Reconsidering the phosphorus limitation of soil microbial activity in tropical forests

1. It has long been believed that soil microbial activity in tropical forest ecosystems is limited by phosphorus (P) rather than nitrogen (N) availability. In this study, we reviewed the methods used to determine the limiting nutrients and evaluated the validity of the widespread P-limitation hypothesis in tropical forest soils.
2. The most commonly used analysis method entails testing whether fertilization increased microbial biomass or soil respiration. Fertilization using microbial biomass as an indicator was not a satisfactory method because standing microbial biomass does not always signal microbial activity. An increase in soil respiration after fertilization was also an insufficient indicator because the negative response shown by organic matter decomposition to nutrient addition can also be driven by nutrient shortage (nutrient mining). Nutrient amendment can also shift microbial communities toward more copiotrophic organisms, which may exhibit lower microbial respiration rates...