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Abstract: We examined the effects of competition from red alder (Alnus rubra Bong.) and paper birch (Betula papyrifera Marsh.) on the growth of western redcedar (Thuja plicata Donn), western hemlock (Tsuga heterophylla Sarg.), and Douglas-fir (Pseudotsuga menziesii Franco) at a site near Maple Ridge, British Columbia, Canada. At this site, the three coniferous species and two broadleaf species had been planted in 1999 as part of a long-term experiment examining effects of broadleaf density on conifer growth. Red alder and paper birch were planted alone and as a 50:50 mixture at four densities (0, 277, 556, and 1150stemsha−1). Red alder density was positively correlated with total available nitrogen in soil measured using ion-exchange membranes whereas density of paper birch was not. For Douglas-fir only, foliar N concentration was positively related to red alder density. Relationships between stem volume increment and competition indices varied between the three conifer species: (1) For Douglas-fir the highest correlations were obtained using a distance-independent competition index based on broadleaf crown surface area and diffuse transmittance (DIFN) measured using LAI-2000 plant canopy analyzers had the lowest R 2 of the competition measures tested; (2) for western redcedar the highest correlations were with DIFN and the second best competition measures were distance-dependent indices; (3) for western hemlock broadleaf competition did not have significant effects on growth. Height of each species at the time of measurement and crown surface area appear to be more important than shade tolerance in affecting conifer growth. At this site, significant reductions in stem volume (30%) of Douglas-fir and western redcedar occurred when red alder density exceeded 500stemsha−1 while paper birch was not detrimental to western redcedar growth until densities exceeded 1000stemsha−1 and birch density did not significantly affect Douglas-fir. The influence of red alder on soil N and foliar N of Douglas-fir may be leading to a weaker relationship between growth and DIFN for Douglas-fir compared to that for western redcedar. [Copyright &y& Elsevier]

There is an increasing interest in mixed conifer-broadleaf stands as a way to increase the diversity and productivity of managed forests. This study examined the impacts of varying densities of planted broadleaf trees on conifer performance, total stand productivity, and understory plant cover 20 years after stand establishment. The study took place in the Malcolm Knapp Research Forest in Maple Ridge, British Columbia. It used a randomized complete block design to compare treatments containing low, moderate, or high broadleaf densities added to a constant conifer density. Each block contained a conifer-only plot as a control. Conifers were composed of equal amounts of western hemlock, western redcedar, and Douglas-fir. Broadleaves were composed of either red alder or paper birch. We found that conifer volume was significantly lower in most broadleaf treatments relative to the control, due to lower hemlock and redcedar volumes. Douglas-fir, on the other hand, had a higher volume—albeit not significant—in the broadleaf treatments. There were no significant differences in total stand volume between any of the treatments and the control. Shrub cover was significantly higher in the low and high alder treatments relative to the control, but there were no differences in shrub cover between birch treatments and the control. The results suggest that low alder density provides a good balance of conifer yield and understory development. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Entomologist is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plots were established in 20 juvenile mixed conifer stands in the Interior Cedar Hemlock biogeoclimatic zone of British Columbia's southern interior region in western Canada to assess mortality and host response to infection in the form of basal lesions caused by Armillaria ostoyae. Western redcedar showed significantly lower mortality and a higher proportion of callused lesions at the root collar than Douglas‐fir and western hemlock. Mortality decreased with increasing tree diameter for all species; however, the rate of decrease was markedly greater for western redcedar than Douglas‐fir or western hemlock. Results from logistic regression analysis showed that the probability of Douglas‐fir being killed is 14.6 times greater than western redcedar in these juvenile stands. Because western redcedar displayed significant resistance to A. ostoyae at both the root and stand level, this species represents an excellent choice as a significant stand component with more susceptible conifers. Should susceptible conifers succumb to Armillaria root disease, western redcedar will likely fill in the stand. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The recent mountain pine beetle (MPB) outbreak has had an impact on the carbon (C) cycling of lodgepole pine forests in British Columbia. This study examines how partial harvesting as a forest management response to MPB infestation affects the net ecosystem production (NEP) of a mixed conifer forest (MPB-09) in Interior BC. MPB-09 is a 70-year-old stand that was partially harvested in 2009 after it had been attacked by MPB. Using the eddy-covariance technique, the C dynamics of the stand were studied over two years and compared to an adjacent clear-cut (MPB-09C) over the summertime. The annual NEP at MPB-09 increased from -108 g Cm-2 in 2010 to-57g Cm-2 in 2011. The increase of NEP was due to the associated increase in annual gross ecosystem photosynthesis (GEP) from 812 g Cm-2 in 2010 to 954 g C m-2 in 2011, exceeding the increase in annual respiration (Re) from 920 g Cm-2 to 1011 g Cm-2 during the two years. During the four month period between June and September 2010, NEP at MPB-09C was -103 g Cm-2, indicating high C losses in the clear-cut. MPB-09 was a C sink during the growing season of both years, increasing from 9g Cm-2 in 2010 to 47 g Cm-2 in 2011. The increase of NEP in the partially harvested stand amounted to a recovery corresponding to a 26 % increase in the maximum assimilation rate in the second year. This study shows that retaining the healthy residual forest can result in higher C sequestration of MPB-attacked stands compared to clear-cut harvesting. [ABSTRACT FROM AUTHOR]

This study investigated the carbon (C) content in boles of twenty western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees. Bole samples were obtained from southern Vancouver Island in British Columbia (Conuma River, south of Muchalat Lake, Apple River, and Harris Creek) from a Western Forest Products Inc. management area, during the summer of 2003. Disks (10 centimeters thick) were obtained from the top of live crown (TLC), the base of live crown (BLC), and at breast height (BH) of each tree. By elemental analysis, C content of 20 genotypes had a mean of ∼53.5% (w/w), standard error of the mean [SEM] 0.1). Since the variation in each tree was so small, and the SEM for each of the positions within the bole was 0.1 and 0.2, we conclude that there was only slight variation among genotypes at the 99% level of confidence in the three positions within the bole. Considerable additional research is needed in order to have accurate estimates of total C content in any tree, and given that there is variation in C content within tree species, and in order to account for C in any forest stand, total C content should be estimated by integrating each individual tree component. [ABSTRACT FROM AUTHOR]

Common species can be major drivers of species richness patterns and make major contributions to biomass and ecosystem function, and thus should be important targets for conservation efforts. However, it is unclear how common species respond to disturbance, because the underlying reasons for their commonness may buffer or amplify their responses to disturbance. To assess how well common species reflect changes in their community (and thus function as indicator species), we studied 58 bird species in 19 mixed conifer patches in northern British Columbia, Canada, between 1998 and 2010. During this time period two disturbance events occurred, stand level timber harvest and a regional-scale bark beetle outbreak. We examined relationships among densities of individual species, total bird density and overall species richness, correlations in abundance among species, and responses to disturbance events. We found three broad patterns. First, densities of common species corresponded more strongly with changes in total bird density and overall species richness than rare species. These patterns were non-linear and species with intermediate-high commonness showed similar or better correspondence than the most common species. Second, common species tended to be more strongly correlated with abundances of all other species in the community than less-common species, although on average correlations among species were weak. Third, ecological traits (foraging guild, migratory status) were better predictors of responses to disturbance than species commonness. These results suggest that common species can collectively be used to reflect changes in the overall community, but that whenever possible monitoring programs should be extended to include species of intermediate-high commonness and representatives from different ecological guilds. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Site preparation alleviates the effects of pinegrass (Calamagrostis rubescens Buckl.) interference on conifers in British Columbia, but little is known about interference mechanisms and appropriate site preparation methods for steep slopes. In this study, lodgepole pine (Pinus contorta Dougl. ex Loud.) was planted in pinegrass controls and small (90 x 90 cm) and large (180 x 90 cm) patches where (i) only pinegrass was removed using glyphosate or (ii) both pinegrass and the forest floor were removed using an excavator. Treatments were replicated three times in east- and west-facing clearcuts and effects were followed for 9 years. Two-year pine survival was 78% in the control and >97% in large patches. All patch treatments improved pine growth, but it was greatest in large chemical patches during the initial 6 years and in both large patch treatments thereafter. Removal of the forest floor reduced foliar and soil nutrients, increased bulk density and soil water availability, decreased porosity and aggregate stability, and reduced ectomycorrhizal diversity and richness. These changes were not observed in chemical patches. All patch treatments increased soil temperatures and reduced frost relative to controls, but more so in large patches. Pinegrass can suppress early pine performance, and large chemical patches that retain the forest floor are best for relieving the multiple environmental stressors. [ABSTRACT FROM AUTHOR]

Investigates the responses of small-mammal populations to a forest herbicide application in a 20-year-old conifer plantation in Maple Ridge, British Columbia. Species that made up the mammal populations; Movements of deer mice; Possible occurrence of changes in composition of the small-mammal community in association with successional stages in advancing from the herbicide-induced habitat alteration.