Does the legacy of historical thinning treatments foster resilience to bark beetle outbreaks in subalpine forests?

Conifer snagfall data in bark-beetle infested subalpine forests at the Fraser Experimental Forest, Colorado, USA

Forest Service Research Data Archive ◽

10.2737/rds-2019-0048 ◽

2019 ◽

Author(s):

Charles C. Rhoades ◽

Robert M. Hubbard ◽

Paul R. Hood ◽

Banning J. Starr ◽

Daniel B. Tinker ◽

...

Keyword(s):

Bark Beetle ◽

Subalpine Forests

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Dendroecological detection of spruce bark beetle outbreaks in northwestern Colorado

Canadian Journal of Forest Research ◽

10.1139/x00-104 ◽

2000 ◽

Vol 30 (11) ◽

pp. 1788-1798 ◽

Cited By ~ 33

Author(s):

Karen S Eisenhart ◽

Thomas T Veblen

Keyword(s):

Tree Ring ◽

Bark Beetle ◽

Large Scale ◽

Tree Mortality ◽

Subalpine Forests ◽

Spruce Bark Beetle ◽

Engelmann Spruce ◽

Spruce Bark ◽

Photographic Evidence ◽

Spruce Beetle

Episodic outbreaks of Dendroctonus rufipennis (Kirby), the spruce bark beetle, have greatly influenced the structure of subalpine forests in northern Colorado. During the 1940s, much of the subalpine zone of northwestern Colorado was severely affected by beetle outbreak; also, tree-ring and photographic evidence suggest that large-scale outbreaks occurred in the 19th century. The present study focused on tree-ring methods to examine the regional extent and synchrony of pre-20th-century beetle outbreaks in northwestern Colorado. Results from examination of both live and dead Engelmann spruce (Picea engelmannii Parry ex Engelm.) tree rings in nine stands were compared with results of previous tree-ring studies in the same region. Evidence of past canopy disturbance included episodes of tree mortality in conjunction with sustained increases in radial growth rates. We identified regional outbreaks of spruce beetle by synchronous and sustained growth release in trees from disjunct stands. These new tree-ring records, along with previously published records, indicate that severe and widespread canopy disturbances, probably spruce beetle outbreaks, affected northwestern Colorado in 1716-1750, 1827-1845, 1860-1870, and 1940-1960. These results support earlier findings that large-scale outbreaks of spruce beetle have long been an important component of the dynamics of subalpine forests in Colorado.

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Containment and concentration of infestations of the western balsam bark beetle, Dryocoetes confusus (Coleoptera: Scolytidae), using the aggregation pheromone exo-brevicomin

Canadian Journal of Forest Research ◽

10.1139/x94-065 ◽

1994 ◽

Vol 24 (3) ◽

pp. 483-492 ◽

Cited By ~ 10

Author(s):

Arthur J. Stock ◽

J.H. Borden ◽

T.L. Pratt

Keyword(s):

Bark Beetle ◽

Aggregation Pheromone ◽

Stand Structure ◽

Nearest Neighbour ◽

Subalpine Forests ◽

Subalpine Fir ◽

Neighbour Distance ◽

Dryocoetes Confusus ◽

And Control

Containment and concentration of infestations of the western balsam bark beetle, Dryocoetes confusus Swaine, was demonstrated when (±)-exo-brevicomin released at 0.4 mg/24 h was applied to single subalpine firs, Abieslasiocarpa (Hook.) Nutt., on a 50-m grid over 9-ha blocks, or released at 0.8 mg (24 h/tree)−1 applied to two trees at 50-m centres over the central 4 ha of 16-ha blocks. Nearest-neighbour distance between red trees and newly mass-attacked trees was 24 m in the central 4 ha of baited 16-ha blocks, compared with 13.8 m in control blocks, suggesting a movement of beetles away from "normal" attack centres. Treatments with exo-brevicomin at two trees per spot concentrated 89% of newly mass-attacked trees within 10 m of baited trees, clearly indicating the potential for semiochemical-based management of D. confusus. Within-stand distribution of attacked trees was highly aggregated (Clark–Evans test), in both treated and control blocks. The highly aggregated pattern of attack in control blocks could have been a product of stand structure, and it is hypothesized that D. confusus plays a role in the regeneration of its host by initiating small gaps that favour subalpine fir reproduction. If so, there is potential for using semiochemicals to manipulate D. confusus populations within a patch or selection logging system to maintain cover in climax subalpine forests.

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