Soil microbial properties in Eucalyptus grandis plantations of different ages

Eucalyptus plantations are increasingly used in Brazil to produce wood and energy, although the long-term consequences for ecosystem processes have rarely been evaluated. We investigated the soil microbial properties (soil microbial C, N, respiration, carbon use efficiency, and microbial C-to-N ratio) among Eucalyptus grandis plantations of differing ages (1 to 4 years) in Northeast Brazil. An adjacent native forest was used as a reference. In general, soil microbial properties decreased in initial years of land-use change, but recovered to conditions comparable to an adjacent native forest after four years in the rainy season, but not in the dry season. The varying effects of Eucalyptus plantations and native forests between seasons may reflect differences in soil microbial communities with different responses to environmental conditions. Our results highlight the importance of long-term monitoring and microbial community analysis in order to adequately assess and understand the impacts of exotic forest plantations on soil microbial properties.