Relevance of use-invariant soil properties to assess soil quality of vulnerable ecosystems : the case of Mediterranean vineyards

Vineyard landscapes in Mediterranean areas represent a strong cultural legacy and support a crucial socioeconomic sector. The sustainability of these landscapes is threatened by rapid changes of soil quality, in the context of global change and intensive management practices. Considering the Languedoc-Roussillon region of southern France as representative of Mediterranean soil and climate conditions, we evaluated the topsoil quality of vineyards at the regional scale, based on a set of 31 physical, chemical and biological soil indicators measured on 164 commercial vineyard plots. Almost all soil parameters were highly variable among plots. Biological activity was low but no systematic perturbation of the trophic web was noticed. The regional variability of use-invariant soil properties (such as calcium carbonate content and texture) was characterized and taken into account for the analysis of dynamic indicators. Invariant soil properties explained up to 25% of the variance of dynamic chemical and biological indicators. Consequently as a tool to improve soil management decision and recommendations, we proposed a grouping of the 164 vineyard plots into functional soil groups determined by soil invariant properties. Information redundancy between different dynamic indicators was analyzed, and their interpretation and limitations as indicators of topsoil quality were discussed. Our study has produced detailed topsoil indicator baselines that can be immediately used as references for winegrowers to appraise the topsoil quality of their vineyard in comparison with others