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.

N/P/K Ratios and CO<sub>2</sub> Concentration Change Nitrogen-Photosynthesis Relationships in Black Spruce

The relationship between photosynthesis and leaf nitrogen concentration is often used to model forest carbon fixation and ratios of different nutrient elements can modify this relationship. However, the effects of nutrient ratios on this important relationship are generally not well understood. To investigate whether N/P/K ratios and CO2 concentration ([CO2]) influence relationships between photosynthesis and nitrogen, we exposed one-year-old black spruce seedlings to two [CO2] (370 and 720 μmol·mol-1), two N/P/K ratio regimes (constant (CNR) and variable (VNR) nutrient ratio) at 6 N supply levels (10 to 360 μmol·mol-1). It was found that photosynthesis (Pn) was more sensitive to nitrogen supply and N/P/K ratios under the elevated [CO2] than under ambient [CO2]; under the elevated [CO2], Pn declined with increases in N supplies above 150 μmol·mol-1 in the CNR treatment but was relatively insensitive to N supplies of the same range in the VNR treatment. Further, our data suggest that the nutrient ratio and the CO2 elevation effects on photosynthesis were via their effects on the maximum rate of carboxylation (Vcmax) but not electron transport (Jmax) or triose phosphate utilization (TPU). The results suggest that the CO2 elevation increased the demand for all three nutrient elements but the increase was greater for N than for P and K. The CO2 elevation resulted in greater photosynthetic use efficiencies of N, P and K, but the increases varied with the nutrient ratio treatments. The results suggest that under elevated [CO2], higher net photosynthetic rates demand different optimal N-P-K ratios than under the current [CO2].

Future dominance by quaking aspen expected following short‐interval, compounded disturbance interaction

AbstractThe spatial overlap of multiple ecological disturbances in close succession has the capacity to alter trajectories of ecosystem recovery. Widespread bark beetle outbreaks and wildfire have affected many forests in western North America in the past two decades in areas of important habitat for native ungulates. Bark beetle outbreaks prior to fire may deplete seed supply of the host species, and differences in fire‐related regeneration strategies among species may shift the species composition and structure of the initial forest trajectory. Subsequent browsing of postfire tree regeneration by large ungulates, such as elk (Cervus canadensis), may limit the capacity for regeneration to grow above the browse zone to form the next forest canopy. Five stand‐replacing wildfires burned ~60,000 ha of subalpine forest that had previously been affected by severe (>90% mortality) outbreaks of spruce beetle (SB,Dendroctonus rufipennis) in Engelmann spruce (Picea engelmannii) in 2012–2013 in southwestern Colorado. Here we examine the drivers of variability in abundance of newly established conifer tree seedlings [spruce and subalpine fir (Abies lasiocarpa)] and resprouts of quaking aspen (Populus tremuloides) following the short‐interval sequence of SB outbreaks and wildfire (2–8 yr between SB outbreak and fire) at sites where we previously reconstructed severities of SB and fire. We then examine the implications of ungulate browsing for forest recovery. We found that abundances of postfire spruce seedling establishment decreased substantially in areas of severe SB outbreak. Prolific aspen resprouting in stands with live aspen prior to fire will favor an initial postfire forest trajectory dominated by aspen. However, preferential browsing of postfire aspen resprouts by ungulates will likely slow the rate of canopy recovery but browsing is unlikely to alter the species composition of the future forest canopy. Collectively, our results show that SB outbreak prior to fire increases the vulnerability of spruce–fir forests to shifts in forest type (conifer to aspen) and physiognomic community type (conifer forest to non‐forest). By identifying where compounded disturbance interactions are likely to limit recovery of forests or tree species, our findings are useful for developing adaptive management strategies in the context of warming climate and shifting disturbance regimes.

Changes in light spectra modify secondary compound concentrations and BVOC emissions of Norway spruce seedlings

Our objective was to study how changes in the light spectra affect growth; the concentration of carbohydrate, chlorophyll, carotenoid, terpene, alkaloid, and phenolic compounds; and the emissions of BVOC (biogenic volatile organic compound) of Norway spruce (Picea abies (L.) Karst.) seedlings. This study was conducted during the growth of the third needle generation in plant growth chambers. The plants were exposed to two light spectra with equal photon flux densities but different proportions of blue light (400–500 nm) produced by LED (light-emitting diode) lamps: (i) control (white light + 12% blue light) and (ii) increased blue light (+B) (white light + 45% blue light). The +B treatment increased the concentrations of total flavonoids and acetophenones in needles. The major changes in the phenolic profile were an accumulation of astragalin derivatives and the aglycone of picein. The +B treatment also decreased concentrations of the main alkaloid compound, epidihydropinidine, and its precursor, 2-methyl-6-propyl-1,6-piperideine; the emission rates of limonene, myrcene, and total monoterpenes; and the concentrations of a few terpenoid compounds, mainly in stems. Growth as well as the carbohydrates and pigments present in the needles were not affected. The results suggest that supplemental blue light shifts carbon allocation between secondary metabolism routes — from alkaloid and terpenoid synthesis to flavonoid and acetophenone synthesis. The changes may affect herbivory and abiotic stress tolerance of Norway spruce.

Effect of High Concentrations of Wood Ash on Soil Properties and Development of Young Norway Spruce (Picea abies (L.) Karst) and Scots Pine (Pinus sylvestris L.)

Wood ash recycling can be a reasonable method for energy producers to decrease waste problems. Using wood ash as a fertilizer or liming material could improve soil macro and micronutrient content in peat soils. Therefore, the effect of wood ash on Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.) juvenile growth and nutrient content in the soil after spreading wood ash in medium to high doses before and after planting seedlings was investigated in peat forests in the Eastern part of Latvia. The aim of the study was to evaluate the effect of high doses of wood ash on soil properties and the growth of planted Norway spruce and Scots pine seedlings up to 10 years after experiment establishment. Wood ash was applied a year before planting seedlings in doses of 5 and 10 t ha−1 and right after planting in concentrations of 5, 10, 15, and 20 t ha−1. Changes in macronutrient content (i.e., phosphorus [P], and potassium [K]) and tree height and diameter at breast height were measured at one and 10 years after establishing the experiment. Fertilization one year prior to planting the seedlings exhibited a positive response on tree height and diameter growth compared to fertilization after the seedlings were planted. Soil samples from fertilized plots one year after establishment contained more P and K in the soil than the control plots. Wood ash application of the highest doses did not reach the overdose limit, as the tree growth (height and diameter at breast height) results of fertilized plots were similar to those of the control fields; therefore, no significant negative effect on tree growth was discovered.

Growth and Development of Seedlings of Scots Pine and European Spruce Container Seedlings Using Various Materials to Neutralise the Substrate

The article analyses the features of growth and development of seedlings of Scots pine and European spruce on substrates in which various materials were used to neutralise them, affecting the reaction of the environment. According to the research results, the highest germination of seeds of both woody species was established on substrates with a ratio of dolomite flour of 30% and chalk of 70%, while in the case of using pure chalk, seed germination was significantly lower. Scots pine seeds germination in the substrate ranged from 77.6% to 90.1%, and European spruce seeds – from 66.4% to 94.3%. During the cultivation of seedlings of Scots pine and European spruce container seedlings, differences in the content of mobile forms of phosphorus are noted in all variants of the experiment. However, no definite pattern was found depending on the share of participation of various types of lime material. In the substrate of seedlings of Scots pine at the end of the growing season, the content of nitrate nitrogen naturally increases from 1069.1 to 1323.6 mg/100 g of absolutely dry substrate with a decrease in the proportion of dolomite and an increase in the proportion of chalk in the lime neutralising material. Another pattern is manifested when growing seedlings of European spruce container seedlings: the lowest content of nitrate nitrogen (412.1 mg/100 g of absolutely dry substrate) is established in the case of mixing dolomite flour and chalk in equal proportions (option 3). Differences in the content of mobile forms of iron were revealed in all experimental versions of the substrate of both woody species. For the cultivation of Scots pine, its amount ranges from 16.67 to 28.81 mg/100 g of absolutely dry substrate, and European spruce – from 18.40 to 20.99 mg/100 g of absolutely dry substrate. In general, low content of mobile iron was observed in the substrate of growing pine and spruce seedlings in containers. In all experimental variants, the height of seedlings of Scots pine container seedlings exceeds the required average height of the aboveground part in accordance with national standard by 1.3-2.0 times, and for seedlings of European spruce the excess was 1.2-1.5 times. In seedlings of Scots pine and European spruce, according to the variants of the experiment, the average height of the aboveground part rises with an increase in the concentration of dolomite in the mixture of neutralising material from 50% and higher

Effect of site preparation under shelterwood on Norway spruce seedlings

ABSTRACT The effect of site preparation (mixed mounding and removal of the humus layer) under a shelterwood of mixed boreal forest along a forest interior-edge gradient on Norway spruce (Picea abies) seedlings was studied two years after planting. Mounds had a positive effect on root development, ectomycorrhiza formation and the absorption of nitrogen (N) and phosphorus (P) in the seedlings, and augmented their survival, growth and biomass. Humus removal had an adverse effect on the root biomass and ectomycorrhiza formation. A decreased soil fertility after the removal of humus led to a low N and P content in the seedlings. Two years after planting, humus removal had not affected the growth of the seedlings, but reduced their biomass. The influence of the forest edge, compared to the interior plot, was mostly associated with a decrease in the stand density, reduced amount of litter and increased light availability for the seedlings.

A model evaluation framework applied to the Forest Vegetation Simulator (FVS) in Colorado and Wyoming lodgepole pine forests

The Forest Vegetation Simulator (FVS) growth and yield model is widely used throughout the United States, but recent studies have reported unexpectedly large bias for some regional model variants. Here we propose a general framework for model evaluation, designed to highlight model strengths and weaknesses and inform calibration efforts. We apply the framework to evaluate the Lodgepole Pine (LP) model of the FVS Central Rockies Variant (FVS-CR), which has rarely been evaluated in the literature despite its widespread use in the western US. We started with a qualitative verification of the structure and logic of the FVS-CR LP model against a modified Bakuzis matrix, determining that it adequately reproduces known patterns of stand dynamics. We then compared stand-level growth simulations to a chronosequence developed from 554 Forest Inventory and Analysis (FIA) plots measured in Colorado and Wyoming lodgepole pine forests. This quantitative validation exercise revealed that the default model settings substantially over-predict basal area and total stand carbon after 50 years for both pure lodgepole pine stands and mixed lodgepole pine stands containing a minor proportion of Engelmann spruce, subalpine fir, and quaking aspen. Using equivalence testing to validate the large-tree diameter increment model against a separate dataset of 3,790 remeasured trees on 124 lodgepole pine FIA plots, we found that the default FVS–CR LP model adequately predicts lodgepole diameter growth, though we observed large variation in model errors. Equivalence tests also revealed systematic under-estimation of spruce–fir and over-estimation of aspen productivity. Finally, we conducted a sensitivity analysis to identify the most important model parameters and data inputs driving simulated stand structure and carbon accumulation in both the short- (50 years) and long-term (200 years). The model shows the greatest sensitivity to initial species composition; a small proportion of aspen, spruce, or fir seedlings led to long-term stand re-structuring and greatly increased carbon accumulation. Other sensitive parameters included site index, the fixed large-tree diameter increment adjustment factor, and the parameter controlling the point at which density-dependent self-thinning begins (maximum stand density index). This evaluation leads us to conclude that the FVS-CR LP model tends to under-estimate tree mortality (particularly in young stands) and the default site index represents relatively high productivity stands, such that re-calibration may often be necessary to capture realistic long-term stand behaviors. Our sensitivity analysis provides guidance for future efforts to re-calibrate the FVS-CR LP model and highlights the importance of collecting site index and seedling species composition data wherever possible to produce the most realistic simulations.

ЭКОНОМИЧЕСКАЯ ОЦЕНКА ИННОВАЦИОННОЙ ТЕХНОЛОГИИ «POT-IN-POT» ДЛЯ ЦЕЛЕЙ ЛЕСОВОССТАНОВЛЕНИЯ

The transition to alternative growing technologies for forest planting material is determined by significant climatic changes and growing demand for woody plants, resistant to unfavorable factors. Development and practical application of innovations is constrained by the lack of investment and information on the economic efficiency of the use of innovative technologies. Container technologies for the production of planting material in tree ornamental nurseries occupy an increasing segment of modern market in Russia and foreign countries. The innovative Pot-in-pot technology combines the advantages of container and soil cultivation of woody plants material. In the article, using cost-effective method and economic feasibility of innovative technology for seedlings' growing has been determined. Investment analysis method, based on estimates of net present value, discounted payback period, and rate of return on invested capital, is used to assess the cultivation of seedlings using innovative Pot-in-Pot technology. The study has made it possible to determine the costs of growing spruce seedlings using Pot-in-Pot technology and economically substantiate the effectiveness of an innovative solution for growing planting material. The use of Pot-in-Pot technology in forestry practice can provide a breakthrough in growing seedlings, resistant to the harmful effects of high temperatures and low moisture requirements. Along with biological effects, the use of technology in forest nurseries can reduce production costs and ensure the economic effect of mass production of seedlings. The adaptation of Pot-in-Pot technology to the conditions of forestry in Russia will accelerate the processes of reforestation in changing climatic conditions, primarily through the production of sustainable planting material with a relatively low cost of cultivation.

Вплив наночастинок СеО2 на проростання насіння та синтез фенолів у проростках ялини європейської

Modern technologies make it possible to obtain nanoparticles of biogenic metals for use as an additional source of micronutrient for plants. However, the complexity of mass application of nanosized metal particles and their oxides is due to the significant differences in physicochemical properties of nanocrystalline structures which are dependent on production technology, nanoparticle size, surface charge (-potential), and stabilization methods. The biocompatibility and nature of nanoparticles has an impact on living organisms. Regarding the effectiveness and feasibility of using cerium dioxide nanoparticles in crop practice, there is no definitive conclusion. Due to difficulty in the preparation of planting material for seedlings of conifers, the study of the effect of nanocrystalline cerium dioxide on plants is not well researched. The aim of our research was to study the effect of nanocrystalline cerium dioxide solution on the germination of spruce seeds and then to evaluate its effect on the synthesis of phenols as components of the antioxidant system within seedlings. The research used methods for determining the germination energy and seed similarities. Other methods used in this research were determining the content of phenolic compounds, flavonoids, and phenolic antioxidants. The results showed that nanocrystalline cerium dioxide in a concentration of solution from 0.1 to 1.0 mg/mL stimulates the germination of spruce seeds. Under the influence of nanoparticles at a concentration of 0.1 mg/L in the tissues of spruce seedlings increases the content of phenolic compounds. The increase in antioxidant activity of phenols in seedling tissues while decreasing their total amount at a concentration of nanocrystalline cerium dioxide from 0.5 to 1.0 mg/L occurs when increasing the total pool of flavonoids, which are determined by high antioxidant activity. Nanocrystalline cerium dioxide is a promising material for stimulating germination energy and on the overall germination of spruce seeds.

Empirical validation of photon recollision probability in single crowns of tree seedlings

Physically-based methods in remote sensing provide benefits over statistical approaches in monitoring biophysical characteristics of vegetation. However, physically-based models still demand large computational resources and often require rather detailed informative priors on various aspects of vegetation and atmospheric status. Spectral invariants and photon recollision probability theories provide a solid theoretical framework for developing relatively simple models of forest canopy reflectance. Empirical validation of these theories is, however, scarce. Here we present results of a first empirical validation of a model based on photon recollision probability at the level of individual trees. Multiangular spectra of pine, spruce, and oak tree seedlings (height = 0.38–0.7 m) were measured using a goniometer, and tree hemispherical reflectance was derived from those measurements. We evaluated the agreement between modeled and measured tree reflectance. The model predicted the spectral signatures of the tree seedlings in the wavelength range between 400 and 2300 nm well, with wavelength-specific bias between −0.048 and 0.034 in reflectance units. In relative terms, the model errors were the smallest in the near-infrared (relative RMSE up to 4%, 7%, and 4% for pine, spruce, and oak seedlings, respectively) and the largest in the visible wavelength region (relative RMSE up to 34%, 20%, and 60%). The errors in the visible region could be partly attributed to wavelength-dependent directional scattering properties of the leaves. Including woody parts of tree seedlings in the model improved the results by reducing the relative RMSE by up to 10% depending on species and wavelength. Spectrally invariant model parameters, i.e. total and directional escape probabilities, depended on spherically averaged silhouette to total area ratio (STAR) of the tree seedlings. Overall, the modeled and measured tree reflectance mainly agreed within measurement uncertainties, but the results indicate that the assumption of isotropic scattering by the leaves can result in large errors in the visible wavelength region for some tree species. Our results help increasing the confidence when using photon recollision probability and spectral invariants -based models to interpret satellite images, but they also lead to an improved understanding of the assumptions and limitations of these theories.

Red Light Controls Adventitious Root Regeneration by Modulating Hormone Homeostasis in Picea abies Seedlings.

Vegetative propagation relies on the capacity of plants to regenerate de novo adventitious roots (ARs), a quantitative trait controlled by the interaction of endogenous factors, such as hormones and environmental cues among which light plays a central role. However, the physiological and molecular components mediating light cues during AR initiation (ARI) remain largely elusive. Here, we explored the role of red light (RL) on ARI in de-rooted Norway spruce seedlings. We combined investigation of hormone metabolism and gene expression analysis to identify potential signaling pathways. We also performed extensive anatomical characterization to investigate ARI at the cellular level. We showed that in contrast to white light, red light promoted ARI likely by reducing jasmonate (JA) and JA-isoleucine biosynthesis and repressing the accumulation of isopentyl-adenine-type cytokinins. We demonstrated that exogenously applied JA and/or CK inhibit ARI in a dose-dependent manner and found that they possibly act in the same pathway. The negative effect of JA on ARI was confirmed at the histological level. We showed that JA represses the early events of ARI. In conclusion, RL promotes ARI by repressing the accumulation of the wound-induced phytohormones JA and CK.

Growth of Fagus sylvatica L. and Picea abies (L.) Karst. Seedlings Grown in Hiko Containers in the First Year after Planting

In forest management in Poland, there are no standards for the quality and suitability for planting seedlings produced in nursery containers; therefore, research contributing to the development of such guidelines is important. We investigated the growth reaction of European beech and Norway spruce seedlings growing in container technology one year after planting on an experimental forest plantation. The seedlings used in the study were three experimental variants grown in a container nursery differing in fertilization. Two heights of seedlings were measured, i.e., after the first growing season on the experimental plantation and the initial (obtained in the forest nursery), and the annual (AHI, cm) and relative height increments (RHI, %) were calculated. The regression of the RHI of seedlings to their initial height was calculated, and the equations obtained were used to determine the optimal range of seedling height at the stage of nursery growth at which they will achieve the maximum increment in the first year of growth on the plantation. The change from foliar fertilization to a mixed one affected beech and spruce seedling parameters; however, it did not affect the diversity of their survival on the experimental plantation. Higher seedlings planted on the experimental plantation were characterized by a smaller RHI. The optimal range for the height of seedlings obtained at the nursery stage of growing, which determined the maximum value of the AHI after the first year of growth after planting, was 18–36 cm for beech and 14–25 cm for spruce.

Eight-year ecophysiology and growth dynamics of Picea rubens seedlings planted in harvest gaps of partially cut stands

In order to compensate for regeneration failure of red spruce (Picea rubens) in the managed temperate mixedwood forest, an enrichment planting study was conducted in yellow birch (Betula alleghaniensis)–conifer stands, in Quebec, Canada. The experimental design compared four cutting treatments: an uncut control (26 m2·ha−1 of merchantable basal area [BA], with mean natural canopy gap areas of ≤ 100 m2 each) and three hybrid single-tree and group-selection cuttings corresponding to a light cut (20% removal; residual BA [RBA]: 21 m2·ha−1; mean harvest gap area: 220 m2), a moderate cut (31% removal; RBA: 18 m2·ha−1; gap area: 270 m2), and a heavy cut (42% removal; RBA: 15 m2·ha−1; gap area: 340 m2). In the cuts, large-sized containerized seedlings of red spruce were planted within harvest gaps, while in the control, seedlings were planted systematically, for comparison. Three years later, a mechanical release treatment was applied in half of planted plots to limit competing vegetation. After eight years, seedling survival in the three cuts was equally high (> 80%), and greater than in the control (40%). Morphophysiological performance of seedlings was best in the heavy cut creating the largest gaps. In general, the release treatment enhanced survival in the control and in the light cut with the smallest gap sizes. Release also improved morphophysiological performance (which, however, remained suboptimal) in all cutting treatments, but especially in the heavy cut. Although red spruce is highly shade-tolerant, the low survival and performance in the control suggest that for this species, seedlings grown with traditional forest nursery practices are not adapted to plantation under a closed canopy. Results indicate that enrichment planting in intermediate-size harvest gaps (of about 340 m2 in area) of partially cut stands (of about 40% in BA) combined to mechanical release could be a good strategy to maintain or reintroduce red spruce and promote its morphophysiological performance.

Growth Responses of Boreal Scots Pine, Norway Spruce and Silver Birch Seedlings to Simulated Climate Warming over Three Growing Seasons in a Controlled Field Experiment

We studied the growth responses of boreal Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L. Karst.) and silver birch (Betula pendula Roth) seedlings to simulated climate warming of an average of 1.3 °C over the growing season in a controlled field experiment in central Finland. We had six replicate plots for elevated and ambient temperature for each tree species. The warming treatment lasted for the conifers for three growing seasons and for the birch two growing seasons. We measured the height and diameter growth of all the seedlings weekly during the growing season. The shoot and root biomass and their ratios were measured annually in one-third of seedlings harvested from each plot in autumn. After two growing seasons, the height, diameter and shoot biomass were 45%, 19% and 41% larger in silver birch seedlings under the warming treatment, but the root biomass was clearly less affected. After three growing seasons, the height, diameter, shoot and root biomass were under a warming treatment 39, 47, 189 and 113% greater in Scots pine, but the root:shoot ratio 29% lower, respectively. The corresponding responses of Norway spruce to warming were clearly smaller (e.g., shoot biomass 46% higher under a warming treatment). As a comparison, the relative response of height growth in silver birch was after two growing seasons equal to that measured in Scots pine after three growing seasons. Based on our findings, especially silver birch seedlings, but also Scots pine seedlings benefitted from warming, which should be taken into account in forest regeneration in the future.

Sustaining the growth of Pinaceae trees under nutrient-limited edaphic conditions via plant-beneficial bacteria.

Lodgepole pine, a prominent Pinaceae tree species native to western North America, is well-known for its ability to thrive in highly disturbed and degraded areas. One such area is the Sub-Boreal Pine-Spruce xeric-cold (SBPSxc) region in British Columbia, Canada, which is characterized by weakly-developed, parched soils that lack an organic forest floor and essential plant-available nutrients. We hypothesized that plant growth-promoting bacteria could play a significant role in sustaining the growth of lodgepole pine trees in the SBPSxc region. Testing this hypothesis, we evaluated plant growth-promoting abilities of six endophytic bacterial strains previously isolated from lodgepole pine trees growing in this region. These bacterial strains significantly enhanced the length and biomass of their natural host (lodgepole pine) as well as a foreign host (hybrid white spruce) in a 540-day long greenhouse trial. This growth stimulation could be linked to the diverse plant growth-promoting (PGP) abilities detected in these strains using in vitro assays for inorganic/organic phosphate-solubilization, siderophore production IAA production, ACC deaminase activity, lytic enzymes (chitinase, β-1,3-glucanase, protease, and cellulase) activity, ammonia production and catalase activity. ACC deaminase activity was also detected in vivo for all strains using ethylene-sensitive plants–canola and tomato. Notably, strains belonging to the Burkholderiaceae family (HP-S1r, LP-R1r and LP-R2r) showed the greatest potential in all PGP assays and enhanced pine and spruce seedling length and biomass by up to 1.5-fold and 4-fold, respectively. Therefore, such bacterial strains with multifarious PGP abilities could be crucial for survival and growth of lodgepole pine trees in the SBPSxc region and could potentially be utilized as bioinoculant for Pinaceae trees in highly disturbed and nutrient-poor ecosystems.

Effect of biochar amendment on the properties of growing media and growth of containerized Norway spruce, Scots pine, and silver birch seedlings

Common practices and several studies have demonstrated the positive effect of biochar amendment on climate change mitigation, soil properties, and plant growth. We performed a greenhouse experiment to assess the potential of wood biochar to improve the properties of the growing media and the growth of seedlings in boreal tree species. We added willow biochar (0%, 5%, 10%, and 20%) to raw peat and measured the growth of Norway spruce (Picea abies (L.) H. Karst.), Scots pine (Pinus sylvestris L.), and silver birch (Betula pendula Roth) seedlings. In addition, the co-effect of biochar amendment with 0%, 50%, and 100% fertilization was estimated. We found that using up to 10% of biochar did not reduce the water retention capacity of the growing media significantly. Moreover, biochar amendment significantly increased carbon, nitrogen, potassium, and phosphorus concentrations and had a significant liming effect on the growing media. The biochar amendment increased the aboveground growth of spruce seedlings and root biomass, as well as the root collar diameter, of birch seedlings. Biochar amendment did not affect the quality of seedlings, estimated by the Dickson’s quality index, for spruce and pine, while the quality of birch increased. Based on our results, biochar has potential in forest seedling production.

Planting time, stocktype and additive effects on the development of spruce and pine plantations in Western Carpathian Mts.

Planting of seedlings is the most reliable and speedy way of forest restoration. Routine spring planting of bareroot seedlings is frequently unsuccessful in central Europe. In this study, the effects of planting time and a spring-pre-planting application of ectomycorrhiza-hydrogel additive Ectovit and hydrogel Stockosorb on the development of bareroot and container Norway spruce and Scots pine seedlings on windthrow area in Western Carpathians, northwest Slovakia were estimated. Survival and aboveground growth parameters during three consecutive years and root dry weight, short root frequency, soil and needle nutrients concentration and ectomycorrhizal fungi root colonization and identification 2 years after planting were assessed. Regardless of planting time and additive, the best developed bareroot spruce (2 + 2) survived significantly better than container spruce (2 + 0), container pine (2 + 0) and especially small-size bareroot pine (1 + 0); bareroot pine was found unsuitable for planting in conditions of planting site. Both additives improved survival of spring-planted container spruce in the summer-drought second year after planting. Container spruce survived and grew significantly better following fall compared to spring planting time. Higher number of short roots was observed in spring than in fall planted bareroot spruce. Neither planting time nor additives affected root dry weight and abundance of ectomycorrhizae. No significant effects of the treatments on pine development were found. Except of K deficiency in container spruce, sufficient or overabundant foliar macro-nutrients concentration was detected. Visual morphotyping of short roots and identification of ectomycorrhizae by DNA analysis indicated inefficient ectomycorrhizal inoculation of seedlings with Ectovit.

Interactions of saprotrophic and root symbiotic fungi control the transformation of humic substances and phosphorus in Norway spruce needle litter

The interactions of fungal guilds have recently been proposed as drivers of organic matter transformation in forest soils. We conducted a pot experiment with Norway spruce seedlings planted in spruce needle litter inoculated with several fungal strains belonging to different ecological guilds (saprotrophic, mycorrhizal, and root endophytic) to assess how the fungi and their interactions affect the transformation of humic substances (HS) and phosphorus (P) in the litter. Several methods for the characterization of P forms and HS were employed, including 31P NMR, UV–Vis and FTIR spectroscopy.Our results show that fungal interactions influence not only the flow of P in decaying (plant) litter but also the transformation of the soil organic matter itself. Pots with saprotrophic Gymnopus androsaceus generally retained more P and prevented the accumulation of phosphonates caused by mycorrhizal Hyaloscypha finlandica, highlighting the strong competitive ability of the former species. The increased mineralization of P caused by G. androsaceus was not observed in the combined treatments, suggesting that other present fungi took up part of the inorganic P. The tested fungi did not affect the amount of HS produced but changed the characteristics of the HS. Mycorrhizal H. finlandica and root endophytic Phialocephala fortinii increased the relative proportion of carboxylic moieties in the HS regardless of the presence or absence of G. androsaceus, probably via the production and incorporation of melanins. The UV–Vis absorbance characteristics of the HS were significantly influenced by fungal interactions. Mycorrhizal H. finlandica and Hebeloma bryogenes retarded humification, as determined by the A4/6 ratio. We attribute the similar shift observed in Serpula himantoides to the partial oxidative degradation of HS.Our study shows that fungal root endophytes can significantly contribute to litter transformation along with mycorrhizal and saprotrophic fungi. The extent and patterns of the transformation seem to be species-dependent in all studied fungal groups.

Seasonal timing and recurrence of methyl jasmonate treatment influence pine weevil damage to Norway spruce seedlings

Defense can be induced in conifer seedlings to reduce pine weevil (Hylobius abietis) damage, by treatment with the plant hormone methyl jasmonate (MJ). Few studies have addressed important practical issues regarding the use of MJ such as treatment incidence and timing, seedling age and its compatibility with plant nursery practices. We examined if levels of pine weevil damage depend on seasonal timing and recurrence of MJ treatment, and if the observed effects depend on plant age. Norway spruce (Picea abies) seedlings from two age cohorts (1 year and 1.5 years old) received four MJ treatments: MJ application before winter storage in the previous year, after winter storage but before spring/summer planting, repeated MJ application (both before winter storage, and before planting) or no MJ application at all. Pine weevil damage was evaluated in a lab and field experiment. We found that the timing and recurrence of MJ treatment affected the amount of damage inflicted by pine weevils in different ways, but these effects were consistent among age cohorts. MJ application before winter storage provided the most effective protection, and this reduction in damage was comparable to that provided by a currently used physical protection method against pine weevil feeding. Our results indicated that MJ can be applied in line with nursery practices (before winter storage) and provides adequate protection for two growing seasons.