Regeneration of salal (Gaultheria shallon) in the central Coast Range forests of Oregon

Abstract

Regeneration of salal (Gaultheria shallon Pursh.) by seedling establishment and vegetative expansion was examined under various forest conditions in the central Coast Range of Oregon. Size and expansion rate of individual clonal fragments were negatively correlated with overstory stand density (p ≤ 0.039). As overstory basal area increased from 25 to 75 m2/ha, mean annual growth percentage of clone rhizome systems decreased from 23.7 to 0.0% and mean total rhizome length decreased from 102 to 0.89 m. Interclonal competition in dense clumps of salal apparently causes rhizomes to die and clones to fragment. In these patches, rhizome biomass and density, aerial stem biomass and density, and total biomass were negatively correlated with overstory density (p ≤ 0.01). For example, in clearcuts, salal clumps had up to 177.7 m rhizome/m2 and 346 stems/m2, whereas patches under dense overstories had as few as 10.6 m rhizome/m2 and 19 stems/m2. Aerial stem populations had uneven-age distributions of aerial stems in all overstory conditions. This structure is apparently maintained through annual production of new ramets. Salal seedling establishment rates were significantly affected by study site location, overstory density, and substrate (p ≤ 0.05). Two-year survival was highest on rotten logs and stumps in thinned stands. Key words: clonal morphology, clone populations, Douglas-fir forests, Gaultheria shallon, seedling establishment, vegetative expansion.