Intensity and importance of competition
All factors significantly (P < 0.05) influenced the intensity of competition except the factor of soil nutrition condition (SNu), and all factors significantly influenced the importance of competition except the interaction of target species and soil nutrition condition (T × SNu). Magnitude of effects (ω2) of all factors explained about 62% and 68% of the total variance in the intensity and importance of competition, respectively; and the factor of neighbor species contributed the most portion to the total variance, with 29.448% for intensity of competition and 31.591% for importance of competition (Table 2).
The competition intensity was not significantly influenced by the interaction of T × SNu in mixture with L. chinensis and inS. grandisS. krylovii mixture system. The competition inhibition enhanced in mixture with L. chinensis while it reduced in S. grandisS. krylovii mixture system with the increase of soil nutrition, respectively (Fig. 2a, 2c). In mixture withA. cristatum , the competition intensity was significantly influenced by the interaction of T × SNu, with the reduction of competition inhibition on S. grandis and the enhancement of competition inhibition on S. krylovii with the increase of soil nutrition (Fig. 2b).
The results of one sample t test showed that five out of 12NImpA were significantly (P < 0.01) negative; and the other seven NImpA were not different with zero. The significantly negativeNImpA on S. grandis was shown in mixture with L. chinensis under both soil nutrition treatments and in mixture with A. cristatum under low nutrition treatment. The significantly negative NImpA on S. krylovii was shown in mixture with L. chinensis or A. cristatum under high nutrition treatment (Fig. 3). In addition, theNImpA on S. grandis in mixture withL. chinensis , and that on S. krylovii in mixture withL. chinensis or A. cristatum were more negative under the high nutrition treatment than those under the low nutrition treatment, respectively.