Ecology of the Jari-Paru microregion I. Chemical and Physical Properties of The Soils From Eight Primary Forest Communities.

Abstract

This paper describes the chemical and physical properties of the soils from eight primary forest communities in the microregion of Jari-Paru, Lower Amazon. Although the Jari soits had lhe same general properties described for the Amazon soils, a large variation was observed among them. Tn texture they varied from almost pure quartz sands to heavy clays. The variation in texture paralleled the region 's relief and geology. Sandy soils occurred in the alluvial undulating plains such as those found southwest of Monte Dourado, formed by Tertiary sediments. The most clayish soits occurred in 135 to 200 metre terraces made by Plio-Pleistocenic sediments. In chemical terms, the soil found in the "varzea" forest had the highest amounts of Phosphorous and other nutrients, as expected. Among the "terra firme" soils, the most fertile ones were those found at the Jari Ecological Station (IBAMA forest), at 450m altitude, which are formed by Paleozoic sediments.