Functional Diversity of Soil Microorganisms in Taiga Forests in the Middle and Late Stages of Restoration after Forest Fires

Fire can significantly affect the structure and function of forest soil microorganisms. Therefore, it is important to study the effects of different fire intensities on soil microbial carbon source utilization capacity in cold-temperate larch forests to protect and utilize forest ecosystems. In this study, we investigated the effects of different burning intensities on the carbon utilization capacity of soil microorganisms in fire sites from 2010 and 2000 using Biolog-Eco technology. Our findings revealed that (1) fire significantly increased soil pH, AN (available nitrogen), and AK (available potassium) (p < 0.05); (2) fire significantly increased the average color change rate (AWCD) of soil microorganisms (p < 0.05); (3) the Shannon index of soil microorganisms increased significantly, whereas the Simpson index and the McIntosh index decreased significantly after the fire—however, the McIntosh index in the 10M site was not altered; (4) the metabolic functions of soil microbial communities differed significantly among different fire intensities—MC (moisture content), TN (total nitrogen), and AK were the most influential soil environmental factors in the soil microbial community; and (5) mid-term fire restoration significantly increased microbial responses to carbohydrates, amino acids, esters, alcohols, amines, and acids, while late-fire burn sites significantly increased the microbial utilization intensity of amino acids, esters, and acids. In conclusion, fire significantly altered the functional diversity of soil microorganisms and microbial activities related to carbon source substrate utilization. Additionally, the ability of microorganisms to utilize a single carbon source substrate was also altered.