Khettou, AhmedIkeb Melaizi, AbdelouahabBouazza Marouf, Khadidja2025-07-142025-07-142025http://dspace.univ-temouchent.edu.dz/handle/123456789/6650The main objective of this study is to evaluate the mycorrhizal infectivity potential (PIM) and microbial activity of degraded soils from a former gravel quarry located in Chaâbet El Leham (Aïn Témouchent). To achieve this, several biological indicators were assessed: mycorrhizal infectivity potential (PIM), arbuscular mycorrhizal fungi (AMF) spore density, culturable fungal microflora, and soil basal respiration. Special attention was given to the role of the pioneer species Euphorbia dendroides in shaping the microbial dynamics of rhizospheric soil. The mycorrhizal infectivity potential of rhizospheric soil is moderate; 32.11 g of soil are needed to mycorrhize 50% of test plants, compared to 77.62 g for bare soil, indicating a clearly higher infectivity potential near plant roots. AMF spore counts were 824 spores/100 g in rhizospheric soil and 405 spores/100 g in bare soil. Microbial counts revealed 1.06 × 10⁶ CFU/g of bacteria and 2.4 × 10⁵ CFU/g of fungi in rhizospheric soil, versus 4.6 × 10⁵ and 2.1 × 10⁴ CFU/g, respectively, in bare soil. Basal respiration was also higher in the rhizospheric soil (5.28 mg CO₂/50 g/48 h) than in bare soil (2.64 mg). These findings show that despite physical and chemical degradation, rhizospheric soil associated with a pioneer plant retains a functional capacity for mycorrhizal symbiosis. This highlights the importance of integrating AMF into ecological restoration strategies for degraded industrial or extractive sites.frMycorrhizal Infectivity Potential (MIP), microbial activity, degraded soils, quarry.Thesis