Probability mapping of iron pan presence in sandy podzols in South-West France, using digital soil mapping

Abstract

This work evaluated two different digital soil mapping methods for mapping the presence of iron pans in South-West France. The presence of iron pans limit rooting depth, thereby affecting available water content for plants and increasing vulnerability of trees to storms. In some cases, it may also limit the water infiltration rate and cause anaerobic conditions limiting rooting depth, biological activity and plant growth. This work evaluates the potential of a road-side survey sampling and subsequent digital soil mapping techniques to map the probability of iron pan presence in a French region. We tested 1) indicator kriging without taking into account ancillary covariates and compared the mapped probability with 2) logistic regression kriging which did account for ancillary covariates. The probability of iron pan occurrence was mapped at a regional level with a reasonable precision but adding ancillary co-variates to the model gave more realistic predictions. Likely, the goodness of the prediction is still hampered by the resolution of the employed DEM and by the spatial distribution of the observation points. Furthermore, we made some suggestions of the possible usage of the iron pan map; probability maps could help regional planning for forestry, agriculture and geotechnical projects.