The influence of substituting native forest by Pinus radiata D. Don and this one by Eucalyptus globulus on the O-horizont and some chemical properties of a Dystric Xerochrepts soil was studied. The site is located in southern Chile, near Concepcion city.
Substitution of the forest covers did not significantly affect the formation of the O-horizont. However, total accumulation of organic detritus and the thickness of the O-horizont were higher under pine. Humification is the dominant process, given the amount of organic detritus, 67% and 55% accumulated at the H layer, under pines and eucalyptus, respectively. While, under pine this figure amounted 47%. The C/N values confirm these figures, suggesting a more fresh condition of detritus under pines (55-66) and an intensive humification under native (49-32) and eucalyptus (45-33). However, the humus formed under native forest seems to be of higher quality with regard to pH, the Ca content and the C/N values. Related to the mineral soil, these results show that the replacement of the native cover significantly reduced acidity and increased, both, the ECEC and V. Whereas, the substitution of pines by eucaliptus increased the acidity and reduced the ECEC and V. The organic matter content of soil was not significantly affected by the treatments tested. It is concluded that, under the experimental conditions tested, the substitution of native forest by pines clearly improved the nutritional status of the soil. Whereas, the substitution of pines by eucalyptus affected the studied chemical properties negatively.