[Correlation analysis on the damage of Mikania micrantha to plant communities in Neilingdind Island of Guandong Province, China].

The analysis showed that 58 species of trees, short-trees and shrubs in Neilingding Island of Guangdong Province were damaged by M. micrantha, of which, woody trees accounted for 67%. Short-trees and sunny shrubs were damaged most seriously, followed by the communities with low canopy density consisted of only 2 dominant species, and those with high canopy density consisted of 5 or 6 dominant species. The coverage of M. micrantha mainly related to the vertical structure of plant communities. The taller the community height and the more the synusia, the lesser was the coverage of M. micrantha. The damaging ratio mainly related to species diversity and community density. The higher the species diversity and community density, the lower the damaging ratio was. The damaging degree mainly related to the coverage of other liana. The more the coverage of other liana, the higher was the damaging degree of M. micrantha.

[Interspecies covariation analysis of dominant tree species in secondary succession of forest communities in Heishiding Natural Reserve, Guangdong Province].

Based on a 2 x 2 contingency table, the Pearson product-moment correlation coefficient and Spearman rank correlation coefficient were used to analyses the interspecies covariation of dominant tree species in different communities of secondary succession series in Heishiding Natural Reserve, Guangdong Province. In early succession stage, 14 pairs of tree species showed a significant interspecies covariation, and 9 pairs of species showed a negative coraviation, indicating that the species pairs needed the same habitats, while five pairs of species showed a positive covariation, which indicated that the species pairs needed different habitats. In the stage of needle broad-leaved mixed forest, only 5 pairs of species showed a significant interspecies covariation, and they were all positive covariation, which indicated the main species needed the same habitats and the interspecies competition were going. In the stage of evergreen broadleaved forest dominated by heliophytes, 4 pairs of species showed a significant interspecies covariation, which was the least one in secondary succession series. Three pairs of them showed a positive covariation. It was the result of interspecies competition that the species pairs needed the same habitats. In the stage of evergreen broadleaved forest dominated by mesophytes, 20 pairs of species showed a significant interspecies covariation, which was the most one in secondary succession series. Nineteen pairs of them showed a positive covariation. It showed positive covariation between species in upper tree layer and in middle or lower tree layer, but dominant species in upper tree layer had no significant interspecies covariation.