Habitat segregation and regeneration patterns of red fir and mountain hemlock in ecotonal forests, lassen volcanic national park, California

Ordination (DCA), direct gradient analysis, and stand structural analysis were used to identify compositional and structural patterns in 35 ecotonal red firmountain hemlock stands in Lassen Volcanic National Park, California. Mountain hemlock-dominated sites were high in altitude, mesic, and soils were coarse textured and low in nutrients. Red fir dominated xeric sites at all altitudes but was more abundant on lower sites. Red fir also preferred more nutrient rich soils. Size structures of red fir and mountain hemlock populations were highly variable but stands contained seedlings, saplings, small stems and large stems of both species. Ecotonal red firmountain hemlock forests appear to be compositionally stable. Seedlings and saplings of both species were most abundant on lower altitude mesic sites and in stands with more open canopies. Stumps, snapped trees, logs, standing dead boles, charcoal and fire scars were present in 80% of the stands. Natural disturbances frequently produce canopy openings that may be sites for tree regeneration.