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Establishment and growth of conifer regeneration following harvest and residue treatments in a western larch-Douglas-fir forest

Author(s): Sarah Jane Pierce
Year Published: 2003
Description:

Forest managers often choose prescriptions that promote natural regeneration of various species that differ in relative shade tolerance. Assessing the response of forest vegetation to alternative treatments in the Inland Northwest is challenging, given that the process takes decades to unfold. In this study, conifer regeneration was examined in a western larch (Larix occidentalis)/Douglas-fir (Pseudotsuga menziesii) forest 25 years after harvest and residue treatments. Harvest treatments included: clearcut, group selection, and shelterwood. Residue treatments included: moderate utilization burned, standard utilization burned, intensive-fiber utilization unburned, and moderate utilization unburned. Subsequent natural conifer regeneration was sampled across all treatments in 2001. Douglas-fir and Engelmann spruce planted between1976-1979 were remeasured and compared to natural conifer regeneration. In addition, growth of a sub-sample of western larch trees in the shelterwood and clearcut harvests was examined in relation to measures of overstory and understory competition.

Natural regeneration was primarily Douglas-fir in all treatments, though larch saplings were typically among the tallest individuals where they occurred. Natural regeneration densities and stocking levels were highest in the shelterwood harvest treatment, and in the two burned residue treatments. Mean heights of the tallest natural regeneration of each species were greater in the clearcuts and group selections than in the shelterwood harvest treatments, and also greater in the burned than the unburned residue treatments. Planted Douglas-fir and Engelmann spruce total height and growth were greatest in the burned treatments of the clearcuts and group selection. Planted trees were consistently taller than natural regeneration Douglas-fir and spruce. Western larch is surviving under the residual overstory of a shelterwood, though recent growth is lower than in other harvest treatments. Under the residual overstory of the shelterwood, western larch growth was positively correlated with initial tree height, and negatively correlated with canopy cover, stand density index, and tall understory cover. Results suggest that after 25 years, the effects of harvest and residue treatments remain evident in the amount and size of natural regeneration, as well as in the size and survival of planted stock. Further, it appears possible to maintain some component of vigorous young larch recruits in partial retention stands.

Citation: Pierce, Sarah Jane. 2003. Establishment and growth of conifer regeneration following harvest and residue treatments in a western larch - Douglas-fir forest. Missoula, MT: University of Montana. 101 p. Thesis.
Topic(s): Fire Effects, Ecological - Second Order, Vegetation, Fuels, Fuel Treatments & Effects, Mechanical treatments
Ecosystem(s): Montane dry mixed-conifer forest, Subalpine dry spruce-fir forest
Document Type: Dissertation or Thesis
NRFSN number: 13144
Record updated: Sep 4, 2019