Tree-size diversity between single- and mixed-species stands in three forest types in western Canada

2005 ◽  
Vol 35 (3) ◽  
pp. 593-601 ◽  
Author(s):  
Pàl Varga ◽  
Han YH Chen ◽  
Karel Klinka
Keyword(s):  
Lodgepole Pine ◽  
Structural Diversity ◽  
Single Species ◽  
Tree Size ◽  
Western Hemlock ◽  
Stand Age ◽  
Western Canada ◽  
Mixed Species ◽  
Western Redcedar ◽  
Size Diversity

Mixed-species stands are hypothesized to be more structurally diverse because of inherent differences in growth rates between tree species. We investigated three combinations of even-aged, single- and mixed-species coniferous stands in western Canada: (i) shade-tolerant western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata (Donn ex D. Don) Spach), (ii) shade-intolerant lodgepole pine (Pinus contorta Dougl. ex Loud.) and western larch (Larix occidentalis Nutt.), and (iii) shade-intolerant lodgepole pine and shade-tolerant black spruce (Picea mariana (Mill.) BSP). We quantified stand structural diversity based on tree diameter and height by using Shannon's index and the coefficient of variation. Regression analysis was applied to examine the relationships between structural diversity, species composition, and stand age. Mixed-species stands of western hemlock and western redcedar had similar structural diversity to their respective single-species stands. Pine–larch and pine–spruce mixed-species stands had higher tree-size diversity than their respective single-species stands. Stand age was a significant factor for tree-size diversity, but its effect changed in different ways depending on the type of mixtures and index used to measure diversity.

scholarly journals The potential of mixing timber assets to financially offset negative effects of deer browsing on western redcedar

2015 ◽  
Vol 91 (04) ◽  
pp. 436-443 ◽  
Author(s):  
Verena C. Griess ◽  
Rajat Panwar ◽  
Julie Cool
Keyword(s):  
Western Hemlock ◽  
Investment Risk ◽  
Financial Indicators ◽  
Negative Effects ◽  
Mixed Species ◽  
Financial Return ◽  
Protective Measures ◽  
Western Redcedar ◽  
Risk Return ◽  
Mixed Species Forest

Western redcedar (WRC) is a highly desirable species in British Columbia's Coastal Western Hemlock zone, both from a management and a conservation perspective. However, it is also highly palatable for ungulates. Existing countermeasures against browsing all have high costs and imperfect results in common. We used the portfolio method to display how diversification can help to lower investment risk. Using risk-return ratios of a WRC and Douglas-fir (DF), we derived species portfolios that yield maximum financial return per unit of risk. Financial indicators were calculated based on Monte Carlo simulations, which consider timber price fluctuation and browsing risk. Results show how economic risks of a forest investment could be reduced by creating a species portfolio. The optimum portfolio leading to most beneficial risk-return combination is 75% WRC and 25% DF if browsing is lowered using protective measures that double planting costs; and 30% WRC and 70% DF if no protective measures are applied. Accordingly, the most desirable risk-return combination is that of a mixed-species forest, whereas the 2 species don't have to be grown in intimate mixtures. Our research sketches a path forward that can help to ensure WRC will remain an important asset in BC's timber portfolio.

Models of the Vertical Distribution of Sapwood Area for Lodgepole Pine and Western Hemlock in Western Canada

2015 ◽  
Vol 61 (6) ◽  
pp. 973-987 ◽  
Author(s):  
Mike G. Cruickshank ◽  
Ian R. Cameron ◽  
Art Groot ◽  
James D. Stewart ◽  
James W. Goudie
Keyword(s):  
Vertical Distribution ◽  
Lodgepole Pine ◽  
Western Hemlock ◽  
Western Canada ◽  
Sapwood Area ◽  
The Vertical Distribution

Ectomycorrhizal mushroom distribution by stand age in western hemlock – lodgepole pine forests of northwestern British Columbia

2005 ◽  
Vol 35 (7) ◽  
pp. 1527-1539 ◽  
Author(s):  
J M Kranabetter ◽  
J Friesen ◽  
S Gamiet ◽  
P Kroeger
Keyword(s):  
British Columbia ◽  
Pinus Contorta ◽  
Nitrogen Availability ◽  
Lodgepole Pine ◽  
Natural Disturbance ◽  
Tsuga Heterophylla ◽  
Western Hemlock ◽  
Stand Age ◽  
Age Classes ◽  
Commercial Forest

Commercial forest rotations are usually shorter than natural disturbance return intervals, which could affect the distribution of ectomycorrhizal fungal (EMF) species dependent on late-seral stands. We examined this potential reduction in species richness by comparing ectomycorrhizal mushroom communities across four age-classes (pole stage, young, mature, and old growth) of western hemlock (Tsuga heterophylla (Raf.) Sarg.) – lodgepole pine (Pinus contorta Dougl. ex Loud.) stands on submesic sites in northwestern British Columbia. Almost 130 species of ectomycorrhizal mushrooms were identified over the 12 sites during the 3-year study period. EMF richness was lowest in pole stands and almost twice as high in the older age-classes. Species composition and abundance were related to stand age, with relatively large differences in communities between the ages of 20 and 120 and relatively smaller differences between 120 and 225 years. Twelve species, including the economically important pine mushroom (Tricholoma magnivelare (Peck) Redhead), were late-seral stand dependent, fruiting in forests that are at least older than 85 years. This distribution of ectomycorrhizal mushrooms across stand ages suggests EMF succession is primarily an accumulation of species and is likely affected by differences in dispersal by ectomycorrhizal fungi, soil properties (increased soil acidity and reduced nitrogen availability), and the rate of stand development. The evidence for EMF species limited to late-seral stands supports the maintenance of some mature forests within these landscapes to conserve EMF richness.

Are mixed-species stands more productive than single-species stands: an empirical test of three forest types in British Columbia and Alberta

2003 ◽  
Vol 33 (7) ◽  
pp. 1227-1237 ◽  
Author(s):  
H YH Chen ◽  
K Klinka ◽  
A -H Mathey ◽  
X Wang ◽  
P Varga ◽  
...  
Keyword(s):  
Pinus Contorta ◽  
Black Spruce ◽  
Lodgepole Pine ◽  
Empirical Test ◽  
Single Species ◽  
Growth Patterns ◽  
Thuja Plicata ◽  
Larix Occidentalis ◽  
Mixed Species ◽  
Stand Volume

Stand volumes were determined for naturally established, even-aged, single- and mixed-species stands involving three combinations of shade-tolerant and shade-intolerant conifers on similar sites: (i) western redcedar – western hemlock (Thuja plicata Donn ex D. Don – Tsuga heterophylla (Raf.) Sarg.), (ii) lodgepole pine – western larch (Pinus contorta Dougl. ex Loud. – Larix occidentalis Nutt.), and (iii) lodgepole pine – black spruce (Pinus contorta – Picea mariana (Mill.) BSP). Stand volume was significantly increased with site index and breast-height age in all three studies. Stand volume was also related to relative stand density in the lodgepole pine – black spruce study. When both species were shade tolerant (hemlock–redcedar), stand volume increased linearly with the proportion of hemlock; the mixed-species stands had intermediate volume compared with single-species stands. The combination of two shade-intolerant species (pine–larch) had lower stand volume than that anticipated from single-species stands, implying that one species may inhibiting the growth of the other. Mixtures of shade-intolerant and shade-tolerant species with different growth patterns (spruce–pine) may be more productive than single-species stands in specific ecological contexts and developmental stages. The effect of one species on the productivity of another species is tree-species and site specific: at maturity, even-aged, mixed-species coniferous stands are not necessarily more productive than single-species stands.

Overturning resistance of western redcedar and western hemlock in mixed-species stands in coastal British Columbia

2007 ◽  
Vol 37 (5) ◽  
pp. 931-939 ◽  
Author(s):  
Kenneth E. Byrne ◽  
Stephen J. Mitchell
Keyword(s):  
British Columbia ◽  
Tsuga Heterophylla ◽  
Western Hemlock ◽  
Thuja Plicata ◽  
Specific Information ◽  
Mixed Species ◽  
Stem Form ◽  
Western Redcedar ◽  
Applied Forces ◽  
Coastal British Columbia

Specific information about the applied forces that cause trees to fail is required to validate mechanistic models of windthrow in different forest types. Static tree-pulling tests were conducted to examine the overturning resistance of western redcedar ( Thuja plicata Donn ex D. Don) and western hemlock ( Tsuga heterophylla (Raf.) Sarg.) in a mixed species second-growth stand in coastal British Columbia. Although widely used, tree-pulling techniques are not standardized. Data from three inclinometers were used to estimate stem deflection, which was found to increase with tree slenderness. Differing methods of fitting stem curvature had a small effect on estimates of self-loading at failure. The distance of the pivot point from the centre of the stem base increased with tree diameter. Accounting for the correct self-loading at failure produced a small difference in the overall turning moment regressions but did not improve the fit of these regressions. However, this difference increased with tree size and warrants consideration in future tree-pulling tests with large or plate-rooted trees. The stem mass – overturning resistance relationship had the best fit and was not significantly different for these species in spite of their differences in wood density and stem form.

scholarly journals Stand structure-dependent mass-ratio and complementarity effects simultaneously drive aboveground biomass in temperate Quercus forests

2021 ◽  
Author(s):  
Wen-Qiang Gao ◽  
xiangdong lei ◽  
Dong-Li Gao ◽  
Yu-Tang Li
Keyword(s):  
Species Richness ◽  
Environmental Factors ◽  
Aboveground Biomass ◽  
Phylogenetic Diversity ◽  
Structural Equation Models ◽  
Stand Structure ◽  
Tree Size ◽  
Stand Age ◽  
Mass Ratio ◽  
Size Diversity

Aim: Forests play a key role in regulating the global carbon cycle, a substantial portion of which is stored in aboveground biomass (AGB). It is well-understood that biodiversity can increase the biomass through complementarity and mass-ratio effects, and the contribution of environmental factors and stand structure attributes to AGB was also observed. However, the relative influence of these factors in determining the AGB of Quercus forests remains poorly understood. Location: Temperate Quercus forests in northeastern China. Methods: Using a large dataset retrieved from 523 permanent forest inventory plots across Northeast China, we examined the effects of integrated multiple tree species diversity components (i.e., species richness, functional and phylogenetic diversity), functional traits composition, environmental factors (climate and soil), stand age, and structure attributes (stand density, tree size diversity) on AGB based on structural equation models. Results: We found that species richness and phylogenetic diversity both were not correlated with AGB. However, functional diversity positively affected AGB via an indirect effect in line with the complementarity effect. Moreover, the community-weighted mean of specific leaf area and height increased AGB directly and indirectly, respectively; demonstrating the mass-ratio effect. Furthermore, stand age, density, and tree size diversity were more important modulators of AGB than biodiversity. Main conclusions: Our study highlights that biodiversity-AGB interaction is dependent on the regulation of stand structure that can be even more important for maintaining high biomass than biodiversity in temperate Quercus forests.

Root structure of western hemlock and western redcedar in single- and mixed-species stands

2002 ◽  
Vol 32 (6) ◽  
pp. 997-1004 ◽  
Author(s):  
X L Wang ◽  
K Klinka ◽  
H Y.H Chen ◽  
L de Montigny
Keyword(s):  
British Columbia ◽  
Forest Floor ◽  
Soil Depth ◽  
Root Density ◽  
Western Hemlock ◽  
Root Structure ◽  
Mixed Species ◽  
Coarse Roots ◽  
Western Redcedar ◽  
Size Classes

Root structure of western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn. ex D. Don) was studied in single- and mixed-species stands of hemlock and western redcedar in Capilano River watershed, University of British Columbia Malcolm Knapp Research Forest, and Mission, southern coastal British Columbia. We sampled roots using a tree-to-tree trench excavation method. In each stand, roots were collected from three randomly located trenches using a 20 × 20 × 10 cm template along (i) a soil depth gradient: forest floor (FF), 0- to 10-cm (MS1), and 10- to 20-cm mineral soil layers (MS2) and (ii) a lateral soil gradient (tree-to-tree trenches). Hemlock–redcedar mixtures had the greatest root density, followed by pure hemlock and redcedar stands. In both pure hemlock stands and hemlock-redcedar mixtures, root density of all size classes (fine, medium, and coarse roots) decreased with increasing soil depth, whereas that of pure redcedar stands peaked at the MS1 layer. Density of roots along the lateral gradient varied among stand types and root size classes. Density of coarse roots was higher towards tree stems, while that of fine and medium roots was more evenly distributed. In the forest floor of the hemlock–redcedar mixtures, root density of all sizes except that of redcedar coarse roots was not related to the distance to stems, but fine root density of hemlock was greater than that of redcedar. The highest root density in the hemlock–redcedar mixtures may indicate the presence of overlapping and intermingling roots and intense competition for available soil resources.

scholarly journals Spore Dispersal by Dothistroma septosporum in Northwest British Columbia

2015 ◽  
Vol 105 (1) ◽  
pp. 69-79 ◽  
Author(s):  
Kennedy Boateng ◽  
Kathy J. Lewis
Keyword(s):  
British Columbia ◽  
Lodgepole Pine ◽  
Summer Precipitation ◽  
Disease Spread ◽  
Spore Dispersal ◽  
Mixed Species ◽  
Inoculum Sources ◽  
Pine Trees ◽  
Dothistroma Septosporum ◽  
Needle Blight

We studied spore dispersal by Dothistroma septosporum, causal agent of a serious outbreak of red band needle blight in lodgepole pine plantations in northwest British Columbia. Spore abundance was assessed at different distances and heights from inoculum sources and microclimatic factors were recorded during two consecutive years. Conidia were observed on spore traps from June to September during periods of rainfall. It was rare to detect spores more than 2 m away from inoculum sources. The timing and number of conidia dispersed were strongly tied to the climatic variables, particularly rainfall and leaf wetness. Should the trend toward increased spring and summer precipitation in the study area continue, the results suggest that disease spread and intensification will also increase. Increasing the planting distances between lodgepole pine trees through mixed species plantations and overall reduction in use of lodgepole pine for regeneration in wet areas are the best strategies to reduce the spread of the disease and enhance future productivity of plantations in the study area.

From single-species advice to mixed-species management: taking the next step

2004 ◽  
Vol 61 (8) ◽  
pp. 1398-1409 ◽  
Author(s):  
Morten Vinther ◽  
Stuart A. Reeves ◽  
Kenneth R. Patterson
Keyword(s):  
North Sea ◽  
Fishery Management ◽  
Single Species ◽  
Mixed Species ◽  
The North ◽  
Recent Approach ◽  
Starting Point ◽  
The North Sea ◽  
Management Advice ◽  
Management Priorities

Abstract Fishery management advice has traditionally been given on a stock-by-stock basis. Recent problems in implementing this advice, particularly for the demersal fisheries of the North Sea, have highlighted the limitations of the approach. In the long term, it would be desirable to give advice that accounts for mixed-fishery effects, but in the short term there is a need for approaches to resolve the conflicting management advice for different species within the same fishery, and to generate catch or effort advice that accounts for the mixed-species nature of the fishery. This paper documents a recent approach used to address these problems. The approach takes the single-species advice for each species in the fishery as a starting point, then attempts to resolve it into consistent catch or effort advice using fleet-disaggregated catch forecasts in combination with explicitly stated management priorities for each stock. Results are presented for the groundfish fisheries of the North Sea, and these show that the development of such approaches will also require development of the ways in which catch data are collected and compiled.

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