Heat-Induced Degradation Processes in Forest Soils

Abstract

Degradation by heating was studied in samples from the top 5 cm of six woolandHumic Cambisols under Ulex and Pinus pinaster stands in N.W. Spain. After heating to various temperatures, the samples were exposed for 30 minutes to simulated rain with an energy of 24.16 joul m^-2 mm^-1. Three kinds of degradation were observed: 1) loss of organic matter and water by volatilization ; 2) dry breakdown ; and 3) wet breakdown. The observed degradation processes correlated well with the differential thermal analysis data. Below 170°C, volatilization losses appeared, but there was no dry breakdown and resistance to wet breakdown increased slightly; between 170°C and 380–460°C, all three kinds of degradation increased greatly; and above 460°C, no further volatilization, non dry breakdown ocurred, and wet breakdown tended to decrease.