Spatial variability of soils under a slash-burn cultivation system in Amazonas-Venezuela

Abstract

This paper analyzes, by geostatistical methods, the spatial variability in soil properties between two contrasting soils: under a recently slashed and burned cultivation system and another one 12- year old secondary forest after slash-burn. The soils are located in a Piaroa Community, Sipapo Forestry Reserve, State of Amazonas-Venezuela. In each field was settled a plot of 20 × 20 m and soil samples were taken approximately 5 m apart from each other with a depth from 0 to 20 cm. The data were located spatially in X-Y coordinates for semivariography and mapping by Kriging. The soil of the area was classified as Cambisol Dístrico (Typic Dystrustep), characterized by a low natural fertility, evidenced through high acidity, low content of organic matter, and very low of calcium, potassium, magnesium, sodium and phosphorus, and high content of aluminium. It was demonstrated that the burning affects the spatial variability of the soils attributes analyzed in this investigation, that is to say, somehow favors the space continuity at nearer distances, while in soils that have remained in rest during a certain time, succession on vegetation promotes a bigger diversity of values (different microhabitats) at nearer distances.