A Hierarchical Analysis of Seed Production by Alnus rubra

Abstract

Abstract This study examined variation in the total number of seed, the number and percent of viable seed produced per catkin in red alder (Alnus rubra) across the following five levels of plant organization: stands, individual trees within stands, branches within trees, catkin clusters within branches and catkins within catkin clusters. Catkins were collected from four stands and seed germinated in the laboratory. When all stands were analyzed together all levels of organization, except branches, accounted for significant variation in all response variables. High elevation stands had significantly higher viable seed production per catkin than low elevation stands. When stands were analyzed separately, branches, but not individual trees, generally accounted for signficant variation in seed production. Although branches within trees can generally be considered autonomous units, a large proportion of variation in production of viable seed occurred both within branches and catkin clusters suggesting that imp...