Does the Practice of Silviculture Build Resilience to the Spruce Beetle? A Case Study of Treated and Untreated Spruce-Fir Stands in Northern Utah

Document Type

Article

Journal/Book Title/Conference

Journal of Forestry

Publication Date

Winter 2-9-2017

Volume

115

Issue

6

Abstract

Silviculturists are under increased pressure to develop treatments that increase resistance and resilience to the spruce beetle (Dendroctonus rufipennis Kirby). Multiple silvicultural systems (i.e., group selection, shelterwood with reserves, and others) have resulted in some short-term increases in resistance. However, less is known about how silvicultural systems, especially ones used over many decades, impact resilience; resilience is defined as a minimum amount of Engelmann spruce (Picea engelmannii Parry ex Engelm.) regeneration to ensure continuity of a spruce component in the future stand. To further explore these concepts, silviculturally treated and untreated stands were sampled after a recent landscape-scale spruce beetle epidemic in northern Utah on the Uinta-Wasatch-Cache National Forest. Both treated and untreated stands had no resistance to the spruce beetle but differed in their resilience. Treated stands had increased resilience due to greater and more consistent stocking of Engelmann spruce regeneration than the untreated stands. When silvicultural systems are developed, special attention should be paid to ensure that conditions created after harvests are conducive for regeneration of the desired species (spruce).

Management and Policy Implications When silviculturists develop a prescription, they use past stand histories to inform current stand conditions and use their ecological understanding of species and site to predict how a management practice will influence the future forest. The level of documentation of past conditions and practices varies among regions, organizations, and individuals. However, this information is critical in understanding both the present and the future. The area surrounding the Wolf Creek Campground in northern Utah is an example of how local knowledge and past documentation were used to explore past, present, and future stand-level risks from the spruce beetle. Spruce beetle management has influenced past management practices and will continue to influence future practices. There is no one simple tool or treatment that will ensure complete resistance to the spruce beetle in western managed forests. Rather, in mature spruce-fir stands, management actions should focus on increasing short-term resistance to build long-term resilience through an increased emphasis on Engelmann spruce regeneration. This type of management may be effective when metrics of resistance and resilience are clearly defined in terms of the overall stand and landscape goals and desired future conditions. Based on these desired future conditions, managers can develop prescriptions and measurable metrics to increase long-term resilience to the spruce beetle.

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