Abstract
Strategies for managing mixed broadleaf-conifer stands in British Columbia (BC) have been under review in recent years as the benefits of mixedwood management have been recognized. More has been learned about the role of broadleaves in forest ecosystems however ecosystem-specific knowledge about the competitive interactions between mixed broadleaf-conifer stands is still scarce. Therefore a competitive interactions study was conducted to facilitate ecosystem-specific management for lodgepole pine (Pinus contorta Dougl. Ex Loud. Var. latifolia Engelm.) and trembling aspen (Populus tremuloides Michx.) in the sub-boreal spruce (SBS) zone of central BC. The experiment was a completely randomized block design with six different aspen densities replicated three times. Each replicate was sampled three times between ages 14 to 19 years. Pine diameter and height growth were influenced by aspen density. Our current quantitative findings suggest that lodgepole pine growth was not impacted when growing with aspen densities up to 2500 stems ha-1. Considering free growing (FTG) and not free growing (NFTG) pine at the time of trial establishment, an insignificant difference was found for DBH, height and crown volume responses. Leaf area index (LAI) and diffuse non-interceptance (DIFN) radiation were also not significantly different between FTG or NFTG trees suggesting our results exceed the current BC’s free growing standard. Further work is recommended to determine whether or not the current free growing standards are appropriate for producing the desired crop outcome.
Highlights
Trembling aspen (Populus tremuloides Michx.) occurs across a wide range of ecosystems in Canada (Chen et al, 2002) and may be found at all latitudes of interior British Columbia (BC); especially in the central interior of the province, where it regenerates naturally with lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) and interior spruce (Picea engelmannii × -glauca) (Newsome et al, 2010, 2003; Kabzems & Garcia, 2004) following harvesting and natural fire disturbance
A variety of mixedwood stands with varying densities of broadleaf and conifer species develop in the subboreal forest as a result of natural stand dynamics following disturbance (Prévost & Pothier, 2003)
Pine DBH growth showed an irregular response with increased aspen density whereas aspen DBH increased with increased aspen density up to 2500 stems ha−1 and thereafter decreased (Figure 1)
Summary
Trembling aspen (Populus tremuloides Michx.) occurs across a wide range of ecosystems in Canada (Chen et al, 2002) and may be found at all latitudes of interior British Columbia (BC); especially in the central interior of the province, where it regenerates naturally with lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) and interior spruce (Picea engelmannii × -glauca) (Newsome et al, 2010, 2003; Kabzems & Garcia, 2004) following harvesting and natural fire disturbance. Latifolia Engelm.) and interior spruce (Picea engelmannii × -glauca) (Newsome et al, 2010, 2003; Kabzems & Garcia, 2004) following harvesting and natural fire disturbance It has a potential impact on conifer species such as: retention of nutrients and soil moisture (Man & Lieffers, 1999; Coopersmith et al, 2000), affecting air and soil temperatures, slowing the spread of Armillaria and Phellinus root rot diseases (Gerlach et al, 1997; Simard et al, 2005) and increaseing mechanical stability (Frivold, 1985; Yang, 1989). Current trends of mixedwood management are not well documented due to a limited understanding of the dynamic processes and a lack of predictive models (Hawkins et al, 2012)
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