Pedogenic Imogolite and Soil Environments: Case Study of Spodosols in Quebec, Canada

Abstract Spodosols similar in parent material, relief, and age but different in soil climate and vegetation were studied along two transects in Quebec, Canada. Soils of the northern transect (between 50 and 52°N) were under spruce ( Picea mariana ) forest in a colder region than that of the southern transect (at 46°N) where the forest was mainly deciduous, dominantly maples ( Acer sp. L.) with greater rooting depth. Major differences in properties of pedons between the two transects were: total organic C in B horizons of the northern pedons was less than half that in southern pedons, and ratios of inorganic to organic amorphous Al and Fe in B horizons of the northern pedons were 5 to 10 times that of the B horizons of the southern transect. Both the lower organic C content and the higher ratios of inorganic to organic amorphous Al and Fe in the pedons of the northern transect may be attributed to the differences in vegetative cover, soil temperature, and biological activities of the two transects. Pedogenic imogolite was detected in all B and some C horizons of the northern transect but in none of the pedons of the southern transect. The high organic C content in the pedons of the southern transect is thought to retard the formation of imogolite. The domination of inorganic forms of amorphous Al and Fe in the spodic and spodic‐like horizons of the northern transect support the hypothesis that much Al and probably some Fe are translocated and deposited as inorganic complexes with Si in some Spodosols. It indicates the desirability of basing the chemical criteria of a spodic horizon on an extractant that removes both organic and inorganic amorphous products of pedogenesis. The currently‐used pyrophosphate extractant removes mainly organic‐associated forms of Al and Fe.