Report

Black bear damage to regenerating conifers in northwestern California

Damage by black bear (Ursus americanus) to second-growth coniferous trees was examined on fourteen sites in coastal Humboldt County, CA. Four different coniferous species were damaged by bears; redwood (Sequoia sempervirens) was the species most often damaged. Redwood was damaged in significantly (P 0.05) greater proportions than it was available on eight of 13 sites investigated. Bear damage ranged from 4.2 ± 2.2 to 72.5 ± 8.2 trees per hectare (x ± SE). On six of seven sites, damaged redwoods had a significantly (P 0.05) larger mean diameter at breast height (dbh) than did the nearest undamaged redwood tree. On nine of 13 sites, the dbh of damaged redwoods was significantly (P 0.05) larger than the mean dbh of redwoods on the site. Significantly (P 0.05) more damaged trees were observed near roads or trails than were expected (based on the forest as a whole). There was a significantly (P 0.05) greater number of trees damaged in the 76-100% girdled category than were expected. Average annual increment of bear damage ranged from 0.3 to 23.5 trees per hectare. The mean annual increment of damage was 6.0 ± 2.2 trees per hectare (x ± SE). The yield loss due to bear damage was estimated using a redwood growth simulation model. Percentage of yield lost ranged from 0.5% to 54.3%, with a mean percentage loss of 21.4% ± 5.0 (x ± SE). Nine sites between the age of 59-61 were surveyed to ascertain the damage present on near-rotation age stands. The mean number of bear damaged trees per hectare was 15.9 ± 3.6 (x ± SE). On all nine sites, greater than 93% of all damaged trees were redwoods.

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