The aim of the present study was to determine the effect of two implanted forest species with different vegetal residue chemical compositions on the biological and biochemical properties of soil. The study site was located in the INTA Forestal Station of Trevelin, Chubut, Argentina. Samples were extracted from soil in forest plots dominated by Radiata Pine (Pinus radiata D. Don.) or European Ash (Fraxinus excelsior L.). Microbial respiration, dehydrogenase activity, community-level physiological profile (CLPP) and index of microbial community functional diversity were used as biological parameters; and acid phosphatase, protease and β-glucosidase activities were employed as biochemical parameters. Microbial respiration, dehydrogenase and acid phosphatase activities showed greater values in soil under European Ash trees; however, significant differences in protease and ß-glucosidase activities were not observed among species. The higher organic C content of soil under European Ash trees and lower lignin and greater N and P content of the leaves of European Ash trees could be responsible for the greater biological and biochemical activities observed in the soil. Principal component analysis (for PC1) showed significant differences in the physiology of microbial communities associated with these forest species. The Shannon-Weaver Index (H) of the functional diversity of microflora did not present significant differences among forest species.