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Janusz J. Zwiazek - One of the best experts on this subject based on the ideXlab platform.
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effects of ph and mineral nutrition on growth and physiological responses of trembling aspen Populus tremuloides jack pine pinus banksiana and white spruce picea glauca seedlings in sand culture
Plants (Basel Switzerland), 2020Co-Authors: Maryamsadat Vaziriyeganeh, Janusz J. ZwiazekAbstract:Responses of trembling aspen (Populus tremuloides), jack pine (Pinus banksiana), and white spruce (Picea glauca) seedlings to root zone pH ranging from 5 to 9 were studied in sand culture in the presence of two mineral nutrition levels. After eight weeks of treatments, effects of pH on plant dry weights varied between the plant species and were relatively minor in white spruce. Higher nutrient supply significantly increased dry weights only in trembling aspen subjected to pH 5 treatment. There was little effect of pH and nutrition level on net photosynthesis and transpiration rates in white spruce and jack pine, but net photosynthesis markedly declined in aspen at high pH. Chlorophyll concentrations in young foliage decreased the most in trembling aspen and jack pine. The effects of high pH treatments on the concentrations of Mg, P, Ca, Mn, Zn, and Fe in young foliage varied between the plant species with no significant decreases of Fe and Zn recorded in trembling aspen and white spruce, respectively. This was in contrast to earlier reports from the studies carried out in hydroponic culture. The sand culture system that we developed could be a more suitable alternative to hydroponics to study plant responses to pH in the root zone. Plant responses to high pH appear to involve complex events with a likely contribution of nutritional effects and altered water transport processes.
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Effects of iron and root zone pH on growth and physiological responses of paper birch (Betula papyrifera), trembling aspen (Populus tremuloides) and red-osier dogwood (Cornus stolonifera) seedlings in a split-root hydroponic system
Acta Physiologiae Plantarum, 2019Co-Authors: Feng Xu, Xiangfeng Tan, Wen-qing Zhang, Janusz J. ZwiazekAbstract:Iron deficiency that is induced by high soil pH is a major factor affecting plant growth in calcareous soils and in some areas that have been reclaimed following industrial activities. Since the effects of high soil pH commonly involve Fe deficiency, in this study, we examined whether Fe provided to part of the root system exposed to low pH would alleviate high pH stress in paper birch ( Betula papyrifera ), trembling aspen ( Populus tremuloides ) and red-osier dogwood ( Cornus stolonifera ) seedlings. The plants were grown in a controlled environment growth room in mineral nutrient solution at pH 5 and 9 and provided with either 0 or 40 µM Fe in a split-root system for 8 weeks. At the end of the treatments, plant dry weights, net photosynthesis, transpiration rates, root ferric-chelate reductase activity, and leaf chlorophyll concentrations were measured, and elemental analyses were carried out in young leaves. The results demonstrated high root zone pH affected Fe, P and Zn concentrations in young leaves. In the three considered species, plants with part of their root system exposed to pH 5 had higher dry weights, net photosynthesis, and transpiration rates compared with the plants with the whole root system immersed in pH 9 solution. High root zone pH reduced photosynthesis, transpiration rates, leaf chlorophyll concentrations and the uptake of Fe, P, and Zn in plants. Partial exposure of the root system to low pH and Fe supply reduced leaf chlorosis and partly alleviated the high pH stress in the studied plants by improving Fe uptake, but did not alleviate root growth reductions.
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hydraulic conductivity and aquaporin transcription in roots of trembling aspen Populus tremuloides seedlings colonized by laccaria bicolor
Mycorrhiza, 2016Co-Authors: Janice E K Cooke, Alejandro G. Pardo, Minna Kemppainen, Janusz J. ZwiazekAbstract:Ectomycorrhizal fungi have been reported to increase root hydraulic conductivity (L pr) by altering apoplastic and plasma membrane intrinsic protein (PIP)-mediated cell-to-cell water transport pathways in associated roots, or to have little effect on root water transport, depending on the interacting species and imposed stresses. In this study, we investigated the water transport properties and PIP transcription in roots of aspen (Populus tremuloides) seedlings colonized by the wild-type strain of Laccaria bicolor and by strains overexpressing a major fungal water-transporting aquaporin JQ585595. Inoculation of aspen seedlings with L. bicolor resulted in about 30 % colonization rate of root tips, which developed dense mantle and the Hartig net that was restricted in the modified root epidermis. Transcript abundance of the aspen aquaporins PIP1;2, PIP2;1, and PIP2;2 decreased in colonized root tips. Root colonization by JQ585595-overexpressing strains had no significant impact on seedling shoot water potentials, gas exchange, or dry mass; however, it led to further decrease in transcript abundance of PIP1;2 and PIP2;3 and the significantly lower L pr than in non-inoculated roots. These results, taken together with our previous study that showed enhanced root water hydraulics of L. bicolor-colonized white spruce (Picea glauca), suggest that the impact of L. bicolor on root hydraulics varies by the ectomycorrhiza-associated tree species.
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laccaria bicolor aquaporin lbaqp1 is required for hartig net development in trembling aspen Populus tremuloides
Plant Cell and Environment, 2015Co-Authors: Alfonso Navarrorodenas, Alejandro G. Pardo, Minna Kemppainen, Janusz J. ZwiazekAbstract:The development of ectomycorrhizal associations is crucial for growth of many forest trees. However, the signals that are exchanged between the fungus and the host plant during the colonization process are still poorly understood. In this study, we have identified the relationship between expression patterns of Laccaria bicolor aquaporin LbAQP1 and the development of ectomycorrhizal structures in trembling aspen (Populus tremuloides) seedlings. The peak expression of LbAQP1 was 700-fold higher in the hyphae within the root than in the free-living mycelium after 24 h of direct interaction with the roots. Moreover, in LbAQP1 knock-down strains, a non-mycorrhizal phenotype was developed without the Hartig net and the expression of the mycorrhizal effector protein MiSSP7 quickly declined after an initial peak on day 5 of interaction of the fungal hyphae with the roots. The increase in the expression of LbAQP1 required a direct contact of the fungus with the root and it modulated the expression of MiSSP7. We have also determined that LbAQP1 facilitated NO, H2 O2 and CO2 transport when heterologously expressed in yeast. The report demonstrates that the L. bicolor aquaporin LbAQP1 acts as a molecular signalling channel, which is fundamental for the development of Hartig net in root tips of P. tremuloides.
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Hebeloma crustuliniforme facilitates ammonium and nitrate assimilation in trembling aspen (Populus tremuloides) seedlings
Tree physiology, 2011Co-Authors: J. Aurea Siemens, Mónica Calvo-polanco, Janusz J. ZwiazekAbstract:This study examined the role of ectomycorrhizal associations in nitrogen assimilation of Populus tremuloides seedlings. Seedlings were inoculated with Hebeloma crustuliniforme and compared with non-inoculated plants. Nitrogen-metabolizing enzymatic properties were also determined in H. crustuliniforme grown in sterile culture. The seedlings and fungal cultures were subjected to nitrogen treatments (including NO₃⁻, NH₄⁺ and a combination of NO₃⁻ + NH₄⁺) for 2 months to examine the effects on growth, nitrogen-assimilating enzyme activities and xylem sap concentrations of NH₄⁺ and NO₃⁻. Seedlings were also provided for 3 days with ¹⁵N-labeled NH₄⁺ and NO₃⁻, and leaf and root ¹⁵N content relative to total nitrogen was measured. Both NO₃⁻ and NH₄⁺ were effective in supporting seedling growth when either form was provided separately. When NO₃⁻ and NH₄⁺ were provided together, seedling growth decreased while enzymatic assimilation of NH₄⁺ increased. Additionally, nitrogen assimilation in inoculated seedlings was less affected by the form of nitrogen compared with non-inoculated plants. Fungal ability to enzymatically respond to and assimilate NH₄⁺ combined with aspen's enzymatic responsiveness to NO₃⁻ was likely the reason for efficient assimilation of both nitrogen forms by mycorrhizal plants.
Victor J. Lieffers - One of the best experts on this subject based on the ideXlab platform.
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effects of soil temperature and time of decapitation on sucker initiation of intact Populus tremuloides root systems
Scandinavian Journal of Forest Research, 2006Co-Authors: Simon M. Landhäusser, Victor J. Lieffers, Tara MulakAbstract:Abstract In a growth chamber experiment, root suckering of aspen (Populus tremuloides Michx.) was assessed in relation to timing of cutting and soil temperature. Aspen seedlings were grown in large pots for 3 years before experimentation. In a 2×2 factorial experiment, 3-year-old seedlings were cut at the end of the dormant period or after leaf flush and grown at two soil temperatures (8 or 20°C) for 39 days. Root systems were evaluated for suckering response and carbohydrate reserve status. There were no differences between the two soil temperatures and times of cut in the number of sucker buds initiated on the roots, but the number of buds that developed into suckers was much greater at 20°C. Cutting the dormant seedlings delayed suckering by nearly a week, resulting in smaller suckers at the time of harvest. However, cutting the seedlings when dormant produced almost twice the number of suckers than when cutting occurred after leaf-out. Total non-structural carbohydrates (TNC) of roots declined from 35...
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signals controlling root suckering and adventitious shoot formation in aspen Populus tremuloides
Tree Physiology, 2006Co-Authors: Xianchong Wan, Victor J. Lieffers, Simon M. Landhäusser, Janusz J. ZwiazekAbstract:We determined the effects of removal of leaves, stem axillary buds, or the entire shoot on root suckering (adventitious shoot formation by roots) and basal stem sprouts in 3- and 4-year-old potted seedlings of aspen (Populus tremuloides Michx.). The greatest number of root suckers (67.9 +/- 8.5 per plant) emerged after excision of the entire shoot. Defoliated and debudded stems were the major source of inhibitory agents for root suckering, although axillary buds and developing new leaves also exerted a significant inhibitory effect. Removal of mature leaves had only a minor effect on root suckering. Removal of a continuous band of bark (girdling) at the base of the stem consistently stimulated growth of adventitious shoots from the stem below the girdle and occasionally promoted root suckering. Exogenous application of indole-3-acetic acid to excised stumps inhibited root suckering and basal stem sprouting. Naphthylphthalamic acid (NPA), an auxin polar transport inhibitor, had no effect on root suckering or stem sprouting when it was applied to the bark of the basal stem. However, NPA significantly increased root suckering when it was applied to the exposed surface of xylem after girdling. These results suggest that polar transport of auxin in the xylem parenchyma is an important inhibitor of root suckering. On decapitated stems, vacuum extraction of xylem sap from the root system lowered the frequency of root suckering compared with decapitation alone, indicating that substance(s) originating in the root system also play a significant role in controlling root suckering.
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Stomatal conductance and xylem sap properties of aspen (Populus tremuloides) in response to low soil temperature
Physiologia Plantarum, 2004Co-Authors: Xianchong Wan, Janusz J. Zwiazek, Simon M. Landhäusser, Victor J. LieffersAbstract:The mechanisms regulating stomatal response following exposure to low (5°C) soil temperature were investigated in aspen (Populus tremuloides Michx.) seedlings. Low soil temperature reduced stomatal conductance within 4 h,but did not alter shoot xylem pressure potential within 24 h. The xylem sap composition was altered and its pH increased from 6.5 to 7.1 within the initial 4 h of the low temperature treatment. However, the increase in abscisic acid (ABA) concentration in xylem sap was observed later, after 8 h of treatment. These changes were accompanied by a reduction in the electrical conductivity and an increase in the osmotic potential of the xylem sap. The timing of physiological responses to low soil temperature suggests that the rapid pH change of the xylem sap and accompanying changes in ion concentration were the initial factors which triggered stomatal closure in low temperature-treated seedlings, and that the role of the more slowly accumulating ABA was likely to reinforce the stomatal closure. When leaf discs were exposed to xylem sap extracted from low soil temperature-treated plants, stomatal aperture was negatively correlated with ABA and positively correlated with K + concentrations of the xylem sap. The stomatal opening in the leaf discs linearly increased in response to exogenous KCl concentrations when K + concentrations were in the similar range to those detected in the xylem sap. The lowest concentration of exogenous ABA to induce stomatal closure was several-fold higher compared with the concentration present in the xylem sap.
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A comparison of growth and physiology in Picea glauca and Populus tremuloides at different soil temperatures
Canadian Journal of Forest Research, 2001Co-Authors: Simon M. Landhäusser, Annie Desrochers, Victor J. LieffersAbstract:Trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) seedlings were grown at uniform air temperatures but different soil temperatures (5, 15, and 25°C), and gas-exchange and growth characteristics were examined during active growth and early dormancy. At 5°C, Populus tremuloides had no root growth and limited growth in leaf area and shoot mass compared with the large increases in leaf and shoot mass at 25°C. In contrast, Picea glauca had some root growth at 5°C and moderate growth of roots at 15 and 25°C; however, there were no differences in aboveground mass at the different soil temperatures. Net assimilation and stomatal conduc- tance in Populus tremuloides were reduced with decreasing soil temperatures, while in Picea glauca soil temperatures did not affect these gas-exchange variables. In both species, root mass was higher in the dormant period than during the growing period, while root volume remained constant. Generally, the growth variables of Populus tremuloides were more suppressed by cold soils than in Picea glauca. Root total nonstructural carbohydrates (TNC) decreased between the active growth and dormancy period by nearly 50% in Populus tremuloides, while there was no change in TNC in Picea glauca. Results suggest a more conservative use of TNC reserves in Picea glauca combined with a tolerance to cold soil temperatures compared with Populus tremuloides.
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seasonal photosynthetic responses to light and temperature in white spruce picea glauca seedlings planted under an aspen Populus tremuloides canopy and in the open
Tree Physiology, 1997Co-Authors: Rongzhou Man, Victor J. LieffersAbstract:Photosynthetic light and temperature response curves were measured seasonally in seedlings of white spruce (Picea glauca (Moench.) Voss) grown for two years in the understory of aspen (Populus tremuloides Michx.) or in the open in central Alberta. Light-saturated rate of net photosynthesis, the optimum temperature for net photosynthesis, transpiration rate, photochemical efficiency, and stomatal and mesophyll conductances increased from spring to summer and declined thereafter, whereas dark respiration rate and compensation and saturation points were highest in spring. Depression of photosynthetic parameters was greater in open-grown seedlings than in understory seedlings during the periods in spring and autumn when night frosts were common. Net photosynthetic rates were similar in understory and open-grown seedlings in summer, but they were significantly lower in open-grown seedlings in spring and autumn. Significantly lower transpiration rates and stomatal conductances in open-grown seedlings than in understory seedlings were also observed at 15 and 25 degrees C in the autumn. Shoot and needle growth were less in open-grown seedlings than in understory seedlings. In summer, when irradiances were low in the aspen understory, understory white spruce seedlings maintained a positive carbon balance by decreasing their compensation and saturation points and increasing their photochemical efficiency compared to spring and autumn.
Richard L Lindroth - One of the best experts on this subject based on the ideXlab platform.
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root secondary metabolites in Populus tremuloides effects of simulated climate warming defoliation and genotype
Journal of Chemical Ecology, 2021Co-Authors: Kennedy F Rubertnason, Kenneth F Raffa, Mary A Jamieson, Richard L LindrothAbstract:Climate warming can influence interactions between plants and associated organisms by altering levels of plant secondary metabolites. In contrast to studies of elevated temperature on aboveground phytochemistry, the consequences of warming on root chemistry have received little attention. Herein, we investigated the effects of elevated temperature, defoliation, and genotype on root biomass and phenolic compounds in trembling aspen (Populus tremuloides). We grew saplings of three aspen genotypes under ambient or elevated temperatures (+4-6 °C), and defoliated (by 75%) half of the trees in each treatment. After 4 months, we harvested roots and determined their condensed tannin and salicinoid (phenolic glycoside) concentrations. Defoliation reduced root biomass, with a slightly larger impact under elevated, relative to ambient, temperature. Elevated temperature decreased condensed tannin concentrations by 21-43% across the various treatment combinations. Warming alone did not alter salicinoid concentrations but eliminated a small negative impact of defoliation on those compounds. Graphical vector analysis suggests that effects of warming and defoliation on condensed tannins and salicinoids were predominantly due to reduced biosynthesis of these metabolites in roots, rather than to changes in root biomass. In general, genotypes did not differ in their responses to temperature or temperature by defoliation interactions. Collectively, our results suggest that future climate warming will alter root phytochemistry, and that effects will vary among different classes of secondary metabolites and be influenced by concurrent ecological interactions such as herbivory. Temperature- and herbivory-mediated changes in root chemistry have the potential to influence belowground trophic interactions and soil nutrient dynamics.
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phenological responses to prior season defoliation and soil nutrient availability vary among early and late flushing aspen Populus tremuloides michx genotypes
Forest Ecology and Management, 2020Co-Authors: Michael A Falk, Jack R Donaldson, Michael T Stevens, Kenneth F Raffa, Richard L LindrothAbstract:Abstract Many spring-feeding insect folivores have evolved to hatch in synchrony with temporal windows of high foliar quality that occur during leaf expansion. In some host-tree species, however, budbreak phenology can shift in response to defoliation during the prior growing season. While this response could have important impacts on the performance of insect folivore species prone to multi-year outbreaks, the prevalence, underlying mechanisms, and ecological ramifications of defoliation-induced phenological shifts are poorly understood. We established a common garden of twelve trembling aspen (Populus tremuloides Michx.) genotypes, and observed the effects of prior-season defoliation and soil-nutrient availability on budbreak phenology during the following spring. Average budbreak phenology was delayed in response to both prior-season defoliation and low soil-nutrient treatments, but these responses were lower in magnitude than those previously shown to occur in response to temperature. Magnitudes of budbreak delay varied significantly among genotypes and were highest among early-flushing aspen. This negative correlation between aspen budbreak phenology and magnitudes of defoliation-induced phenological delay suggests that widespread defoliation could decrease intraspecific variation in aspen budbreak phenology during subsequent growing seasons, potentially allowing larvae to adapt to windows of optimal foliage quality during multi-year outbreaks. These results quantify additional environmental factors that may act in concert with major drivers such as temperature to mediate phenological relationships between aspen and folivorous insects.
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host genetics and environment shape fungal pathogen incidence on a foundation forest tree species Populus tremuloides
Canadian Journal of Forest Research, 2016Co-Authors: Hilary L Barker, Denise R Smith, Glen R Stanosz, Richard L LindrothAbstract:Diseases can markedly alter the ecological and economic value of poplars. To better understand poplar–pathogen interactions, we investigated the independent and interactive effects of tree genotype, soil nutrient limitation, and interspecific competition on incidence of powdery mildew (caused by the fungal obligate pathogen Erysiphe adunca (Wallr.) Fr., 1829) in a foundation tree species, trembling aspen (Populus tremuloides Michx.). We established a common garden of potted aspen saplings, incorporating five tree genotypes, two levels of soil nutrients (low and high), and two levels of competition (with and without grass). We then surveyed natural incidence of powdery mildew and aspen vigor (i.e., growth). Incidence of powdery mildew varied among aspen genotypes, and variance in incidence shifted among environments in which the trees were grown. Added soil nutrients increased powdery mildew incidence on aspen, whereas grass competition had the opposite effect. Interestingly, grass competition either enhan...
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adaptations of quaking aspen Populus tremuloides michx for defense against herbivores
Forest Ecology and Management, 2013Co-Authors: Richard L Lindroth, Samuel B St ClairAbstract:Abstract Quaking aspen (Populus tremuloides) is a quintessential “foundation species” in early-successional forest ecosystems throughout much of North America. Although subject to damage by hundreds of species of herbivores, aspen has persisted in these environments due largely to a suite of defense strategies: resistance (traits that deter herbivores), tolerance (traits that facilitate recovery from damage) and escape (traits that reduce exposure to herbivores). Here, we review the current state of knowledge about aspen defense against herbivores, with particular focus on montane habitats of western North America. The principal chemical defenses of aspen are phenylpropanoid-derived compounds, including phenolic glycosides (salicinoids) and condensed tannins. Phenolic glycosides reduce feeding, growth and survival of insect herbivores and deter feeding by mammalian herbivores. Expression of chemical defense traits is strongly influenced by genotype, development, environment (biotic and abiotic) and interactions among those factors, and high levels of defense exact a cost to growth. The value of tolerance as a defense strategy likely increases with tree age. Both tolerance and escape via vertical growth are also highly genetically variable in aspen. The efficacy of aspen defense systems is context-dependent. Under conditions of low to moderate herbivore pressure, chemical defenses serve as effective deterrents, and well-defended genotypes are selectively favored. Under conditions of high herbivore pressure – whether insect or mammal – resistance fails and trees sustain high levels of damage. Under these conditions, genotypes with high levels of tolerance are likely selectively favored. Large-scale landscape modifiers, coupled with genetic, developmental and local environmental variation, produce temporal and spatial mosaics of defense across western landscapes. Competition with conifers, fire severity, and extreme climatic events all influence expression of defense and response to herbivore damage in aspen. Aspen’s extraordinary genetic variation and phenotypic plasticity are no match for the environmental stressors, particularly ungulate browsing, contributing to its decline in portions of the Interior West. Management approaches should capitalize on the genetic and environmental factors known to contribute to diverse expression of defense in aspen, while maintaining herbivore population densities below levels that overwhelm all combinations of defense traits.
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genotypic differences and prior defoliation affect re growth and phytochemistry after coppicing in Populus tremuloides
Journal of Chemical Ecology, 2012Co-Authors: Adam C Gusse, Michael T Stevens, Richard L LindrothAbstract:Although considerable research has explored how tree growth and defense can be influenced by genotype, the biotic environment, and their interaction, little is known about how genotypic differences, prior defoliation, and their interactive effects persist in trees that re-grow after damage that severs their primary stem. To address these issues, we established a common garden consisting of twelve genotypes of potted aspen (Populus tremuloides) trees, and subjected half of the trees to defoliation in two successive years. At the beginning of the third year, all trees were severed at the soil surface (coppiced) and allowed to regenerate for five months. Afterwards, we counted the number of root and stump sprouts produced and measured the basal diameter (d) and height (h) of the tallest ramet in each pot. We collected leaves one and two years after the second defoliation and assessed levels of phenolic glycosides, condensed tannins, and nitrogen. In terms of re-growth, we found that the total number of sprouts produced varied by 3.6-fold among genotypes, and that prior defoliation decreased total sprout production by 24%. The size (d2h) of ramets, however, did not differ significantly among genotypes or defoliation classes. In terms of phytochemistry, we observed genotypic differences in concentrations of all phytochemicals assessed both one and two years after the second defoliation. Two years after defoliation, we observed effects of prior defoliation in a genotype-by-defoliation interaction for condensed tannins. Results from this study demonstrate that genotypic differences and impacts of prior defoliation persist to influence growth and defense traits in trees even after complete removal of above-ground stems, and thus likely influence productivity and plant-herbivore interactions in forests affected by natural disturbances or actively managed through coppicing.
Simon M. Landhäusser - One of the best experts on this subject based on the ideXlab platform.
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seasonal patterns of water uptake in Populus tremuloides and picea glauca on a boreal reclamation site is species specific and modulated by capping soil depth and slope position
Plant and Soil, 2019Co-Authors: Morgane Merlin, Simon M. LandhäusserAbstract:Soil water availability is important for tree growth and varies with topographic position and soil depth. We aim to understand how two co-occurring tree species with distinct rooting and physiological characteristics respond to those two variables during two climatically distinct growing seasons. Growing season (May to September) sap and transpiration fluxes were monitored using heat ratio method sap flow sensors on Populus tremuloides and Picea glauca in 2014 and 2015 growing along a hillslope with two different soil cover depths providing different rooting spaces. Across the two growing seasons, a shallow rooting space was the main factor limiting aspen’s leaf area and cumulative sap flux, whereas responses of white spruce were more limited by topographical position. Generally, sap and transpiration fluxes decreased with the season; however, a large precipitation event during the 2015 summer triggered a significant recovery in sap and transpiration fluxes in white spruce, while in aspen this response was more muted. The two species distinct rooting and physiological characteristics produced contrasting water uptake and water use dynamics in response to rooting space, soil water availability and climate, inviting a more detailed exploration of sap flux and its interactions with climatic and edaphic variables.
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tamm review seedling based ecology management and restoration in aspen Populus tremuloides
Forest Ecology and Management, 2019Co-Authors: Simon M. Landhäusser, Bradley D Pinno, Karen E MockAbstract:Abstract Quaking or trembling aspen (Populus tremuloides Michx.) is a foundational tree species, which is native, common, and broadly distributed in North America. The ecology of aspen has been extensively studied throughout its range, but both research and forest management practices have focused primarily on its ability to regenerate asexually via root suckering. The seed-based reproductive ecology of aspen has received comparatively little attention, and information on the underlying processes, mechanisms, and requirements of seed regeneration tends to be scattered, somewhat anecdotal, or based only on localized research efforts. Here we review and explore some of the variables that influence the sexual reproduction and early establishment of aspen. We focus this review on western North America, where trembling aspen plays a dominant ecological role and may be disproportionately impacted by climate change. This synthesis presents existing information and identifies critical knowledge gaps in our understanding of seed –based aspen regeneration, in particular as it relates to flowering and seed production, as well as germination, first year growth, and survival of aspen seedlings. This information is discussed further in the context of aspen ecology and its application in both passive and active management approaches to aspen seedling regeneration and restoration.
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Regeneration dynamics of planted seedling-origin aspen (Populus tremuloides Michx.)
New Forests, 2018Co-Authors: Carolyn M. King, Simon M. LandhäusserAbstract:Aspen ( Populus tremuloides Michx.) is a foundational tree species of the North American boreal forest. After disturbance, clonal aspen stands quickly achieve canopy closure by sending up numerous clonal shoots (root suckers) from their lateral root system. Controlled aboveground disturbance will commonly induce prolific root suckering and thereby increase stem density in clonal aspen stands, but it is unclear if increases in stem density will be observed in planted seedling-origin aspen stands. The objectives of this study were to determine (1) overall root suckering response of planted aspen to aboveground disturbance; (2) if different cut heights of the stem or infliction of root damage impact the number of root suckers produced. We found that planted aspen regenerated readily after disturbance, averaging five root suckers per cut tree. However, individual response was highly variable, ranging from zero to 29 root suckers per root system. Of the cut trees, 75% produced at least one root sucker and 60% produced at least one stump sprout. Cutting trees close to the soil surface produced more root suckers than leaving a 25 cm stump. While root system size (mass and length) was well correlated with aboveground measures of planted aspen, root suckering was not related to root system size. As a result of increased forest reclamation efforts in the boreal forest region the planting of aspen has become a more common practice, necessitating a better understanding of the regeneration dynamics and root suckering potential of these planted and seedling-origin aspen forests.
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effects of soil temperature and time of decapitation on sucker initiation of intact Populus tremuloides root systems
Scandinavian Journal of Forest Research, 2006Co-Authors: Simon M. Landhäusser, Victor J. Lieffers, Tara MulakAbstract:Abstract In a growth chamber experiment, root suckering of aspen (Populus tremuloides Michx.) was assessed in relation to timing of cutting and soil temperature. Aspen seedlings were grown in large pots for 3 years before experimentation. In a 2×2 factorial experiment, 3-year-old seedlings were cut at the end of the dormant period or after leaf flush and grown at two soil temperatures (8 or 20°C) for 39 days. Root systems were evaluated for suckering response and carbohydrate reserve status. There were no differences between the two soil temperatures and times of cut in the number of sucker buds initiated on the roots, but the number of buds that developed into suckers was much greater at 20°C. Cutting the dormant seedlings delayed suckering by nearly a week, resulting in smaller suckers at the time of harvest. However, cutting the seedlings when dormant produced almost twice the number of suckers than when cutting occurred after leaf-out. Total non-structural carbohydrates (TNC) of roots declined from 35...
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signals controlling root suckering and adventitious shoot formation in aspen Populus tremuloides
Tree Physiology, 2006Co-Authors: Xianchong Wan, Victor J. Lieffers, Simon M. Landhäusser, Janusz J. ZwiazekAbstract:We determined the effects of removal of leaves, stem axillary buds, or the entire shoot on root suckering (adventitious shoot formation by roots) and basal stem sprouts in 3- and 4-year-old potted seedlings of aspen (Populus tremuloides Michx.). The greatest number of root suckers (67.9 +/- 8.5 per plant) emerged after excision of the entire shoot. Defoliated and debudded stems were the major source of inhibitory agents for root suckering, although axillary buds and developing new leaves also exerted a significant inhibitory effect. Removal of mature leaves had only a minor effect on root suckering. Removal of a continuous band of bark (girdling) at the base of the stem consistently stimulated growth of adventitious shoots from the stem below the girdle and occasionally promoted root suckering. Exogenous application of indole-3-acetic acid to excised stumps inhibited root suckering and basal stem sprouting. Naphthylphthalamic acid (NPA), an auxin polar transport inhibitor, had no effect on root suckering or stem sprouting when it was applied to the bark of the basal stem. However, NPA significantly increased root suckering when it was applied to the exposed surface of xylem after girdling. These results suggest that polar transport of auxin in the xylem parenchyma is an important inhibitor of root suckering. On decapitated stems, vacuum extraction of xylem sap from the root system lowered the frequency of root suckering compared with decapitation alone, indicating that substance(s) originating in the root system also play a significant role in controlling root suckering.
Kurt S Pregitzer - One of the best experts on this subject based on the ideXlab platform.
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plant growth biomass partitioning and soil carbon formation in response to altered lignin biosynthesis in Populus tremuloides
New Phytologist, 2007Co-Authors: Wendy M Loya, Jessica E Hancock, Christian P Giardina, Vincent L Chiang, Kurt S PregitzerAbstract:We conducted a glasshouse mesocosm study that combined (13)C isotope techniques with wild-type and transgenic aspen (Populus tremuloides) in order to examine how altered lignin biosynthesis affects plant production and soil carbon formation. Our transgenic aspen lines expressed low stem lignin concentration but normal cellulose concentration, low lignin stem concentration with high cellulose concentration or an increased stem syringyl to guaiacyl lignin ratio. Large differences in stem lignin concentration observed across lines were not observed in leaves or fine roots. Nonetheless, low lignin lines accumulated 15-17% less root C and 33-43% less new soil C than the control line. Compared with the control line, transformed aspen expressing high syringyl lignin accumulated 30% less total plant C - a result of greatly reduced total leaf area - and 70% less new soil C. These findings suggest that altered stem lignin biosynthesis in Populus may have little effect on the chemistry of fine roots or leaves, but can still have large effects on plant growth, biomass partitioning and soil C formation.
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atmospheric co2 soil n availability and allocation of biomass and nitrogen by Populus tremuloides
Ecological Applications, 2000Co-Authors: Kurt S Pregitzer, Peter S Curtis, Christoph S Vogel, William E Holmes, John LussenhopAbstract:Our ability to predict whether elevated atmospheric CO2 will alter the cycling of C and N in terrestrial ecosystems requires understanding a complex set of feedback mechanisms initiated by changes in C and N acquisition by plants and the degree to which changes in resource acquisition (C and N) alter plant growth and allocation. To gain further insight into these dynamics, we grew six genotypes of Populus tremuloides Michx. that differ in autumnal senescence (early vs. late) under experimental atmospheric CO2 (35.7 and 70.7 Pa) and soil-N availability (low and high) treatments. Atmospheric CO2 concentrations were manipulated with open-top chambers, and soil-N availability was modified in open-bottom root boxes by mixing different proportions of native A and C horizon soil. Net N mineralization rates averaged 61 ng N·g−1·d−1 in low-N soil and 319 ng N·g−1·d−1 in high-N soil. After 2.5 growing seasons, we harvested above- and belowground plant components in each chamber and determined total biomass, N concentration, N content, and the relative allocation of biomass and N to leaves, stems, and roots. Elevated CO2 increased total plant biomass 16% in low-N soil and 38% in high-N soil, indicating that the growth response of P. tremuloides to elevated CO2 was constrained by soil-N availability. Greater growth under elevated CO2 did not substantially alter the allocation of biomass to above- or belowground plant components. At both levels of soil-N availability, elevated CO2 decreased the N concentration of all plant tissues. Despite declines in tissue N concentration, elevated CO2 significantly increased whole-plant N content in high-N soil (ambient = 137 g N/chamber; elevated = 155 g N/chamber), but it did not influence whole-plant N content in low-N soil (36 g N/chamber). Our results indicate that plants in high-N soil obtained greater amounts of soil N under elevated CO2 by producing a proportionately larger fine-root system that more thoroughly exploited the soil. The significant positive relationship between fine-root biomass and total-plant N content we observed in high-N soil further supports this contention. In low-N soil, elevated CO2 did not increase fine-root biomass or production, and plants under ambient and elevated CO2 obtained equivalent amounts of N from soil. In high-N soil, it appears that greater acquisition of soil N under elevated CO2 fed forward within the plant to increase rates of C acquisition, which further enhanced plant growth response to elevated CO2.
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clonal variation in above and below ground growth responses of Populus tremuloides michaux influence of soil warming and nutrient availability
Plant and Soil, 1999Co-Authors: John S King, Kurt S Pregitzer, Donald R ZakAbstract:Trembling aspen (Populus tremuloides Michx.) is the most widely distributed tree species in North America making it important to terrestrial carbon and nutrient cycles. Due to anthropogenic climate change high latitude temperatures are expected to increase, making it necessary to assess the feedback between above- and below-ground carbon pools to increased temperature at sites of both high and low N-availability. We grew four clones of aspen at two levels of soil temperature and two levels of soil N-availability for 98 days and quantified photosynthesis, growth, biomass allocation, and root length production and mortality. High soil temperature increased rates of photosynthesis (65%), resulting in greater whole-plant growth (37%) through increases in roots, stems, and foliage; however these increases generally occurred only in soil of high N-availability. Root:shoot biomass allocation varied between clones but was unaffected by the soil temperature or N-availability treatments. Root length production and mortality increased at elevated soil temperature, but this response was modified by soil N-availability. At high soil temperature, soil N-availability had little effect on root dynamics, while at low soil temperature, high soil N-availability increased both the production and mortality (turnover) of roots. We conclude that trembling aspen has the potential for substantially greater growth and root turnover under conditions of warmer soil at sites of both high and low N-availability, but that allometric patterns of growth are under strong genetic, rather than environmental control.
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genotypic variation for condensed tannin production in trembling aspen Populus tremuloides salicaceae under elevated co2 and in high and low fertility soil
American Journal of Botany, 1999Co-Authors: Jennifer L Mansfield, Peter S Curtis, Donald R Zak, Kurt S PregitzerAbstract:The carbon/nutrient balance hypothesis suggests that leaf carbon to nitrogen ratios influence the synthesis of secondary compounds such as condensed tannins. We studied the effects of rising atmospheric carbon dioxide on carbon to nitrogen ratios and tannin production. Six genotypes of Populus tremuloides were grown under elevated and ambient CO(2) partial pressure and high- and low-fertility soil in field open-top chambers in northern lower Michigan, USA. During the second year of exposure, leaves were harvested three times (June, August, and September) and analyzed for condensed tannin concentration. The carbon/nutrient balance hypothesis was supported overall, with significantly greater leaf tannin concentration at high CO(2) and low soil fertility compared to ambient CO(2) and high soil fertility. However, some genotypes increased tannin concentration at elevated compared to ambient CO(2), while others showed no CO(2) response. Performance of lepidopteran leaf miner (Phyllonorycter tremuloidiella) larvae feeding on these plants varied across genotypes, CO(2), and fertility treatments. These results suggest that with rising atmospheric CO(2), plant secondary compound production may vary within species. This could have consequences for plant-herbivore and plant-microbe interactions and for the evolutionary response of this species to global climate change.