Abstract:

Exploring tree population distribution patterns and interspecific spatial associations are helpful in elucidating the mechanisms underlying species coexistence in forest communities. We analyzed population distribution patterns and interspecific adult-adult spatial associations of common tree species at scales of 0-50 m in five 1-ha warm temperate secondary forest plots near Beijing, China. We found that: (1) all species showed aggregated spatial patterns at some scales; aggregation occurred mainly at neighborhood scales of < 15 m, tended to peak within a 1-m radius around focal conspecific trees, and the percentage of species exhibiting a random or regular pattern increased with scale, mainly occurring at scales of > 15 m; (2) the proportion of species pairs showing non-significant associations was high (~50%), and even in those species pairs that showed significant associations, segregation and partial overlap were dominant association types. Few species pairs (~4%) showed mixing. We feel that population spatial distribution of trees, particularly the observed prevalence of conspecific aggregation, in these plots was regulated by seed dispersal limitation and environmental heterogeneity. Moreover, aggregated distributions also promoted interspecific segregation and partial overlap. It is possible that distribution patterns were associated with habitats. Few species pairs showed interspecific mixing, in this case, interspecific competition exclusion difficultly occured, but in the interior of conspecific aggregation, density dependence should be a dominant mechanism regulating population distributions. Our findings contribute to a clearer understanding of the mechanisms influencing the structure of these forests.

Key words: species coexistence, aggregation, segregation, seed dispersal limitation, environmental heterogeneity, habitat associations, density dependence