Growth rates of rhizosphere microorganisms depend on competitive abilities of plants and N supply.
Plant-microbial interactions under N-limiting conditions are governed by competitive abilities of plants for N. Our study aimed to examine how two plant species of strawberry, Fragaria vesca L. (native species) and Duchesnea indica (Andrews) Focke (an invasive plant in central Europe), growing in intra-specific and inter-specific competition alter the functions of rhizosphere microorganisms in dependence on N availability. By intra-specific competition at low N level, a 2.4-fold slower microbial-specific growth rate was observed under D. indica characterized by smaller root biomass and lower N content in roots compared with F. vesca. By inter-specific competition of both plants at low N level, microbial growth rates were similar to those for D. indica indicating that plants with stronger competitive abilities for N controls microbial community in the rhizosphere. Since a high N level smoothed the differences between plant species in root and microbial biomass as well as in microbial growth rates under both intra-specific and inter-specific competition, we conclude that competitive abilities of plant species were crucial for microbial growth in the rhizosphere only under N imitation.