Postdispersal seed predation of white spruce in cutblocks in the boreal mixedwoods: a short-term experimental study

2004 ◽  
Vol 34 (4) ◽  
pp. 907-915 ◽  
Author(s):  
Susan H Peters ◽  
S Ellen Macdonald ◽  
Stan Boutin ◽  
Richard A Moses
Keyword(s):  
Small Mammals ◽  
Seed Predation ◽  
Picea Glauca ◽  
Seedling Recruitment ◽  
White Spruce ◽  
Forest Edge ◽  
Seed Loss ◽  
Boreal Mixedwoods ◽  
Initial Seed

We conducted a 1-year study to examine the influence of postdispersal seed predation by small mammals and other vertebrate predators on seedling recruitment rates (percentage of seeds surviving to seedling stage) and seed loss of white spruce (Picea glauca (Moench) Voss) in recently logged areas in the boreal mixedwood forest in north-central Alberta. Experimental exclosures showed that predators reduced recruitment rates, on average, by 46% for seeds exposed to predation for 6 weeks in the summer and by 79% for seeds exposed to predation between autumn (seed dispersal) and the following summer (germination). We were unable to detect an influence of initial seed density on recruitment rates. A seed tray experiment suggested that predators can detect and consume 80%–94% of white spruce seeds available in cutblocks within 1 month of sowing and that seed predation rates do not vary predictably with distance from the cutblock–forest edge. Our results suggest that vertebrate seed predators, especially small mammals, have the potential to severely affect recruitment rates of white spruce in recent cutblocks, although long-term work is needed to understand how predators might affect recruitment under natural conditions with predator and seed densities that vary in space and time.

scholarly journals Application of Nursery Testing in Long-Term White Spruce Improvement Programs

2007 ◽  
Vol 24 (4) ◽  
pp. 296-300 ◽  
Author(s):  
Yuhui Weng ◽  
Kathy Tosh ◽  
Yill Sung Park ◽  
Michele S. Fullarton
Keyword(s):  
Picea Glauca ◽  
Genetic Correlations ◽  
Field Tests ◽  
Field Performance ◽  
White Spruce ◽  
Height Growth ◽  
Positive Assortative Mating ◽  
The Family ◽  
Improvement Programs

Abstract Polycross-pollinated white spruce (Picea glauca [Moench] Voss) families were evaluated in field and retrospective nursery tests in 1989, 1991, and 1992, respectively. Height growth was measured at age 10 for the field tests and at ages 1 to 6 for the retrospective nursery tests. Except for a few cases, the family mean correlations between nursery and field heights were significant for the 1989 and 1992 series, and their corresponding genetic correlations ranged from low to medium (from 0.37 to 0.74). Because of heavy noncrop competition, height growth in the 1991 nursery series showed consistently lower heritabilities and correlations with field performance compared with those of the other two series. Early nursery selection by theoretical prediction was generally efficient for the 1989 and 1992 series. Rank classification analysis indicated that application of early nursery selection should be used with caution for identifying elite families but could be used to cull inferior families or clones, apply multiple-stage selection, or perform positive assortative mating.

Hexazinone Gridballs™ applied with concurrent underplanting of white spruce in boreal mixedwoods: 7-year results

1986 ◽  
Vol 62 (4) ◽  
pp. 226-232 ◽  
Author(s):  
R. F. Sutton
Keyword(s):  
Picea Glauca ◽  
Ground Surface ◽  
White Spruce ◽  
Separation Distance ◽  
Stem Volume ◽  
Weed Growth ◽  
M 10 ◽  
The Mean ◽  
Boreal Mixedwoods ◽  
Maximum Separation

In mid-June 1978, hexazinone Gridball™ pellets were individually placed on the ground surface in two10-m × 10-m plots at each of two grid spacings in moderate-to-dense, woody weed growth in each of three boreal mixedwood stands in the Chapleau and Manitouwadge areas of Ontario. The rates of application were equivalent to 0.0, 1.4 and 4.2 kg a.i./ha. In these and a similar number of untreated plots, 16 white spruce (Picea glauca [Moench] Voss) were planted centrally in each plot at the same grid spacings used for the Gridballs™ but offset so as to give maximum separation between outplants and herbicide. The main study was supplemented by another to determine safe separation distance. GridballsTM at close spacing very significantly (P 0.01) increased growth of white spruce: at one location, the mean stem volume of spruce 7 years after planting was 438% that of spruce in the no-herbicide treatment; at a second location the comparable value was 503%. The evidence suggests that white spruce may be established in the boreal mixedwoods by underplanting and, concurrently, applying Gridballs™ at 1-m × 1-m spacing.

Are mixtures of aspen and white spruce more productive than single species stands?

1999 ◽  
Vol 75 (3) ◽  
pp. 505-513 ◽  
Author(s):  
Rongzhou Man ◽  
Victor J. Lieffers
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
White Spruce ◽  
Single Species ◽  
Physical Separation ◽  
Soil Resource ◽  
Mixedwood Forests ◽  
Environmental Extremes ◽  
Spruce Stands ◽  
Boreal Mixedwoods

In boreal mixedwood forests, aspen (Populus tremuloides) and white spruce (Picea glauca) commonly grow in mixture. These species may avoid competition through differential shade tolerance, physical separation of canopies, phenological differences, successional separation, and differences in soil resource utilization. Aspen may also be able to positively affect the growth of white spruce by improving litter decomposition and nutrient cycling rates, controlling grass and shrub competition, ameliorating environmental extremes, and reducing pest attack. These positive relationships likely make mixed-species stands more productive than pure stands of the same species. The evidence regarding the productivity of pure versus mixed aspen/white spruce stands in natural unmanaged forests is examined in this paper. Key words: Tree mixture; productivity; boreal mixedwoods; aspen; white spruce

Pre-dispersal seed predation of white spruce cones in logged boreal mixedwood forest

2003 ◽  
Vol 33 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Susan Peters ◽  
Stan Boutin ◽  
Ellen Macdonald
Keyword(s):  
Seed Predation ◽  
Picea Glauca ◽  
Natural Regeneration ◽  
White Spruce ◽  
Tamiasciurus Hudsonicus ◽  
Red Squirrels ◽  
Tree Crowns ◽  
Tree Retention ◽  
Boreal Mixedwood Forest ◽  
Mixedwood Boreal Forest

Predation of white spruce (Picea glauca (Moench) Voss) cones by red squirrels (Tamiasciurus hudsonicus Erxleben) was quantified in the mixedwood boreal forest of Alberta in cutblocks with seed tree retention and in adjacent uncut forest, during 3 years with varying levels of cone crop (1998, 1999, 2000). Percent cone loss was quantified by comparison of paired pre- and post-caching photographs of tree crowns. Cone loss from seed trees in cutblocks was significantly lower than from control trees in adjacent uncut forest (48.5 vs. 54.9%). Although the number of cones produced per tree declined by 42% and the percentage of trees producing cones declined by approximately 48% between 1998 and 2000, there was no corresponding increase in the percentage of cones harvested by squirrels. Percent cone loss was significantly lower from single seed trees in cutblocks, as compared with seed trees left in patches of more than 20 trees (33.4 vs. 50.5%). Cone predation significantly reduced the amount of seed available for natural regeneration using a seed tree system. Although blowdown may be reduced if seed trees are left in patches, leaving white spruce seed trees as singles in cutblocks may reduce the level of cone predation.

scholarly journals Implications of selected approaches for regenerating and managing western boreal mixedwoods

2005 ◽  
Vol 81 (4) ◽  
pp. 559-574 ◽  
Author(s):  
Philip G Comeau ◽  
Richard Kabzems ◽  
John McClarnon ◽  
Jean L Heineman
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Management Strategies ◽  
Structural Diversity ◽  
White Spruce ◽  
Forest Types ◽  
Successful Management ◽  
Flexible Planning ◽  
Boreal Mixedwoods ◽  
Stand Conditions

We describe a range of approaches for managing boreal mixedwood stands composed of trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) in British Columbia and Alberta. Successful management of these complex forests requires a combination of well-defined objectives at the landscape level and flexible planning at the stand level. A variety of management strategies must be applied concurrently across the landscape to ensure that the natural mix of forest types and structural diversity is maintained. Selected approaches are discussed with regard to their suitability to particular stand conditions and sets of objectives, the types of tending and harvesting activities required, expected outcomes, and costs. The three approaches discussed are: 1) creation and management of two-storied intimate mixtures; 2) creation of a single-storied mixture of aspen and white spruce; and, 3) creation of a mosaic of discrete patches of each species. Key words: boreal mixedwood management, mixedwood silvicultural systems, aspen, white spruce, planning

Juvenile response to conifer release alternatives on aspen-white spruce boreal mixedwood sites.Part I: Stand structure and composition

2005 ◽  
Vol 81 (4) ◽  
pp. 538-547 ◽  
Author(s):  
Douglas G Pitt ◽  
F. Wayne Bell
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Stand Structure ◽  
Foliar Application ◽  
White Spruce ◽  
Fibre Production ◽  
Stem Volume ◽  
Stem Quality ◽  
Commercial Species ◽  
Boreal Mixedwoods

Stand structure and composition for planted white spruce (Picea glauca (Moench) Voss) and other naturally regenerating commercial species were compared seven years after the testing of five conifer release alternatives on three boreal mixedwood sites. No release resulted in aspen (Populus tremuloides Michx.) -dominated stands with 89% stocking and the highest basal areas (BAs, 5.1 m2/ha) and stem volume indices (SVIs, 10.7 m3/ha) observed. Release by manual or machine cutting increased planted spruce BA and SVI by 67 and 38%, respectively. However, this treatment also caused significant root and stump suckering of aspen, more than doubling stem densities and increasing stocking by 12% over untreated areas. Although cutting reduced the height of aspen from 6 m (untreated) to 2–3 m, equal to or just taller than planted spruce, it is likely that future growth will result in deciduous-dominated mixedwoods. Broadcast foliar application with Release® herbicide temporarily reduced the size of aspen, without causing the increased regeneration observed following cutting. This produced a more varied stand structure that promoted the stature of planted spruce, doubling dominant spruce stocking, BAs, and SVIs, and leading to a more balanced mixedwood. Broadcast release with Vision® herbicide produced conifer-dominated stands with few deciduous stems; these areas contained the lowest observed BAs (1.7 m2/ha) and SVIs (1.9 m3/ha). Relatively low planting densities (1350 sph), coupled with near complete deciduous removal in these plots, created very open-grown conditions that threaten overall productivity and stem quality of the spruce. The five approaches tested are capable of producing a range of stand conditions found in a healthy boreal mixedwood landscape. Key words: boreal mixedwoods, white spruce, trembling aspen, vegetation management, fibre production

scholarly journals Creating boreal mixedwoods by planting spruce under aspen: successful establishment in uncertain future climates

2016 ◽  
Vol 46 (10) ◽  
pp. 1217-1223 ◽  
Author(s):  
Richard Kabzems ◽  
Philip G. Comeau ◽  
Cosmin N. Filipescu ◽  
Bruce Rogers ◽  
Amanda F. Linnell Nemec
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Basal Area ◽  
Cost Effective ◽  
White Spruce ◽  
Understory Vegetation ◽  
Severe Drought ◽  
Boreal Mixedwoods ◽  
Uncertain Future ◽  
Canadian Boreal Forest

Planting white spruce (Picea glauca (Moench) Voss) under established aspen (Populus tremuloides Michx.) stands has substantial potential for regenerating mixedwood ecosystems in the western Canadian boreal forest. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. Under future climatic regimes with more frequent and severe drought episodes, underplanting may be a cost-effective strategy for lowering the risk of mortality in mixedwood regeneration. We examine the growth of white spruce during the first 18 years after being planted beneath a 39-year-old stand of trembling aspen. Treatments included thinning from over 6000 stems·ha−1 to 3000, 2000, and 1000 stems·ha−1 and fertilization. Initial stimulation of understory vegetation by fertilization had no measureable effect on spruce heights or diameters at year 18. Aspen thinning treatments did not have a significant effect on spruce height growth rates after spruce crowns had emerged above the understory shrub layer due to rapid aspen basal area increases after thinning. Small, but significant, increases for spruce height and diameter were present in the 1000 and 2000 stem·ha−1 aspen thinnings. A much wider range of aspen stand conditions may be suitable for planting spruce to create mixedwood ecosystems than has been previously considered.

scholarly journals Regeneration of aspen following partial and strip understory protection harvest in boreal mixedwood forests

2009 ◽  
Vol 85 (4) ◽  
pp. 631-638 ◽  
Author(s):  
Alison D Lennie ◽  
Simon M Landhäusser ◽  
Victor J Lieffers ◽  
Derek Sidders
Keyword(s):  
Forest Management ◽  
Key Words ◽  
Populus Tremuloides ◽  
Picea Glauca ◽  
Basal Area ◽  
White Spruce ◽  
Mixedwood Forests ◽  
Partial Harvest ◽  
Second Year

Trembling aspen regeneration was studied in 2 types of partial harvest systems designed to harvest mature aspen but protect immature spruce and encourage natural aspen regeneration. Two partial harvest systems, where the residual aspen was either left in strips or was dispersed uniformly, were compared to traditional clearcuts. After the first and second year since harvest, aspen sucker density and growth was similar between the 2 partial harvests, but was much lower than in the clearcuts. However, in the partial cuts the regeneration density was very much dependent on the location relative to residual trees. The density of regeneration was inversely related to the basal area of residual aspen; however, sucker height was inversely related to the basal area of the residual spruce. Although there were adequate numbers of suckers after partial harvest, their viability and contribution to the long-term productivity of these mixedwood stands is not clear. Key words: silvicultural systems, forest management, residual canopy, white spruce, Populus tremuloides, Picea glauca, traffic

Windthrow as an important process for white spruce regeneration

2002 ◽  
Vol 78 (5) ◽  
pp. 732-738 ◽  
Author(s):  
Jean-Claude Ruel ◽  
Marius Pineau
Keyword(s):  
Key Words ◽  
Picea Glauca ◽  
Abies Balsamea ◽  
White Spruce ◽  
Balsam Fir ◽  
Differential Mortality ◽  
Important Process ◽  
Mature Stands

White spruce (Picea glauca (Moench.) Voss.) is frequently found in association with balsam fir (Abies balsamea (L.) Mill.) in virgin stands. However, its regeneration is less aggressive than that of balsam fir. The persistance of white spruce in the canopy might be explained by differential mortality and windthrow. Windthrow could play an important role in creating favourable seedbeds and providing increased light. This paper examines the contribution of windthrow for white spruce regeneration in balsam fir-dominated forests. Experimental windthrows were created and regeneration establishment monitored for three seasons. Windthrow greatly modified the availability of seedbeds and enhanced white spruce establishment. Older natural windthrows were sampled to conclude that this effect was still evident more than five years after windthrow occured. We also noticed that white spruce benefited more from the disturbance than did balsam fir. Finally, sampling conducted in mature stands showed that mature white spruce stems were more abundant on the mounds created by old uprootings, indicating that this effect is maintained in the long term. Even though balsam fir also benefited from windthrow, the benefit was proportionally greater for white spruce. Key words: Picea glauca, Abies balsamea, windthrow, microtopography, regeneration

Are mineral soils exposed by severe wildfire better seedbeds for conifer regeneration?

2006 ◽  
Vol 36 (8) ◽  
pp. 1943-1950 ◽  
Author(s):  
Kevin J Kemball ◽  
G. Geoff Wang ◽  
A Richard Westwood
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Pinus Banksiana ◽  
Seedling Recruitment ◽  
Black Spruce ◽  
Mineral Soil ◽  
White Spruce ◽  
Jack Pine ◽  
Conifer Regeneration ◽  
Mineral Soils

We examined jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) BSP), and white spruce (Picea glauca (Moench) Voss) seed germination and seedling recruitment in aspen (Populus tremuloides Michx.) and conifer mixedwood stands following the 1999 Black River fire in southeastern Manitoba, Canada. Three postfire seedbed types were tested: scorched (surface litter only partially consumed), lightly burned (surface litter consumed with little or no duff consumption), and severely burned (complete consumption of litter and duff exposing mineral soil). Seeds were sown in 1999, 2000, and 2001, and each cohort was monitored for 3 years. In 1999, severely burned seedbeds had poor germination, while scorched seedbeds had the highest germination. The reverse was true in 2001. After the first growing season, continued survival of seedlings was greater on severely burned seedbeds for all three cohorts. However, better survival on severely burned seedbeds was not sufficient to overcome poor germination in 1999 and 2000. When using artificial seeding to promote conifer regeneration, we recommend a delay of one full year after a severe spring fire for jack pine and two full years for black spruce and white spruce on boreal aspen and conifer mixedwood sites.

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