Characterization of soil ecosystems in Costa Rica using microbial community metrics.
The goals of the research presented in this issue of Tropical Ecology were to demonstrate that differences in soil DNA-based microbial community characteristics, biomass, microbial activity, and C and N nutrient dynamics can be used as indicators of environmental change, specifically to show how land management, restoration strategies and climate change may be impacting the soil ecosystems of lowland forests and montane cloud forests of Costa Rica. In the studies conducted in lowland secondary forests, the bacterium Frankia was found to be critical for nitrogen-fixation in the soils associated with nitrogen-fixing tree Pentaclethra macroloba, but Frankia, Rhizobium, Archaea, and Type II methanotrophs were also collectively important in recuperation of the soil N and in enhancing microbial biomass C via more efficient use of organic C. These same secondary forest soils had greater levels of inorganic P and N, organic carbon, and microbial activity, and were more fungal-dominant soil ecosystem than grasslands of the same age. In an adjacent primary forest, the bromeliad Bromelia pinguin was found to demonstrate significant antifungal effects on the forest soil, resulting in decreases in fungal abundance, microbial biomass, and efficiency of organic C use. Lastly, in the Monteverde cloud forests, microbial metrics were used to show that habitats with the greatest soil moisture had more fungal-dominated soils, and unique fungal and bacterial population compositions. Given the importance of tropical soils in global C storage, their degradation, and current restoration efforts in these forests, as well as the very clear threat of decreases in precipitation due to climate change, belowground metrics should be considered as early indicators of the effects of forest restoration and/or further environmental disturbances. We hope that these articles will stimulate future studies in these important areas of Costa Rica.