Jack Pine Regeneration Research Articles

Forest resilience and regeneration dynamics following wildfire disturbance

AbstractSpecies that are adapted to specific disturbance regimes may be sensitive to changes such as severity, frequency, and extent of ecosystem perturbation. Along range margins, these sensitivities may be exacerbated by concurrent changes in climate resulting in loss of resilience and shifts to alternative ecosystem states. Pinus banksiana (jack pine) is a serotinous species dependent on fire disturbance to open cones, release seed, reduce understory competition, and expose mineral soil. The Altona Flat Rock in northern New York is a globally rare sandstone pine barrens, at the southern edge of jack pine's range. In the summer of 2018, a wildfire burned approximately 200 ha of the Flat Rock barrens, providing the opportunity to study post‐disturbance jack pine and understory resilience. We aimed to establish if jack pine regeneration would occur, and if so, would it be influenced by fire severity, pre‐fire stand characteristics, and competition. We predicted that higher seedling densities would be associated with higher burn severity, higher pre‐fire jack pine stand density, and lesser understory competition. We collected seedling density and understory composition data annually from 2019 to 2022 across 45 plots spanning the disturbed and adjacent undisturbed barrens. In 2021 and 2022, seedling heights were also collected. Seedling densities following the disturbance ranged from 275,385 to 390,513 ha−1; = 357,821 ha−1. Jack pine seedling density was positively associated with fire severity and moss abundance for all years. Pre‐fire stand density along with ericaceous shrub, grass, and duff abundance were also positively associated with seedling density in some years. Seedling height was positively associated with fire severity along with grass and blueberry abundance. These factors, for both establishment/survival and growth, point to the importance of seed supply, microsite conditions, and facilitation in jack pine regeneration success. At this point, it does not appear that the interaction of disturbance with changing climate has shifted enough to prevent the recovery of this ecosystem to its pre‐disturbance jack pine‐dominated state. However, ongoing climate change may still have an impact on seedlings/saplings as this forest continues to mature.

Managing forest habitat for conservation-reliant species in a changing climate: The case of the endangered Kirtland’s Warbler

Conservation and recovery of species of concern necessitates evaluating forest habitat conditions under changing climate conditions, especially in the early stages of the delisting process. Managers must weigh implications of near-term habitat management activities within the context of changing environmental conditions and a species’ biological traits that may influence their vulnerability to changing conditions. Here we applied established population-habitat relationships based on decades of monitoring and research-management collaborations for the Kirtland’s Warbler (Setophaga kirtlandii) to project potential impacts of changing environmental conditions to breeding habitat distribution, quantity, and quality in the near future. Kirtland’s warblers are habitat-specialists that nest exclusively within dense jack pine (Pinus banksiana) forests between ca. 5–20 years of age. Using Random Forests to predict changes in distribution and growth rate of jack pine under future scenarios, results indicate the projected distribution of jack pine will contract considerably (ca. 75%) throughout the Lake States region, U.S.A. in response to projected environmental conditions in 2099 under RCP 4.5 and 8.5 climate scenarios regardless of climate model. Reduced suitability for jack pine regeneration across the Lake States may constrain management options, especially for creating high stem-density plantations nesting habitat. However, conditions remain suitable for jack pine regeneration within their historical and current core breeding range in northern Lower Michigan and several satellite breeding areas. Projected changes in jack pine growth rates varied within the core breeding area, but altered growth rates did not greatly alter the duration that habitat remained suitable for nesting by the Kirtland’s Warblers. These findings contribute to Kirtland’s Warbler conservation by informing habitat spatial planning of plantation management to provide a constant supply of nesting habitat based on the spatial variability of potential loss or gain of lands environmentally suitable for regenerating jack pine in the long-term.

Fire and forest recovery on seismic lines in sandy upland jack pine (Pinus banksiana) forests

Networks of narrow linear (∼3–12 m wide) forest disturbances used for petroleum exploration (seismic lines) are common throughout Alberta’s boreal forest. These ‘seismic’ lines have often failed to recover trees decades after their initial disturbance, especially within treed peatland and jack pine (Pinus banksiana) forests. This has led to regional increases in forest fragmentation contributing to declines in threatened woodland caribou. Restoration of seismic lines to forests is now a top priority for conservation and recovery of woodland caribou, but are expensive and often ignore the occurrence of wildfires that may destroy restoration investments (planted trees), yet also recruit trees. This is especially relevant to jack pine forests that burn more frequently than other forests and depend on moderate to high intensity fires to release seeds en masse from their serotinous cones. Although much is known about jack pine tree recruitment following fire, little is known about patterns of tree recovery on seismic lines and how this varies with fire severity, line width (forest gap size), and line orientation. Here we examine natural tree recovery across a gradient in fire severity (defined as percent overstory tree mortality) with different seismic line characteristics (forest gap width and orientation), as compared to adjacent forest stands, in jack pine forests 5-years post-fire in northeast Alberta, Canada. Overall, jack pine regeneration was consistently 2-fold higher on seismic lines compared to adjacent burned forests with stem density increasing with fire severity in both sites, especially when fire severity was greater than 40%. We suggest that the observed increases in tree regeneration on seismic lines may be due to (1) removal of biomass and exposure of mineral soils on seismic lines creating more favorable conditions for jack pine seeds and seedlings; and/or (2) increases in available light resulting in better growing conditions and survival for this shade-intolerant species. Finally, we suggest that natural recovery (passive restoration) of seismic lines should be expected post-fire in jack pine stands and thus active restoration of these sites through silviculture and tree planting may not be the wisest use of limited restoration dollars if fires are locally common.

A neutral modeling approach for designing spatially heterogeneous jack pine plantations in northern Lower Michigan, USA

Jack pine-dominated ecosystems in northern Lower Michigan are heavily managed using a harvesting and planting regime designed to provide breeding habitat for the federally endangered Kirtland’s warbler. These plantations do not resemble naturally-regenerated patterns of jack pine, but few data exist after which alternate planting configurations may be modeled. Our objective was to use quantitative analyses to construct new planting configurations that better mimic the spatial patterns of natural post-fire regeneration. We used high-resolution color imagery of a 2000 wildfire to map jack pine saplings and the point density function in ArcMap to quantify the spatial heterogeneity that follows large wildfires in this region. Based on metrics calculated from this analysis of landscape pattern, we used a neutral modeling approach to develop prototypical planting configurations. Jack pine regeneration in the burned area occurred as a series of high-density patches within a matrix of moderate- to low-density regeneration. In contrast, the planted areas were dominated by a single, high-density class with large patch sizes and little heterogeneity. We were able to construct neutral models that were not significantly different from the actual landscape using the metrics we calculated. Though highly successful for Kirtland’s warbler habitat, current jack pine plantations in northern Lower Michigan do not emulate natural post-fire patterns. Quantifying the spatial pattern of regeneration following wildfires may inform neutral landscape models, which will be important tools for managers as they attempt to better emulate natural patterns within plantation design.

Young jack pine and high severity fire combine to create potentially expansive areas of understocked forest

Jack pine is a fire adapted species considered to regenerate well after fires of all severities. The Richardson Fire was an extreme megafire event that burned 576,000ha of jack pine dominated boreal forest in 2011 in northern Alberta, Canada. Initial scouting immediately after the fire identified a great deal of variability in jack pine regeneration seemingly related to fire severity and pre-fire stand composition. We sampled tree regeneration in 56 pure jack pine stands across the range of fire severity and pre-fire stand ages 1year post-fire. We found that jack pine regeneration density was greater in older stands (>60years old) compared to younger stands (<30years old) and in moderate severity burns compared to high severity burns. In young stands with high severity burns, jack pine regeneration averaged only 1164 seedlings per hectare which is well below current stand densities indicating a potentially understocked future forest. At the landscape level, we extrapolated fire severity to the entire fire area using pre and post-fire satellite imagery and found that the area of young jack pine stands which had a high severity burn, and therefore likely low seedling regeneration, was greater than 130,000ha with most of this area occurring in patches greater than 500ha in size. Overall, our results suggest that young jack pine may not be as resilient to high severity fires as previously thought and that a large area of burned boreal forest may be at risk of conversion from a closed canopy forest to a more open canopy woodland ecosystem given the predicted changes in fire regime.

Jack pine regeneration and crown fires

The effect of crown fires on Pinus banksiana Lamb. regeneration was studied in separate forest- and cone-burning experiments. Nine plots (0.56–2.25 ha) of jack pine trees near Fort Providence, Northwest Territories, were burned using crown fires to determine the effects of fire intensity, rate of fire spread, depth of burn, and postfire duff depth on seed viability and regeneration. Fire intensities were 36 902 – 93 476 kW/m, and fire spread rates were 24–70 m/min. Depths of burn were low (2.0–3.6 cm), and postfire duff depths averaged 2.0–5.5 cm. Postfire seed rain was highly variable (64–634 seeds/m2), but seed viability was near 67% on all plots. Jack pine regeneration was also highly variable (7–79 seedlings/m2). In the cone-burning experiment, the germination rate increased from 41% (unheated cones) to 64% after 10 s of burning but decreased sharply after 30 s. Flame temperature did not significantly affect viability. Cone-burning results suggest that the postfire seed rain originated from the upper canopy, where flame duration was 5–15 s, and seed in the lower canopy was consumed by fire. Seed rain and regeneration were primarily influenced by understory fine fuel consumption (and therefore, fire intensity), tree height, and live crown base height.

Contrasting modes of survival by jack and pitch pine at a common range limit

Freezing tolerance, reproductive development, and seed germination of jack pine (Pinus banksiana Lamb.) and pitch pine (Pinus rigida Mill.) were compared in a small sympatric population in Acadia National Park in Maine, at the southern range limit of the former and the northern limit of the latter. Freezing tolerances of vegetative shoots and roots were similar for both species. Both species flower prolifically, and there was no evidence of differences in either pollen viability, cone survival, or proportion of viable seed (65–70% of the total). Regeneration success (established seedlings ranging from 1 to 13 years old) was similar overall for both species, but success by species varied greatly in some years. Jack pine regeneration was significantly associated with thinner soils, while pitch pine regeneration was associated with thicker soils in hollows. Jack pine seed germinated significantly faster than pitch pine seed, especially when day–night temperature was reduced. Pitch pine seedlings always exhibited a significantly higher shoot/root ratio than those of jack pine. The most northerly provenances of jack pine germinated significantly faster than those from the most southerly provenances. Jack pine also germinated at a significantly higher percentage than pitch pine in exposed granite sand. Thus relatively cool, dry conditions may favor establishment of jack pine seedlings, while pitch pine establishment may be favored in warmer, wetter conditions.

Harvest treatment, scarification and competing vegetation affect jack pine establishment on three soil types of the boreal mixed wood of northwestern Quebec

A split–split-plot sowing experiment was undertaken on the effects of seedbed and competing vegetation on jack pine ( Pinus banksiana Lamb.) establishment in the boreal mixed wood of northwestern Quebec. Between 3 and 33% of sown seeds germinated and survived as seedlings after two growing seasons. Negligible jack pine seeds or seedlings came from residual seed trees. Scarification had a lesser effect on pine seed germination on clay soil than on till or sand. This difference could be explained by lower soil surface temperatures. Vegetation control and absence of forest cover had a strong positive effect on seedling survival. Nothing indicates that jack pine regeneration would be more difficult on clay than on more typical coarse-textured sands. However, competing vegetation, mainly aspen ( Populus tremuloides Michx.), on sites with clay soils could be a critical factor affecting jack pine seedling mortality because of its abundance and persistence through time. Jack pine regeneration after cutting is less abundant than after fire, probably because of the delay between the opening of the stand and seed dispersal.

Natural regeneration of jack pine following harvesting and site preparation in the Clay Belt of northwestern Quebec

A 36-ha experiment was carried out to assess the possibility of naturally regenerating jack pine stands following harvesting on clay soils of northwestern Quebec. Although differences between treatments were not statistically significant, there was a trend toward a positive effect of one treatment combining on-site delimbing and scarification with the Silva Wadell™ cone scarifier on jack pine seedling density (up to 10 000/ha) and distribution (50% of 1 m2 plots with at least one seedling, corresponding to 94% with 4 m2 plots), two years after harvest. However, scarified microsites contained fewer seedlings than expected and undisturbed humus contained more seedlings than expected. This result, contrary to what is generally reported in the literature may be explained either by the fairly humid conditions, favourable to germination and seedling establishment, occurring on clay sites or by the scarifier spreading the cone-bearing slash outward. Seedling abundance and distribution improved substantially from the first year to the second year following treatment. Although the irregular branch distribution over the cutover area appears to have limited regeneration success, combining on-site delimbing with soil scarification could lead to relatively good stocking of jack pine regeneration that could be enhanced by some fill-planting. This regeneration method could constitute an alternative to planting jack pine on clay. However, vegetation control to remove aspen competition might be necessary. Key words: jackpine, silviculture, natural regeneration, boreal mixed wood

Phase initiale de régénération après feu des populations conifériennes subarctiques

The objective of this study was to investigate the first stage of post-fire regeneration of black spruce and jack pine in a black spruce woodland and a jack pine forest burned over in 1989 in the Radisson's region, in northern Quebec. Emphasis was given to determine the optimal microsites for black spruce and jack pine regeneration. Our results show that the burned over jack pine forest offers better substrates for seedling germination than the burned over black spruce one. A total of 139 seedlings were observed in the jack pine forest, whereas only 42 were recorded in the black spruce forest. In the jack pine forest, burned over humus was the preferred substrate for germination. Soil moisture content correlated with seed germination of both species. Soil temperatures at −5 cm and the soil surface influenced survival of black spruce seedlings in the jack pine forest

Ecological factors affecting abundance of advanced growth in jack pine (Pinus banksiana Lamb.) stands of the boreal forest of northwestern Quebec

Natural regeneration in jack pine (Pinus banksiana Lamb.) stands in Quebec is only sufficient 4% of the time and up to only 33% of the time in mixed stands. This study evaluates the usefulness of forest ecological types as defined by the Quebec Ministry of Forests in predicting abundance of advanced growth in pure and mixed jack pine stands of the Abitibi region, in north-western Quebec. Trees above 1.3 m in height and up to 5 cm DBH were tallied in 102 quadrats of 20 × 20 metres to evaluate advanced growth densities. No significant difference in advanced growth densities was observed between the two main types of surficial geological deposit in the region, lacustrine clays and glacial tills. Only shallow till and organic deposits over bedrock and fluvio-glacial sands showed significantly higher advanced growth densities. Prediction can be improved by using ecological variables such as soil texture, moisture regime, distance from a seed source and stand composition. Abundance of black spruce (Picea mariana (Mill.) B.S.P.) regeneration is positively associated with the proportion of sand in the soil profile and with drier sites; advanced growth of balsam fir (Abies balsamea (L.) Mill.) and white spruce (Picea glauca (Moench) Voss.) is weakly associated with the distance to a fire-preserved zone containing seed trees. Abundance of pin cherry (Prunus pensylvanica L.f.), probably associated with canopy openings, is positively linked with abundance of balsam fir and white spruce advanced growth. Jack pine regeneration by means of advanced growth occurs almost exclusively in jack pine stands on sand; higher proportions of hardwoods in the overstory appear to be negatively linked to jack pine advanced growth. Although the site variables studied showed some significant relationships with advanced growth abundance (maximum R2 = 0.32) which were slightly improved with stand composition variables (maximum R2 = 0.38), no satisfactory predictive model could be implemented. Key words: jack pine, advanced growth, ecological classification

Jack Pine Regeneration Following Postcut Burning under Seed Trees in Central Saskatchewan

An experimental burn in conjunction with a seed-tree system was successful in regenerating jack pine (Pinus banksiana Lamb.) on a fresh to somewhat moist upland, loamy till, cutover site in central Saskatchewan. About 20 well-formed, uniformly spaced seed trees per hectare were left standing during timber harvest. The ignition of logging slash was carried out under preselected weather and fuel conditions so that favorable seedbeds and adequate seed dispersal from the seed trees were produced. Four growing seasons after burning, jack pine stocking by 4-m2 quadrats was 90% with 12 195 seedlings/ha. Aspen (Populus tremuloides Michx.), to a lesser degree black spruce (Picea mariana [Mill.] B.S.P.), and other companion tree species also regenerated with the pine. Various seedbed and regeneration characteristics as well as height growth rates are discussed. Key words: Pinus banksiana, slash burning, seed-tree system, forest regeneration, growth rates, central Saskatchewan.

Simulated Acid Rain Effects on Jack Pine Seedling Establishment and Nutrition

AbstractA greenhouse study examined the effects of simulated acid rain on jack pine (Pinus banksiana Lamb.) seedling development and the Grayling sand (Typic Udipsamments) growth medium. Five rain pH levels (2.0, 2.5, 3.0, 4.0, 4.7) and two soil horizons (A/E, Bw1) were included as levels of factors. Soil pH decreased only at rain pH 3.0 and below. Exchangeable Ca and Mg were reduced at pH 2.0 in A/E horizon soil only. Germination of jack pine was inhibited at pH 2.0 on both soils. Mortality of germinants was over 95% on both soils at pH 2.0, 42% on A/E soil at pH 2.5, and 2 to 13% in other treatment combinations. Seedling top weight increased and root weight decreased on both soils at pH 2.5. In seedlings grown at pH levels 2.5 to 4.7, tissue concentrations of N, K, Ca, Na, Mn, Zn, and Al increased, but P and Mg were reduced, as rain pH decreased. At pH 2.5, Al toxicity and deficiencies in P and Mg were indicated. Simulated rain approximating pH levels typical of precipitation in northern lower Michigan (&gt; 3.0) did not adversely affect jack pine regeneration or soil properties of the Grayling sand during the 75‐d study.

Multiple successional pathways on recently disturbed jack pine sites in Michigan

Jack pine communities in northern lower Michigan recently disturbed by clearcutting, deliberate burning, or wildfire were studied over three growing seasons, and were compared to undisturbed jack pine stands. Newly disturbed sites generally had more vascular plant species than mature forests. Many of these species did not persist, especially on burned sites, and species richness declined sharply the second year after fire. In several cases annual and biennial species dominated first-year burns but were unimportant thereafter. Several pathways of early successional development were evident on the disturbed sites, which was facilitated by jack pine regeneration failure on all but one of the disturbed sites. Unburned clearcuts rapidly developed into Carex meadows, with few other species of any importance. This pathway was also followed on some deliberately-burned and wildfire sites. Other burned areas developed a stratified canopy of shrubs and early successional hardwoods, and were rich in species and high in cover. Stand replacement by jack pine occurred on one mature jack pine site burned by wildfire. Jack pine regeneration failure has been attributed to numerous factors involving: seed loss due to fire and predation, and low germination and seedling survival due to inadequate seedbed, drought, competition, pathogens, grazing and high surface temperatures. Index of similarity comparisons showed that different sites of the same post-disturbance age were significantly ( P < 0.01) less similar in species composition than a single site sampled in 2 or 3 consecutive years. Post-disturbance age was not a particularly strong indicator of species composition on these sites, because each site had a different assemblage of species (30–40% dissimilarity among sites of the same disturbance class and post-disturbance age). Therefore, the individualistic nature of each site, rather than age following disturbance, is the dominant aspect in understanding successional relationships in these communities.

Plantation Establishment in the Boreal Forest: Glyphosate, Hexazinone, and Manual Weed Control

One manual and two chemical (mist-blown foliar spray of glyphosate and hexazinone) methods of vegetation control were applied in two 17.1 m × 17.1 m plots per treatment in a 1969 boreal cutover in Forest Section B7 where natural jack pine (Pinus banksiana Lamb.) regeneration, mostly about 1 m tall, was overtopped by post-harvest deciduous growth, including sapling aspen (Populus tremuloides Michx.). Season of application(fall = September 1976; summer = July 1977) and, for the chemical treatments, rate of application (0. 1, 2, and 4 kg ai/ha) were evaluated for their effect on (a) deciduous competition, (b) natural jack pine regeneration, and (c) white spruce (picea glauca [Moench] Voss) outplanted as bare-root 2 + 2 stock in June 1978. Annual or more frequent assessments were made through 1983. With (a), manual treatment was more effective in summer than in fall but did not effect sustained control. Of the fall-applied herbicide treatments, only glyphosate at 2 and 4 kg ai/ha was efficacious. Sustained control over several years was obtained with summer-applied glyphosate and, to a lesser degree, hexazinone. With (b), jack pine was not benefited by any treatment. With (c), frost and browsing obscured treatment effects, but the "best" control of deciduous vegetation was probably silviculturally detrimental to the spruce.

Evaluation of Fire-produced Seedbeds for Jack Pine Regeneration in Central Ontario

Burning and seeding were successfully used to regenerate jack pine after cutting in central Ontario. Two years after seeding, the depth of post-burn humus was measured under 2769 seedlings, of which 729 were dominant ones of known height. Generally, jack pine frequency distribution and heights of dominant jack pine were strongly affected by the depth of residual humus. The relationships were curvilinear and mostly inverse. They were subsequently used as guides in seedbed evaluation.

Some Aspects of the Life History and Ecology of the Pitch Nodule Maker, Petrova albicapitana (Busck) (Lepidoptera-Olethreutidae)

The widespread presence of the pitch nodule maker in pine plantations and jack-pine regeneration in Manitoba and Saskatchewan stimulated this investigation. Although this insect is not causing serious damage at present it could become a problem should the area of pine plantations be increased in Manitoba and Saskatchewan.