Fire suppression has significantly increased canopy cover, litter depth, and stem density in many
western forests, altering microsite conditions that affect tree seedling establishment. We conducted studies in a
mixed-conifer forest in the Sierra Nevada, California, to determine relationships between established understory
trees and microsite quality, and to examine the effect of fire intensity and shrub cover on seedling establishment.
Most of the conifer species were found on microsites with relatively high soil moisture and relatively low direct
solar radiation. All species had greater frequency under shadier conditions except for Jeffrey pine, which was
found on drier, more open microsites. Although seedlings were more abundant on mineral soil than expected,
intact litter and forest floor was not a barrier to establishment. Mortality of planted seedlings was high,
particularly in exposed areas. Although shrub cover may initially aid survival, few conifer saplings were present
in shrub-dominated patches, possibly because shrubs can be aggressive competitors for soil moisture. The
lack of regeneration, logs, or snags in many openings suggest that large gaps are hostile environments for
tree seedlings. Results suggest that reductions in shrub cover may benefit tree establishment, but increasing
understory light and decreasing surface soil moisture through canopy cover reductions may not. FOR. SCI.
51(3):198 –210.Keywords: Prunus emarginata, Old-growth, Abies magnifica, Natural regeneration, Pinus jeffreyi, Quercus kelloggii, Arctostaphylos patula, Pinus labertiana, Abies concolor, Calocedrus decurrens, Fire, Shrub competition, Ceanothus cordulatus, Microclimat
