Important Findings
We founded that the competition responses were mediated by the identities of neighbors and target species. (1) When in mixture withLeymus chinensis , both intensity and importance of competition negatively increased with the increase of soil nutrition. The competition importance was significantly negative on S. grandisunder both soil nutrition treatments and on S. krylovii under the high soil nutrition treatment, supporting Grime’s theory. (2) When inS. grandisS. krylovii mixture system, the competition inhibition decreased while competition importance showed no significant effects on both target species with the increase of soil nutrition, indicating competitive reduction. (3) When in mixture withAgropyron cristatum , the competition intensity significantly influenced by the interaction between target species and soil nutrition, suggesting competitive change along the soil nutrition gradient. The competition importance was significantly negative on S. grandisunder the low soil nutrition treatment and on S. krylovii under the high soil nutrition treatment. Ultimately, our results demonstrate that the identities of both target and neighbor species influenced the responses of intensity and importance of competition to the change of soil nutrition condition. Several mechanisms potentially contributed to these different competition effects on different target species.
Keywords: competitive change, competitive reduction, intensity of competition, importance of competition, soil nutrition change, species-dependent