ChileanJAR

The number of fungi and actinomyces in volcanic-ash derived soils is very high while bacteria is clearly depressed. From a microbiological standpoint and unlike non-volcanic soils, this constitutes the most striking feature of these soils. High levels of organic carbon, indicating organic matter accumulation, high water retention capacity and high agregation percentages would be a consequence of biochemical activities, particularly enzymatic ones, sustained by such unusual microbial ecology. By the other hand, low pH values in the soil environment depress bacteria multiplication, thus favoring indirectly fungi and actinomyces competition. Physico-chemical conditions created iri the soil systems by amorphous allophanic active surfaces would enhance adsorption, and consequently stabilization, of the microbial humic polymers and other metabolic products. It is concluded that soils derived from volcanic ashes in Chile represent mature ecosystems wherein biochemical processes mainly supported by fungi and actinomyces, are being enhanced by physicochemical mechanisms, furnished by the inorganic components in the natural environment.