IS LONG-TERM AGRICULTURE NECESSARY TO CREATE STRONG SOIL-LANDSCAPE RELATIONS? USING PRAIRIE SOILS AS A TEST

This contribution focuses on the long-term creation and disruption of strong soil-landscape relations. Recent simulation work using the soil-landscape evolution model LORICA, has led to the suggestion that forest cover, through irregular but constant uprooting of trees, prevents or disrupts strong soil-landscape relations – and that deforestation followed by tillage is able to establish such relations within a few hundred years. These findings frame empirical work in a never-used forest in Europe that showed weak soil-landscape relations and widespread findings of strong soil-landscape relations in agricultural land. A key open question is whether an absence of both forest and agriculture still leads to strong soil-landscape relations. LORICA simulations from the same study suggest that this should be the case. Here, we present soil-landscape data from a never-ploughed native grassland in Kansas to test that hypothesis. Data were collected in two sub-catchments of Konza Prairie Biological Preserve, one of the remaining natural tallgrass prairies. In each catchment, about 50 points were sampled using a conditioned Latin Hypercube scheme. Composite soil samples from each location were analyzed for soil organic matter and texture. Then, soil-landscape relations were quantified using geomorphometric explanatory variables adapted to the local lithology, and compared with the published strength of such relations from forest and arable land. In addition, semivariograms were used to assess whether substantial spatial autocorrelation is present in native prairie soils. Spatial autocorrelation and soil-landscape relations were weaker than expected for most soil properties, leading us to reject our hypothesis. This seems to suggest that tillage, rather than the absence of trees, is the main factor creating strong soil-landscape relations in many of our landscapes.