Morphological features related to agriculture and faunal activity in three loess-derived soils in France

Abstract

Three soils developed in Late Weichselian loess in France were studied to document morphological features related to agricultural and faunal activities. One soil had been in deciduous forest at least 100 years, one had been in permanent grass pasture for at least 25 years, and one had been annually cultivated for at least 50 years. The investigation included field descriptions, chemical and physical characterizations, and thin section studies. The surface horizon (Ap) of the cultivated soil was thicker than surface horizons of the forest and pasture soils, probably because of deep tillage (to about 35 cm depth). Another probable effect of deep tillage of the cultivated soil was to mix horizons, destroying evidence of an eluvial zone near the soil surface. Soil in both forest and pasture exhibited numerous features related to faunal activity in both surface and subsurface horizons, including large channels, abundant fecal pellets, channel infillings, and organic intercalations. These features were correlated with rather weak expression of illuvial clay accumulations in pores of the B horizons, although bulk characterization indicated the presence of argillic horizons. In contrast, B horizons of the cultivated soil had somewhat lesser macroporosity and fewer fecal pellets, infillings, and intercalations but strongly expressed illuvial coatings. With the assumption that the three soils had similar morphologies before cultivation, the observations suggest that greater faunal activity in the soils in forest and pasture led to more significant disruption of illuvial pedological features than in the soil under cultivation.