Effects of climate change on soil respiration and carbon processing in Mediterranean and semi-arid regions: An experimental approach

Recent regional climate-change models indicated significant changes in the temporal and spatial distribution of rainfall in the Mediterranean-Basin region. Understanding the consequences of rainfall alterations for soil respiration and carbon processing in these regions is essential, considering their crucial functions for soil fertility and ecosystem functioning. Our aim was to evaluate the effect of rainfall manipulations and shrub cover on a soil microbial community within a climate-change framework. Three rainfall-manipulation treatments were designed to reflect potential changes in precipitation regimens: supplemented winter rainfall; winter drought; and control. Soil samples were collected seasonally under shrub (Sarcopoterium spinosum) canopies and between shrubs. Our results indicate significantly (p < 0.05) higher soil moisture in the supplemented winter-rainfall treatment in the Mediterranean and semi-arid sites in the second winter, mainly due to differences in the rainfall distribution pattern. Microbial biomass was significantly (p < 0.05) higher under dry conditions compared to more mesic conditions. Soil abiotic parameters, e.g., moisture, organic carbon, and dissolved organic carbon, were significantly higher in the shrub understory compared to open spaces at the semi-arid site. The present study elucidates that the multifaceted importance of shrub cover as an organic-matter donor, prolonging moisture availability and moderating temperature and radiation, increases under arid conditions.

► Microbial biomass was higher under dry conditions than mesic conditions.
► Soil abiotic parameters were higher in shrub-understory at semi-arid site.
► Shrub-cover importance as organic-matter donor increases under arid conditions.