Survival Of Spruce Seedlings Research Articles

Beetlemania: Is the bark worse than the bite? Rocky Mountain subalpine forests recover differently after spruce beetle outbreaks and wildfires

Due to the shifting global climate, the frequency and severity of disturbances are increasing, inevitably causing an increase in disturbances overlapping in time and space. Bark beetle epidemics and wildfires have historically shaped the disturbance regimes of Western North American forests. Their interactive effects on stand dynamics and recovery are inadequately studied in Picea engelmannii (Engelmann spruce)-Abies lasiocarpa (subalpine fir) dominant forests; understanding these interactions is imperative to the management and health of forested ecosystems. This study focuses on the effects of epidemic Dendroctonus rufipennis (spruce beetle) outbreaks, high-severity fires, and the subsequent species and structural diversity of subalpine forest regeneration and structure in Northern Colorado and Southern Wyoming. We compared tree seedling densities and species composition, surface fuel loading, and stand structure characteristics across 80 sites that experienced either high tree mortality from epidemic spruce beetle outbreaks (>50% affected basal area), high-severity wildfire, post-outbreak high-severity wildfire (1–3 years post-outbreak), or no disturbance (control). The beetle outbreak sites span multiple years post-outbreak from 1996 to 2017, ultimately comprising a chronosequence of beetle-affected stands. Analyses indicate a significant increase in fuel loading over time-since-outbreak, as aerial fuels are transferred to the forest floor following high tree mortality. Tree seedling densities among outbreak and control sites differ significantly from burned areas, indicating that wildfires override the effects of repeated disturbances on regeneration. There was consistent Engelmann spruce seedling survival following beetle outbreaks, providing evidence for stable forest recovery following a single disturbance. However, fire was a dominate force in determining post-disturbance species composition, indicating continued prevalence of high severity fire may prove detrimental for the persistence of spruce-fir species, while promoting shifts toward more drought and fire tolerant tree species (e.g., Pinus contorta). It is critical to understand post-disturbance fuel dynamics and stand recovery to identify hazards for subsequent fire suppression, implement treatments to enhance forest resilience, and to understand the potential consequences of climate-induced shifts in disturbance regimes on forest health.

Black spruce (Picea mariana) restoration in Kalmia heath by scarification and microsite mulching

Canopy removing disturbance such as clearcutting and fire in nutrient-poor boreal and temperate forests often create shrub-dominated vegetation causing significant delay in forest succession. Lack of favourable microsites for black spruce seedling establishment and growth has been identified as the primary cause for conifer regeneration failure in post-fire Kalmia heath in eastern Canada. The aim of this study was to compare the growth performance of black spruce planted in scarified plots and in microsites developed by a novel technique called micro-site mulching (MSM) in Kalmia heaths. We hypothesized that because of vegetation removal and exposure of mineral soil in scarified and MSM treatments, planted black spruce would suffer from frost heaving and animal browsing, but these treatments may offer better seedling growth by ameliorating the inhibitory effects of Kalmia organic matter and providing with favourable soil moisture, soil temperature, soil respiration and nutrient availability. We conducted this study in a 13year-old post-fire Kalmia heath in Triton Brook, Newfoundland, Canada (48°30′N, 50°00′W). We measured black spruce seedling survival and growth annually for three complete growing seasons and soil nutrient availability one year post-planting. In all three treatments black spruce seedling survival was >90%. About 20% of the seedlings in scarified and MSM treatments suffered herbivore damage and frost heaving with little damage in control plots. Black spruce in scarified and MSM plots were associated with significantly higher growth than control, with differences amplified each consecutive year since planting. Higher seedling growth in scarified and MSM plots was associated with higher soil moisture, lower organic matter content, and lower soil temperature. Soil nutrient differences in treatments had little effect on seedling growth. Since MSM treatment produced substantially less soil disturbance with similar or better seedling growth than scarification, we suggest MSM as a preferred site preparation technique in Kalmia heath in contexts where large-scale soil disturbance by standard mechanized scarification is undesirable. The novelty of his paper is the development of MSM as a potential alternative to scarification in creating suitable microsites for planted black spruce to restore forest cover in ericaceous heaths. However, an operationally suitable MSM tool must be developed and a longer-term (10years) monitoring is necessary before the method can be applied as a restoration tool.

Spatio-temporal modelling of ground vegetation development in mountain spruce forests

More complex models of forest ecosystems are required to understand how land-cover changes can impact vegetation dynamics and spatial pattern. In order to document spatio-temporal modelling abilities, the observations conducted in the declined climax mountain Norway spruce forest during the recovery period (1995–2006) are used for simulation and spatial analysis in the GIS environment. The developed spatio-temporal model is used for simulation of forest vegetation dynamics in a mountain spruce forest in the framework of regeneration processes after stress from air pollution. In order to explore the spatial and temporal phenomena of regeneration processes, the spatio-temporal model is based on a large set of ordinary differential equations that solve dynamic processes in sets of microsites arranged in grids for each ground vegetation species and each age group of Norway spruce seedlings. The spatial extent of the explored site is composed of a set of 50 × 50 microsites. Each microsite is represented by a square with dimensions of 1 m × 1 m. The presented simulation studies are mainly focused on seedlings from the seed year 1992, in order to explore the longest monitored time series of survival. It is based on exponential growth models that are related to the environmental conditions for each microsite. The canopy gaps based on estimates of the local crown projected area, the soil type layer, and the dominant grass density are used to provide case simulation studies. The first case study simulates the influence of microsite positions in relation to the local tree crown projections on the survival of spruce seedlings. It is assumed that the density of the trees is the main factor that determines the light and heat supply to the ground level of the Norway spruce seedlings. The second case study extends the previous study to include terms that determine the growth ratio in dependence on the crown projection area. The third case study provides further extensions in order to simulate growth ratio relations to the local soil type. The fourth case study demonstrates the local influence of the dominant grasses, such as Avenella flexuosa and Calamagrostis villosa, on the natural regeneration of Norway spruce. Starting from the conditions at the sites before the recovery period, the case simulation studies are able to project the short-term succession for a regeneration decade and the approximate long-term development. In addition to the standard simulation procedures based on solution of ordinary differential equations, spatio-temporal modelling in the GIS environment is able to provide spatial data management, analysis and visualization of the data.

The influence of soil rutting severity on regeneration potential and seedling performance for black spruce-dominated peatlands

Excessive rutting continues to be recorded in post-harvest compliance inspections in black spruce peatlands across Ontario. These qualitative, visual assessments, however, cannot provide the necessary data to determine a site disturbance threshold that is linked to poor regeneration and seedling growth. In an attempt to provide this quantitative link, harvested black spruce [Picea mariana (Mill.) B.S.P.] peatland sites were surveyed and divided into severely rutted (non-compliant), moderately rutted, and non-rutted (compliant) blocks. In 1995, 2001, and 2006, each block was assessed for areal extent of rutting, number of plantable spots, moisture status, planting medium, competition level, stand density, species composition, and black spruce seedling survival and growth. Black spruce seedling survival in the severely-rutted block was significantly lower when compared with either the moderately rutted or the non-rutted blocks. A derived seedling survival model identified moisture class as having the largest influence on the probability of seedling survival. In terms of seedling growth, however, it was the non-rutted blocks that had the poorest performance. Based on a canonical discriminant analysis (CDA), competition factors, particularly ericaceous shrub cover, were the most important microsite factors influencing black spruce seedling growth. Overall, the moderately rutted block generated conditions that resulted in high conifer recruitment and good seedling survival and growth. Although the inference space of the study is small, the results suggest that black spruce peatland sites may benefit from a moderate level of site disturbance caused during harvest operations. Key words: Rutting severity, black spruce peatlands, survival, growth, microsite assessment

White spruce regeneration following a major spruce beetle outbreak in forests on the Kenai Peninsula, Alaska

Between 1987 and 2000, a spruce beetle ( Dendroctonus rufipennis) outbreak infested 1.19 million ha of spruce ( Picea spp.) forests in Alaska, killing most of the large diameter trees. We evaluated whether these forests would recover to their pre-outbreak density, and determined the site conditions on which spruce germinated and survived following the spruce beetle outbreak in forests of the Anchor River watershed, Kenai Peninsula, Alaska. White spruce ( Picea glauca) and Lutz's spruce ( Picea × lutzii), a hybrid between white and Sitka spruce ( Picea sitchensis), dominate the study area. We measured the pre- and post-outbreak density of spruce in 108 3 m × 80 m plots across the study area by recording all live trees and all dead trees >1.5 m tall in each plot. To determine the fine scale site conditions on which spruce germinated and survived, we measured ground surface and substrate characteristics within 20 cm circular plots around a subset of post-outbreak spruce seedlings. The density of post-outbreak spruce (855/ha) was adequate to restock the stands to their pre-outbreak densities (643/ha) for trees >1.5 m tall. We could not accurately estimate recovery for pre-outbreak spruce seedlings because dead seedlings may have decayed in the 5–18 years since the beetle outbreak occurred. At the fine scale, spruce that germinated post-outbreak grew on a wide variety of substrates including downed log, stump, mesic organic mat, peat, hummocks and mineral soil. They exhibited a strong preference for downed logs (53%) and stumps (4%), and most (91%) of the downed logs and stumps that spruce rooted on were heavily decayed. This preference for heavily decayed logs and stumps was especially evident given that their combined mean cover was only 2% in the 3 m × 80 m plots. Within the 3 m × 80 m plots, spruce seedling survival was negatively correlated with bluejoint ( Calamagrostis canadensis) litter cover.

Germination and Survival of Spruce Seedlings Following Fire in Northwestern Alberta

Abstract Thirty semipermanent plots were established in a 10 ha (24.7 ac) spruce stand the spring following a winter harvest and subsequent prescribed burn to monitor germination by month and overwinter survival of spruce seedlings. Seventy percent of all germination occurred in June with regeneration densities as high as 800,000 germinants ha-1 (323,755 ac-1). Most germination occurred, and overwinter survival was highest in depressed microsites. Overwinter survival averaged 68,000 seedlings ha-1 (27,520 ac-1), with June germinants having greater survival then July or August germinants. Only three new germinants were detected the second spring following the prescribed burn. North. J. Appl. For. 20(1):45–47.

Influence of ecological conditions on Engelmann spruce ( Picea engelmannii) and subalpine fir ( Abies lasiocarpa) germinant survival and initial seedling growth in south-central British Columbia

The influence of seedbed (undisturbed forest floor, burned forest floor, and mineral soil), light (closed forest, open forest, and clearcut), and competing vegetation (present, not present) on germination and initial seedling survival and growth of subalpine fir ( Abies lasiocarpa) and Engelmann spruce ( Picea engelmannii) was investigated after applying seeds to small (1 m 2) plots established in each of the two major site types present in the wet cold Engelmann spruce–subalpine fir biogeoclimatic subzone (ESSFwc) of south-central British Columbia. Seedling survival and growth generally did not differ between site types and were little influenced by competing vegetation. After three growing seasons, the number of living seedlings of both species increased as the degree of forest floor disturbance increased. The number of living fir seedlings increased as the amount of light increased whereas partial shade benefitted spruce seedling survival. After two growing seasons, surviving fir seedlings had grown larger, (height, basal diameter, and crown volume) and were generally less influenced by seedbed, light, and competition, than spruce seedlings. Spruce seedling growth was greatest on undisturbed forest floor seedbeds in clearcut areas. If ESSFwc forests are to be naturally regenerated with Engelmann spruce and subalpine fir, clearcutting with exposure of mineral soil would be the optimum treatment for promoting fir seed germination and initial seedling growth as long as a seed source is present and sufficient seed survives predation. If spruce is to be promoted, provision of partial shade initially, for up to 2 yrs, and provision of small patches of mineral soil should assist seedling survival and minimize potential growth losses.

Hexazinone site preparation improves black spruce seedling survival and growth

Granular (PRONONE 10G and 5G) and liquid (VELPAR L) hexazinone (1 to 4 kg ai ha−1) were applied to a northern New Brunswick clearcut (loams, silt loams, and clay loams) to reduce raspberry [Rubus idaeus L. var. strigosus (Michx.) Maxim] competition. Treatment, using skidder-mounted herbicide application equipment, was completed in May and September 1986, with planting of 2+2, bareroot, black spruce seedlings [Picea mariana (Mill.) B.S.P.] in June 1986 and in June 1987. Seedling survival and growth were measured yearly for five growing seasons after planting. By August 1991, raspberry cover for three treatments remained less than that for controls. Survival of seedlings planted approximately one month after spring treatment was less than controls, but seedling height and stem diameter were greater than that of control seedlings for most treatments. Survival and growth of seedlings planted approximately one year after spring treatment or nine months after fall treatment were greater than that of control seedlings for most treatments. Fifth-year height and stem diameter of seedlings planted nine months after fall treatment were negatively correlated with raspberry height (r2 = 0.729, height and 0.745, diameter), decreasing as raspberry height increased. Over the five-year observation period, hexazinone formulation did not affect raspberry control, but did affect seedling survival and growth. Spring treatment with PRONONE 10G (2 kg ai ha−1), with planting delayed by one year, provided the best treatment to achieve both optimal seedling survival and growth during plantation establishment. Key words: liquid hexazinone, granular hexazinone, site preparation, black spruce, growth parameters, seedling survival, raspberry competition

Short-term Performance of Two Sulfonylurea Herbicides: Efficacy, Seedling Survival, and Growth

Abstract Metsulfuron (ALLY or ESCORT), 36 and 72 g ai/ha (~ 0.5 and 1.0 oz ai/ac), and sulfometuron (OUST), 150, 300, and 450 g ai/ha (~ 2.1, 4.2, and 6.3 oz ai/ac), were applied to a northern New Brunswick clearcut (silty clay loam and silty clay soils) to reduce raspberry competition. Treatment, using skidder-mounted herbicide application equipment, occurred in May and August 1986, with planting of 2+2, bareroot, black spruce seedlings in June 1986 and in June 1987. Seedling survival and growth were measured yearly for 5 growing seasons after planting. By August 1991, raspberry cover was less in some treatments than in controls. Survival of seedlings planted 1 month after spring treatments was less than controls, and no significant stem volume increases were observed. Survival of seedlings planted approximately 1 yr after spring treatments was greater than that of control seedlings. Survival of seedlings planted after some summer treatments also was poor, and no significant stem volume increases were noted for seedlings planted after site preparation with sulfometuron. Optimal stem volume increases over control seedlings were observed for seedlings planted 1 yr after spring sulfometuron treatment. These increases occurred sooner than for seedlings planted 1 yr after spring metsulfuron treatment or after summer metsulfuron treatment. Fifth-year stem volume for these seedlings was correlated with raspberry cover (r² = 0.44), decreasing as raspberry cover increased. We conclude that the use of other less expensive silvicultural herbicides may provide equally effective raspberry control and better black spruce seedling survival and growth. North. J. Appl. For. 12(2):80-85.

The Effect of Peatland Drainage and Planting Position on the Growth of White Spruce Seedlings

Abstract The effects of peatland drainage and planting position (peat hummock top, midslope, and bottom) on 2+0 barefoot white spruce seedling survival and growth and foliar nutrients were tested over a 2-yr period. Seedling survival was 44%-56% on hummock tops compared to 80%-96% on hummock midslopes and bottoms. Size of seedling at planting significantly affected survival. Final biomass on drained sites was 34%-53% greater than on undrained peatlands. Foliar nutrient levels were deficient on both drained and undrained peatlands. Foliar nitrogen, however, was significantly higher on the drained site and varied between the different planting positions. Seedling survival and growth was best on midslopes and hummock bottoms on the drained site, and best only on midslopes in the undrained site. Hummock tops were the least favorable planting position on both drained and undrained sites. North. J. Appl. For. 10(4):154-160.