Influence of land use changes on landscape factors and characteristics of a Pliocene basin

Abstract

The impact of human activities on the landscape and its factors: soil, water, vegetation, geomorphology, etc., reaches nowadays unprecedented levels. A quali-/quantitative knowledge of landscape changes is needed to understand the anthropogenic influence and to create models in order to generate scenarios to assess the future trends of the landscape system. This is much more necessary when dealing with landscapes that at present are to withstand an accelerated and stronger anthropic stress. The paper’s aims are to present the effects of land use changes in the 1976-1994 period on landscape factors and characteristics in the northern part of the Asso River basin (Siena, Italy). The Asso River basin is included in the «Siena Graben» located in Central Italy (Tuscany). Data on lithology, hydrological basin orders, slopes, that is slope types and their length, height as relief energy and slope gradient, landforms as type, frequency and position along the slopes and land use were acquired by aerial photograph interpretation and controlled on the ground, at the slope level. In order to analyse relationships among the data, statistical basic and cluster analyses were carried out. Results show that in the above said period land use changes covered about 15% of the studied area and influenced the persistence of about 25% landforms. Arable lands and pastures and natural grasslands show increases of about 8% and 2% respectively. Vineyards and olive groves decrease of about 2% and complex cultivation patterns of about 3%. Forested areas show a slight increase of their extensions. Taking each landform into account, it results that most of the types decrease their presence in the range from 50% to 26%; the highest value is reached by shallow seated gravitational deformation; the lowest one is marked by biancana. An exception is shown by calanco potential areas with an increase of about 5%. Balza remain constant in time. The effects of land use changes on the landscape are explained both qualitatively and quantitatively. Cluster analysis shows that in general land use changes are mainly linked to slope gradient, to previous land use, to slope type and to lithology. Landforms are linked to all of the said factors. Slope length and height appear to be linked but statistically very distant from the other landscape factors. Statistical and cluster analyses confirm most of what highlighted by the aerial photograph interpretation and ground controls. The adopted methodology can be used in handling data for landscape analysis and in Geographical Information System applications and modelling, as statistical parameters and derivates show strong weights and linkages among the variables taken into account.