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. grandis – S. krylovii mixture system. The competition
inhibition enhanced in mixture with L. chinensis while it reduced
in S. grandis – S. 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.