Around 40% of the original Brazilian savannah territory is occupied by pastures dominated by fast-growing exotic C4 grasses, which impact ecosystem nutrient cycling. The restoration of these areas depends on the re-establishment of soil processes. We assessed how restoration of abandoned pastures through direct seeding of native species and land-management practices (burning and ploughing) affect soil nutrient cycling dynamics compared to native savannahs. We compared the activity of soil enzymes related to carbon (C), nitrogen (N) and phosphorus (P) cycling, as well as soil microbial biomass and soil chemical properties, such as pH and the concentration of N, P, potassium (K) and soil organic matter, among abandoned pastures, native savannah and restored areas. Abandoned pastures had faster nutrient turnover than native savannah, dominated by slow-growing native species. This pattern was evident from the overall higher biomass-specific enzyme activity in abandoned pastures than in native savannah. Compared with native savannah, restored areas had similar levels of soil enzyme activity, but lower microbial biomass and soil organic matter. Synthesis and application: The low enzyme activity in restored areas was likely related to a reduced soil organic carbon concentration due to practices such as burning and ploughing, rather than plant-soil feedback. The lower immobilization of nutrients in microbial biomass and lower retention of nutrients in restored areas, compared with native savannah, is expected to favour the re-establishment of fast-growing exotic species. Furthermore, the modifications of soil chemical and microbial properties related to abandonment of pastures did not influence restoration outcomes, because land-management practices applied prior to direct seedling had a major impact on the soil microbial community and soil fertility. Therefore, restoration of abandoned pastures should consider a greater focus on restoring soil carbon and nutrient cycling.
|Date made available||2022|