Effects on rainfall gradient on tree water consumption ans soil fertility on Quercus pyrenaica forests in the Sierra de Gata (Spain)

Abstract

Calculation of water consumption and nutrient fluxes were made for four Quercus pyrenaica forests along a rainfall gradient, located in the "Sierra de Gata" mountains (CW Spain), to obtain information about the evolution of fertility in long tems. It is concluded that the water content at the beginning of the active growth penod of the vegetation depends mainly of the soil characteristics; for that, there was a positive correlation between the annual evapotranspiration and the precipitation in the May-August penod, but not with annual precipitation. So, the greater abundance of rainfall in the wet season did not tend substantially to increase water consumption by the vegetation. On the other hand, there was a high correlation between the volume of annual rainwater and that of drained water; the excess of water in the soil produced on winter gives as result a nutnent leaching of the soil and a consequent l o s ~of fertility. This was confirmed by the net balance of several bioelements, the CdA1 ratio and pH of the soil solution, and canopy leaching values.