Emulating Succession of Boreal Mixedwood Forests in Alberta Using Understory Protection Harvesting

Authors

Ivan Bjelnanovic, University of AlbertaFollow
Philip G. Comeau, University of AlbertaFollow
Sharon Meredith, West Fraser Mills Ltd.Follow
Brian Roth, The Forest Growth Organization of Western CanadaFollow

Document Type

Article

Author ORCID Identifier

Phil Comeau https://orcid.org/0000-0003-2578-4289

Brian Roth https://orcid.org/0000-0002-0510-1500

Journal/Book Title/Conference

Forests

Volume

13

Issue

4

Publisher

MDPI AG

First Page

533

Last Page

533

Publication Date

3-30-2022

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

Understory protection harvesting is a form of partial cutting that can be used in aspen (Populus tremuloides Michx.)-dominated stands that have understories of white spruce (Picea glauca (Moench) Voss). This practice involves removing 75% to 85% of the merchantable aspen while minimizing damage to the advance spruce regeneration, in addition to leaving 15% to 25% of the aspen standing to reduce potential windthrow of the spruce understory. In this paper, we summarize results from 18 stands measured 10 to 12 years after understory protection harvest. Diameter growth of spruce increased during the first five years after harvest while height growth increased during the second five-year period (5 to 10 or 7 to 12 years after release). Consistent with other studies, mortality rates of aspen trees ≥7.1 cm DBH (diameter breast height, 1.3 m) averaged 45.0% over the 10–12 year period following harvesting. Spruce mortality averaged 27.5% over the same 10–12 year period. Substantial aspen regeneration was evident across most harvested blocks, with aspen sapling densities 10–12 years from harvest being higher in removal (14,637 stems⋅ha⁻¹) than in buffer areas (6686 stems⋅ha⁻¹) and in extraction trails (7654 stems⋅ha⁻¹). Spruce sapling (>1.3 m height and DBH) densities averaged 1140 stems⋅ha⁻¹ in removal areas at ages 10–12, with these trees likely being present as seedlings at the time of harvest. Mixedwood Growth Model projections indicate merchantable volumes averaging 168 m³⋅ha⁻¹ (conifer) and 106 m³⋅ha⁻¹ (deciduous) 70 years from harvest, resulting in MAI (mean annual increment) for this period averaging 2.0 m³⋅ha⁻¹⋅y⁻¹ with MAI for a full 150-year rotation of approximately 2.5 m³⋅ha⁻¹⋅y⁻¹.

Recommended Citation

Bjelanovic, I., P. Comeau, S. Meredith, and B. Roth. 2022. Emulating Succession of Boreal Mixedwood Forests in Alberta Using Understory Protection Harvesting. Forests 13:533.