Microbial biomass acts as a source of plant nutrients in dry tropical forest and savanna

MORE than half of all tropical soils are highly weathered, leached and impoverished, requiring the ecosystem to develop nutrient-conserving mechanisms^1,2. Nutrient retention and withdrawal mechanisms are most effective in nutrient-poor systems^3,4. Thus, although dry tropical forests and savanna have the potential capacity to grow at high rates^5,6, this capacity is strictly limited by climate and nutrients. Our studies on these nutrient-poor ecosystems show that a reciprocal relationship exists between microbial biomass and plant growth rate. This suggests that microbial immobilization may be a main source of nutrients for the plants and may lead to nutrient conservation.