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Survival and growth of planted white spruce (Picea glauca (Moench) Voss) were assessed at year 15 in boreal mixedwood stands of northern Alberta, Canada, in stands that were deciduous-dominated prior to logging or were conifer-dominated. Three overstory retention levels (0%, 50%, and 75% retention) and four site preparation treatments (mound, high speed mix, scalp, and no treatment) were evaluated. In deciduous-dominated stands, planted spruce performed best in the 50% retention; here, stem volume was at least double that of any other retention treatment after 15 years. In contrast, spruce had reduced growth in coniferous-dominated stands in both 50% and 75% retention treatments compared with the 0% retention. Survival of planted spruce was unaffected by level of retention, but survival was lower in coniferous-dominated stands than in deciduous-dominated stands; in the coniferous-dominated stands, survival was better with mounding and mixing and lowest with scalp treatments. All height variables tended to be greater in the mix and mound site preparation treatments. Finally, the best estimates of future total growth (regenerated spruce and deciduous combined) in the coniferous-dominated stands were in the clearcut treatment. In terms of regenerated spruce growth, the best estimates occurred in the deciduous-dominated – 50% retention stand planted with soil mixing–mounding treatments, where projected growth of spruce was comparable with that of open-grown and tended stands in Alberta's boreal forests. [ABSTRACT FROM AUTHOR]

Drought tolerance of trees may be affected by competition, but most studies quantifying the relationship do not consider the effect of stem clustering. Trees are often clustered in interior Douglas-fir ( Pseudotsuga menziesii var. glauca (Mayr) Franco) forests near the grassland interface in central British Columbia due to past harvesting practices or habitat management for mule deer ( Odocoileus hemionus hemionus (Rafinesque, 1817)). Climate change projections indicate continued increases in temperature, an outcome that would stress trees growing in dry environments. Trees placed in different states of competition by mechanical harvesting in the 1970s were sampled to provide a 40-year comparison of three levels of competition during 1-2 year droughts. Tree-ring analysis was used to assess the reduction in growth during drought years and resumption of growth in subsequent years. A clear separation of growth rates was evident between open-growing trees, trees on the edge of harvesting trails, and trees within the unharvested interior. Edge trees had intermediate growth rates but no differences were found in the long-term climate-growth relationship compared with open-growing trees. Both Edge and Open classes showed less relative growth reduction during droughts than Interior trees growing between harvest trails. Precipitation throughfall rates and competition for resources are likely driving short-term drought tolerance in combination with other factors. [ABSTRACT FROM AUTHOR]

In tolerant hardwood forests of eastern North America, multiple-aged silvicultural systems rely on advanced regeneration to restock the forests. Evaluation of the long-term influence of advanced regeneration on the mature stand is critical for improving management practices. We used a retrospective approach to evaluate the influence of advanced regeneration present at the time of harvest on the current (2012) stand structure and the quality of the growing stock. The study was carried out in partially harvested stands in northwestern New Brunswick, Canada. Trees were sampled from stands with varying degrees of harvest intensities, times since harvest, and site characteristics. Pre-existing advanced regeneration contributed the bulk of trees in the 10-19 cm diameter class across the stands. In stands with low-intensity harvest, the overstory was dominated by sugar maple ( Acer saccharum Marsh.) that originated as advanced regeneration. In stands with high-intensity harvest, however, yellow birch ( Betula alleghaniensis Britt.) pre-existing advanced regeneration dominated the overstory. The probability of sugar maple and yellow birch being acceptable growing stock peaked at a diameter at breast height (DBH) of about 30-40 cm, while other species combined peaked at a DBH of around 20-25 cm. Our results suggest that harvest intensities based on the dominant advanced regeneration composition and harvesting systems that minimize the risk of physical damage to advanced regeneration are required to achieve partial harvesting objectives. [ABSTRACT FROM AUTHOR]

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Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry 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 Forestry Chronicle is the property of Canadian Institute of Forestry 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.)