NUTRIENT STATUS OF AMAZONIAN CAATINGA FORESTS IN A SEASONALLY DRY AREA - NUTRIENT FLUXES IN LITTER FALL AND ANALYSES OF SOILS

Amazonian caatinga, a low-stature forest type confined to seasonally w aterlogged white-sand soils, occurs at La Esmeralda (Orinoco basin) un der a lower rainfall than at San Carlos (Rio Negro basin), where many previous studies have been made. The nutrient status of forest types a t La Esmeralda are compared and related to those of forests at San Car los. At La Esmeralda, stature declines from well-drained palm-rich for est (PRF), via waterlogged tall caatinga (TC), to superficially waterl ogged short caatinga (SC). Along this sequence, total fine litter fall decreased (7.6, 6.7, and 5.2 Mg.ha(-1).year(-1)), N flux decreased (6 6, 59, and 40 kg.ha(-1).year(-1)), Ca flux increased (27, 44, and 85 k g.ha(-1).year(-1)), P flux decreased nonsignificantly, and there was n o trend in Mg or K fluxes. Resin-exchangeable P concentrations of 0-10 cm soil samples increased along the sequence (20, 28, and 30 mu g.g(- 1)). The conclusion that N is in increasingly short supply as a result of waterlogging agrees with results previously obtained at San Carlos . The P flux in leaf litter fall of forests at La Esmeralda (range 1.0 -1.3 kg.ha(-1).year(-1)) is lower than that of tall caatinga at San Ca rlos (2.0 kg.ha(-1).year(-1)) or ''typical'' rain forests (mean 2.6 kg .ha(-1).year(-1)), suggesting that P is also relatively scarce.