selected stands where bear damage is thought to occur in western Oregon. ... desirable forage items, will peel conifers to feed on the sugar and carbohydrate.
Black bear peeling in industrial forests of western Oregon: an analysis of economic impacts Kristina Kline1, Jimmy D. Taylor1,2, and Anita T. Morzillo3 1. Department of Forest Ecosystems and Society, Oregon State University 2. USDA, APHIS, WS National Wildlife Research Center, Oregon Field Station 3. Department of Natural Resources and the Environment, University of Connecticut
Introduction Black bears (Ursus americanus) emerge from their dens, and in the absence of more desirable forage items, will peel conifers to feed on the sugar and carbohydrate rich vascular tissues. Trees that are fully girdled eventually die, while those that are wounded become more susceptible to disease and insect infestations which in turn reduces wood quality. In western Oregon, younger Douglas-fir (Pseudotsuga menziesii) stands (15-35 years) that are intensively managed are more susceptible to damage as thinning and fertilization allows trees to grow more vigorously and produce more of the nutrients bears require. Dying trees have a signature red canopy and are detected in annual aerial forest health surveys, however, wounded trees are not detected by aerial surveys. Damage estimates for northwest Oregon are reported annually through these surveys, but no estimates of economic impact are evaluated. Timber loss to bears across part of western Oregon has been estimated at ~$11.5 million using landowner survey data. While informative, these estimates used broad assumptions to derive primary impacts and did not address secondary impacts, which our study aims to do. Our study uses a ground based stratified random sampling design to refine damage estimates which will inform a regional economic model in order to estimate economic loss at multiple spatial scales while including scenarios using black bear management strategies. Wounded tree
Fully girdled tree
Methods
Preliminary Results
Using spatial data from USFS/ODF’s aerial health surveys as well as stand inventory data from landowners, and aerial imagery, we randomly selected stands where bear damage is thought to occur in western Oregon. One acre circular plots were set up around regions of red crowns on aerial images. Fifty-six stands were surveyed for damage frequency and severity using these plots. Each tree within the acre was visited to identify if it was damaged and the cause of damage. If damaged by bear, the % circumference peeled and age of damage was documented. If damaged by root disease, the type of root disease was also identified.
Next Steps
7% of stands sampled contained bear peeling as the primary damage agent 13% contained bear peeling and root disease 79% contained root disease as the primary damage agent Almost all bear damaged stands ranged in age from 23-34 years 70 % of bear damaged stands had tree densities of less than 360 TPA In the most heavily bear damaged stand, 17% of trees were damaged Fully girdled to wounded ratio of 1:1.4 45
9
42 # Bear Damaged Stands (n = 11)
40
# Stands (n = 56)
35 30 25 20 15 10 5
7 4
3
0
7
7 6 5
Bear Damage & Root Disease
Root Disease only
Other Animal & Root Disease
Figure 6. Stands damaged by agent
A pair of stands in both the western Cascades and Coast Range will be selected for a case study to look at how damage and resulting loss in timber volume differs between a stand where damage has been successfully curbed due to bear management and a stand where damage continues to be a problem regardless of bear management efforts. This will elucidate how continual bear damage can impact landowners at a finer scale.
4
4 3
3 2 1 Trees/Ac < 360
Trees/Ac > 360
< 4% of acre > 4% of acre Damaged Damaged
Figure 7. Stand level damage characteristics
Figure 2. Aerial imagery with 1-acre plots and red crowns Figure 9. Forest Vegetation Simulator (FVS) growth model models expected volume at harvest
140 120
# Trees (n = 139)
120 100
82 80
40 19
0 Recent Damage (0-2 yrs)
Figure 4. Bear killed red crown
Figure 5. Examining a damaged tree
References
57
60
20
Figure 3. Black bear peeling
Using frequency and severity data along with GNN tree level data for damaged stands, stands will be modeled with FVS to determine expected volume at harvest age with and without bear damage. Volume estimates will be used to inform an economic model to estimate the direct, indirect, and induced effects of black bear peeling to Oregon’s economy.
0 Bear Damage only
Figure 1. Study Area
8
8
An additional 70 stands will be surveyed this year to determine frequency and severity of bear damage.
Old Damage (3+ yrs)
Fully Girdled Wounded
Figure 8. Tree level damage characteristics
Flowers, R., M. McWilliams, and A. Kanaskie. 2012. Memorandum: 2012 aerial survey of tree mortality in northwest Oregon. Oregon Department of Forestry, Salem, OR. 7 pages. Kanaskie, A., G. Irwin, J. Chetock, and D. Overhulser. 1990. Black bear damage to forest trees in northwest Oregon 1988-1989. Pest Management Report 90-1. Oregon Department of Forestry, Salem, OR. 37 pages. Kimball, B.A., E.C. Turnblom, D.L. Nolte, D.L. Griffin, and R.M. Engeman. 1998b. Effects of thinning and nitrogen fertilization on sugars and terpenes in Douglas-fir vascular tissues: implications for black bear foraging. Forest Science 44:599-602. Nolte, D.L., Dykzeul, M. 2002. Wildlife impacts on forest resources. In: Clark, L., Hone, J., Shivik, J.A., Watkins, R.A., Vercauteren, K.C., Yoder, J.K., eds. Human conflicts with wildlife: economic considerations. Proceedings, 3rd National wildlife research center special symposium; 2000 August 1-3; Fort Collins, CO. [Fort Collins, CO]: U.S. Department of Agriculture, Wildlife Services, National Wildlife Research Center: 163-168.
