Effect of local stand density on reproductive processes of the sub-boreal conifer Picea jezoensis Carr. (Pinaceae)

The effect of local pollen donor density (conspecific) and local total tree density (all species) on pollen pool diversity, outcrossing rate, and filled seed ratio were examined in a natural stand of the sub-boreal conifer Picea jezoensis   Carr. Seed cones were collected from 17 mother trees, and the percentage of filled seed were calculated for five cones per tree. In addition, local stand density of pollen donors and total trees were investigated within r<30r<30 m from the focal mother trees. Using four polymorphic microsatellite markers, the average pairwise kinship coefficient FSFS and multilocus outcrossing rate tmtm were estimated on germinated seedlings sampled from 14 mother trees. FSFS showed significant positive correlation to local total tree density (r=0.541r=0.541, p=0.046p=0.046). Since FSFS is inversely proportional to the effective number of pollen donors NepNep, genetic diversity of pollen pool was decreased in mother trees with higher local total tree density. Applying a generalized linear mixed model to filled seed ratio and local stand density of pollen donors and total trees, a negative impact of local pollen donors on filled seed ratio was found. We conclude that both local stand density as well as global stand density are important in the management of a natural stand of P. jezoensis.