Potential impacts of aridity on structural and functional status of a southern Mediterranean Stipa tenacissima steppe

• The current investigation provides evidence that southern Mediterranean Stipa tenacissima steppes vary both structurally and functionally along a gradient of aridity.
• Our findings suggest that increasing aridity may promote the loss of plant cover, reinforce erosive processes and deteriorate nutrient cycling in S. tenacissima steppes.
• Overall, the current research highlighted that future climatic conditions will dramatically affect the functioning of southern Mediterranean S. tenacissima steppes from Tunisia, particularly in the more arid sites.

Over the last decades, there has been a growing interest in evaluating the predicted potential impacts of future climatic conditions on ecosystem functioning. Ecological indicators developed to assess ecosystem functioning strongly rely on soil and vegetation variables.In the current investigation, we evaluated the structural and functional status of a southern Mediterranean Stipa tenacissima steppe along an increasing aridity gradient. We estimated also the predicted effects of aridity on their functioning.The wide variation of LFA indices, vegetation structural attributes and soil properties among the different study sites revealed structural and functional heterogeneity in S. tenacissima steppes with the increasing aridity. Correlations obtained between LFA indices and most patch attributes showed the importance of vegetation structural attributes on the functioning of S. tenacissima steppes. On the other hand, correlations found between LFA indices and most measured soil variables verified the significance of LFA indices in monitoring soil functioning in southern Mediterranean S. tenacissima steppes.The strong negative relationships observed between aridity and stability, nutrient cycling indices demonstrated that increasing aridity can reinforce erosive processes and deteriorate nutrient cycling (i.e. aridity decreased soil carbon, nitrogen and enzymatic activities).Similarly, aridity was negatively related to vegetation structural attributes including patch cover and landscape organization index. This finding suggests that any increase in aridity can promote the loss of perennial vegetation cover.The current investigation highlighted that predicted increasing aridity will dramatically affect the functioning of southern Mediterranean S. tenacissima steppes, especially in the more arid areas.