Seedbed variation from the interior through the edge of a large wildfire in Alberta

2005 ◽  
Vol 35 (7) ◽  
pp. 1640-1647 ◽  
Author(s):  
David F Greene ◽  
S Ellen Macdonald ◽  
Steve Cumming ◽  
Lynn Swift
Keyword(s):  
Populus Tremuloides ◽  
Life Histories ◽  
Fire Severity ◽  
Mineral Soil ◽  
Basal Area ◽  
White Spruce ◽  
Forest Composition ◽  
Fire Intensity ◽  
Soil Exposure ◽  
In Fire

Despite the importance of seedbeds in the life histories of many plant species, there has been little study of the seedbeds created by wildfire in fire-prone vegetation types such as the boreal forest. Both within the interior and at the edge of a very large (>100 000 ha) 2001 wildfire in the mixedwood boreal region of Alberta, we examined the postfire duff depth and the percent coverage of seedbed types. Minimizing the effect of site and forest composition, we looked only at Picea glauca (Moench) Voss – Populus tremuloides Michx. sites burned during a single day of high fire intensity. Good seedbeds (thin humus and exposed mineral soil, with or without ash) averaged 35% coverage within the interior of the fire but varied enormously among stands. There was a weak but significant positive correlation between prefire percent white spruce basal area and percent mineral soil exposure; that is, there is some tendency for conifer stands to create the seedbeds best suited for their own germinants. Fire severity played a clear role in mineral soil exposure, which was greatest in areas with 100% canopy mortality. Mineral soil exposure was far less at the edges of the fire, averaging only 5% even in areas where all trees had been killed; the burn edge was characterized by superficial flaming combustion with no evidence of substantial duff removal via smoldering combustion. In short, the areas where white spruce seed will be most common after the fire, the edges, are where the worst seedbeds in the burn will be found. Regeneration microsites at fire edges appear to be better suited to regeneration of broadleaf species, via suckering; the persistence of white spruce in fire-prone landscapes continues to be difficult to explain.

Patterns of initial versus delayed regeneration of white spruce in boreal mixedwood succession

2006 ◽  
Vol 36 (6) ◽  
pp. 1597-1609 ◽  
Author(s):  
Vernon S Peters ◽  
S Ellen Macdonald ◽  
Mark RT Dale
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Fire Severity ◽  
Mineral Soil ◽  
White Spruce ◽  
Mixedwood Forests ◽  
Regeneration Period ◽  
Postfire Regeneration ◽  
Distance To Seed Source ◽  
Mixedwood Stands

The timing of white spruce regeneration in aspen (Populus tremuloides Michx.) – white spruce (Picea glauca (Moench) Voss) boreal mixedwood stands is an important factor in stand development. We examined boreal mixedwood stands representing a 59-year period of time since fire and determined (1) whether and when a delayed regeneration period of white spruce occurred, (2) whether the relative abundance of initial (<20 years) versus delayed (≥20 years postfire) regeneration is related to seed availability at the time of the fire, and (3) what are the important regeneration substrates for initial versus delayed regeneration. Initial regeneration occurred primarily on mineral soil or humus, while delayed regeneration established primarily on logs and peaked 38–44 years after fire. Of the 20 stands investigated, seven were dominated by initial regeneration, six were dominated by delayed regeneration, and seven were even mixtures of both. The dominance of a site by initial or delayed regeneration could not be simply explained by burn timing relative to mast years or distance to seed source; our results suggested that fire severity and the competitive influence of initial regeneration on delayed regeneration were important at fine scales. Based on our results we describe several possible postfire successional pathways for boreal mixedwood forests.

Recruitment of Picea mariana, Pinus banksiana, and Populus tremuloides across a burn severity gradient following wildfire in the southern boreal forest of Quebec

2004 ◽  
Vol 34 (9) ◽  
pp. 1845-1857 ◽  
Author(s):  
D F Greene ◽  
J Noël ◽  
Y Bergeron ◽  
M Rousseau ◽  
S Gauthier
Keyword(s):  
Boreal Forest ◽  
Populus Tremuloides ◽  
Pinus Banksiana ◽  
Fire Severity ◽  
Mineral Soil ◽  
Basal Area ◽  
Published Data ◽  
Crown Fire ◽  
Conifer Species ◽  
Seed Supply

Most studies of postfire tree recruitment have occurred in severely burned portions, despite the fact that partial burning is common. In this study we examined regeneration following a 1997 fire in the boreal forest of Quebec. A model of postfire recruitment was elaborated using parameters such as the proportion of trees killed (severity), the proportions of postfire seedbed types and their associated juvenile survivorship, the available seed supply, the available bud supply (for Populus tremuloides Michx.), and the granivory rate. All three species had peak recruitment in the first or second summer, and the recruitment episode was essentially finished after the third year. Mineral soil and surviving Sphagnum were the best seedbeds for both conifer species. Seedbed frequency was essentially independent of crown fire severity except for surviving Sphagnum, which was concentrated primarily where severity was light. Conifer fecundity was much lower in the lightly burned stands, a result we attribute to a higher granivory rate. The fecundity (seedlings/basal area for the conifers or suckers/basal area for Populus) in the severe sites was typical of the few other North American studies of postfire recruitment, where the published data permit us to make the comparison.

Heterogeneity in fire severity within early season and late season prescribed burns in a mixed-conifer forest

2006 ◽  
Vol 15 (1) ◽  
pp. 37 ◽  
Author(s):  
Eric E. Knapp ◽  
Jon E. Keeley
Keyword(s):  
Sierra Nevada ◽  
Prescribed Burning ◽  
Fire Severity ◽  
Basal Area ◽  
Conifer Forest ◽  
Fuel Loading ◽  
Early Season ◽  
Late Season ◽  
Fuel Loads ◽  
In Fire

Structural heterogeneity in forests of the Sierra Nevada was historically produced through variation in fire regimes and local environmental factors. The amount of heterogeneity that prescription burning can achieve might now be more limited owing to high fuel loads and increased fuel continuity. Topography, woody fuel loading, and vegetative composition were quantified in plots within replicated early and late season burn units. Two indices of fire severity were evaluated in the same plots after the burns. Scorch height ranged from 2.8 to 25.4 m in early season plots and 3.1 to 38.5 m in late season plots, whereas percentage of ground surface burned ranged from 24 to 96% in early season plots and from 47 to 100% in late season plots. Scorch height was greatest in areas with steeper slopes, higher basal area of live trees, high percentage of basal area composed of pine, and more small woody fuel. Percentage of area burned was greatest in areas with less bare ground and rock cover (more fuel continuity), steeper slopes, and units burned in the fall (lower fuel moisture). Thus topographic and biotic factors still contribute to the abundant heterogeneity in fire severity with prescribed burning, even under the current high fuel loading conditions. Burning areas with high fuel loads in early season when fuels are moister may lead to patterns of heterogeneity in fire effects that more closely approximate the expected patchiness of historical fires.

Prescribed Burning White Spruce Slash in Interior Alaska

1986 ◽  
Vol 3 (1) ◽  
pp. 16-18 ◽  
Author(s):  
John Zasada ◽  
Rodney Norum
Keyword(s):  
Organic Material ◽  
Prescribed Burning ◽  
Mineral Soil ◽  
White Spruce ◽  
Flood Plain ◽  
Organic Horizon ◽  
Forest Types ◽  
Mechanical Site Preparation ◽  
Interior Alaska ◽  
Soil Exposure

Abstract Broadcast burning following harvesting on flood-plain sites in Alaska substantially decreased residual organic material and increased exposed mineral soil. Two forest types were studied: white spruce/alder/feathermoss and white spruce/alder/lingenberry/feathermoss. The latter site contained permafrost. Fuel was reduced 67% and 81%, respectively; organic horizon thickness was decreased 43% to 2.9 in (7.4 cm) and 55% to 2.5 in (6.4 cm), respectively; and mineral soil exposure was 13% and 8%, respectively. Burning created good conditions for planting on both types. In addition, mechanical site preparation to increase mineral soil exposure appears to be necessary to achieve adequate, well-distributed regeneration from seed. North. J. Appl. For. 3:16-18, Mar. 1986.

Subalpine forest damage from a severe windstorm in northern Colorado

2001 ◽  
Vol 31 (12) ◽  
pp. 2089-2097 ◽  
Author(s):  
Thomas T Veblen ◽  
Dominik Kulakowski ◽  
Karen S Eisenhart ◽  
William L Baker
Keyword(s):  
Populus Tremuloides ◽  
Basal Area ◽  
Stand Density ◽  
Wind Damage ◽  
Forest Damage ◽  
Forest Composition ◽  
Subalpine Forest ◽  
Individual Tree ◽  
Northern Colorado ◽  
Standing Dead

As windstorm intensity increases above some threshold, disturbance spread and damage patterns are expected to be less strongly shaped by preblowdown forest composition and structure than by the pattern of the storm itself. We examined this generalization by analyzing differences in wind damage among tree species and stands following a severe blowdown in 1997 affecting over 10 000 ha of subalpine forest in the Routt Divide area of northern Colorado, U.S.A. Individual tree traits such as species, height, and status as standing dead or alive strongly influenced the amount and type (uprooting vs. snapping) of wind damage. Populus tremuloides Michx. exhibited much less uprooting and overall damage than the conifers. Among the canopy trees of the conifer species, Pinus contorta Dougl. ex. Loud and Abies lasiocarpa (Hook.) Nutt. sustained the lowest and highest rates of snapping, respectively. Standing dead conifers were more likely to be snapped than uprooted, and taller trees were more likely to be damaged than shorter trees. Stand-level characteristics such as stand density, amount of dead basal area, and species composition were predictive of the amount of wind damage for areas of moderate- but not high-severity blowdown. Even in such an extreme windstorm as the Routt blowdown, which had estimated wind speeds of 200–250 km/h, individual tree attributes and stand-level characteristics significantly influenced the severity and type of wind damage.

Predicting natural regeneration of white spruce in boreal mixedwood understories

2001 ◽  
Vol 77 (6) ◽  
pp. 1006-1013 ◽  
Author(s):  
James D. Stewart ◽  
Simon M. Landhäusser ◽  
Kenneth J. Stadt ◽  
Victor J. Lieffers
Keyword(s):  
Picea Glauca ◽  
Mineral Soil ◽  
Clay Fraction ◽  
Basal Area ◽  
White Spruce ◽  
Height Growth ◽  
Feather Moss ◽  
Moss Cover ◽  
Rotten Wood ◽  
Soil Clay

Successful mixedwood management in the boreal forest of Alberta requires better knowledge of the occurrence and success of natural white spruce regeneration. In this study we developed statistical models to predict the natural establishment and height growth of understory white spruce (Picea glauca (Moench) Voss) in the boreal mixedwood forest in Alberta using data from 148 provincial permanent sample plots, supplemented by measurements of the amount and height growth of regenerating white spruce, and the amount and type of available substrate. A discriminant model correctly classified 73% of the sites as to presence or absence of a white spruce understory based on the amount of spruce basal area, rotten wood, ecological nutrient regime, soil clay fraction and elevation, although it explained only 30% of the variation in the data. On sites with a white spruce understory, a regression model related the abundance of regeneration to rotten wood cover, spruce basal area, pine basal area, soil clay fraction, and grass cover (R2 = 0.36). About half of the seedlings surveyed grew on rotten wood, and only 3% on mineral soil, and seedlings were 10 times more likely to have established on these substrates than on litter. Exposed mineral soil was rare, covering only 0.3% of the observed transect area, rotten wood covered 4.5%, and litter/undisturbed forest floor covered the remainder. The regression models developed for average relative height growth rate included feather moss cover, stand age and birch basal area for seedlings ≤ 1 m (R2 = 0.23), and feather moss cover, elevation, other moss cover and soil clay fraction for seedlings between 1 m and 3 m (R2 = 0.27). Key words: Picea glauca, seedling establishment, seedbeds, site factors, coarse woody debris, predictive models, mixedwood management

scholarly journals Drought Increases Vulnerability of Pinus ponderosa Saplings to Fire-Induced Mortality

Fire ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 56
Author(s):  
Raquel Partelli-Feltrin ◽  
Daniel M. Johnson ◽  
Aaron M. Sparks ◽  
Henry D. Adams ◽  
Crystal A. Kolden ◽  
...  
Keyword(s):  
Pinus Ponderosa ◽  
Water Status ◽  
Western United States ◽  
Radiative Energy ◽  
Forest Composition ◽  
Fire Intensity ◽  
Surface Fires ◽  
Composition And Structure ◽  
In Fire ◽  
The Impact

The combination of drought and fire can cause drastic changes in forest composition and structure. Given the predictions of more frequent and severe droughts and forecasted increases in fire size and intensity in the western United States, we assessed the impact of drought and different fire intensities on Pinus ponderosa saplings. In a controlled combustion laboratory, we exposed saplings to surface fires at two different fire intensity levels (quantified via fire radiative energy; units: MJ m−2). The recovery (photosynthesis and bud development) and mortality of saplings were monitored during the first month, and at 200- and 370-days post-fire. All the saplings subjected to high intensity surface fires (1.4 MJ m−2), regardless of the pre-fire water status, died. Seventy percent of pre-fire well-watered saplings recovered after exposure to low intensity surface fire (0.7 MJ m−2). All of the pre-fire drought-stressed saplings died, even at the lower fire intensity. Regardless of the fire intensity and water status, photosynthesis was significantly reduced in all saplings exposed to fire. At 370 days post-fire, burned well-watered saplings that recovered had similar photosynthesis rates as unburned plants. In addition, all plants that recovered or attempted to recover produced new foliage within 35 days following the fire treatments. Our results demonstrate that the pre-fire water status of saplings is an important driver of Pinus ponderosa sapling recovery and mortality after fire.

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

Pre-wildfire fuel treatments affect long-term ponderosa pine forest dynamics

2007 ◽  
Vol 16 (1) ◽  
pp. 128 ◽  
Author(s):  
Barbara A. Strom ◽  
Peter Z. Fulé
Keyword(s):  
Ponderosa Pine ◽  
Stand Structure ◽  
Fire Severity ◽  
Stable State ◽  
Basal Area ◽  
Fire Intensity ◽  
Fuel Treatments ◽  
Alternative Stable State ◽  
Pine Regeneration ◽  
Crown Base Height

The 2002 Rodeo–Chediski fire, the largest wildfire in south-western USA history, burned over treated stands and adjacent untreated stands in the Apache–Sitgreaves National Forest, setting the stage for a natural experiment testing the effectiveness of fuel reduction treatments under conditions of extraordinary fire severity. In seven pairs of treated–untreated study sites measured 2 years after the fire, thinning was strongly associated with reduced burn severity. Treated areas had more live trees, greater survival, and reduced fire intensity as indicated by crown base height and bole char. Ponderosa pine regeneration was patchy but more dense in treated areas. We assessed decade- to century-long effects of the pre-wildfire fuel treatments using the Forest Vegetation Simulator (FVS). Differences between treated and untreated areas were projected to persist for several decades after the fire in terms of stand structure characteristics and for at least 100 years in terms of species composition, with ponderosa pine making up ~60% of basal area in treated areas but only 35% in untreated areas. Future ecosystem development may take the trajectory of recovery to a ponderosa pine/Gambel oak forest or of a shift to an alternative stable state such as an oak-dominated shrubfield, with untreated areas more apt to undergo a shift to a shrubfield state. Current management decisions about fuel treatments have multi-century legacies.

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