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 Seed masting causes fluctuations in optimum litter size and lag load in a seed predator

2018 ◽  
Author(s):  
Andrew McAdam ◽  
Stan Boutin ◽  
Ben Dantzer ◽  
Jeff Lane
Keyword(s):  
Litter Size ◽  
Picea Glauca ◽  
Life Histories ◽  
Local Density ◽  
White Spruce ◽  
Tamiasciurus Hudsonicus ◽  
Seed Predator ◽  
Red Squirrels ◽  
Seed Predators ◽  
Seed Crops

The episodic production of large seed crops by some perennial plants, is referred to as masting and is known to increase seed escape by alternately starving and swamping seed predators. These pulses of resources, however, might also act as an agent of selection on the life histories of seed predators, which could indirectly enhance seed escape by inducing an evolutionary load on seed predator populations. Lag loads in seed predators could result from mast-induced shifts in optimum phenotypes that exceed the capacity of seed predators to adaptively track optimum phenotypes through phenotypic plasticity. Alternatively, masting could generate mismatches in selection across generations, where adaptation to the parental environment leads to maladaptation in the offspring environment. Here we measured natural selection on female North American red squirrels (Tamiasciurus hudsonicus) across 28 years and five white spruce (Picea glauca) masting events. Red squirrel litter sizes were similar to optimum litter sizes during non-mast years, but were well below optimum litter sizes during resource-rich mast years. Mast events, therefore caused selection for larger litters (B = 0.25) and a lag load (L = 0.25) on red squirrels during mast years. Furthermore, we found that the annual fitness of spruce trees was negatively related to the local density of squirrels during mast years, indicating that the observed lag load on squirrels enhanced the number of spruce cones escaping squirrel predation. Although, the frequency of mast events and the demography of red squirrels were such that offspring and parents often experienced opposite environments with respect to the mast, we found no effect of environmental mismatches across generations on either offspring survival or population growth. Instead, squirrels plastically increased litter sizes in anticipation of mast events, which partially, although not completely, reduced the lag load resulting from this change in food availability. Variable selection on litter size caused by white spruce mast events, therefore, induced a lag load on the population of red squirrels that was not affected by whether individual squirrels were born during mast (matching) or non-mast (mismatching) conditions.

VIABILITY OF WHITE SPRUCE SEED FROM SQUIRREL-CUT CONES

1964 ◽  
Vol 40 (1) ◽  
pp. 98-110 ◽  
Author(s):  
J. W. Bruce Wagg
Keyword(s):  
Picea Glauca ◽  
Seed Viability ◽  
White Spruce ◽  
Mature Seed ◽  
Tamiasciurus Hudsonicus ◽  
Red Squirrel ◽  
Red Squirrels

A study was made of the viability of white spruce, Picea glauca, seed obtained from seven cone caches of red squirrels, Tamiasciurus hudsonicus. Habits of the red squirrel, relation of seed viability to cone-caching activities and the relation of viability of seed obtained from the cached cones to the cones on the trees are described.Viability of see from cached cones does not vary between the time squirrels began to cache cones in quantity and the time the last cones are cached. Seed from the cached cones showed a higher percentage of viability than seed of cones collected from trees, because some of the mature seed had fallen from the partially open cones on the trees resulting in an increase in the percentage of undeveloped seed in progressive cone collections.

scholarly journals Effects of substrate availability and competing vegetation on natural regeneration of white spruce on logged boreal mixedwood sites

2018 ◽  
Vol 48 (4) ◽  
pp. 324-332 ◽  
Author(s):  
Nicola A. Kokkonen ◽  
S. Ellen Macdonald ◽  
Ian Curran ◽  
Simon M. Landhäusser ◽  
Victor J. Lieffers
Keyword(s):  
Picea Glauca ◽  
Natural Regeneration ◽  
Negative Impact ◽  
Mineral Soil ◽  
Soil Surface ◽  
White Spruce ◽  
Solid Wood ◽  
Seedling Mortality ◽  
Competing Vegetation ◽  
Survival And Growth

Given a seed source, the quality of available substrates is a key factor in determining the success of white spruce (Picea glauca (Moench) Voss) natural regeneration. We examined the influence of substrate and competing vegetation on survival and growth of natural regeneration of white spruce up to 4 years following harvesting in deciduous-dominated upland boreal mixedwood sites. Feather moss, thick soil surface organic layers, litter, and solid wood were poor substrates for establishment. Early successional mosses establishing on mineral soil, thin organics, and rotten wood were generally favourable microsites but were not highly available on postharvest sites. Mineral soil substrates were not as suitable as expected, likely because on a postlogged site, they are associated with unfavourable environmental characteristics (e.g., low nutrient availability, exposure). There was some evidence that survival and growth of seedlings were improved by surrounding vegetation in the first years, but heavy competing vegetation had a negative impact on older seedlings. Burial by aspen litter greatly increased seedling mortality, especially when combined with a brief period of submergence due to heavy spring snowmelt. The results provide insight into conditions under which natural regeneration could be an option for establishing white spruce following harvesting of deciduous-dominated boreal mixedwood forests.

scholarly journals The Role of Red Squirrels (Tamiasciurus Hudsonicus) in Shaping Spatial Patterns of Serotiny in Lodgepole Pine (Pinus Contorta) Forests

2011 ◽  
Vol 34 ◽  
pp. 139-145
Author(s):  
Matt Talluto ◽  
Craig Benkman
Keyword(s):  
Seed Predation ◽  
Pinus Contorta ◽  
Lodgepole Pine ◽  
Canopy Cover ◽  
Ecosystem Processes ◽  
Tamiasciurus Hudsonicus ◽  
Individual Species ◽  
Red Squirrels ◽  
Long Term Storage ◽  
Sapling Density

Understanding the effects of individual species on community- and ecosystem-level processes is of critical importance in ecology. Recent work has demonstrated that variation in genetically controlled traits within foundation species can have large implications for ecosystem processes. Identifying these traits and the selective pressures on them is crucial in understanding how ecosystems are structured and how the systems will respond to disturbance. Serotiny, the long-term storage of seeds in the canopy, is thought to be an adaptation to stand replacing fire. Seeds from serotinous plants are released following a fire, and the proportion of serotinous trees determines sapling density following a fire. The effects of serotiny are not limited to the serotinous species, as sapling density is an important determinant of plant community structure and ecosystem processes (including primary productivity and nutrient cycling). Seed predation may select against serotiny, however, no studies have addressed how the relative strengths of selection from fire and seed predation combine to produce the spatial pattern of serotiny on the landscape. Here, we report on an ongoing study of the effects of selection from seed predation in lodgepole pine (Pinus contorta), a serotinous North American conifer. Red squirrels are negatively associated with serotiny at broad geographic scales, and may select against the serotinous trait. This project examined the correlation between red squirrel density and the frequency of serotiny in lodgepole pine forests and the mechanisms underlying potential selection against serotiny by red squirrels. Specifically, we tested whether this correlation was present at landscape scales, whether the fitness of serotinous trees was reduced in the presence of red squirrels, and what factors controlled the density of red squirrels. Preliminary results indicate that serotiny and squirrel density is negatively correlated, but only at low elevations. In the presence of squirrels, we observed significantly lower cone survival in serotinous trees, suggesting reduced fitness. Squirrel density was strongly affected by several measures of forest structure, including species composition, overhead canopy cover, and tree size (mean DBH).

The effect of mechanical site preparation on ectomycorrhizae of planted white spruce seedlings in conifer-dominated boreal mixedwood forest

2008 ◽  
Vol 38 (7) ◽  
pp. 2072-2079 ◽  
Author(s):  
Lance W. Lazaruk ◽  
S. Ellen Macdonald ◽  
Gavin Kernaghan
Keyword(s):  
Picea Glauca ◽  
Untreated Control ◽  
White Spruce ◽  
Site Preparation ◽  
Organic Layer ◽  
Root Tips ◽  
Mechanical Site Preparation ◽  
Clear Cut ◽  
Mixed Treatment ◽  
Boreal Mixedwood Forest

We characterized the ectomycorrhizae (ECM) of planted white spruce ( Picea glauca (Moench) Voss) seedlings as affected by mechanical site preparation (MSP) of clear-cut conifer-dominated boreal mixedwood forest. Relative abundance, richness, and composition of the ECM community were compared among untreated control, mixed, mounded, and scalped site preparation treatments. On >11 000 root tips, we observed 16 ECM morphotypes. Those common to the nursery in which the seedlings were raised were most abundant ( Thelephora americana , Wilcoxina -like (E-strain), Amphinema byssoides , Phialocephala -like (MRA)). Seedlings in the untreated controls had lower abundances of these, but higher abundances of other ECM, which were not present in the nursery of origin but were indigenous to these forest stands. In terms of ECM composition, the “mixed” treatment was most similar to the untreated control, while the “scalped” and “mound” treatments showed significantly different ECM communities than the controls. Our results suggest that MSP may facilitate continued dominance by ECM that establish on seedlings in the nursery while slowing the natural succession towards the natural forest ECM. MSP treatments that leave some surface organic matter relatively intact may impact ECM less than those that remove or bury the organic layer.

Regeneration alternatives for upland white spruce after burning and logging in interior Alaska

1999 ◽  
Vol 29 (4) ◽  
pp. 413-423 ◽  
Author(s):  
R V Densmore ◽  
G P Juday ◽  
J C Zasada
Keyword(s):  
Growth Rates ◽  
Picea Glauca ◽  
Natural Regeneration ◽  
White Spruce ◽  
Site Preparation ◽  
Seed Source ◽  
Positive Effects ◽  
Interior Alaska

Site-preparation and regeneration methods for white spruce (Picea glauca (Moench) Voss) were tested near Fairbanks, Alaska, on two upland sites which had been burned in a wildfire and salvage logged. After 5 and 10 years, white spruce regeneration did not differ among the four scarification methods but tended to be lower without scarification. Survival of container-grown planted seedlings stabilized after 3 years at 93% with scarification and at 76% without scarification. Broadcast seeding was also successful, with one or more seedlings on 80% of the scarified 6-m2 subplots and on 60% of the unscarified subplots after 12 years. Natural regeneration after 12 years exceeded expectations, with seedlings on 50% of the 6-m2 subplots 150 m from a seed source and on 28% of the subplots 230 m from a seed source. After 5 years, 37% of the scarified unsheltered seed spots and 52% of the scarified seed spots with cone shelters had one or more seedlings, but only 16% of the unscarified seed spots had seedlings, with and without funnel shelters. Growth rates for all seedlings were higher than on similar unburned sites. The results show positive effects of burning in interior Alaska, and suggest planting seedlings, broadcast seeding, and natural seedfall, alone or in combination, as viable options for similar sites.

Natural regeneration of white spruce in aspen-dominated boreal mixedwoods following harvesting

2010 ◽  
Vol 40 (3) ◽  
pp. 585-594 ◽  
Author(s):  
Jonathan Martin-DeMoor ◽  
Victor J. Lieffers ◽  
S. Ellen Macdonald
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Natural Regeneration ◽  
Boreal Forests ◽  
Weather Conditions ◽  
White Spruce ◽  
Woody Vegetation ◽  
Silvicultural Treatments ◽  
Boreal Mixedwoods ◽  
Time Of Harvest

In some boreal forests sites, there are considerable amounts of natural regeneration of white spruce ( Picea glauca (Moench) Voss) after logging, even without silvicultural treatments to encourage establishment. We assessed the factors controlling the amount of this regeneration 8–15 years postharvest on previously aspen-dominated ( Populus tremuloides Michx.) boreal mixedwood sites. We surveyed 162 transects across 81 cutovers, exploring the effects of mast years, season of harvest, distribution of seed trees, weather conditions around the time of harvest, and abundance of grass or woody vegetation on white spruce regeneration. Substantial amounts of naturally regenerated white spruce were found; however, sites with no seed trees had virtually no spruce regeneration. Average stocking was 7% (percentage of 9 m2 plots along a transect across a cutover that had at least one seedling), ranging from 0% to 62%. Stocking levels were higher in cutblocks that had been harvested in the summer, prior to seedfall of a mast year, and where there was a seed source within 60 m. Stocking was lower when conditions were cool and wet the year before and 2 years after harvest and when the site contained extensive cover of grass or woody vegetation.

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.

The role of hair-cap mosses (Polytrichum spp.) in natural regeneration of white spruce (Picea glauca (Moench) Voss)

1997 ◽  
Vol 92 (1-3) ◽  
pp. 19-28 ◽  
Author(s):  
William C. Parker ◽  
Stephen R. Watson ◽  
Daryll W. Cairns
Keyword(s):  
Picea Glauca ◽  
Natural Regeneration ◽  
White Spruce

Effects of partial cutting on the ectomycorrhizae of Picea glauca forests in northwestern Alberta

2005 ◽  
Vol 35 (6) ◽  
pp. 1442-1454 ◽  
Author(s):  
Lance W Lazaruk ◽  
Gavin Kernaghan ◽  
S Ellen Macdonald ◽  
Damase Khasa
Keyword(s):  
Picea Glauca ◽  
Effective Means ◽  
White Spruce ◽  
Root Tip ◽  
Root Tips ◽  
Partial Cutting ◽  
Disturbance Intensity ◽  
Tree Retention ◽  
Green Tree Retention ◽  
The Impact

This study assessed the impact of various harvesting practices (including those designed to emulate natural disturbances) on ectomycorrhizae (ECM) associated with white spruce (Picea glauca (Moench) Voss) in northwestern Alberta, Canada. Treatments included clearcuts, partial cuts (dispersed green-tree retention with 20%, 50%, and 75% residual live trees, and aggregated green-tree retention), unharvested control sites, and a burned stand. The percentage of active white spruce root tips and ECM richness and diversity, as observed in soil cores collected throughout the study site, all decreased with increasing disturbance intensity. Effects were particularly pronounced in clearcuts, machine corridors used for access by harvesting equipment in the dispersed green-tree retention stands, and in burned areas. Reductions in ECM biodiversity could be attributed to the sensitivity of late-stage ectomycorrhizae (e.g., Cortinarius spp., Lactarius spp., and Russula spp.) to soil disturbances and changes in microclimate associated with harvesting or burning. Areas of dispersed and aggregated green-tree retention were not dramatically different than unharvested forest in terms of root tip density and ECM richness, diversity, and composition. Harvesting practices that retain a percentage of residual live trees, either dispersed throughout the cutting unit or in aggregated patches, could be an effective means of maintaining ectomycorrhizal biodiversity at the stand level.

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