| Broad-leaved Korean pine forest is the main secondary forest community type formed by the top community in Jiaohe region after being disturbed.In order to understand the growth dynamics of community vegetation in this region,accelerate the recovery process of degraded secondary forest,and provide reference for its scientific management,50 20 m * 20 m fixed plots of broadleaved Korean pine forest in Jiaohe region of Jilin Province were selected as the research objects in this paper.The community composition,species diversity characteristics,structural characteristics and niche characteristics were studied.The main conclusions are as follows:（1）There are 94 species of vascular plants in 43 families,75 genera and 7 species of gymnosperms,1 family,4 genera and 7 species,38 families,67 genera and 82 species of angiosperms,and 4 families,4 genera and 5 species of ferns.The families with more species mainly include Umbelliferae,Pinaceae,Liliaceae,Saxifragaceae,Rosaceae;species diversity can be determined according to the Shannon-wiener diversity index,Margalef richness index,and Simpson dominance index.（2.72,5.10,0.91）> tree layer（2.65,3.54,0.91）> shrub layer（1.85,2.04,0.79）,and according to Pielou evenness index,shrub layer（0.77）> tree layer（0.76）> herb layer（0.70）,the number of species of herbs and trees in the community is more,and the distribution of shrubs is more uniform;The vegetation types of the community were mainly distributed in the north temperate zone,and the flora composition and life form spectrum showed obvious temperate characteristics.（2）The overall diameter class distribution of the community was inverted ’ J ’ type,and the negative exponential power function had good fitting effect,and the community was relatively stable;among them,the diameter class distribution structure of the dominant species Juglans mandshurica is reasonable,and it is relatively stable at this stage.However,there is a significant lack of diameter class in the small diameter class of the tree.Considering the high mortality rate of its seedlings,it is predicted that it will gradually decline in the future;The diameter class distribution of the subdominant species Pinus koraiensis showed an inverted "J" shape,the survival curve was concave,the seedling mortality was high but the diameter class was continuous,and it had a tendency to become a progressive population.Acer mandshuricum,the main associated species in the community,showed a strong trend of progress;The distribution of diameter class of Picea koraiensis,Tilia amurensis and Fraxinus mandshurica is "L" type,there are a certain number of large trees in the main forest layer,and the regeneration is not good,showing the trend of declining species.（3）The vertical distribution of dominant tree species in the community generally showed a trend of decreasing gradually with the increase of height;Pinus koraiensis and its associated species have a large number of distribution in the height of 15-20 m.Juglans mandshurica is the dominant species in the height of 20-25 m;in the horizontal distribution,Pinus koraiensis and the main associated species all show a clustered distribution on a small scale,and gradually change to a random distribution with the increase of the research scale,and the Juglans mandshurica presents a random distribution on all scales;The dominant species pairs showed no correlation at most research scales（69%-91%）,and the number of positive and negative correlation species pairs was relatively small（2%-18%）.In 0-45 m scale,the number of negative associated species is higher than that of positive associated species,and after 45 m,the number of positive associated species increases.（4）According to the mean value of comprehensive niche breadth and niche overlap,the overall competition intensity of the three levels was tree layer（1.63,0.72）> herb layer（1.42,0.61）>shrub layer（1.15,0.48）.The niche overlap value of species does not have an inevitable positive correlation with the niche breadth value and the important value,and there are differences in the demand for different soil nutrients among species at different levels.The niche overlap of vegetation in the community is generally high,and the interspecific competition is fierce,which is in the process of intense succession. |
