N-pool in volcanic ash-derived soils in Chile and its changes in deforested sites

Changes in N-distribution patterns in volcanic-ash of Chile after deforestation of a primary forest were measured. There is a clear tendency towards the depletion of N linked to high molecular weight fractions (humin, humic acid fractions) after the disturbance. These changes are illustrated schematically in relation to N input and output and to rhizosphere behavior after deforestation. and its pattern distribution within soil organic macromolecules is postulated to be a good indicator of N-dynamics in soils, which could be applied to detect soil deterioration processes. As an experimental model, it is proposed to characterize organic-N as N-fulvic, N-humic, N-humin and light organic-N.