A field methodology for assessing man-made disturbance in forest soils developed in loess

Ancient forests which have never been under agriculture often have larger e cological and pedological value than later established forests. We made a r econstruction of the land use history of the Meerdaal forest complex in cen tral Belgium since 1759. Soil profiles of 33 recent forest sites and of con tiguous ancient forest parcels were examined morphologically by augering to 120 cm depth, pH(KCl) was determined on samples from every horizon. The da ta were analysed by Principal Component Analysis, and the axes were used as a basis for derivation of horizon parameters. Former agricultural land use since 1759 can still be recognized in three soil morphological characteris tics: colour of the eluviation horizon, intactness of the horizon containin g illuviated clay and thickness of the organic layer. These parameters were combined into a 'naturalness index: which differs significantly between an cient and recent forest and can be easily and cost-effectively obtained to assess the degree of man made disturbance of forests on loess-derived soils .