Gender-related distributions of Fraxinus mandshurica in secondary and old-growth forests

This study presents new findings about gender-related spatial distributions of the strictly dioecious tree species Fraxinus mandshurica. The observations were collected in three large field plots in secondary and old-growth forests in northeastern China, covering the 4-year period from 2005 to 2008. Tree diameters were not significantly different between genders in the young secondary forests. In the old-growth forest, however, the diameters of male trees were significantly greater than those of female trees. The sex ratio did not significantly deviate from 1:1 in the secondary forests, but was male-biased in the old-growth forest. Spatial segregation between genders was found in the secondary forests, but male and female trees were spatially independent in the old-growth forest. This research complements the current knowledge about sex ratios in secondary and old-growth forests, and about spatial patterns and intra- and intersexual interactions of the dioecious species, F. mandshurica. The available evidence suggests that male and female individuals show a different response to specific microenvironments in the three forest successional stages, which suggests that there are differences in resource requirements between genders.