This study aimed to examine the dynamics of soil functional indicators under the influence of deadwood in old mixed beech forests in northern Iran. In January and February 2006, several strong wind events occurred in the forest of Khanikan, which led to severe windthrow. All the fallen trees remained in the protected parcel and were not removed. Immediately after tree felling in the studied areas, five common tree species [Fagus orientalis (Fagus), Acer velutinum (Acer), Carpinus betulus (Carpinus), Alnus subcordata (Alnus), and Tilia begonifolia (Tilia)] with the highest abundance of deadwood (with 14 individual trees) were marked as permanent plots for monitoring their effect on soil functions. Wood samples were collected from the trunks and soil samples (0–10 cm depth) from the lower part of deadwood in August 2011, 2016, and 2021. In addition, soil samples were taken from areas that did not have deadwood as control areas. For the study of soil biological parameters, soil samples were collected in August and November (2011, 2016, and 2021). However, for monitoring soil N transformation, soil samples were taken in August, September, November, and December (2011, 2016, and 2021). We found that Alnus and Carpinus deadwood had higher N, K, P, and Ca contents than deadwood of other species. Higher values of C and Mg were observed in Fagus deadwood in the final stages of sampling (2021). Anlus deadwood enhanced the stability of soil aggregates, soil nutrient contents, as well as soil enzyme and microbial activities, and soil fauna and microflora populations during the decay process. Based on our findings, the intensity of soil functions increased in the order control < Fagus < Tilia < Acer < Carpinus < Alnus, which corresponds to the increasing quality of the deadwood of the tree species. Our data emphasize that retaining deadwood is highly effective in boosting carbon and nutrient cycling in forest ecosystems, which may have implications for forest management strategies to improve soil ecological functions and forest sustainability. Although our observations were obtained in an old mixed beech forest, the importance of deadwood on soil functional characteristics can also be assumed in a broader range of forest environments, but this requires further investigation to determine the mechanisms that explain these phenomena. [ABSTRACT FROM AUTHOR]