Shoot and root sensitivity of containerized black spruce,white spruce and jack pine seedlings to late fall freezing

Damage to containerized forest seedlings due to freezing can occur in the fall or early winter in Canadian forest nurseries. The following spring, damage to shoots and impairment of growth is observed. The objectives of this experiment were to measure the impact of late fall low temperatures (0° to --30°C) on whole seedlings of the three most common species used for reforestation in Quebec: black spruce (BS), white spruce (WS) and jack pine (JP). Impacts of freezing temperatures on (i) whole seedling and apical bud mortality, (ii) shoot growth and root mortality, (iii) stem electrical resistance, (iv) shoot and root water relations, (v) concentrations of N, P, K, Ca, Mg, and total sugars in shoots were assessed. JP showed the highest rate of whole seedling mortality while WS showed the highest rate of apical bud mortality. JP was the most severely affected: destruction of the root system at low temperatures as well as a reduction of shoot growth and stem diameter and a decrease (more negative) in shoot and root water potential. WS showed a reduction of shoot growth despite no apparent damage to the root system at low temperatures. BS was not affected by temperatures as low as --30°C. Nutrient and sugar concentrations were not affected by low temperature treatments.     

Relationships between frost hardiness,root growth potential,and photosynthesis of nursery-grown white spruce seedlings

• Context  

Root growth is a characteristic to which nursery personnel is particularly attentive. The increase in root growth of white spruce seedlings in the autumn relies on the current season’s photosynthates. Needle hardening or a decrease in the mass of photosynthetically active foliage as a result of early frost may negatively affect the seedling’s photosynthetic capacity and its ability to fuel root growth.     

Relationships between the root system size and its hydraulic properties in white spruce seedlings

Seedlings grown under different N supply were examined for relationships between root system size attributes and its hydraulic properties. These relationships were also studied on seedlings of different stock types (grown in different container types). Measurements with root pressure probes were taken at various times after germination, under applied hydrostatic pressure and non-limiting soil moisture. Different N-treatments and stock types were used solely to produce seedling of different sizes, especially root system sizes. Specific root hydraulic conductivity (Lp_r) typically declined with an increasing root system size and correlations between Lp_r and the root system size attributes were often negative. The flow of water through the root system correlated well with root system size attributes only in young (3–4 month old) seedlings but the correlations were inconsistent among different N treatments and stock types. Neither the root system surface area nor dry weight reliably reflected its ability to absorb and conduct water. Generally, the amount of water delivered through the root system and available for transpiration per unit or leaf surface area or unit of leaf dry weight correlated poorly or negatively with the root system size. Practical and scientific implications of the findings are discussed. *Paper presented at Forest Seedling Root Development Conference: From the Nursery to the Field, Eugene, Oregon, May 12–13, 2004.     

Effect of photon flux density on carbon assimilation and chlorophyll a fluorescence of cold-stored white spruce and lodgepole pine seedlings

White spruce (Picea glauca (Moench.) Voss) and lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings previously held in dark, frozen storage (-2 degrees C) for 2.5 or 6 months, and nursery-grown white spruce seedlings lifted in summer were exposed to photon flux densities (PFDs) similar to those that might be encountered at planting. Photosynthetic gas exchange and chlorophyll a (chl a) fluorescence were examined in cold-stored and summer-lifted seedlings before and after a 9 h-exposure to artificial illumination of high PFD (2000 micro mol m(-2) s(-1)) or low PFD (ca. 500 micro mol m(-2) s(-1)), and during exposure to 400 micro mol m(-2) s(-1) for 4-9 days. In the 2.5-month-stored and summer-lifted seedlings, the high-PFD treatment caused a small decrease in carbon fixation and a large decrease in the ratio of variable to maximum fluorescence (F(v)/F(m)) relative to the effect of the low-PFD treatment. In contrast, in the 6-month-stored seedlings the high-PFD treatment caused a significant decrease in rate of light-saturated carbon fixation but little decrease in F(v)/F(m) relative to the effect of the low-PFD treatment, indicating that the mechanisms for maintaining integrity of the photochemical apparatus had changed during the storage interval.     

Acquired thermotolerance of jack pine, white spruce and black spruce seedlings

The acquired thermotolerance of first-year seedlings of jack pine (Pinus banksiana Lamb.) hardened at 36, 38, 40 or 42 degrees C for 90, 180 or 360 minutes and of black spruce (Picea mariana (Mill.) B.S.P.) hardened at 34, 36, 38 or 40 degrees C for 30, 90, 180 or 360 minutes was determined by comparison of needle damage to that of non-hardened seedlings (25 degrees C) following exposure to temperatures of 49 and 47.5 degrees C, respectively. Compared to seedlings kept at 25 degrees C, heat injury sustained from exposure to high temperatures was markedly reduced following hardening for 180 minutes at 36 and 38 degrees C in jack pine and black spruce, respectively. Increasing the exposure time at 36 degrees C in jack pine, and at 36 to 40 degrees C in black spruce, also reduced needle damage. The duration of increased thermotolerance was investigated in jack pine, black spruce and white spruce (Picea glauca (Moench) Voss) by comparing heat injury from high temperatures in non-hardened seedlings and in seedlings hardened at 38 degrees C for 180 minutes a day for either 1, 3 or 6 days. In all three species, the duration of acquired thermotolerance increased with the number of days of heat hardening. For jack pine and white spruce seedlings hardened at 38 degrees C for 6 days, increased thermotolerance persisted for at least 14 and 10 days, respectively, after the end of the hardening treatment. In contrast, the thermotolerance of black spruce seedlings hardened at 38 degrees C for 6 days remained elevated for only 4 days.     

Differences in growth and mineral nutrition of seedlings produced from ten white spruce seed orchards

To meet the needs for improved spruce seeds in the province of Quebec, Canada, 17 first-generation white spruce seed orchards (SO) were established. These SOs are located in different bioclimatic domains and contain seed trees originating from geographically and genetically distinct sources. To evaluate the influence of SO on seedling growth and morphology, seedlings produced with seeds originating from the ten most commonly used first-generation white spruce SO in Quebec were raised under similar nursery conditions. Tissue nutrient concentrations of seedlings evolved similarly among seed orchards during the second growing season. At the end of the growing season, only shoot phosphorus concentrations were significantly different. When modeled with a logistic function, there was a significant difference between height and diameter growth curve parameters of seedlings from distinct SO during the second growing season. These differences led to significant differences in the height and shoot dry mass of the seedlings at the end of their second growing season, but not in their diameter or root dry mass. The ten SOs were clustered in two groups according to the above-ground characteristics of their progeny. This limited amount of morphological diversity suggests that expanding the size of the present seed zones may be an appropriate course of action for white spruce seed production in Quebec.     

Root hydraulic conductivity and root growth capacity of black spruce (Picea mariana) seedlings

The relationship between root elongation and root hydraulic conductivity was investigated in 1-year-old, overwintered black spruce (Picea mariana (Mill.) seedlings. Hydraulic conductivity was estimated by observing water flux through decapitated roots under positive pressure. Five hydraulic conductivity parameters were estimated: (1) water flux under a minimal pressure of 0.2 MPa (J(v, min)); (2) pressure at which a linear relationship between water flux and pressure began (P(min)); (3) slope of the linear water flux-pressure relationship (L(v)); (4) pressure at which the linear relationship between water flux and pressure ended (P(max)); and (5) maximum water flux (J(v, max)). Between day 1 and day 2 after thawing of the growing medium, there were significant increases in L(v) and J(v, max) but there was little, if any, root elongation. Root elongation averaged 5.4 cm seedling(-1) 5 days after thawing and 88.2 cm seedling(-1) 20 days after thawing. Root hydraulic conductivity increased with new root length initially. But between days 20 and 30, when new root length nearly doubled, P(min) was the only measure of hydraulic conductivity that increased significantly. There were significant correlations (P < 0.05) between white root length and both J(v, min) (r(2) = 0.90) and J(v, max) (r(2) = 0.91).     

Estimating biomass of white spruce seedlings with vertical photo imagery

Estimation of individual tree seedling biomass isrequired in a variety of forest management andresearch applications such as assessment of netprimary productivity and carbon sequestrationpotential of forest stands, understory forest fuelinventories, and development of silviculturalguidelines to promote the growth of desired treespecies. Photo imagery is a promising non-destructivemethod for estimating the aboveground biomass of treeseedlings. This method was tested using naturallyregenerated white spruce (Picea glauca (Moench)Voss) seedlings growing in the understory of a mixedconifer shelterwood in central Ontario. In the fall of1997, 45 seedlings were sampled from plots exposed toone of three mechanical release treatments (earlyspring release, mid summer release, and no release(control)) in 1994. Each seedling was photographed inthe field to measure the vertical projected area(silhouette area) of the aboveground portion of theseedling. Seedlings were harvested, basal diameter andtotal height measured, and biomass (dry mass) offoliage, branches, main stem and total abovegroundplant tissue determined. Regression analysis revealeda strong relationship between both silhouette area andbasal diameter, and seedling biomass. Coefficients ofdetermination for regression equations usingsilhouette area were equal to 0.892, 0.918, 0.926, and0.937 for the main stem, branches, foliage, and totalaboveground biomass, respectively. Respectivecoefficients of determination for regression equationsusing basal diameter were 0.960, 0.945, 0.953, and0.977. Silhouette area-based equations for totalaboveground and foliar biomass differed significantly(P < 0.005) among release treatments. Nosignificant differences among treatments were observedbetween silhouette area-based equations for biomass ofbranches and main stem (P > 0.05), or betweenbasal diameter-biomass (allometric) equations for allcomponents (P > 0.1). The method was thentested by validating the biomass equations using anindependent data set from 35 white spruce seedlingsfrom the same site and cohort, but exposed todifferent treatments and microenvironmentalconditions. For each seedling, biomass components werepredicted using silhouette area-based and allometricequations, and a relative error of predictioncalculated. The mean relative error for silhouettearea-based predictions varied among biomass componentsfrom –20.25% to –3.21%, with standard deviation ofthe error ranging from 23.04% to 33.44%. The meanrelative error for allometric equations ranged from–2.46% to –21.75%, with standard deviations of23.34% to 32.61%. These results suggest that: (1)photo imagery can be used as an alternative to moretraditional allometric methods of biomass estimation,and (2) general (developed for a broad range ofgrowing conditions) equations derived by either methodare preferable to those specifically calibrated for agiven growing environment.     

Weed control increases nitrogen retranslocation and growth of white spruce seedlings on a reclaimed oil sands soil

Early establishment of seedlings in reclaimed oil sand areas is often limited by low nutrient and water availability due to factors such as strong understory vegetation competition. Management practices such as nursery fertilization and field weed control could help early establishment of planted seedlings and reclamation success. We investigated the effect of nursery nutrient loading and field weed control on the growth, nitrogen (N) retranslocation within seedling components, and plant N uptake from the soil for white spruce (Picea glauca [Moench] Voss) seedlings planted on a highly competitive reclaimed oil sands site for two years. Exponential fertilization during nursery production increased the root biomass but not the nutrient reserve in the seedling. In the field experiment, on average across the treatments, 78 and 49% of the total N demand of new tissue growth in the first and second year were met by N retranslocation, respectively. Though exponential fertilization did not affect N retranslocation, it increased the percent height and root collar diameter growth. Weed control increased not only the growth of seedlings by increasing soil N availability, but also N retranslocation within the seedlings in the second year after outplanting. We conclude that vegetation management by weed control is feasible in improving the early growth of white spruce seedlings planted on reclaimed soils and facilitate tree establishment in the oil sands region. Optimization of the nursery exponential N fertilization regime for white spruce may further help with early revegetation of reclaimed oil sands sites.     

Effects of soil temperature on shoot and root growth and nutrient uptake of 5-year-old Norway spruce seedlings

Soil temperature is a main factor limiting root growth in the boreal forest. To simulate the possible soil-warming effect of future climate change, 5-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were subjected to three simulated growing seasons in controlled environment rooms. The seedlings were acclimated to a soil temperature of 16 degrees C during the first (GS I) and third growing seasons (GS III), but were assigned to random soil-temperature treatments of 9, 13, 18 and 21 degrees C during the second growing season (GS II). In GS II, shoot diameter growth was lowest in the 21 degrees C treatment and root growth was lowest in the 9 degrees C treatment. In GS III, shoot height and root length growth improved in seedlings that had been kept at 9 degrees C during GS II, indicating compensatory growth in response to increased soil temperature. The temporary decrease in soil temperature had no long-lasting significant effect on seedling biomass or total nutrient uptake. At the end of GS III, fine roots of seedlings exposed to a soil temperature of 21 degrees C in GS II were distributed more evenly between the organic and mineral soil layers than roots of seedlings in the other treatments. During GS II and GS III, root growth started earlier than shoot growth, decreased during the rapid shoot elongation phase and increased again as shoot growth decreased.     

Effects of cold storage and water stress on water relations and gas exchange of white spruce (Picea glauca) seedlings

To determine the effects of lifting time and storage on water-stress resistance of nursery-grown white spruce (Picea glauca (Moench) Voss) seedlings, we compared gas exchange, water relations and mortality of 3-year-old seedlings lifted in October 1991 and stored at -2 degrees C for 3 months with seedlings lifted in January 1992. The seedlings were placed in nutrient solution and subjected to -1.1 or -2.7 MPa water stress induced by polyethylene glycol 3350 for 9 days. Water stress, but not lifting time, had a significant effect on seedling net assimilation, symplastic volume and turgor loss point. In a second experiment, seedlings lifted in October 1991 were stored at -2 degrees C for 7 months and compared with seedlings lifted in May 1992. The seedlings were planted in pots, and their gas exchange and water relation parameters measured in response to gradual water stress. The results suggest that prolonged cold storage retards photosynthetic recovery of seedlings after planting. Higher rates of net assimilation in seedlings lifted in May were not directly related to their water status. Nonstomatal limitations were the primary factor influencing photosynthetic rate. We conclude that the inferior ability of cold-stored seedlings to tolerate water stress was due to poor osmotic adjustment and a lag in recovery of photosynthesis.     

Effect of thawing regime on growth and mortality of frozen-stored Norway spruce container seedlings planted in cold and warm soil

One-year-old frozen-stored Norway spruce (Picea abies (L.) Karst.) container seedlings were planted in a controlled environment providing an air temperature of 22°C and soil temperature of 9±1 or 18±1°C. At planting the root plugs were either frozen or had been thawing for 4 days at 9°C. During a 5-week growing period, in both cold and warm soil the root growth and height growth were less in frozen-planted seedlings than in thawed seedlings. In addition, frozen-planting delayed bud burst and increased mortality. Soil temperature, however, had no effect on bud burst or mortality. Low soil temperature retarded root growth of seedlings thawed before planting but resulted in both retarded root growth and height growth if root plugs were frozen when planted. These results indicate that planting Norway spruce seedlings with frozen root plugs constitutes a considerable risk for successful forest regeneration at soil temperatures normally prevailing in Fennoscandia in spring or early summer especially if the soil is dry at the time of the planting.     

Characterizing the frost sensitivity of black spruce photosynthesis during cold acclimation

We used photosynthetic light response curves to measure and model the responses of two provenances of 3-year-old black spruce (Picea mariana (Mill.) BSP) seedlings to severe artificial frost treatments applied at 2-week intervals during cold acclimation. Black spruce seedlings responded to cold acclimation with long-term suppression of photosynthetic capacity (Amax) and apparent quantum-use efficiency (alpha'). Short-term reductions in both photosynthetic parameters following frost treatments were dependent on the extent of cold acclimation of the seedlings and the severity of the frost treatments. Large reductions in Amax in response to the frost treatments were observed in seedlings that had undergone little cold acclimation and these reductions were associated with an irreversible reduction in alpha'. Such seedlings recovered only partially during the subsequent 23 days, whereas seedlings in most other treatments showed complete recovery of Amax after 13 days. The impact of frost treatments on Amax and alpha' did not vary with seedling provenance. We propose an algorithm that predicts the combined effects of cold acclimation and severe freezing temperatures on the extent of the suppression of A(max) during autumn. The algorithm is based on (1) the maximum Amax observed during the growing season, (2) the accumulation of cold degree-days, based on a minimum nocturnal temperature < 5 degrees C, and (3) the severity of freezing temperatures during autumn. The parameters developed in the algorithm showed that cold acclimation of black spruce seedlings had a greater impact on the reduction of Amax in autumn than did the severe frost treatments. Mean Amax of seedlings subjected to artificial frosts showed a strong correlation with values predicted by the algorithm (r2 = 0.91).     

Nutrient enrichment of white spruce seedlings during nursery culture and initial plantation establishment

Growth and nutrient dynamics of bare-root white spruce (Picea glauca (Moench) Voss) seedlings were monitored for three years in a nursery and for one season after planting to assess effects of three nursery fertilization regimes. Nitrogen (totaling 0, 650, and 1300 kg N ha(-1) for 3 years) was applied conventionally in equal amounts during the growing season. The high-N treatment, representing a nutrient loading regime, was also applied seasonally at exponentially increasing rates as a fourth treatment. By the end of the 3-year nursery rotation, the N treatments had stimulated growth by 104-180% and nutrient uptake by as much as 381, 224 and 145% for N, P and K, respectively, inducing large accumulations of N and P in both conventionally and exponentially loaded seedlings. Compared with exponentially loaded seedlings, the concentrations of nutrients were less in conventionally loaded seedlings although their biomass was larger (31%). High nutrient reserves in the seedlings at the end of the nursery rotation resulted in increased biomass production (40-190%) after planting, which was related to the ability of the seedlings to retranslocate internal reserves for new growth, despite little or no net uptake of nutrients during the first season after planting. Compared with conventionally loaded seedlings, retranslocation was greater in exponentially loaded seedlings, which had accumulated larger and more readily available nutrient reserves during the nursery phase. The shortness of this study limits its usefulness for predicting the persistence of the loading response after planting, but we postulate that the high nutrient status of loaded seedlings at the end of the nursery rotation will contribute to future growth through increased nutrient storage and retranslocation, thus prolonging the loading response.     

Chlorophyll fluorescence as an indicator of frost hardiness in white spruce seedlings from different latitudes

This study examined the utility of variable chlorophyll fluorescence (F_var) to detect freezing damage in white spruce seedlings of four seedlots. Logistic regression analysis done for freezing tests in September showed that visible needle damage from freezing could be estimated by the F_var attributes F_o/I_ABS(r²=0.94), F_p(r²=0.98), F_v/F_m (r²=0.99), and F₁(r²=0.86). The regression curves indicated that for all four fluorescence attributes, inflection points occurred between 10 and 20% visible needle damage. The lack of a relationship between fluorescence attributes and visible seedling needle damage in October through December is because the minimum temperature (–18 and –24°C respectively) applied was insufficient to cause needle damage. Freezing-induced changes to F_var attributes can be detected which also result in photosynthetic rate decreases when no visible needle damage, and even electrolyte conductivity changes are evident. F_var attribute differences due to freezing can be resolved to the seedlot level. The Fvar curve feature manifested 5 seconds after dark-adapted seedlings have been exposed to light (F_5s) will estimate (r²=0.76) photosynthetic rate after freezing.     

Effects of artificial shade on early performance of white spruce seedlings planted on clearcuts

Chlorophyll fluorescence, chlorophyll content, growth, and mortality of white spruce (Picea glauca [Moench] Voss) seedlings were monitored for 2 years after planting under three scenarios of artificial shade: no-shade (control), shade in summer only, and shade all year. The shade frames allowed 50–60% light transmission, with limited effects on air temperature, relative humidity, soil temperature, and soil moisture around seedlings. Based on fluorescence yield and chlorophyll content measurements, summer-only shade reduced photoinhibition and photooxidation, especially in summer and fall; extending to all year shading did not further reduce either photoinhibition or photooxidation. Shade tended to reduce seedling diameter and mortality, but after 2 years the cumulative effect on mortality was not statistically significant. Study results support the establishment of white spruce seedlings under partial forest canopy, especially on sites with harsh environmental conditions.     

Effect of three species of bacteria on damping-off,root rot development,and ectomycorrhizal colonization of lodgepole pine and white spruce seedlings

Interactions between three species of bacteria (Burkholderia cepacia, Pseudomonas chlororaphis and Pseudomonas fluorescens), an ectomycorrhizal fungus (Paxillus involutus), and three root pathogenic fungi (Fusarium moniliforme, Fusarium oxysporum and Rhizoctonia solani) were studied. Burkholderia cepacia significantly reduced the in vitro mycelial growth of P. involutus, whereas, B. cepacia, Ps. chlororaphis, Ps. fluorescens and P. involutus reduced the mycelial growth of F. moniliforme, F. oxysporum and R. solani. Culture filtrates of B. cepacia, Ps. chlororaphis, Ps. fluorescens and P. involutus reduced conidial germination and increased the formation of chlamydospores of F. moniliforme and F. oxysporum. Burkholderia cepacia also reduced the formation of ectomycorrhizal short roots by P. involutus on lodgepole pine (Pinus contorta) and white spruce (Picea glauca) seedlings 2 months after inoculation. However, no significance difference in mycorrhizal short roots was observed after 4 months. The fungicide Anchor (a mixture of carboxine and thiram) significantly reduced root rot severity and increased the survival of lodgepole pine seedlings grown in a growth mix infested with F. moniliforme, F. oxysporum and R. solani. Control of the diseases of white spruce caused by these pathogens was not as successful. Treatment of seeds with either B. cepacia or P. involutus alone significantly increased the survival of seedlings grown in a mix that was inoculated with F. moniliforme and reduced the root rot severity caused by F. moniliforme and F. oxysporum, but not R. solani. Higher seedling survival and lower root rot severity were observed when conifer seeds were concomitantly inoculated with one of the bacterial species, P. involutus and Anchor.     

The susceptibility of white spruce seedlings to overwinter injury and their post-injury field responses

Foliar and stem injury was assessed in white spruce (Picea glauca (Moench) Voss) seedlings planted in the spring and in the summer of 1992 and injured during their first overwintering on two sites in the southeastern boreal forest of British Columbia. Freeze-desiccation appears to be the main cause of the injury. Seedlot effect on the injury was significant, while planting time effect was not. Although the seedlot effect may be confounded with stock-type effect, analyses indicated increasing injury with increasing seedling height and declining ground-level diameter. Seedling vigour (height and diameter increments in the previous growing season) was also significantly related to the injury which increased with increasing vigour but the significance of this relationship varied from site to site. Condition of injured seedlings generally declined further during the post-injury growing season. This decline was greater in spring-planted than in summer-planted seedlings. Excavated root systems of container-grown seedlings showed the majority of post-planting root growth originating from the bottom-third of the nursery-container plug, deeper than 10 cm from the soil surface. This is seen as a factor potentially contributing to desiccation injury as the soil in the geographic region often remains frozen at these depths long into spring.     

Physiological recovery of freezer-stored white and Engelmann spruce seedlings planted following different thawing regimes

Logistic problems of large-scale reforestation necessitate freezer-storage of conifer seedlings. Frozen stock is typically thawed slowly at low temperatures for up to several weeks before shipping to the plantation site, but the necessity of this practice is questionable. Experiments were conducted to study effects of different thawing regimes on photosynthetic recovery, frost hardiness, water relations and growth initiation in interior spruce (white spruce (Picea glauca (Moench) Voss) and Engelmann spruce (Picea engelmannii Parry) hybrid complex). One year-old container-grown seedlings were planted after 9 days post-storage thawing at 5–15 °C or still frozen, directly from the freezer. During a 29 day observation period after planting, both groups showed changes in xylem water potential (_w), carbon fixation (A), stomatal conductance (g _s ), chlorophyll a fluorescence and xanthophyll cycle pigments. Treatment differences in fluorescence and pigments peaked within one hour after planting. All differences in _w, A, g _s , ratio of internal to external CO₂ concentration (C_i/C_a), fluorescence, pigments and root number disappeared after 5 to 8 days. Terminal bud burst occurred 2.6 days earlier in the pre-thawed seedlings. When seedlings were rapidly thawed in the dark at 21 °C they achieved maximum _w (–0.2 MPa) in 3–4 hour. When evaluated 45 min after planting, A, g _s , C_i/C_a and fluorescence values of rapidly thawed seedlings were intermediate between those for seedlings planted frozen or after 9 days slow thawing, showing that the recovery process was well underway a few hours after removal from the freezer. These results suggested that a suitable on-site operational protocol for rapid thawing might be to lay frozen bundles on the ground at ambient temperature overnight. In field trials of this method, rapidly thawed seedlings broke bud 3.3 days later than slowly thawed stock and also had greater frost hardiness at time of planting. Height, shoot and root mass did not differ after 3 months growth.     

Effects of overstory retention and site preparation on growth of planted white spruce seedlings in deciduous and coniferous dominated boreal plains mixedwoods

Survival and growth of planted white spruce was assessed under partial harvest treatments and different site preparation techniques in mixedwood forests of two compositions prior to logging: deciduous dominated (d-dom) – primarily comprised of mature trembling aspen (Populus tremuloides Michx.) and coniferous dominated (c-dom) – primarily comprised of mature white spruce (Picea glauca (Moench) Voss). Levels of overstory retention were 0% (clearcut), 50% and 75% of original basal area, and site preparation techniques were inverted mounding, high speed mixing, scalping and control (no treatment). The survival and growth of white spruce were assessed seven years after planting. The experiment was established as a part of the Ecosystem Management Emulating Natural Disturbance (EMEND) experiment located in northern Alberta, Canada. In the c-dom, the 50% and 75% retention of overstory resulted in reduced growth and survival of white spruce seedlings compared to clearcuts. In contrast, in the d-dom, the seedlings performed best in sites that had 50% of the overstory retained. For the c-dom, the mounding and mixing treatments yielded the best growth of spruce seedlings, while scalping yielded the worst. In the d-dom, spruce growth was highest in sites with the mixing treatment. In the d-dom, growth and survival of the planted spruce was greater than in the c-dom. The natural regeneration of deciduous trees was suppressed by the retention of canopy regardless of original composition.