Relaciones agua-suelo-vegetación.-Influencia del cambio de uso en la tasa de infiltración de Andisoles (Tenerife, I. Canarias)

Abstract

ABSTRACT The volcanic island of Tenerife (Canary Islands) has a wide variety of Andisols which have formed on recent pyroclast materials (Udands, Ustands, Xerands and Vitrands). The Udands are situated on the northern side of the island, at heights where condensation of the trade winds occurs (900-1600m), while the Ustands are also located mostly on this side, albeit at a lower altitudinal strip. Under natural conditions, these soils present favourable physical properties, with high structural stability and resistance to water erosion. The aim of the present work is to study modifications in the Basic Infiltration Rate (BIR) caused by a change in the use of the soils. 26 Udands zones (11 natural and 15 modified) were selected along with 11 Ustands zones (4 natural and 7 modified). The typical vegetation in the natural zones is, in the case of the Udands, ‘fayal-brezal’ (Myrica faya, Erica arborea) or Canarian pine (Pinus canariensis), and pine in the case of the Ustands. The main modifications to use were as follows: deforestation, deforestation and grazing, repopulation of pines, abandoned farmland or farmland currently in use. The infiltration velocity was estimated using the double ring method, with at least three repetitions. The results obtained show that, in the soils with natural vegetation, the BIR is higher in the Udands (very fast) than in the Ustands (fast), averaging 575 mmh-1 compared to 150 mmh-1. In the soils with modified cover the values fall to 96 mmh-1 and 91 mmh-1 respectively. We conclude that modified use leads to a drastic reduction in the BIR of Andisols, causing it to change from very fast-fast to moderately fast, with the consequent increase in runoff and water erosion.