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Regeneration Responses to Management for Old-Growth Characteristics in Northern Hardwood-Conifer Forests

A Demographic Approach to Evaluating Tree Population Sustainability

Department of Forest and Wildlife Ecology, University of Wisconsin‐Madison, Madison, WI 53706, USA
Author to whom correspondence should be addressed.
Forests 2017, 8(2), 46;
Received: 5 October 2016 / Revised: 2 February 2017 / Accepted: 16 February 2017 / Published: 16 February 2017
Quantitative criteria for assessing demographic sustainability of tree populations would be useful in forest conservation, as climate change and a growing complex of invasive pests are likely to drive forests outside their historic range of variability. In this paper, we used CANOPY, a spatially explicit, individual‐tree model, to examine the effects of initial size distributions on sustainability of tree populations for 70 northern hardwood stands under current environmental conditions. A demographic sustainability index was calculated as the ratio of future simulated basal area to current basal area, given current demographic structure and density‐dependent demographic equations. Only steeply descending size distributions were indicated to be moderately or highly sustainable (final basal area/initial basal area ≥0.7 over several tree generations). Five of the six principal species had demographic sustainability index values of <0.6 in 40%–84% of the stands. However, at a small landscape scale, nearly all species had mean index values >1. Simulation experiments suggested that a minimum sapling density of 300 per hectare was required to sustain the initial basal area, but further increases in sapling density did not increase basal area because of coincident increases in mortality. A variable slope with high q‐ratios in small size classes was needed to maintain the existing overstory of mature and old‐growth stands. This analytical approach may be useful in identifying stands needing restoration treatments to maintain existing species composition in situations where forests are likely to have future recruitment limitations. View Full-Text
Keywords: forest health; forest simulation; northern hardwoods; population viability analysis;  q‐ratio; size distributions; uneven‐aged management forest health; forest simulation; northern hardwoods; population viability analysis;  q‐ratio; size distributions; uneven‐aged management
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MDPI and ACS Style

Halpin, C.R.; Lorimer, C.G. A Demographic Approach to Evaluating Tree Population Sustainability. Forests 2017, 8, 46.

AMA Style

Halpin CR, Lorimer CG. A Demographic Approach to Evaluating Tree Population Sustainability. Forests. 2017; 8(2):46.

Chicago/Turabian Style

Halpin, Corey R., and Craig G. Lorimer. 2017. "A Demographic Approach to Evaluating Tree Population Sustainability" Forests 8, no. 2: 46.

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