Vegetation and soils of tidal floodplains of the Amazon estuary: a comparison of varzea adn terra firme forests in Para, Brazil
1999
Montagnini, F. | Muniz-Miret, N. (Yale School of Forestry and Environmental Studies, 370 Prospect St., New Heaven, CT 06511 (USA))
Vegetatation and soils of tidal floodplains of the Amazon estuary: a comparison of varzea and terra firme forests in Para, Brazil. The floodplains of sediment-rich rivers comprise 200,000 square kilometres of the Amazon basin. Varying flood regimes within this region contribute to different forest formations along the basin. This study compared tree species composition, forest-floor litter biomass, and soil chemistry of three sequentially-aged secondary forest stands of tidal "varzea" (5, 15 and 35 years old) and one "terra firme" (non inundated) stand of mature forest in the southern Amazon estuary. Tree species diversity was much lower in the varzeas than in the terra firme. Total tree basal area was highest in the terra firme, followed by the 35-, 15-, and 5-year varzeas respectively. In each varzea site, the Leguminosae and Palmae families comprised more than 50 per cent of total basal area. Forest-floor litter was significantly higher in the terra firme than in the varzea sites. Water drainage was an important influence on vegetation and soil chemistry among the varzea sites. Concentrations of basic cations (Ca, Mg and K) and extractable P were higher in the soils of the three varzeas than of the terra firme. The pH of the top soil in the terra firme was significantly lower than in all other sites except the oldest varzea. Total C concentration in the soil was highest in the 5- and 35-year varzeas. Total soil N also was higher in the tidal varzeas than in the terra firme site. Interpretation of these findings was limited due to lack of proper site replication, and because age and inundation regimes both varied among sistes. However, the results tend to confirm the expectation that soils of tidal varzeas are more fertile than those of terra firme sites, and that tidal varzeas present a more limited species composition than terra firme forests.
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