Can density management improve marketability of jack pine stands managed for Kirtland's warbler habitat? / Megan Machusko.

Multiple land-management agencies have implemented a management program in which ca. 1,550 hectares of high-density jack pine (Pinus banksiana) plantations are established annually to provide a continuous supply of breeding habitat for the conservation-reliant Kirtland's warbler (KW; Setophaga kirtlandii). These KW habitat plantations are established at a much higher density than a traditional forestry plantation, resulting in increased competition that results in slower individual tree growth and delayed attainment of merchantable size. Pre-commercial thinning (PCT) after stands age out of KW breeding habitat is an option to reduce densities and increase individual tree vigor and growth for the remaining years of the rotation. I initiated a small plot-level thinning experiment to assess the growth response to PCT of high-density jack pine plantations planted for KW habitat. In addition, two stands of KW jack pine plantations were put out for commercial bid to assess the costs and residual stand characteristics of operational scale PCT. The increase in diameter growth response was 16% for the 11-14 year age class, 30% for the 19-26 year age class, and 55% for the 27-35 year age class. After 25 years of age, there was a sharp drop in live crown ratio (LCR), indicating that increased competition for light results in lifting of the live crowns. Therefore, thinning as soon as possible after KW occupancy ends, and before 25 years when LCRs drop rapidly, would have the greatest impact on growth of the residual trees. Under my most optimistic scenario (2% rate of return), PCT would need to increase final harvest volume by 139% for mechanical thinning and 233% for hand thinning to break-even financially. I conclude that PCT does not appear to be financially feasible at any rate of return. Even though PCT of KW plantations may never break-even financially, the practice may be justified on public lands if it can accelerate attainment of marketability while increasing resilience to climatic warming.

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