REGENERATION BEHAVIOR OF COMPETING PLANTS AFTER CLEAR-CUTTING - IMPLICATIONS FOR VEGETATION MANAGEMENT

Regeneration characteristics and population dynamics of four major com peting plants, trembling aspen (Populus tremuloides Michx.), pin cherr y (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 si te was planted with jack pine two years after clearcutting. Regenerati on 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, 27 580 and 14 60 0 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 bea ked hazel for that period was very little (6 and 2%, respectively). Co mparison of species' clonal characteristics of above- and below-ground components indicates that trembling aspen and pin cherry possess simi lar vegetative regeneration strategies that differ from those of green alder and beaked hazel. Ordination of the results of canonical variat e analysis of the eight vegetative parameters of the four species arra nged the species into two significantly different groups. Based on spe cies regeneration strategies, two potential competition strategies wer e identified: a vertical competition strategy (VCS) and a horizontal c ompetition strategy (HCS). We argue that the degree and duration of co mpetition can be predicted from the density and ratio of VCS and HCS p lants on a site once sufficient empirical data on the species' competi tive abilities are gathered. We suggest that future studies should rel ate the regeneration strategies, population dynamics and competitive a bilities of competing plants to competition tolerance of crop trees. T his will fine tune our prediction about species interaction based on t he present model and better justify the need for vegetation control in tervention. (C) 1997 Elsevier Science B.V.