Root exudates are able to mobilize nitrogen (N) from soil organic matters (i.e. N mining), which helps plants adapt to N limitation. However, the mechanism of N mining is less known.
    We conducted in situ experiments in an N limited temperate forest on two dominant species and two of their congeneric species. The N mineralization processes in bulk soils were compared with rhizosphere soils receiving root exudates. Our aim was to elucidate; 1) whether root exudates release C or N limitation on microbial growth and enzymatic activity, and 2) how is the magnitude of N mining regulated by the microbial processes mentioned above.  
    The microbial biomass C (N) and enzymatic activities related with the concentration of exudate-C but not with exudate-N. The magnitude of N mining related with both microbial biomass C (N) and enzymatic activities. Since the C/N ratio of microbial biomass was not affected by exudates, our results suggested that the N mining is a process that labile C from root exudates stimulate microbial growth and the microbial stoichiometric demand for N further stimulate N mineralization.