Indices based on surface indicators predict soil functioning in Mediterranean semi-arid steppes

Abstract

Methodologies based on indicators occupy a prevalent place when assessing ecosystem functioning and monitoring desertification processes because they are affordable yet do not compromise accuracy. The landscape function analysis (LFA), developed in Australia by David Tongway (CSIRO), uses soil surface indicators to assess the condition of a given ecosystem by producing three numerical indices (stability, infiltration and nutrient cycling) reflecting the status of basic soil functions. None of the previous studies aiming to validate the LFA indices have explored how they relate to surrogates of soil functioning using a large number of test sites capturing different climatic and soil conditions. We aimed to do so using data gathered in 29 Stipa tenacissima steppes in Spain. The nutrient cycling index was strongly correlated with soil variables related to microbial activity and nutrient cycling, such as soil pH, total soil N and P, soil respiration and phosphatase and β-glucosidase activities. Strong correlations between the infiltration index and both soil compaction and the water holding capacity of soils were found. The stability index was also significantly correlated with most of the soil variables evaluated. These relationships were evident in both gypsum and calcareous soils. Our results indicate that the LFA indices may be employed as surrogates of soil variables related to nutrient cycling and water infiltration in semi-arid S. tenacissima steppes. The LFA methodology has an enormous potential to assist land managers and policy makers in the establishment of cost-effective desertification monitoring and restoration programs in semi-arid environments.