Positive priming effects through microbial P-mining in tropical forest soils under N2-fixing trees

ABSTRACT Phosphorus (P) addition is thought to have a minimal effect on the priming of preexisting soil organic carbon (C) mineralization after C addition. We hypothesized and tested that positive priming effects are driven by microbial P-mining under P-limitation when a relatively small amount of glucose is added to N-rich and P-poor tropical forest soils with N2-fixing trees. The results showed that the addition of glucose alone (C) and the addition of C together with mineral N (CN) induced positive priming effects, while the addition of C together with mineral P (CP) and the addition of CNP did not, suggesting that positive priming effects occurred through microbial P-mining. The acid phosphatase activities were not much different in all treatments. The results support our hypothesis and suggest that positive priming effects will occur through microbial P-mining, independently of the hydrolysis of organic P esters with phosphatases, under P-limitation in N-rich and P-poor tropical forest soils.