Clonality-dependent dynamic change of plant community in temperate grasslands under nitrogen enrichment

Clonal plants with diverse growth forms are dominant in plant community of temperate grasslands and sensitive to enhanced atmospheric nitrogen (N) deposition. However, whether and how clonal plants with different growth forms differ in their responses to N deposition remains unclear. We investigated the long-term (14-year) and short-term (4-year) effects of N addition on clonal plants of three growth forms (clumper, stoloniferous and rhizomatous clonal plants) in temperate grasslands of northern China by monitoring the clonal traits and belowground meristems. We found that, for the first time, the effects of N addition on clonal plants were dependent on N-addition duration and growth forms of clonal plants. Short-term N addition enhanced growth of clumper clonal plants, while long-term N addition favored growth of rhizomatous clonal plants and suppressed growth of stoloniferous clonal plants. We further revealed that clumper clonal plants can preempt space by tillering rapidly, thus conferring their dominance in the community and suppressing vegetative reproduction of stoloniferous clonal plants upon exposure to short-term N enhancement. In contrast, long-term N addition depressed initiation of buds and tillering of clumper clonal plants. Moreover, long-term N addition shortened rhizome internode and enhanced vegetative reproduction of rhizomatous clonal plants, leading to their ultimate dominance in the steppe community. Our results highlight the important roles of belowground meristems and clonal traits in control of dynamic changes of plant community in response to N enrichment. These findings provide a new perspective to understand N-induced changes in plant community of temperate grasslands.