The recurring cycles of biancana badlands: Erosion, vegetation and human impact

The biancana badlands, a typical element of the southern Tuscany landscape, were in expansion for centuries, until bulldozers began erasing them for land reclamation purposes. Over the last 10-15years some of the scattered remnants of biancanas have been placed under protection in order to preserve their biodiversity and their particular cultural and geomorphological landscapes. Rural abandonment and the lack of appropriate management practices have contributed to vegetation encroaching on biancana badland slopes, causing a loss of elements of high ecological and cultural values, as well as eroded spots. The aim of this paper is to explore the direction and rate of change in land use of the biancana badland landscapes over the last 50years, evaluating the erosion-vegetation dynamics and examining the processes involved in two biancana badlands, "Lucciola Bella" and "Crete di Camposodo & Crete di Leonina", which are Sites of Community Importance. First, we analysed the landscape changes that occurred in the biancana areas from 1954 to 2005, comparing old and recent land use maps. TWINSPAN classification was applied on selected plots of a plant dataset to distinguish vegetation types and identify the indicator species of each different type. We then evaluated soil erodibility on the eroded biancana surfaces, regosols and well-developed vertisols, which represent the coexisting extremes of the soil situation within the biancana badlands. We empirically assessed the effects of a few roots on saturated soil shear strength to introduce direct links between plants and soil processes. Our results showed a decrease in bare or scarcely vegetated spots of 0.9ha y-1: if the encroachment continues to progress at this rate, in 35-40years from now all the biancana domes will be completely re-vegetated. Encroachment on the most eroded biancanas was mainly ascribed to generalist ruderal species, such as Avena fatua and Dactylis glomerata. We showed that rills and subsurface micropipes are characterized by the same erosion processes, meaning that they can be contrasted and eventually halted by the same means, and we observed a clear positive trend that will substantially suppress rilling at very low plant cover (no more than 20%). Badlands were previously kept alive by limited but nonetheless devastating grazing activities. If this picture is correct, then mimicking traditional badland grazing practices seems to be a necessary step towards saving the landscape and biodiversity that the protected areas were established to preserve.