Precommercial Thinning Increases Spruce Yields in Boreal Mixedwoods in Alberta, Canada
A few studies in young mixedwood stands demonstrate that precommercial thinning of aspen at early ages can improve the growth of spruce and increase stand resilience to drought. However, information on tree and stand responses to thinning in older mixedwood stands is lacking. To address this need, a...
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MDPI AG
2021-03-01
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| Series: | Forests |
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| Online Access: | https://www.mdpi.com/1999-4907/12/4/412 |
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| author | Ivan Bjelanovic Phil Comeau Sharon Meredith Brian Roth |
| author_facet | Ivan Bjelanovic Phil Comeau Sharon Meredith Brian Roth |
| author_sort | Ivan Bjelanovic |
| collection | DOAJ |
| description | A few studies in young mixedwood stands demonstrate that precommercial thinning of aspen at early ages can improve the growth of spruce and increase stand resilience to drought. However, information on tree and stand responses to thinning in older mixedwood stands is lacking. To address this need, a study was initiated in 2008 in Alberta, Canada in 14 boreal mixedwood stands (seven each at ages 17 and 22). This study investigated growth responses following thinning of aspen to five densities (0, 1000, 2500, 5000 stems ha<sup>−1</sup> and unthinned (control)). Measurements were collected in the year of establishment, and three and eight years later. Mortality of aspen in the unthinned plots was greater than in the thinned plots which were not significantly different amongst each other. Eight years following treatment, aspen diameter was positively influenced by thinning, while there was no effect on aspen height. The density of aspen had no significant effect on the survival of planted spruce. Spruce height and diameter growth increased with both aspen thinning intensity and time since treatment. Differentiation among treatments in spruce diameter growth was evident three years from treatment, while differentiation in height was not significant until eight years following treatment. Yield projections using two growth models (Mixedwood Growth Model (MGM) and Growth and Yield Projection System (GYPSY)) were initialized using data from the year eight re-measurements. Results indicate that heavy precommercial aspen thinning (to ~1000 aspen crop trees ha<sup>−1</sup>) can result in an increase in conifer merchantable volume without reducing aspen volume at the time of harvest. However, light to moderate thinning (to ~2500 aspen stems ha<sup>−1</sup> or higher), is unlikely to result in gains in either deciduous or conifer merchantable harvest volume over those of unthinned stands. |
| first_indexed | 2024-03-10T12:47:41Z |
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| issn | 1999-4907 |
| language | English |
| last_indexed | 2024-03-10T12:47:41Z |
| publishDate | 2021-03-01 |
| publisher | MDPI AG |
| record_format | Article |
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| spelling | doaj.art-b016bb3ccc994f24884dcedb28f1058e2023-11-21T13:22:34ZengMDPI AGForests1999-49072021-03-0112441210.3390/f12040412Precommercial Thinning Increases Spruce Yields in Boreal Mixedwoods in Alberta, CanadaIvan Bjelanovic0Phil Comeau1Sharon Meredith2Brian Roth3Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2H1, CanadaDepartment of Renewable Resources, University of Alberta, Edmonton, AB T6G 2H1, CanadaWestfraser Mills Ltd., Hinton, AB T7V 1V7, CanadaThe Forest Growth Organization of Western Canada, Hinton, AB T7V 1V3, CanadaA few studies in young mixedwood stands demonstrate that precommercial thinning of aspen at early ages can improve the growth of spruce and increase stand resilience to drought. However, information on tree and stand responses to thinning in older mixedwood stands is lacking. To address this need, a study was initiated in 2008 in Alberta, Canada in 14 boreal mixedwood stands (seven each at ages 17 and 22). This study investigated growth responses following thinning of aspen to five densities (0, 1000, 2500, 5000 stems ha<sup>−1</sup> and unthinned (control)). Measurements were collected in the year of establishment, and three and eight years later. Mortality of aspen in the unthinned plots was greater than in the thinned plots which were not significantly different amongst each other. Eight years following treatment, aspen diameter was positively influenced by thinning, while there was no effect on aspen height. The density of aspen had no significant effect on the survival of planted spruce. Spruce height and diameter growth increased with both aspen thinning intensity and time since treatment. Differentiation among treatments in spruce diameter growth was evident three years from treatment, while differentiation in height was not significant until eight years following treatment. Yield projections using two growth models (Mixedwood Growth Model (MGM) and Growth and Yield Projection System (GYPSY)) were initialized using data from the year eight re-measurements. Results indicate that heavy precommercial aspen thinning (to ~1000 aspen crop trees ha<sup>−1</sup>) can result in an increase in conifer merchantable volume without reducing aspen volume at the time of harvest. However, light to moderate thinning (to ~2500 aspen stems ha<sup>−1</sup> or higher), is unlikely to result in gains in either deciduous or conifer merchantable harvest volume over those of unthinned stands.https://www.mdpi.com/1999-4907/12/4/412boreal mixedwoodsprecommercial thinninggrowth responsesthinning effectsyield projectionstrembling aspen |
| spellingShingle | Ivan Bjelanovic Phil Comeau Sharon Meredith Brian Roth Precommercial Thinning Increases Spruce Yields in Boreal Mixedwoods in Alberta, Canada Forests boreal mixedwoods precommercial thinning growth responses thinning effects yield projections trembling aspen |
| title | Precommercial Thinning Increases Spruce Yields in Boreal Mixedwoods in Alberta, Canada |
| title_full | Precommercial Thinning Increases Spruce Yields in Boreal Mixedwoods in Alberta, Canada |
| title_fullStr | Precommercial Thinning Increases Spruce Yields in Boreal Mixedwoods in Alberta, Canada |
| title_full_unstemmed | Precommercial Thinning Increases Spruce Yields in Boreal Mixedwoods in Alberta, Canada |
| title_short | Precommercial Thinning Increases Spruce Yields in Boreal Mixedwoods in Alberta, Canada |
| title_sort | precommercial thinning increases spruce yields in boreal mixedwoods in alberta canada |
| topic | boreal mixedwoods precommercial thinning growth responses thinning effects yield projections trembling aspen |
| url | https://www.mdpi.com/1999-4907/12/4/412 |
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