 20-year-old pasture. The CD rate of the silt fractions und…
Factors influencing carbon decomposition of topsoils from the Brazilian Amazon Basin
The influence of texture and local climate, especially precipitation, on C decomposition was evaluated in topsoils under forest and pastures at different sites located in the western, central, and eastern Brazilian Amazon Basin. Independent of the geographical location and vegetation cover, C decomposition was lower in topsoils of fine texture with a sand/clay ratio of less than 1, compared to topsoils of coarse a texture with a sand/clay ratio ranging from 2 to 8. In the former, the low sand/clay ratio appears to reduce C decomposition. In the latter, besides the effect of the high sand/clay ratio, the local climate, especially the annual precipitation, seems to play an important role in c…