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Thinning Jeffrey pine stands to reduce susceptibility to bark beetle infestations in California, U.S.A.Author(s): Christopher J. Fettig; Christopher J. Hayes; Karen J. Jones; Stephen R. McKelvey; Sylvia L. Mori; Sheri L. Smith
Source: Agricultural and Forest Entomology 14: 111-117
Publication Series: Scientific Journal (JRNL)
Station: Pacific Southwest Research Station
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- Bark beetles (Coleoptera: Curculionidae, Scolytinae) are commonly recognized as important tree mortality agents in coniferous forests of the western U.S.A.
- High stand density is consistently associated with bark beetle infestations in western coniferous forests, and therefore, thinning has long been advocated as a preventive measure to alleviate or reduce the amount of bark beetle-caused tree mortality.
- The objective of this study was to determine the effectiveness of thinning to reduce stand susceptibility to bark beetle infestations over a 10-year period in Pinus jeffreyi forests on the Tahoe National Forest, California, U.S.A. Four treatments were replicated three times within 1-ha square experimental plots. Treatments included thinning from below (i.e., initiating in the smallest diameter classes) to a residual target basal area (cross-sectional area of trees at 1.37 m in height) of: (1) 18.4 m2/ha (low density thin), (2) 27.6 m2/ha (medium density thin), (3) 41.3 m2/ha (high density thin), and (4) no stand manipulation (untreated control).
- Throughout the study, 107 trees died due to bark beetle attacks. Of these, 71% (75 trees) were Abies concolor killed by Scolytus ventralis; 20.6% (22 trees) were Pinus ponderosa killed by Dendroctonus ponderosae; 4.7% (5 trees) were P. jeffreyi killed by Dendroctonus jeffreyi; 1.8% (2 trees) were P. jeffreyi killed by Ips pini; 0.9% (1 tree) were P. jeffreyi killed by Orthotomicus (=Ips) latidens; 0.9% (1 tree) were P. ponderosa killed by both D. brevicomis and D. ponderosae; and 0.9% (1 tree) were P. jeffreyi killed by unknown causes.
- In the low density thin, no pines were killed by bark beetles during the 10-year period. Significantly fewer trees (/ha/yr) were killed in the low density thin than the high density thin or untreated control. No significant treatment effect was observed for the percentage of trees (/yr) killed by bark beetles.
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CitationFettig, Christopher J.; Hayes, Christopher J.; Jones, Karen J.; McKelvey, Stephen R.; Mori, Sylvia L.; Smith, Sheri L. 2012. Thinning Jeffrey pine stands to reduce susceptibility to bark beetle infestations in California, U.S.A. Agricultural and Forest Entomology 14: 111-117.
KeywordsDendroctonus brevicomis, Dendroctonus jeffreyi, Dendroctonus ponderosae, Ips, Pinus jeffreyi, Pinus ponderosa, Scolytinae, silviculture
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