Soil evolution after land-reshaping in mountains areas (Aosta Valley, NW Italy)

Mountain agriculture needs to face several limitations related to climate and topography. Land levelling, reshaping, and terracing are widely adopted in Europe, in order to ease mechanization and make agriculture more rentable. However, while the economic and productive benefits of these operations are well known, the effects on soil chemical and physical properties are not always assessed, and need constant monitoring over time. Intense soil rebuilding has been carried out in Aosta Valley (NW Italian Alps) to improve the accessibility and mechanization, including irrigation, of mountain grasslands. In this research we present studied on 3 soil chronosequences established in grasslands subject to soil rebuilding practices. The aim was to investigate the effects of land-reshaping operations on soil chemical and physical properties over time, by comparing changes in some selected soil properties such as organic C and soil laboratory indexes for quantifying soil structural resistance. The soil profiles generally showed a simpler morphology after rebuilding. Soil structure and consistency, that are recognized as soil physical quality indicators, after a sharp negative effect of the disturbance (i.e. decrease in Liquid limit, increased soil aggregates loss) generally showed a trend towards the restoration of the characteristics of the original soils in the medium or long-term time span. Despite the limited sample size, the results represent a first attempt to assess the effects of a technique which is being more and more applied in a mountain region, such as the Aosta Valley Region, where manufactured soils are a significant part of agricultural land. The main findings of our research indicated that: 1) structure and consistency of soils (i.e. aggregate loss, LL, PL) can be used as indicators of soil quality in response of anthropogenic soil disturbance due to land-reshaping operations, as they reflect the evolution of soil properties after intense disturbance; 2) after disturbance, soil recovery was relatively quick, despite the strong deterioration of the physical quality in the immediate (~6-12 months) aftermath of the operations.