Comparing Different Methods to Determine Soil Physical Quality in a Mediterranean Forest and Pasture Land

Soil physical quality (SPQ) can be assessed by different experimental methodologies and criteria and the optimal/critical values or ranges for SPQ indicators are still approximate. Sampling soils with minimal anthropic pressures should allow improvements in SPQ assessment. Different experimental methodologies and criteria were applied to sample a Mediterranean oak forest (Quercus ilex L.) and pasture land, in Sicily, with a varying degree of anthropic disturbance. Soil water retention was determined in the laboratory and the field, using the BEST (Beerkan Estimation of Soil Transfer parameters) procedure of soil hydraulic characterization. Capacity-based indicators, the S index, and location and shape parameters of the pore volume distribution function were calculated for assessing SPQ. With the laboratory data, only the criterion using the capacity-based indicators suggested that SPQ increased as external pressures decreased. Therefore, this criterion appeared to be more reliable than the other tested criteria in the sampled environment. The field method was more prone to suggest good conditions and less able to signal differences between plots as compared with the laboratory method. A forest soil with a good SPQ has an ability to store and provide water to plant roots similar to, but it is more aerated than, a good agricultural soil. Developing BEST for SPQ assessment is advisable since parameters descriptive of the soil water transport properties can be collected with a single experiment. Simultaneous characterization of dendrometric and soil parameters at other sites is recommended to explore the relationships between SPQ indicators and characteristics of the forest cover.