Short-term nutrient addition improves soil organic carbon accumulation in tropical forest

Background and Aims: Highly weathered tropical forests are widely recognized as nitrogen (N)-rich and phosphorus (P)-poor, and the input of nutrienteffects soil carbon (C) cycling and storage in these ecosystems. In topsoil, short-term nutrient additionmay not only effect soil organic C (SOC) pools directly, but also impact soil C cycling and conversion process indirectly through altering soil microbial C use efficiency (CUE). However, the effects of short-term nutrient addition on soil C accumulation mechanisms remain unclear. The aim of this study was to clarify the mechanisms of SOC responding to short-term nutrient addition. Methods: This study conducted a one-year N and P additions experiment in the tropical forest of Hainan, China. The SOC, soil C fractions (POC and MAOC), microbial biomass, enzyme activities, and physicochemical properties at depths of 0–10 cm, 10–20 cm and 20–40 cm were measured. Results: The results showed that short-term nutrient addition increased SOC (8.91–20.03%), POC (6.65–24.90%), and MAOC (8.74–19.89%) in the topsoil (0–10 cm and 10–20 cm), whereas no significant changes occurred in the subsoil (20–40 cm). The results of Pearson’s correlation analysis revealed that litter biomass and CUE were significantly positively correlated with SOC. The partial least squares-path model showed that short-term nutrient addition influences the SOC by altering physicochemical properties and microbial characteristics. Conclusions: These results suggested that the short-term nutrient addition increased SOC through increased soil properties and decreased microbial activities. Such information could provide insight to understand the effects of nutrient addition on soil C pool in tropical forest.