Regeneration behavior of competing plants after clear cutting: implications for vegetation management

Regeneration characteristics and population dynamics of four major competing plants, trembling aspen (Populus tremuloides Michx.), pin cherry (Prunus pensylvanica L.f.), green alder (Alnus viridis spp. crispa (Aiton) Turril) and beaked hazel (Corylus cornuta Marsh.) were studied from a seven-year-old clearcut in northwestern Ontario, Canada. The site was planted with jack pine two years after clearcutting. Regeneration strategies and population dynamics of these plants were studied by determining their crown diameter, stem density, stem height, stem age, depth of sprouting center, inter-sprout distance, oven-dry weight of shoots, roots plus rhizomes by nondestructive and destructive sampling. Stem density of trembling aspen and pin cherry in 1992 was 4580 and 3600 stems per ha respectively. Much higher stem density was obtained in green alder and beaked hazel during the same time, 27580 and 14600 stems per ha respectively. Substantial reduction in stem density was recorded in trembling aspen (45%) and pin cherry (69%) over two years, 1992–1994. However, reduction in stem density of green alder and beaked hazel for that period was very little (6 and 2%, respectively). Comparison of species' clonal characteristics of above- and below-ground components indicates that trembling aspen and pin cherry possess similar vegetative regeneration strategies that differ from those of green alder and beaked hazel. Ordination of the results of canonical variate analysis of the eight vegetative parameters of the four species arranged the species into two significantly different groups. Based on species regeneration strategies, two potential competition strategies were identified: a vertical competition strategy (VCS) and a horizontal competition strategy (HCS). We argue that the degree and duration of competition can be predicted from the density and ratio of VCS and HCS plants on a site once sufficient empirical data on the species' competitive abilities are gathered. We suggest that future studies should relate the regeneration strategies, population dynamics and competitive abilities of competing plants to competition tolerance of crop trees. This will fine tune our prediction about species interaction based on the present model and better justify the need for vegetation control intervention.