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.