Researches have shown that the rhizosphere priming effects (RPEs) apparently affect the organic matter decomposition and nutrient (especially Nitrogen) cycling.  

The effect induces 4 times increase in the decomposition rate of soil organic matter. The effect is as big as the effect of temperature and moisture. So, the effect is important in the source-sink transitions of Carbon in terrestrial ecosystem. However, effects of tree species and intraspecific competition on RPEs are poorly understood. 

Prof. WANG Peng and Dr. YIN Liming in the research team of Underground Ecological Process from Institute of Applied Ecology (IAE) took 3 tree species: Cunninghamialanceolata, Larixkaempferiand, Fraxinusmandshurica by growing them at two planting densities for 140 days. They determined the RPE on soil organic carbon (C) decomposition, gross and net nitrogen (N) mineralization and net plant N acquisition by 13C and 15N tracer technics.

Those species have different rhizosphere type, growth rate, fine root properties and widely distributed and are planted in China as material and investigated the impact of tree species and interspecific competition on the RPE.  

The results showed that differences in RPE among species were associated with differences in plant biomass. Gross N mineralization and net plant N acquisition increased, but net N mineralization decreased by rhizosphere, as the RPE on soil organic C decomposition increased. Intraspecific competition reduced the RPE on soil organic C decomposition, gross and net N mineralization, and net plant N acquisition, especially for ash and Chinese fir. 

Microbial N mining may explain the overall positive RPEs across species, whereas intensified plant-microbe competition for N may have reduced the RPE with intraspecific competition.  

Overall, the species-specific effects of tree species play an important role in modulating the magnitude and mechanisms of RPEs and the intraspecific competition on soil C and N dynamics. 

The results were published entitled "Rhizosphere Priming Effects on Soil Carbon and Nitrogen Dynamics among Tree Species with and without Intraspecific Competition" in Journal New Phytologist.