Growth Of Black Spruce Seedlings Research Articles

Mechanical scarification can reduce competitive traits of boreal ericaceous shrubs and improve nutritional site quality

Abstract Ericaceous shrubs often interfere with the growth of black spruce seedlings on regenerating forest sites in Eastern Canada. Mechanical site preparation such as scarification may improve this situation, but it is uncertain whether this is solely due to a reduction in direct competition from the shrubs, or also from a sustained improvement in nutritional site quality. We sampled experimental plots in two boreal climate regions (i.e. warmer-drier Abitibi vs. cooler-wetter Côte-Nord) where scarification, performed 18 years earlier, had increased the growth of black spruce relative to non-scarified plots. Trees of scarified plots had closed the canopy more than trees of non-scarified plots in Côte-Nord, but not in Abitibi. Total ground cover of ericaceous shrubs was lower in scarified plots at both sites, the main species being Kalmia angustifolia (i.e. Kalmia) in Abitibi and Rhododendron groenlandicum (i.e. Labrador tea) in Côte-Nord. Scarified plots at both sites had significantly shorter current-year ericaceous rhizomes than non-scarified plots, but the difference between treatments was significantly greater in Côte-Nord than in Abitibi. In Côte-Nord, ericaceous shrubs on scarified plots had a lower specific rhizome mass, higher specific leaf area, lower tannin and higher N concentrations in leaves and litter, and lower N use efficiency than on non-scarified plots. By comparison, scarification in Abitibi affected only one foliar property, namely a reduction in the C:N ratio of Kalmia leaf litter. Forest floor N mineralization rates and black spruce needle N concentrations were higher in scarified than non-scarified plots across both sites. Taken collectively, results suggest that mechanical scarification on ericaceous shrub-dominated cutovers can reduce competitive traits of boreal ericaceous shrubs and improve nutritional site quality, especially in cooler-wetter climates.Highlights

Development of a Biochar-Based Substrate Added with Nitrogen from a Mining Effluent for the Production of Picea mariana Seedlings

Ammoniacal nitrogen (N-NH3) is one of the pollutants that has adverse effects on the environment and is present in most effluents generated by mining operations. Therefore, mining companies must manage it to keep it below the regulated discharge criteria to avoid environmental contamination. In this context, the present study aims to valorize N-NH3 in the form of ammonium sulphate ((NH4)2SO4) for the manufacture of biochar pellets used as growth substrates for the production of forest seedlings. The biochar was first produced by fast pyrolysis, at 320 °C, and different recipes of pellets were then prepared to evaluate their hardness, binder type and content, humidity and durability. The optimal granule chosen was composed of biochar, corn starch and canola oil. Six combinations of different compositions were then prepared as substrates for black spruce growth: (1) Peat (P); (2) Peat and bulk biochar (PB); (3) Peat and bulk biochar impregnated with ammonium sulfate (PBAS); (4) Peat and biochar pellets impregnated with water (PBPeW); (5) Peat and biochar pellets impregnated with an ammonium sulfate solution (PBPeAS); (6) Peat, biochar pellets impregnated with ammonium sulfate and perlite (PBPeASPer). The effects of these substrates on the growth of black spruce seedlings, as well as fertilizer leaching, were measured. The results show that seedling biomass is equivalent to the control for the granular treatment, but higher biomass was obtained with bulk biochar (PB). This shows that a quarter of peat could be replaced by biochar to obtain similar or even better results of biomass yield and, consequently, solve part of the supply issue. As to plant nutrition, no tendency was observed for the experiments apart from the higher proportion of Ca in spruce needles. The prepared biochar-based pellet substrate appears to not only be advantageous for spruce production but also for other uses such as golf courses, forestry producers and horticultural nurseries using conventional fertilizers and peat as growing media. In addition, these approaches could help the Abitibi-Témiscamingue region in Québec, Canada to build a local circular economy.

Kalmia removal increases nutrient supply and growth of black spruce seedlings: An effect fertilizer cannot emulate

In Canada's eastern boreal forest, the stagnant growth of black spruce ( Picea mariana (Mill.) BSP) seedlings is often observed in the presence of ericaceous shrubs such as Kalmia angustifolia L. Many mechanisms, including allelopathic interference, reduced soil N mineralization, soil enzymes inhibition, and direct resource competition have been proposed to explain poor spruce growth in the presence of Kalmia. However, the relative importance of direct competition versus indirect interference remains unclear. Our objective was thus to adequately isolate the “ Kalmia effect” from other growth-limiting factors and to determine if removal of Kalmia also resulted in fundamental changes in the biochemical properties of the forest floor. By sampling plots established in 2000, we evaluated how Kalmia eradication and spot fertilization influenced soil nutrient availability, N mineralization rates, microbial basal respiration and biomass, as well as planted black spruce seedling growth, dimensions, and foliar nutrient concentrations 6 years later. We measured higher extractable-P, mineralizable-N, seedling dimensions and growth rates, as well as lower extractable-K, total-K, basal respiration and microbial biomass, in plots without Kalmia than in those where Kalmia had been maintained from 2000 to 2006. Our results thus confirmed that Kalmia eradication over 6 years not only improved the growth and nutrition of black spruce seedlings, but also resulted in fundamental changes in the biochemical properties of the forest floor. We demonstrated that along with direct competition for resources, Kalmia interferes indirectly with black spruce by modifying nutrient cycling and energy fluxes in soil. Higher indices of available C in plots with Kalmia corroborates that Kalmia tannins or rhizodeposition may reduce N mineralization by stimulating microbial immobilization, a relation that however needs to be confirmed with longer term laboratory incubations. Our results indicated that although it had a positive influence on seedling growth, the fertilization effect was confined to the first few years following treatment application, and failed to influence soil processes as did Kalmia eradication. Further monitoring will indicate if the increased litterfall in fertilized plots will eventually initiate a second wave of fertilizer-induced changes to soil processes, as observed in other ecosystems.

The effect of carbon and nutrient loading during nursery culture on the growth of black spruce seedlings: a six-year field study

We tested the effects of exponential nutrient loading and springtime carbon loading during nursery culture on the field performance of black spruce (Picea mariana (Mill.) B.S.P.). Seedlings were grown from seed with a conventional, fixed dose fertilizer (10 mg N seedling−1) or an exponential nutrient loading regime (75 mg N seedling−1). The following spring, seedlings were exposed for two weeks to either ambient (370 ppm) or elevated levels of CO2 (800 ppm) and then planted in the field; seedling growth was followed for the next six years. Exponential nutrient loading increased seedling height, stem diameter and leader growth, with the largest increases in height and leader length occurring in the first three years after outplanting. Carbon loading increased seedling height and leader length, but only in seedlings that had been exponentially nutrient loaded. A combination of carbon and nutrient loading increased shoot height 26%, stem diameter 37% and leader length 40% over trees that received neither treatment. These results demonstrate that the growth enhancement seen under exponential nutrient loading is maintained under field conditions for at least six years. Carbon loading just before outplanting was a useful supplement to nutrient loading, but was ineffective in the absence of nutrient loading.

Growth of black spruce seedlings planted in burned, logged, and undisturbed boreal mixedwood stands of southeastern Manitoba

Growth of black spruce seedling planted in burned, harvested, and undisturbed boreal mixedwood stands was studied in southeastern Manitoba. Although seedlings on each site were subjected to similar light competition (measured by % of full sunlight received at the middle crown of each crop seedling in 1998), mean annual growth of height, root collar diameter and aboveground biomass was different among the three sites, with burned > logged > undisturbed. During each of last seven years (1992 to 1998 except 1997), the burned site had greater annual height growth than the logged and undisturbed sites. Similarly, the logged site had greater height growth than the undisturbed site except 1997 and 1998. Relative competition intensity (calculated based on annual height growth from 1992 to 1998) fluctuated between 0.70 to 0.76 on the undisturbed site, increased from 0.48 to 0.73 on the logged site, and increased from 0.23 to 0.74 on the burned site. Relative competition intensity remained similar in the most recent three years (1996–1998) despite larger differences found in earlier years (1992–1995) between sites. A significant relationship was found between the relative competition intensity and % full sunlight on each site. Results from this case study suggested that, by affecting the development of competing vegetation, the type/intensity of past disturbances created different competition dynamics for black spruce seedlings planted on the burned, logged and undisturbed sites. Key words: interspecific competition, vegetation management, competition dynamics, plantation

Effect of straw residues on black spruce seedling growth and mineral nutrition, under greenhouse conditions

The potential allelopathic (phytotoxic or beneficial) effect of barley, oat, and wheat straw mulches was evaluated on growth, mineral nutrition, and mycorrhizal status of black spruce seedlings, under greenhouse conditions. The various straws did not affect spruce seedling height growth over a 2-month growth period. The newly formed fine roots of treated and control seedlings were mycorrhizal. Oat and wheat straw significantly enhanced foliar phosphorus content, as compared with the control. All treatments significantly depressed foliar manganese content, indicating that the straws could exert a detrimental effect on manganese uptake. Therefore, it is suggested that monitoring the status of manganese in planted spruce seedlings when using allelopathic cover straw mulches be used as a method for preventing the establishment of weed species.

AL uptake by black spruce seedlings: Persistence of organic acids in al treated rooting cultures

Experiments were conducted to monitor the pH and the persistence of simple organic acids (oxalic, citric, malic, glycolic acid) with and without Al complexation in rooting cultures (sand, peat, solution-only) under non-sterile conditions, and to characterize pertinent short-term responses of black spruce seedlings (Picea mariana [Mill.]) to subsequent changes in the rooting solutions. It was shown that the organic acids decayed within about five days unless the cultures were treated with a decay-controlling fungicide such as Captan, an antoxidant containing N-(trichloromethylthio)-4-cyclohexene-12-dicarboximide. Aluminum complexation did not increase the persistence of the organic acids except for oxalic acid. In all cases, the decay of the organic acids (or of the equivalent carboxylates) led to a simultaneous increase of solution pH which was most pronounced in the non-buffered solution cultures without Al. Captan did not affect the growth of black spruce seedlings, but was lethal to yellow birch (Betula alleghaniensis Britton) seedlings. The pH of tissuemized roots taken from the black spruce seedlings following treatments with oxalate and citrate (within and without Al) reflected the change of pH within the culture solutions.

Inhibition of black spruce seedling growth by forest-floor substrates of central Newfoundland

The objective of this study was to determine if seedbed substrates consisting of F and H organic matter and Ae and Bf mineral material inhibited seed germination and subsequent seedling growth of black spruce. The study was conducted with seedbed substrates collected from eight pure blackspruce stands of four age classes (15, 30, 45 and 60 years) in central Newfoundland. No significant effect on percentage germination or primary shoot growth of seedlings was obtained when grown on F and H organic matter, Ae and Bf mineral material. However, growth and development of primary roots was significantly reduced in the F and H organic matter and Ae mineral material compared to the controls (washed sand). The inhibitory effect increased with stand age. The affected seedlings did not produce normal primary roots with root hairs. The primary root cells of the affected seedlings were significantly broader and shorter compared to the control seedlings. Mineral material from the Bf horizon did not have any significant effect on primary root growth of black spruce seedlings.

Allelopathic potential of Kalmia angustifolia to black spruce ( Picea mariana)

Effects of water extracts of leaves, root, litter and soil of Kalmia angustifolia were tested on seed germination and primary root and shoot development of black spruce seedlings. Litter and soil extracts were found to be most inhibitory to primary root development. There was no significant difference in germination percentage and shoot growth of seedlings due to the treatments. Inhibition of root development in the affected seedlings was attributed to unknown water soluble substance(s) present in the litter and soil under Kalmia plants. The affected seedlings produced a curved blunt-ended extension of the root-shoot transition region which was devoid of a root cap and root hairs. A stair-step-pot sand culture experiment in the greenhouse indicated that water leachate passing through both Kalmia canopy and soil significantly reduced the early growth of black spruce seedlings. Reductions of 23, 44, and 47% in height growth were observed in the 1st, 2nd and 3rd month, respectively, after planting. This decrease in plant growth may be caused by chemical interference in the mycorrhizal association of black spruce due to the presence of Kalmia.

The Effect of Excess Soil Copper on the Growth of Black Spruce and Green Alder Seedlings

Increasing additions of Cu to soil up to 150 ppm decreased the growth of black spruce (Picea mariana [Mill.] B.S.P.) seedlings as measured by dry-weight production in 13-14 wk of growth after germination. The addition of lime and/or fertilizer improved the growth of black spruce seedlings at all Cu levels. Generally, fertilizer improved growth more at low Cu levels, and lime improved growth more at high Cu levels. Increased soil Cu concentrations had a much more drastic effect on the growth of green alder (Alnus crispa [Ait.] Pursh) seedlings, and lime fertilizer additions had much less of an ameliorative effect. In fact, the addition of lime at low Cu levels was in itself detrimental to alder seedling growth. Nodule biomass per seedling was very closely related to seedling biomass. In the unlimed soil there was no nodule production at Cu applications above 100 ppm. Nodule activity, however, seemed to be less affected by Cu per se than by the effect of Cu on the whole plant. Green alder would not appear, therefore, to be a useful species to use in the reclamation of soils with high Cu concentrations.