Niche and interspecific association of dominant tree populations of Zelkova schneideriana communities in eastern China

Background: Zelkova schneideriana Hand.-Mazz., is an endangered species mainly distributed in subtropical China. Currently, little is known about its niche and interspecific association. Questions: What are the niche characteristics of Z. schneideriana and other associated species? What are the interspecific associations between these species? Study sites and dates: Z. schneideriana communities in Jiangsu, China in 2019. Methods: Twenty-one 400 m2 plots were studied for importance value, niche breadth and overlap, interspecific association of Z. schneideriana communities. Results: In 39 species of tree layer, Z. schneideriana had the greatest importance value and niche breadth. For the first 10 dominant species, a considerable difference was detected by the Levins index (1.75 - 19.84) and Shannon-Wiener index (0.77 - 3.02). Forty-four out of the 45 species pairs had the value of niche similarity indices ≤ 0.5; 38 species pairs had the value of niche overlap indices ≤ 0.5. Overall interspecific association was not a significantly negative association for variance ratio < 1. χ2 test and Spearman’s correlation coefficient further revealed that above 60 % of species pairs had negative associations, suggesting most dominant species were slightly associated with other species or even independent. Conclusions: Z. schneideriana was a constructive species. Dissimilarity in environmental requirements was found among most dominant tree species, thus decreasing competition. This is likely due to the unstable community in the early stage of succession.