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Mixing tree species and density management to reduce drought susceptibility in coastal plantation forests of British Columbia
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- Author / Creator
- Lukose, Surabhi
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The coastal forests of British Columbia have been experiencing longer and more intense
droughts in recent years. To evaluate the effects of species composition and density on
drought sensitivity, a study was conducted in a Douglas-fir:western redcedar plantation
established in 1992, in the eastern variant of the Coastal Western Hemlock very dry
maritime (CWHxm1) bio- geoclimatic subzone along the east side of Vancouver Island.
This plantation consists of a 4x3 factorial design with four different species mixtures
(Douglas-fir:western redcedar mixtures of 1:0, 1:1, 1:3, and 0:1) at three different planting
densities (500, 1000, and 1500 stems/ha). In summer 2022, measurements were taken to
evaluate soil moisture, drought tolerance and water use efficiency of these stands. Soil
moisture decreased with increasing stand density except for pure Douglas-fir stands which
had consistently low soil moisture at all densities. Drought indices calculated from tree
core data showed that drought resistance, resilience and recovery increased with
decreasing stand basal area. Wood carbon isotopic data indicated that western redcedar
trees in their pure stands had higher water use efficiency at lower basal area and these
trees were sensitive to drought compared to Douglas-fir trees. Douglas-fir benefitted when
mixed with Western redcedar and showed higher water use efficiency in mixed stands
compared to pure stands both during wet and dry years. In conclusion, reducing stand
basal area, which can be achieved by mixing the two species and controlling stand
density, can help reduce the drought susceptibility of these forests to long-term drought -
- Subjects / Keywords
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- Graduation date
- Fall 2024
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.