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Azim U. Mallik - One of the best experts on this subject based on the ideXlab platform.
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Recruitment and ontogenic patterns of stunting and growth release of black spruce (Picea mariana) in post-fire Kalmia heaths
Forest Ecology and Management, 2018Co-Authors: Azim U. Mallik, Dmitri KravchenkoAbstract:Abstract Recruitment of seed regenerating plants after disturbance depends on adequate seed supply and favourable microsites that allow germination and seedling establishment (safe sites). Forest disturbance in nutrient stressed conifer-ericaceous communities in boreal and temperate forests become quickly dominated by ericaceous shrubs and restrict tree recruitment. Habitat filter due to limitation of safe sites has been attributed to inadequate seedling regeneration. Furthermore, large proportions of the regenerating seedlings exhibit stunted growth but some over time exhibit growth release. Despite wide occurrence of poor natural regeneration of conifers in ericaceous shrubs, the ontogenic patterns of stunting and growth release of conifer seedlings received little attention. We used post-fire black spruce- Kalmia ecosystems to study this. We hypothesized that (i) post-fire residual OM thickness controls seedling recruitment by limiting safe sites even in presence of sufficient seed supply, (ii) black spruce density of a site depends on its OM depth, which controls safe sites, and (iii) partially safe sites, which permit germination and seedling establishment with stunted growth, can become safe sites overtime allowing growth release. We experimentally tested black spruce seed regeneration on seedbeds with variable OM thickness and studied the ontogenic patterns of seedling/sapling growth in eight post-fire Kalmia heaths along an 8–34 year chronosequence. We found that despite ample seed supply OM depth controls seedling recruitment. In the chronosequence study we found only 17.8% of burnt area accounts for occupied safe sites, recruiting only 317 seedlings/ha and only 13% of them exhibit normal growth, others remain stunted for 5–20 yrs. With time, successive cohorts of stunted seedlings overcome growth check. Black spruce density was negatively associated with OM depth and Kalmia cover. The probability of growth release was associated negatively with OM depth and positively with soil respiration. We conclude that poor black spruce regeneration in Kalmia heath is largely due to safe site limitation controlled by OM depth, which also controls seedling stunting and growth release. The novelty of this work is the discovery of ontogenic patterns of conifer seedlings in nutrient stressed habitats. Our findings have implications for tree regeneration in other environmentally and nutritionally stressed ecosystems such as treelines.
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Belowground interactions between Kalmia angustifolia and Picea mariana: roles of competition, root exudates and ectomycorrhizal association
Plant and Soil, 2016Co-Authors: Azim U. Mallik, Shekhar R. Biswas, Laura C. Siegwart CollierAbstract:Background and aims Belowground competition and allelopathic interference of neighbouring plants play important roles in shaping plant performance. We assessed the effect of belowground interactions involving root competition, root exudates and ectomycorrhizal (ECM) association between Kalmia and black spruce on above- and belowground biomass increment and foliar nutrient content of black spruce seedlings. We predicted that root competition and root exudates of Kalmia would exert a negative impact on black spruce performance, while ECM in black spruce would exert positive impacts on its performance.
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Growth release of stunted black spruce (Picea mariana) in Kalmia heath: The role of ectomycorrhizal fungi and near-ground microclimate
Canadian Journal of Forest Research, 2016Co-Authors: Philippe St. Martin, Azim U. MallikAbstract:Naturally regenerating and planted black spruce (Picea mariana (Mill.) B.S.P.) in post-fire landscapes in eastern Canada often exhibit stunted growth in the presence of ericaceous shrubs such as Kalmia angustifolia L. After a period of stunted growth, some seedlings experience a growth release, exhibiting growth rates closer to normally growing seedlings. We hypothesized that an increase in colonization of root tips by ectomycorrhizal (ECM) fungi is responsible for this release and that the percentage of root tips colonized by ECM fungi would be higher on seedlings that had a released or normally growing neighbour within close proximity. We quantified ECM fungi diversity and abundance from 255 soil cores from stunted, released, and normally growing black spruce seedlings sampled in two Kalmia-dominated sites in Newfoundland. Growth and microsite characteristics around each seedling were also measured. We found that normal and released seedlings had significantly higher proportions of ECM fungi root tips t...
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Black spruce (Picea mariana) restoration in Kalmia heath by scarification and microsite mulching
Forest Ecology and Management, 2016Co-Authors: Azim U. Mallik, Dmitri KravchenkoAbstract:Abstract 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 13 year-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 (10 years) monitoring is necessary before the method can be applied as a restoration tool.
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Morphological and ecophysiological responses of sheep laurel (Kalmia angustifolia L.) to shade
Forestry, 2012Co-Authors: Azim U. Mallik, Jian R. Wang, Laura S. Siegwart-collier, Bruce A. RobertsAbstract:Summary Dominant understorey shrubs can interfere with tree recruitment and affect forest succession. In boreal forests of eastern Canada, Kalmia angustifolia grows vigorously dominating post-harvest black spruce (Picea mariana (Mill.) BSP) forests and interferes with tree regeneration. Kalmia is a dominant understorey in all stages of forest development, but its response to canopy light level is unknown. We studied the morphological and physiological responses of Kalmia in open sun (control) and experimentally low, medium and high shades allowing 100, 60, 32 and 19 per cent of full sunlight representing 0, 40, 68, and 81 per cent shade, respectively. We tested the hypothesis that Kalmia responds positively to moderate shade by adapting morphologically with larger leaf area and fewer flowering shoots and physiologically by increased stomatal conductance, photosynthesis and foliar nitrogen than low or high shade. We found significantly increased leaf area, specific leaf area and decreased flowering shoots with increasing shade. Kalmia aboveground biomass was 31 per cent higher in low shade and 22 per cent lower in high shade compared with control. The highest maximum photosynthetic capacity (Amax) of Kalmia (9 µmol CO2 m 2 s 1 ) was found in control (full sunlight) and the lowest (5 µmol CO2 m 2 s 1 ) in the medium-shade treatment. We concluded that Kalmia adapts to moderate shade by morphological plasticity, reproductive trade-off (avoiding sexual reproduction) and physiological acclimation to low light.
Robert L Bradley - One of the best experts on this subject based on the ideXlab platform.
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The spread of Kalmia angustifolia on black spruce forest cutovers contributes to the spatial heterogeneity of soil resources.
PloS one, 2018Co-Authors: Gilles Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Kalmia angustifolia is a boreal ericaceous shrub that can rapidly spread on black spruce forest cutovers in eastern Canada, where CPRS (i.e. Cutting with Protection of Regeneration and Soils") is practiced. The proliferation of Kalmia often coincides with a reduction in the growth rate of regenerating black spruce seedlings. We report on a study where we compared the local effects of Kalmia and black spruce seedling patches (i.e. two types of "Vegetation") on chemical and biochemical soil properties in CPRS cutovers within mesic spruce-moss and xeric spruce-lichen ecosystems, as well as in four mature spruce-moss forests (i.e. three "Site Types"). Results from 13C-CPMAS-NMR revealed lower O-alkyl C (i.e. carbohydrates), higher aromatic C (i.e. lignin and other phenolics) and higher carbonyl-C (i.e. amide-C and carboxyl groups) in spruce-moss than in spruce-lichen forest floors (F-horizon). In spite of these distinctions, we observed only a small number of Site Type x Vegetation interactions controlling soil properties. Vegetation had a significant effect on ten forest floor properties. Most notably, Kalmia patches had higher concentrations of condensed tannins and lower mineral N cycling. On the other hand, Site Type had a relatively greater effect on the deeper podzolic-B horizons, where mineral N and microbial activity were higher in mature spruce-moss forests than in the cutovers. Green and senescent Kalmia leaves collected at these sites had higher N, tannin and phenolic concentrations than green and senescent spruce needles. A 25 month litter bag study found lower decomposition of Kalmia leaf litter in spruce patches on spruce-lichen cutovers compared to spruce patches on spruce-moss cutovers, or to Kalmia patches on spruce-lichen cutovers. Given that black spruce seedlings obtain most of their nutrients from the forest floor, our results suggest that CPRS may have long-term negative effects on black spruce forest productivity if the spread of Kalmia is left unchecked.
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Chemical properties of fresh and senescent Kalmia leaves, Kalmia roots, and fresh and senescent spruce needles collected on different site types.
2018Co-Authors: Gilles D. Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Chemical properties of fresh and senescent Kalmia leaves, Kalmia roots, and fresh and senescent spruce needles collected on different site types.
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Mineral podzolic B horizon properties that were significantly (P
2018Co-Authors: Gilles D. Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Different upper-case letters indicate significant differences between Site Types, whereas significant differences between spruce and Kalmia patches are written at the top of each frame. Vertical lines = 1 SD.
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Mineral Ae horizon properties that were significantly (P
2018Co-Authors: Gilles D. Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Different upper-case letters indicate significant differences between Site Types, whereas significant differences between spruce and Kalmia patches are written at the top of each frame. Significant Site Type x Vegetation interactions are explained in the Results section. Vertical lines = 1 SD.
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Forest floor F-layer properties that were significantly (P
2018Co-Authors: Gilles D. Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Different upper-case letters indicate significant differences between Site Types, whereas significant differences between spruce and Kalmia patches are written at the top of each frame. Significant Site Type x Vegetation interactions are explained in the Results section. Vertical lines = 1 SD.
Nelson Thiffault - One of the best experts on this subject based on the ideXlab platform.
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Regenerating Kalmia sites in Québec: What we know and what we wish we knew
2014Co-Authors: Nelson Thiffault, Ph. D, F. EngAbstract:On some sites, invasion by ericaceous shrubs can induce ecosystem retrogression, a phenomenon that has important effects on forest productivity, and possibly biodiversity. Fine-tuning and optimization of management strategies for invaded sites are clearly needed, along with the development of preventive silvicultural approaches based on solid ecological grounds. We recently demonstrated how Kalmia and Vaccinium dominate the nutrient uptake processes, and that their recalcitrant humus has striking impacts on soil temperature. Kalmia and associated species do not seem to directly influence soil temperature or moisture, or to induce water stress to planted seedlings. Ongoing research, in collaboration with academic and industrial partners, will provide further understanding of ericad distribution in Québec’s boreal forest, their impacts on conifer seedlings and soil microbiology, and their responses to innovative silvicultural systems
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The Relative Importance of Nitrogen vs. Moisture Stress May Drive Intraspecific Variations in the SLA-RGR Relationship: The Case of Picea mariana Seedlings
2013Co-Authors: Robert L Bradley, Nelson ThiffaultAbstract:Copyright © 2013 Philippe LeBel et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Plants acclimate to nitrogen (N) or moisture stress by respectively increasing photosynthetic N use efficiency (PNUE) or water use efficiency (WUE), in order to maximize their relative growth rate (RGR). These two phenotypic adapta-tions have opposite effects on specific leaf area (SLA). Thus, intraspecific variations in the SLA-RGR relationship should reflect the relative importance of N vs. moisture stress in plants. In this study, we measured needle gas ex-changes and N concentrations in order to derive PNUE and WUE, as well as SLA and RGR of black spruce (Picea mariana) seedlings growing on a rapidly drained site in the presence or absence of Kalmia angustifolia. The eradication of Kalmia had resulted in a ~140 % increase in seedling growth over a 6 year period. We found a negative SLA-RGR relationship where Kalmia had been eradicated, and a positive one where Kalmia had been maintained. Kalmia eradica-tion resulted in higher WUE when measurements were made directly on the seedlings, and in lower PNUE when twigs were rehydrated prior to gas exchange measurements. Our data suggest that the bigger seedlings on Kalmia-eradicated plots increase RGR by decreasing SLA, as a means of coping with moisture stress. By contrast, increasing SLA on non-eradicated plots may be a means of coping with nutrient stress exerted by Kalmia. The SLA-RGR relationship coul
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The Relative Importance of Nitrogen vs. Moisture Stress May Drive Intraspecific Variations in the SLA-RGR Relationship: The Case of Picea mariana Seedlings
American Journal of Plant Sciences, 2013Co-Authors: Philippe Lebel, Robert L Bradley, Nelson ThiffaultAbstract:Plants acclimate to nitrogen (N) or moisture stress by respectively increasing photosynthetic N use efficiency (PNUE) or water use efficiency (WUE), in order to maximize their relative growth rate (RGR). These two phenotypic adaptations have opposite effects on specific leaf area (SLA). Thus, intraspecific variations in the SLA-RGR relationship should reflect the relative importance of N vs. moisture stress in plants. In this study, we measured needle gas exchanges and N concentrations in order to derive PNUE and WUE, as well as SLA and RGR of black spruce (Picea mariana) seedlings growing on a rapidly drained site in the presence or absence of Kalmia angustifolia. The eradication of Kalmia had resulted in a ~140% increase in seedling growth over a 6 year period. We found a negative SLA-RGR relationship where Kalmia had been eradicated, and a positive one where Kalmia had been maintained. Kalmia eradication resulted in higher WUE when measurements were made directly on the seedlings, and in lower PNUE when twigs were rehydrated prior to gas exchange measurements. Our data suggest that the bigger seedlings on Kalmia-eradicated plots increase RGR by decreasing SLA, as a means of coping with moisture stress. By contrast, increasing SLA on noneradicated plots may be a means of coping with nutrient stress exerted by Kalmia. The SLA-RGR relationship could potentially be used to identify the limiting resource for black spruce seedlings in different environments.
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Initial distance to Kalmia angustifolia as a predictor of planted conifer growth
New Forests, 2012Co-Authors: Nelson Thiffault, Geneviève Picher, Isabelle AugerAbstract:In the Canadian boreal forest, conifer plantations are mainly used to overcome poor natural regeneration following harvesting or wildfires. However, competitive interactions can impair the successful establishment of forest plantations, especially in the presence of ericaceous species, such as Kalmia angustifolia, that are good competitors for soil resources. We used data from a silvicultural trial established in northwestern Quebec (Canada) to test the hypothesis that Kalmia’s effect on seedling growth is an asymptotic nonlinear function of proximity to Kalmia at time of planting. Our main objective was to derive species-specific thresholds of Kalmia-proximity tolerance at the time of planting for boreal sites prone to Kalmia invasion following harvesting. Using nonlinear quantile regressions (90th percentile), height, diameter and growth of planted Picea mariana and Pinus banksiana seedlings over 8 years was regressed against the initial distance to the nearest Kalmia stem at time of planting. We also investigated the relation between annual growth and the distance to nearest Kalmia stem during any given year between age 2 and 8-years. Finally, we evaluated how mechanical soil scarification influenced Kalmia recovery over time by looking at its rate of spread, estimated from mean distance to planted seedlings over 8 years. Silvicultural treatments increased the intercepts and asymptotes of all variables for Pinus. However, asymptotic values for Picea could not be identified, thus precluding threshold assessment for initial distance to Kalmia at planting for this species. For Pinus planted on scarified sites, a Kalmia-free radius of 60 cm would lead to ~80 to 85 % of the 90th percentile of maximum potential height at age 8 years. Mechanical scarification created Kalmia-free microsites that were rapidly re-invaded by spread of Kalmia; planting immediately following soil preparation of these sites is therefore important for ensuring successful plantation establishment.
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Controlling Kalmia and reestablishing conifer dominance enhances soil fertility indicators in central Newfoundland, Canada
Canadian Journal of Forest Research, 2009Co-Authors: Martin T. Moroni, Nelson Thiffault, Brian D Titus, Christina Mantec. Mante, Franz MakeschinAbstract:Growth rates of young conifers can be poor on disturbed sites dominated by Kalmia angustifolia L. Hence, a conifer revegetation trial was established on a Kalmia-dominated site to evaluate the effects of various silvicultural options and planted species on selected soil organic layer characteristics. Larix laricina (Du Roi) K. Koch, Pinus banksiana Lamb., and Picea mariana (Mill.) BSP seedlings were planted in plots with or without Kalmia control with herbicides. The effect of fertilizer amendment was also assessed. Seventeen years postplanting, organic layer fertility indicators suggest that soil fertility improved after Kalmia control and conifer reestablishment, especially if nitrogen (N) – phosphorus – potassium fertilizer was also applied. When Kalmia was controlled, aerobically mineralizable N and exchangeable sodium concentrations were increased; fertilizer addition to herbicided plots also increased exchangeable potassium and calcium concentrations, and cation exchange capacity compared with untre...
Gilles Joanisse - One of the best experts on this subject based on the ideXlab platform.
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The spread of Kalmia angustifolia on black spruce forest cutovers contributes to the spatial heterogeneity of soil resources.
PloS one, 2018Co-Authors: Gilles Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Kalmia angustifolia is a boreal ericaceous shrub that can rapidly spread on black spruce forest cutovers in eastern Canada, where CPRS (i.e. Cutting with Protection of Regeneration and Soils") is practiced. The proliferation of Kalmia often coincides with a reduction in the growth rate of regenerating black spruce seedlings. We report on a study where we compared the local effects of Kalmia and black spruce seedling patches (i.e. two types of "Vegetation") on chemical and biochemical soil properties in CPRS cutovers within mesic spruce-moss and xeric spruce-lichen ecosystems, as well as in four mature spruce-moss forests (i.e. three "Site Types"). Results from 13C-CPMAS-NMR revealed lower O-alkyl C (i.e. carbohydrates), higher aromatic C (i.e. lignin and other phenolics) and higher carbonyl-C (i.e. amide-C and carboxyl groups) in spruce-moss than in spruce-lichen forest floors (F-horizon). In spite of these distinctions, we observed only a small number of Site Type x Vegetation interactions controlling soil properties. Vegetation had a significant effect on ten forest floor properties. Most notably, Kalmia patches had higher concentrations of condensed tannins and lower mineral N cycling. On the other hand, Site Type had a relatively greater effect on the deeper podzolic-B horizons, where mineral N and microbial activity were higher in mature spruce-moss forests than in the cutovers. Green and senescent Kalmia leaves collected at these sites had higher N, tannin and phenolic concentrations than green and senescent spruce needles. A 25 month litter bag study found lower decomposition of Kalmia leaf litter in spruce patches on spruce-lichen cutovers compared to spruce patches on spruce-moss cutovers, or to Kalmia patches on spruce-lichen cutovers. Given that black spruce seedlings obtain most of their nutrients from the forest floor, our results suggest that CPRS may have long-term negative effects on black spruce forest productivity if the spread of Kalmia is left unchecked.
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Sequestration of soil nitrogen as tannin-protein complexes may improve the competitive ability of sheep laurel (Kalmia angustifolia) relative to black spruce (Picea mariana).
The New phytologist, 2008Co-Authors: Gilles Joanisse, Robert L Bradley, Caroline M. Preston, Gary D. BendingAbstract:Summary • The role of litter tannins in controlling soil nitrogen (N) cycling may explain the competitive ability of Kalmia relative to black spruce (Picea mariana), although this has not been demonstrated experimentally. • Here, the protein-precipitation capacities of purified tannins and leaf extracts from Kalmia and black spruce were compared. The resistance to degradation of tannin–protein precipitates from both species were compared by monitoring carbon (C) and N dynamics in humus amended with protein, purified tannins or protein–tannin precipitates. The purity of the precipitates was verified using solid-state 13C nuclear magnetic resonance (NMR) spectra. The ability of mycorrhizal fungi associated with both species to grow on media amended with tannin–protein complexes as the principal N source was also compared. • The protein precipitation capacity of Kalmia tannins was superior to those of black spruce. Humus amended with protein increased both mineral and microbial N, whereas humus amended with tannin–protein precipitates increased dissolved organic N. Mycorrhizal fungi associated with Kalmia showed better growth than those associated with black spruce when N was provided as tannin–protein precipitates. • These data suggest that Kalmia litter increases the amount of soil N sequestered as tannin–protein complexes, which may improve the competitive ability of Kalmia relative to black spruce by favouring N uptake by mycorrhizas associated with the former.
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Do late-successional tannin-rich plant communities occurring on highly acidic soils increase the DON/DIN ratio?
Biology and Fertility of Soils, 2008Co-Authors: Gilles Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Previous studies suggested that late-successional tannin-rich plant communities increase the amount of dissolved organic N (DON) relative to dissolved inorganic N (DIN) in decomposing litter. We devised an experiment to test this hypothesis by adding varying proportions of black spruce (Picea mariana) and tannin-rich Kalmia angustifolia litter to forest floor samples collected on six black spruce cutovers. An increasing proportion of Kalmia litter increased condensed tannin and total phenolic concentrations over the course of a 46-week incubation period. Mineral N concentrations did not vary among treatments in spite of much higher total N concentrations in Kalmia litter. This was more likely due to the formation of protein–tannin complexes rather than microbial immobilization of N, as indicated by the decline in available C with increasing Kalmia litter on two of the five sampling dates. There was a significant positive linear trend between the proportion of Kalmia litter and the DON/DIN ratio on one sampling date (week 13) only. Results suggest that the DON/DIN ratio is controlled by confounding factors (e.g., tannins bonding with non-extractable humus particles) and has limited value for describing ecological succession.
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Soil enzyme inhibition by condensed litter tannins may drive ecosystem structure and processes: the case of Kalmia angustifolia.
The New phytologist, 2007Co-Authors: Gilles Joanisse, Robert L Bradley, Caroline M. Preston, Alison D. MunsonAbstract:Kalmia angustifolia is an ericaceous shrub that can rapidly spread on recently harvested boreal forest sites, causing a slow-down in soil nutrient cycling and reduced growth of spruce seedlings. It has been hypothesized that tannins released from Kalmia litter suppress soil enzyme activity, and are thus important in controlling ecosystem structure and processes. Here the effects of different concentrations of tannins extracted from both Kalmia and black spruce (Picea mariana) foliage were tested on enzyme activities of soil extracts. Then the effects of various Kalmia-black spruce litter mixtures on soil enzyme activity were investigated. Lastly, the correlation between Kalmia cover in the field and soil enzyme activity was measured. Both tannin types suppressed beta-glucosidase and acid phosphatase activities, and the magnitude of these effects was concentration-dependent. beta-glucosidase and amidase activity decreased linearly with an increasing Kalmia : spruce litter ratio added to soil. A field survey of 24 sites revealed a negative relationship between percentage Kalmia cover and beta-glucosidase activity. Collectively, results of the three experiments converge to support the claim that enzyme inhibition by litter tannins has evolved as an important mechanism controlling ecosystem processes and structure following Kalmia invasion on recently disturbed forest sites.
Caroline M. Preston - One of the best experts on this subject based on the ideXlab platform.
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The spread of Kalmia angustifolia on black spruce forest cutovers contributes to the spatial heterogeneity of soil resources.
PloS one, 2018Co-Authors: Gilles Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Kalmia angustifolia is a boreal ericaceous shrub that can rapidly spread on black spruce forest cutovers in eastern Canada, where CPRS (i.e. Cutting with Protection of Regeneration and Soils") is practiced. The proliferation of Kalmia often coincides with a reduction in the growth rate of regenerating black spruce seedlings. We report on a study where we compared the local effects of Kalmia and black spruce seedling patches (i.e. two types of "Vegetation") on chemical and biochemical soil properties in CPRS cutovers within mesic spruce-moss and xeric spruce-lichen ecosystems, as well as in four mature spruce-moss forests (i.e. three "Site Types"). Results from 13C-CPMAS-NMR revealed lower O-alkyl C (i.e. carbohydrates), higher aromatic C (i.e. lignin and other phenolics) and higher carbonyl-C (i.e. amide-C and carboxyl groups) in spruce-moss than in spruce-lichen forest floors (F-horizon). In spite of these distinctions, we observed only a small number of Site Type x Vegetation interactions controlling soil properties. Vegetation had a significant effect on ten forest floor properties. Most notably, Kalmia patches had higher concentrations of condensed tannins and lower mineral N cycling. On the other hand, Site Type had a relatively greater effect on the deeper podzolic-B horizons, where mineral N and microbial activity were higher in mature spruce-moss forests than in the cutovers. Green and senescent Kalmia leaves collected at these sites had higher N, tannin and phenolic concentrations than green and senescent spruce needles. A 25 month litter bag study found lower decomposition of Kalmia leaf litter in spruce patches on spruce-lichen cutovers compared to spruce patches on spruce-moss cutovers, or to Kalmia patches on spruce-lichen cutovers. Given that black spruce seedlings obtain most of their nutrients from the forest floor, our results suggest that CPRS may have long-term negative effects on black spruce forest productivity if the spread of Kalmia is left unchecked.
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Chemical properties of fresh and senescent Kalmia leaves, Kalmia roots, and fresh and senescent spruce needles collected on different site types.
2018Co-Authors: Gilles D. Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Chemical properties of fresh and senescent Kalmia leaves, Kalmia roots, and fresh and senescent spruce needles collected on different site types.
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Mineral podzolic B horizon properties that were significantly (P
2018Co-Authors: Gilles D. Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Different upper-case letters indicate significant differences between Site Types, whereas significant differences between spruce and Kalmia patches are written at the top of each frame. Vertical lines = 1 SD.
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Mineral Ae horizon properties that were significantly (P
2018Co-Authors: Gilles D. Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Different upper-case letters indicate significant differences between Site Types, whereas significant differences between spruce and Kalmia patches are written at the top of each frame. Significant Site Type x Vegetation interactions are explained in the Results section. Vertical lines = 1 SD.
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Forest floor F-layer properties that were significantly (P
2018Co-Authors: Gilles D. Joanisse, Robert L Bradley, Caroline M. PrestonAbstract:Different upper-case letters indicate significant differences between Site Types, whereas significant differences between spruce and Kalmia patches are written at the top of each frame. Significant Site Type x Vegetation interactions are explained in the Results section. Vertical lines = 1 SD.
