Changes in fungal abundance and biochemical properties of soil through a temporal restoration of forests

Changes due to the exploratory management of the soil and cultivated plant species can interfere with the cycling of nutrients vital for soil fertility. This biogeochemical cycling of soil is an interaction of physical, chemical, and biological processes that can be altered by land use change and management. Therefore, the objective of this study was to evaluate soil quality indicators in sand-extraction-degraded areas that had been reforested at different times and compare them to an unrestored area and native forest fragments. The five areas reforested with native Atlantic Forest species were 20, 17, 10, 7, and 5 years old. The fungal abundance, microbial respiration rate, enzyme activity, and C content were evaluated in soil samples collected at a depth of 10 cm. In addition, the total organic carbon, soluble carbon content, total carbohydrates, moisture, organic matter, and pH of these soils were studied. Our results verified a significant improvement in the fertile fraction of these soils due to the action of microorganisms in the different reforestation areas. The longer the reforestation period, the more the soil exhibited similar characteristics to native forests and approached the level of primary forests. The unrestored sand mining degraded soil area had the poorest fungal community and the least biochemical activity, which was less than the fungal abundance and activity of the most recent reforestation. These results suggest that the use of microbial and enzymatic activities as soil quality indicators is a viable approach to assess the impact suffered from past uncontrolled exploitation in areas that are undergoing ecological restoration processes of native forests. • Microbiological and biochemical indicators demonstrate the role of soil functionality. • Gradual recovery was found in the soils in different phases of reforestation. • The fungal soil abundance was higher in the forested areas than in the degraded areas. • Older reforested areas presented higher fungal abundance than younger reforested areas. • Soils with greater organic carbon stocks promoted increased fungal abundance.