Establishing an index and identification of limiting parameters for characterizing soil quality in Mediterranean ecosystems

• Selection of the most appropriate indicators to obtain an index of soil quality
• Index ratio obtained with the parental material, type and land use of soil
• Identification of the limiting parameters of the soil in Mediterranean ecosystems

The aim of this work was to develop a suitable index for characterizing the quality of soils in semiarid Mediterranean ecosystems. The preliminary estimate of the attributes involved in soil quality was made taking into account the opinion of experts and our own experience in such ecosystems. These attributes were based on different physical (granulometry, aggregate stability, water holding capacity at 33 and 1500 Kpa, available water, bulk density, particle density and plant cover) and biochemical (organic carbon, nitrogen, pH in water and potassium chloride, electrical conductivity, cation exchange capacity, available ions such as sodium, potassium, magnesium, iron, copper, manganese and zinc, and dehydrogenase activity) properties of the soil related with its sustainability. Principal components analysis (PCA) was used to discriminate between the initial variables considered, in order to select those that may be included in an index that reflects the quality of soils in semiarid Mediterranean agricultural areas. The index obtained includes variables related with the physical properties of the soil, chemical fertilization and biological activity. The index potentially reflects the variations that occur in agricultural land and may be considered a suitable tool for the early detection of changes in the soil and for monitoring the effects that human actions may have on it.