Use of BEST procedure to assess soil physical quality in the baratz lake catchment (Sardinia, Italy)

Conversion of Mediterranean maquis and/or natural forest into agro-pastoral lands is a cause of soil degradation in many Mediterranean areas. Indicators of soil physical quality (SPQ) quantitatively linked to soil hydraulic properties are a valuable tool to assess the effect of land use changes. In this investigation, the Beerkan Estimation of Soil Transfer parameters (BEST) procedure for soil hydraulic characterization was used to estimate SPQ indicators. Four areas of the Baratz Lake watershed, Sardinia, Italy, characterized by both typical natural vegetation (holm oak [Quercus ilex L.] forest and high maquis) and degraded vegetation (grassland established after fire or clearing of the maquis) were considered. The SPQ was assessed by either independently measured soil physical attributes, like soil bulk density, organic C content, saturated hydraulic conductivity, and sorptivity, and capacitive and dynamic indicators calculated from the water retention curve estimated by the BEST procedure. Measured and estimated SPQ indicators unanimously showed that clearing of the maquis caused a severe deterioration of SPQ associated with soil compaction, organic matter loss, and decrease of macropore volume and soil aeration capacity as well as reduced water circulation. A different and unexpected result was obtained for the fire-affected area, where the SPQ was comparable to that of the neighboring oak forest area. We deduced that vegetation restoration after fire passage contributed to maintain a high organic matter content and to mitigate rain compaction effects. We concluded that SPQ indicators derived by applying the BEST procedure are suitable to detect land degradation in the natural environments studied.