The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Priit Kupper - One of the best experts on this subject based on the ideXlab platform.
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Elevated Atmospheric Humidity prolongs active growth period and increases leaf nitrogen resorption efficiency of silver birch.
Oecologia, 2020Co-Authors: Katrin Rosenvald, Krista Lõhmus, Priit Kupper, Gristin Rohula-okunev, Reimo Lutter, Arvo TullusAbstract:Climate models predict increasing amounts of precipitation and relative Atmospheric Humidity for high latitudes in the Northern Hemisphere. Therefore, tree species must adjust to the new climatic conditions. We studied young silver birches (Betula pendula Roth) in a long-term (2012–2018) free air Humidity manipulation experiment, with the aim of clarifying the acclimation mechanisms to elevated relative Atmospheric Humidity. In 2016–2018, stem radial increment (measured by dendrometers) and leaf abscission were monitored, and the leaf N and P resorption efficiencies were determined. Biomass allocation was estimated, and the seasonal dynamics of foliar NPK storage was assessed. Humidification increased N resorption efficiency by 11%. The annual means of N resorption efficiency varied from 41 to 52% in control and from 50 to 59% in humidified stands. The P resorption efficiency was strongly affected by weather conditions and varied between years from 25 to 66%. Higher foliar NPK storages at the end of growing season and delayed leaf fall allowed to extend the growth period in humidified plots, which resulted in a week longer stem radial growth. Although stem diameter growth of humidified birches recovered after 5 years, tree height retardation persisted over the seven study years, resulting in increased stem taper (diameter to height ratio) under humidification. Additionally, humidification increased the share of the bark in stem biomass and the number of branches per crown length. The acclimation of silver birches to increased air Humidity entails changes in forest N cycle and in birch timber quality.
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coppicing improves the growth response of short rotation hybrid aspen to elevated Atmospheric Humidity
Forest Ecology and Management, 2020Co-Authors: Arvo Tullus, Katrin Rosenvald, Priit Kupper, Reimo Lutter, Ants Kaasik, Arne SellinAbstract:Abstract Aspens are fast-growing clonal trees with a wide circumboreal distribution range, suitable for the production of pulp and bioenergy. The adaptability of aspen short-rotation coppice systems to climate change has rarely been investigated. For a large part of aspens’ northern range, climate models predict an increase in precipitation and, consequently, in Atmospheric Humidity. Our aim was to clarify the long-term effect of elevated air Humidity on vegetative reproduction capacity and dynamics of above-ground growth and size structure in aspen stands. We analysed tree growth data from two consecutive 6-year rotations (a planted and a coppice generation) in experimental short-rotation hybrid aspen (Populus tremula L. × P. tremuloides Michx.) stands in the Free Air Humidity Manipulation (FAHM) experiment in Estonia. In three plots, mean relative air Humidity was elevated by 7% and three plots were controls. Across two rotation periods, the humidification effect on tree height and/or stem basal area increment was year-dependent (p
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Elevated Atmospheric Humidity shapes the carbon cycle of a silver birch forest ecosystem: A FAHM study.
The Science of the total environment, 2019Co-Authors: Krista Lõhmus, Arvo Tullus, Katrin Rosenvald, Ivika Ostonen, Mai Kukumägi, Veiko Uri, Jürgen Aosaar, Mats Varik, Priit Kupper, Raili TorgaAbstract:Processes determining the carbon (C) balance of a forest ecosystem are influenced by a number of climatic and environmental factors. In Northern Europe, a rise in Atmospheric Humidity and precipitation is predicted. The study aims to ascertain the effect of elevated Atmospheric Humidity on the components of the C budget and on the C-sequestration capacity of a young birch forest. Biomass production, soil respiration, and other C fluxes were measured in young silver birch (Betula pendula Roth) stands growing on the Free Air Humidity Manipulation (FAHM) experimental site, located in South-East Estonia. The C input fluxes: C sequestration in trees and understory, litter input into soil, and methane oxidation, as well as C output fluxes: soil heterotrophic respiration and C leaching were estimated. Humidified birch stands stored C from the atmosphere, but control stands can be considered as C neutral. Two years of elevated air Humidity increased C sequestration in the understory but decreased it in trees. Humidification treatment increased remarkably the C input to the soil. The main reason for such an increase was the higher root litter input into the soil, brought about by the more than two-fold increase of belowground biomass production of the understory in the humidification treatment. Elevated Atmospheric Humidity increased C sequestration in young silver birch stands, mitigating increasing CO2 concentration in the atmosphere. However, the effect of elevated Atmospheric Humidity is expected to decrease over time, as plants and soil organisms acclimate, and new communities emerge.
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Growth of northern deciduous trees under increasing Atmospheric Humidity: possible mechanisms behind the growth retardation
Regional Environmental Change, 2016Co-Authors: Arne Sellin, Krista Lõhmus, Priit Kupper, Jaak Sober, Anu Sõber, Meeli Alber, Markku Keinänen, Jenna Lihavainen, Elina Oksanen, Arvo TullusAbstract:Increasing Atmospheric Humidity—a climate trend predicted for northern Europe—will reduce water flux through vegetation. Diminished transpirational water flux impacts various physiological processes, causing growth decline in deciduous trees. We propose, based on the results obtained from the long-term free air Humidity manipulation experiment, concurrent mechanisms to explain the growth deceleration due to increases in relative air Humidity. Reduced Atmospheric evaporative demand diminishes nutrient uptake and leads to lower leaf nutritional status and to an unbalanced foliar phosphorus/nitrogen ratio (P:N), resulting in a decline in leaf photosynthetic capacity. Elevated relative Humidity induces readjustment of foliar metabolism: disturbed N metabolism, accumulation of starch and changes in secondary metabolite contents probably impair both photosynthetic performance and growth. Increased carbohydrate content in the leaves suggests that sink strength of trees is reduced under elevated Humidity. As a consequence of the stress, foliar development is hindered, observed at individual leaf or whole-tree foliage levels, lowering production potential of trees proportionally to their foliar area. Larger investments in stem xylem in relation to foliage cause an increase in the ratio of non-photosynthetic to photosynthetic tissues, leading to larger maintenance respiration costs determined by the volume of parenchymatous tissue. An increase in the proportion of living parenchyma cells in relation to dead xylem elements in sapwood additionally enhances respiration costs. Disproportionate changes in hydraulic versus stomatal conductance become a critical factor in the case of weather extremes, which limit canopy conductance and may induce dysfunction of the hydraulic system. Increasing environmental Humidity creates favourable conditions for development of pathogens, increasing frequency of fungal damage.
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Responses of sap flow, leaf gas exchange and growth of hybrid aspen to elevated Atmospheric Humidity under field conditions
AoB PLANTS, 2014Co-Authors: Aigar Niglas, Priit Kupper, Arvo Tullus, Arne SellinAbstract:An increase in average air temperature and frequency of rain events is predicted for higher latitudes by the end of the 21st century, accompanied by a probable rise in air Humidity. We currently lack knowledge on how forest trees acclimate to rising air Humidity in temperate climates. We analysed the leaf gas exchange, sap flow and growth characteristics of hybrid aspen (Populus tremula × P. tremuloides) trees growing at ambient and artificially elevated air Humidity in an experimental forest plantation situated in the hemiboreal vegetation zone. Humidification manipulation did not affect the photosynthetic capacity of plants, but did affect stomatal responses: trees growing at elevated air Humidity had higher stomatal conductance at saturating photosynthetically active radiation (gs sat) and lower intrinsic water-use efficiency (IWUE). Reduced stomatal limitation of photosynthesis in trees grown at elevated air Humidity allowed slightly higher net photosynthesis and relative current-year height increments than in trees at ambient air Humidity. Tree responses suggest a mitigating effect of higher air Humidity on trees under mild water stress. At the same time, trees at higher air Humidity demonstrated a reduced sensitivity of IWUE to factors inducing stomatal closure and a steeper decline in canopy conductance in response to water deficit, implying higher dehydration risk. Despite the mitigating impact of increased air Humidity under moderate drought, a future rise in Atmospheric Humidity at high latitudes may be disadvantageous for trees during weather extremes and represents a potential threat in hemiboreal forest ecosystems.
Krista Lõhmus - One of the best experts on this subject based on the ideXlab platform.
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Elevated Atmospheric Humidity prolongs active growth period and increases leaf nitrogen resorption efficiency of silver birch.
Oecologia, 2020Co-Authors: Katrin Rosenvald, Krista Lõhmus, Priit Kupper, Gristin Rohula-okunev, Reimo Lutter, Arvo TullusAbstract:Climate models predict increasing amounts of precipitation and relative Atmospheric Humidity for high latitudes in the Northern Hemisphere. Therefore, tree species must adjust to the new climatic conditions. We studied young silver birches (Betula pendula Roth) in a long-term (2012–2018) free air Humidity manipulation experiment, with the aim of clarifying the acclimation mechanisms to elevated relative Atmospheric Humidity. In 2016–2018, stem radial increment (measured by dendrometers) and leaf abscission were monitored, and the leaf N and P resorption efficiencies were determined. Biomass allocation was estimated, and the seasonal dynamics of foliar NPK storage was assessed. Humidification increased N resorption efficiency by 11%. The annual means of N resorption efficiency varied from 41 to 52% in control and from 50 to 59% in humidified stands. The P resorption efficiency was strongly affected by weather conditions and varied between years from 25 to 66%. Higher foliar NPK storages at the end of growing season and delayed leaf fall allowed to extend the growth period in humidified plots, which resulted in a week longer stem radial growth. Although stem diameter growth of humidified birches recovered after 5 years, tree height retardation persisted over the seven study years, resulting in increased stem taper (diameter to height ratio) under humidification. Additionally, humidification increased the share of the bark in stem biomass and the number of branches per crown length. The acclimation of silver birches to increased air Humidity entails changes in forest N cycle and in birch timber quality.
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Elevated Atmospheric Humidity shapes the carbon cycle of a silver birch forest ecosystem: A FAHM study.
The Science of the total environment, 2019Co-Authors: Krista Lõhmus, Arvo Tullus, Katrin Rosenvald, Ivika Ostonen, Mai Kukumägi, Veiko Uri, Jürgen Aosaar, Mats Varik, Priit Kupper, Raili TorgaAbstract:Processes determining the carbon (C) balance of a forest ecosystem are influenced by a number of climatic and environmental factors. In Northern Europe, a rise in Atmospheric Humidity and precipitation is predicted. The study aims to ascertain the effect of elevated Atmospheric Humidity on the components of the C budget and on the C-sequestration capacity of a young birch forest. Biomass production, soil respiration, and other C fluxes were measured in young silver birch (Betula pendula Roth) stands growing on the Free Air Humidity Manipulation (FAHM) experimental site, located in South-East Estonia. The C input fluxes: C sequestration in trees and understory, litter input into soil, and methane oxidation, as well as C output fluxes: soil heterotrophic respiration and C leaching were estimated. Humidified birch stands stored C from the atmosphere, but control stands can be considered as C neutral. Two years of elevated air Humidity increased C sequestration in the understory but decreased it in trees. Humidification treatment increased remarkably the C input to the soil. The main reason for such an increase was the higher root litter input into the soil, brought about by the more than two-fold increase of belowground biomass production of the understory in the humidification treatment. Elevated Atmospheric Humidity increased C sequestration in young silver birch stands, mitigating increasing CO2 concentration in the atmosphere. However, the effect of elevated Atmospheric Humidity is expected to decrease over time, as plants and soil organisms acclimate, and new communities emerge.
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Growth of northern deciduous trees under increasing Atmospheric Humidity: possible mechanisms behind the growth retardation
Regional Environmental Change, 2016Co-Authors: Arne Sellin, Krista Lõhmus, Priit Kupper, Jaak Sober, Anu Sõber, Meeli Alber, Markku Keinänen, Jenna Lihavainen, Elina Oksanen, Arvo TullusAbstract:Increasing Atmospheric Humidity—a climate trend predicted for northern Europe—will reduce water flux through vegetation. Diminished transpirational water flux impacts various physiological processes, causing growth decline in deciduous trees. We propose, based on the results obtained from the long-term free air Humidity manipulation experiment, concurrent mechanisms to explain the growth deceleration due to increases in relative air Humidity. Reduced Atmospheric evaporative demand diminishes nutrient uptake and leads to lower leaf nutritional status and to an unbalanced foliar phosphorus/nitrogen ratio (P:N), resulting in a decline in leaf photosynthetic capacity. Elevated relative Humidity induces readjustment of foliar metabolism: disturbed N metabolism, accumulation of starch and changes in secondary metabolite contents probably impair both photosynthetic performance and growth. Increased carbohydrate content in the leaves suggests that sink strength of trees is reduced under elevated Humidity. As a consequence of the stress, foliar development is hindered, observed at individual leaf or whole-tree foliage levels, lowering production potential of trees proportionally to their foliar area. Larger investments in stem xylem in relation to foliage cause an increase in the ratio of non-photosynthetic to photosynthetic tissues, leading to larger maintenance respiration costs determined by the volume of parenchymatous tissue. An increase in the proportion of living parenchyma cells in relation to dead xylem elements in sapwood additionally enhances respiration costs. Disproportionate changes in hydraulic versus stomatal conductance become a critical factor in the case of weather extremes, which limit canopy conductance and may induce dysfunction of the hydraulic system. Increasing environmental Humidity creates favourable conditions for development of pathogens, increasing frequency of fungal damage.
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The effects of elevated Atmospheric Humidity on soil respiration components in a young silver birch forest
Agricultural and Forest Meteorology, 2014Co-Authors: Mai Kukumägi, Ivika Ostonen, Jürgen Aosaar, Mats Varik, Priit Kupper, Marika Truu, Ingmar Tulva, Jaak Sober, Krista LõhmusAbstract:The predicted increase in precipitation at northern latitudes is an important factor affecting the functioning of forest ecosystems, yet the influence of increased Atmospheric Humidity on the forest ecosystem carbon cycle is still largely unknown. Our objectives were to determine the effect of elevated Atmospheric Humidity on soil respiration in silver birch (Betula pendula Roth.) plantations in a Free Air Humidity Manipulation experimental facility (FAHM). Soil respiration was monitored monthly from May to October, in 2008 and 2009 in three control and in three misting plots; soil temperature and soil moisture were measured simultaneously. Fine-root and rhizome biomass of the understory was measured by sequential soil cores. Soil microbial biomass and basal respiration were measured using manometric respirometers. After the first two years of manipulation, humidification led to lower soil respiration. Soil temperature was the main factor influencing seasonal dynamics of soil respiration, describing up to 75% of the total variation of soil respiration. Soil moisture had a weak negative effect on soil respiration. Humidification caused a remarkable increase in below-ground biomass and the production of the understory, and a 28% increase in the basal respiration of microbes. However, above-ground biomass and root turnover rate of the understory were almost unchanged. Hence, elevated Atmospheric Humidity significantly affects carbon cycle of deciduous forest. However, further studies are necessary for a better understanding of soil respiration response to changes in Atmospheric Humidity, in order to predict carbon balance in changing climate conditions.
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Climate Change at Northern Latitudes: Rising Atmospheric Humidity Decreases Transpiration, N-Uptake and Growth Rate of Hybrid Aspen
PloS one, 2012Co-Authors: Arvo Tullus, Arne Sellin, Krista Lõhmus, Priit Kupper, Jaak Sober, Leopold Parts, Tea Tullus, Anu Sõber, Hardi TullusAbstract:At northern latitudes a rise in Atmospheric Humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in response to elevated Atmospheric Humidity (on average 7% over the ambient level) in a free air experimental facility during three growing seasons (2008–2010) in Estonia, which represents northern temperate climate (boreo-nemoral zone). Data were collected from three humidified (H) and three control (C) plots, and analysed using nested linear models. Elevated air Humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA) in H plots. The magnitude and significance of the Humidity treatment effect – inhibition of above-ground growth rate – was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO3− in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and Atmospheric CO2 concentration, might be smaller than expected at high latitudes if a rise in Atmospheric Humidity simultaneously takes place.
Paul Deacon - One of the best experts on this subject based on the ideXlab platform.
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a comparison between Atmospheric Humidity and vacuum cyanoacrylate fuming of latent fingermarks
Forensic Science International, 2015Co-Authors: Kevin J. Farrugia, Joanna Fraser, Lauren Friel, Duncan Adams, Nicola Attardmontalto, Paul DeaconAbstract:A number of pseudo-operational trials were set up to compare the Atmospheric/Humidity and vacuum cyanoacrylate fuming processes on plastic carrier bags. The fuming processes were compared using two-step cyanoacrylate fuming with basic yellow 40 (BY40) staining and a one-step fluorescent cyanoacrylate fuming, Lumicyano 4%. Preliminary work using planted fingermarks and split depletions were performed to identify the optimum vacuum fuming conditions. The first pseudo-operational trial compared the different fuming conditions (Atmospheric/Humidity vs. vacuum) for the two-step process where an additional 50% more marks were detected with the Atmospheric/Humidity process. None of the marks by the vacuum process could be observed visually; however, a significant number of marks were detected by fluorescence after BY40 staining. The second trial repeated the same work in trial 1 using the one-step cyanoacrylate process, Lumicyano at a concentration of 4%. Trial 2 provided comparable results to trial 1 and all the items were then re-treated with Lumicyano 4% at Atmospheric/Humidity conditions before dyeing with BY40 to provide the sequences of process A (Lumicyano 4% Atmospheric-Lumicyano 4% Atmospheric-BY40) and process B (Lumicyano 4% vacuum-Lumicyano 4% Atmospheric-BY40). The number of marks (visual and fluorescent) was counted after each treatment with a substantial increase in the number of detected marks in the second and third treatments of the process. The increased detection rate after the double Lumicyano process was unexpected and may have important implications. Trial 3 was performed to investigate whether the amount of cyanoacrylate and/or fuming time had an impact on the results observed in trial 2 whereas trial 4 assessed if the double process using conventional cyanoacrylate, rather than Lumicyano 4%, provided an increased detection rate. Trials 3 and 4 confirmed that doubling the amount of Lumicyano 4% cyanoacrylate and fuming time produced a lower detection rate than the double process with Lumicyano 4%. Furthermore, the double process with conventional cyanoacrylate did not provide any benefit. Scanning electron microscopy was also performed to investigate the morphology of the cyanoacrylate polymer under different conditions. The Atmospheric/Humidity process appears to be superior to the vacuum process for both the two-step and one-step cyanoacrylate fuming, although the two-step process performed better in comparison to the one-step process under vacuum conditions. Nonetheless, the use of vacuum cyanoacrylate fuming may have certain operational advantages and its use does not adversely affect subsequent cyanoacrylate fuming with Atmospheric/Humidity conditions.
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A comparison between Atmospheric/Humidity and vacuum cyanoacrylate fuming of latent fingermarks.
Forensic science international, 2015Co-Authors: Kevin J. Farrugia, Joanna Fraser, Lauren Friel, Duncan Adams, Nicola Attard-montalto, Paul DeaconAbstract:A number of pseudo-operational trials were set up to compare the Atmospheric/Humidity and vacuum cyanoacrylate fuming processes on plastic carrier bags. The fuming processes were compared using two-step cyanoacrylate fuming with basic yellow 40 (BY40) staining and a one-step fluorescent cyanoacrylate fuming, Lumicyano 4%. Preliminary work using planted fingermarks and split depletions were performed to identify the optimum vacuum fuming conditions. The first pseudo-operational trial compared the different fuming conditions (Atmospheric/Humidity vs. vacuum) for the two-step process where an additional 50% more marks were detected with the Atmospheric/Humidity process. None of the marks by the vacuum process could be observed visually; however, a significant number of marks were detected by fluorescence after BY40 staining. The second trial repeated the same work in trial 1 using the one-step cyanoacrylate process, Lumicyano at a concentration of 4%. Trial 2 provided comparable results to trial 1 and all the items were then re-treated with Lumicyano 4% at Atmospheric/Humidity conditions before dyeing with BY40 to provide the sequences of process A (Lumicyano 4% Atmospheric-Lumicyano 4% Atmospheric-BY40) and process B (Lumicyano 4% vacuum-Lumicyano 4% Atmospheric-BY40). The number of marks (visual and fluorescent) was counted after each treatment with a substantial increase in the number of detected marks in the second and third treatments of the process. The increased detection rate after the double Lumicyano process was unexpected and may have important implications. Trial 3 was performed to investigate whether the amount of cyanoacrylate and/or fuming time had an impact on the results observed in trial 2 whereas trial 4 assessed if the double process using conventional cyanoacrylate, rather than Lumicyano 4%, provided an increased detection rate. Trials 3 and 4 confirmed that doubling the amount of Lumicyano 4% cyanoacrylate and fuming time produced a lower detection rate than the double process with Lumicyano 4%. Furthermore, the double process with conventional cyanoacrylate did not provide any benefit. Scanning electron microscopy was also performed to investigate the morphology of the cyanoacrylate polymer under different conditions. The Atmospheric/Humidity process appears to be superior to the vacuum process for both the two-step and one-step cyanoacrylate fuming, although the two-step process performed better in comparison to the one-step process under vacuum conditions. Nonetheless, the use of vacuum cyanoacrylate fuming may have certain operational advantages and its use does not adversely affect subsequent cyanoacrylate fuming with Atmospheric/Humidity conditions.
Arvo Tullus - One of the best experts on this subject based on the ideXlab platform.
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Elevated Atmospheric Humidity prolongs active growth period and increases leaf nitrogen resorption efficiency of silver birch.
Oecologia, 2020Co-Authors: Katrin Rosenvald, Krista Lõhmus, Priit Kupper, Gristin Rohula-okunev, Reimo Lutter, Arvo TullusAbstract:Climate models predict increasing amounts of precipitation and relative Atmospheric Humidity for high latitudes in the Northern Hemisphere. Therefore, tree species must adjust to the new climatic conditions. We studied young silver birches (Betula pendula Roth) in a long-term (2012–2018) free air Humidity manipulation experiment, with the aim of clarifying the acclimation mechanisms to elevated relative Atmospheric Humidity. In 2016–2018, stem radial increment (measured by dendrometers) and leaf abscission were monitored, and the leaf N and P resorption efficiencies were determined. Biomass allocation was estimated, and the seasonal dynamics of foliar NPK storage was assessed. Humidification increased N resorption efficiency by 11%. The annual means of N resorption efficiency varied from 41 to 52% in control and from 50 to 59% in humidified stands. The P resorption efficiency was strongly affected by weather conditions and varied between years from 25 to 66%. Higher foliar NPK storages at the end of growing season and delayed leaf fall allowed to extend the growth period in humidified plots, which resulted in a week longer stem radial growth. Although stem diameter growth of humidified birches recovered after 5 years, tree height retardation persisted over the seven study years, resulting in increased stem taper (diameter to height ratio) under humidification. Additionally, humidification increased the share of the bark in stem biomass and the number of branches per crown length. The acclimation of silver birches to increased air Humidity entails changes in forest N cycle and in birch timber quality.
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coppicing improves the growth response of short rotation hybrid aspen to elevated Atmospheric Humidity
Forest Ecology and Management, 2020Co-Authors: Arvo Tullus, Katrin Rosenvald, Priit Kupper, Reimo Lutter, Ants Kaasik, Arne SellinAbstract:Abstract Aspens are fast-growing clonal trees with a wide circumboreal distribution range, suitable for the production of pulp and bioenergy. The adaptability of aspen short-rotation coppice systems to climate change has rarely been investigated. For a large part of aspens’ northern range, climate models predict an increase in precipitation and, consequently, in Atmospheric Humidity. Our aim was to clarify the long-term effect of elevated air Humidity on vegetative reproduction capacity and dynamics of above-ground growth and size structure in aspen stands. We analysed tree growth data from two consecutive 6-year rotations (a planted and a coppice generation) in experimental short-rotation hybrid aspen (Populus tremula L. × P. tremuloides Michx.) stands in the Free Air Humidity Manipulation (FAHM) experiment in Estonia. In three plots, mean relative air Humidity was elevated by 7% and three plots were controls. Across two rotation periods, the humidification effect on tree height and/or stem basal area increment was year-dependent (p
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Elevated Atmospheric Humidity shapes the carbon cycle of a silver birch forest ecosystem: A FAHM study.
The Science of the total environment, 2019Co-Authors: Krista Lõhmus, Arvo Tullus, Katrin Rosenvald, Ivika Ostonen, Mai Kukumägi, Veiko Uri, Jürgen Aosaar, Mats Varik, Priit Kupper, Raili TorgaAbstract:Processes determining the carbon (C) balance of a forest ecosystem are influenced by a number of climatic and environmental factors. In Northern Europe, a rise in Atmospheric Humidity and precipitation is predicted. The study aims to ascertain the effect of elevated Atmospheric Humidity on the components of the C budget and on the C-sequestration capacity of a young birch forest. Biomass production, soil respiration, and other C fluxes were measured in young silver birch (Betula pendula Roth) stands growing on the Free Air Humidity Manipulation (FAHM) experimental site, located in South-East Estonia. The C input fluxes: C sequestration in trees and understory, litter input into soil, and methane oxidation, as well as C output fluxes: soil heterotrophic respiration and C leaching were estimated. Humidified birch stands stored C from the atmosphere, but control stands can be considered as C neutral. Two years of elevated air Humidity increased C sequestration in the understory but decreased it in trees. Humidification treatment increased remarkably the C input to the soil. The main reason for such an increase was the higher root litter input into the soil, brought about by the more than two-fold increase of belowground biomass production of the understory in the humidification treatment. Elevated Atmospheric Humidity increased C sequestration in young silver birch stands, mitigating increasing CO2 concentration in the atmosphere. However, the effect of elevated Atmospheric Humidity is expected to decrease over time, as plants and soil organisms acclimate, and new communities emerge.
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Growth of northern deciduous trees under increasing Atmospheric Humidity: possible mechanisms behind the growth retardation
Regional Environmental Change, 2016Co-Authors: Arne Sellin, Krista Lõhmus, Priit Kupper, Jaak Sober, Anu Sõber, Meeli Alber, Markku Keinänen, Jenna Lihavainen, Elina Oksanen, Arvo TullusAbstract:Increasing Atmospheric Humidity—a climate trend predicted for northern Europe—will reduce water flux through vegetation. Diminished transpirational water flux impacts various physiological processes, causing growth decline in deciduous trees. We propose, based on the results obtained from the long-term free air Humidity manipulation experiment, concurrent mechanisms to explain the growth deceleration due to increases in relative air Humidity. Reduced Atmospheric evaporative demand diminishes nutrient uptake and leads to lower leaf nutritional status and to an unbalanced foliar phosphorus/nitrogen ratio (P:N), resulting in a decline in leaf photosynthetic capacity. Elevated relative Humidity induces readjustment of foliar metabolism: disturbed N metabolism, accumulation of starch and changes in secondary metabolite contents probably impair both photosynthetic performance and growth. Increased carbohydrate content in the leaves suggests that sink strength of trees is reduced under elevated Humidity. As a consequence of the stress, foliar development is hindered, observed at individual leaf or whole-tree foliage levels, lowering production potential of trees proportionally to their foliar area. Larger investments in stem xylem in relation to foliage cause an increase in the ratio of non-photosynthetic to photosynthetic tissues, leading to larger maintenance respiration costs determined by the volume of parenchymatous tissue. An increase in the proportion of living parenchyma cells in relation to dead xylem elements in sapwood additionally enhances respiration costs. Disproportionate changes in hydraulic versus stomatal conductance become a critical factor in the case of weather extremes, which limit canopy conductance and may induce dysfunction of the hydraulic system. Increasing environmental Humidity creates favourable conditions for development of pathogens, increasing frequency of fungal damage.
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Impact of elevated Atmospheric Humidity on anatomical and hydraulic traits of xylem in hybrid aspen
Functional Plant Biology, 2015Co-Authors: Anna Katarzyna Jasińska, Märt Rahi, Merryl Alber, Arvo Tullus, Arne SellinAbstract:This study was performed on hybrid aspen saplings growing at the Free Air Humidity Manipulation site in Estonia. We investigated changes in wood anatomy and hydraulic conductivity in response to increased air Humidity. Two hydraulic traits (specific conductivity and leaf-specific conductivity) and four anatomical traits of stem wood – relative vessel area (VA), vessel density (VD), pit area and pit aperture area – were influenced by the Humidity manipulation. Stem hydraulic traits decreased in the apical direction, whereas branch hydraulic characteristics tended to be greatest in mid-canopy, associated with branch size. A reduction in VD due to increasing Humidity was accompanied by a decrease in vessel lumen diameter, hydraulically weighted mean diameter (Dh), xylem vulnerability index and theoretical hydraulic conductivity. VA and Dh combined accounted for 87.4% of the total variation in kt of branches and 85.5% of that in stems across the treatments. Characters of branch vessels were more stable, and only the vessel-grouping index (the ratio of the total number of vessels to the total number of vessel groupings) was dependent on the interactive effect of the treatment and canopy position. Our results indicate that the increasing Atmospheric Humidity predicted for high latitudes will result in moderate changes in the structure and functioning of the hybrid aspen xylem.
Arne Sellin - One of the best experts on this subject based on the ideXlab platform.
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coppicing improves the growth response of short rotation hybrid aspen to elevated Atmospheric Humidity
Forest Ecology and Management, 2020Co-Authors: Arvo Tullus, Katrin Rosenvald, Priit Kupper, Reimo Lutter, Ants Kaasik, Arne SellinAbstract:Abstract Aspens are fast-growing clonal trees with a wide circumboreal distribution range, suitable for the production of pulp and bioenergy. The adaptability of aspen short-rotation coppice systems to climate change has rarely been investigated. For a large part of aspens’ northern range, climate models predict an increase in precipitation and, consequently, in Atmospheric Humidity. Our aim was to clarify the long-term effect of elevated air Humidity on vegetative reproduction capacity and dynamics of above-ground growth and size structure in aspen stands. We analysed tree growth data from two consecutive 6-year rotations (a planted and a coppice generation) in experimental short-rotation hybrid aspen (Populus tremula L. × P. tremuloides Michx.) stands in the Free Air Humidity Manipulation (FAHM) experiment in Estonia. In three plots, mean relative air Humidity was elevated by 7% and three plots were controls. Across two rotation periods, the humidification effect on tree height and/or stem basal area increment was year-dependent (p
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Northern Forest Trees Under Increasing Atmospheric Humidity
Progress in Botany, 2018Co-Authors: Elina Oksanen, Arne Sellin, Markku Keinänen, Jenna Lihavainen, Sarita Keski-saari, Sari Kontunen-soppela, Anu SõberAbstract:Several climate change scenarios predict increasing precipitation for northern latitudes and several other regions in the globe, leading to increase in Atmospheric water vapour content [expressed as increased relative Humidity (RH) or as decreased water vapour pressure deficit (VPD)] and environmental wetness. Plants are known to be sensitive to high Humidity (low VPD) as indicated by changes in stomatal function, transpiration, mineral nutrient uptake, growth, development, sugar metabolism and leaf epicuticular wax composition in several species and studies. To understand the impact of increasing Humidity (lower VPD) on forest ecosystems, a long-term and large-scale field experiment (FAHM, Free Air Humidity Manipulation) is conducted in Estonia with silver birch and hybrid aspen, representing widespread deciduous species in northern Europe. The experiment revealed that high Humidity is an important climatic factor, causing reduction in growth rate of the aboveground parts, leaf biomass and area, bud size, sap flux and earlier bud break and delayed leaf fall. In the belowground parts, root biomass (fine-root biomass in particular) was increased although the root compartment was exposed to anaerobic conditions, increased soil pH and soil water potential, with lowered soil respiration and altered microbial and fungal communities. In the leaves, high Humidity shifted the metabolism towards nonstructural carbohydrates, antioxidants and phenolic compounds, while nutrient (N and P) content, photosynthesis, dark respiration, hydraulic conductance and the density of glandular trichomes were reduced. The change in the chemical composition of the surface wax layer resulted in lower hydrophobicity, exposing the leaves for fungal pathogen attacks. In the stem, N and P content in wood and number of living parenchyma cells were increased, while the stem wood density was reduced and wood chemistry altered. Reduction in the growth rates under high Humidity was more pronounced in hybrid aspen than in silver birch. Birch showed more efficient adjustment of leaf and root morphology, hydraulic architecture, primary carbon and nitrogen metabolism and leaf surface properties mitigating the negative impacts of high Humidity. At the ecosystem level, high Humidity altered soil processes (moisture content, microbiota, nitrification), with potential to affect competition and species composition. A complementary laboratory study with birch demonstrated that additional N supply can counteract the effects of low VPD on cellular metabolism and leaf surface wax quality.
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Growth of northern deciduous trees under increasing Atmospheric Humidity: possible mechanisms behind the growth retardation
Regional Environmental Change, 2016Co-Authors: Arne Sellin, Krista Lõhmus, Priit Kupper, Jaak Sober, Anu Sõber, Meeli Alber, Markku Keinänen, Jenna Lihavainen, Elina Oksanen, Arvo TullusAbstract:Increasing Atmospheric Humidity—a climate trend predicted for northern Europe—will reduce water flux through vegetation. Diminished transpirational water flux impacts various physiological processes, causing growth decline in deciduous trees. We propose, based on the results obtained from the long-term free air Humidity manipulation experiment, concurrent mechanisms to explain the growth deceleration due to increases in relative air Humidity. Reduced Atmospheric evaporative demand diminishes nutrient uptake and leads to lower leaf nutritional status and to an unbalanced foliar phosphorus/nitrogen ratio (P:N), resulting in a decline in leaf photosynthetic capacity. Elevated relative Humidity induces readjustment of foliar metabolism: disturbed N metabolism, accumulation of starch and changes in secondary metabolite contents probably impair both photosynthetic performance and growth. Increased carbohydrate content in the leaves suggests that sink strength of trees is reduced under elevated Humidity. As a consequence of the stress, foliar development is hindered, observed at individual leaf or whole-tree foliage levels, lowering production potential of trees proportionally to their foliar area. Larger investments in stem xylem in relation to foliage cause an increase in the ratio of non-photosynthetic to photosynthetic tissues, leading to larger maintenance respiration costs determined by the volume of parenchymatous tissue. An increase in the proportion of living parenchyma cells in relation to dead xylem elements in sapwood additionally enhances respiration costs. Disproportionate changes in hydraulic versus stomatal conductance become a critical factor in the case of weather extremes, which limit canopy conductance and may induce dysfunction of the hydraulic system. Increasing environmental Humidity creates favourable conditions for development of pathogens, increasing frequency of fungal damage.
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Impact of elevated Atmospheric Humidity on anatomical and hydraulic traits of xylem in hybrid aspen
Functional Plant Biology, 2015Co-Authors: Anna Katarzyna Jasińska, Märt Rahi, Merryl Alber, Arvo Tullus, Arne SellinAbstract:This study was performed on hybrid aspen saplings growing at the Free Air Humidity Manipulation site in Estonia. We investigated changes in wood anatomy and hydraulic conductivity in response to increased air Humidity. Two hydraulic traits (specific conductivity and leaf-specific conductivity) and four anatomical traits of stem wood – relative vessel area (VA), vessel density (VD), pit area and pit aperture area – were influenced by the Humidity manipulation. Stem hydraulic traits decreased in the apical direction, whereas branch hydraulic characteristics tended to be greatest in mid-canopy, associated with branch size. A reduction in VD due to increasing Humidity was accompanied by a decrease in vessel lumen diameter, hydraulically weighted mean diameter (Dh), xylem vulnerability index and theoretical hydraulic conductivity. VA and Dh combined accounted for 87.4% of the total variation in kt of branches and 85.5% of that in stems across the treatments. Characters of branch vessels were more stable, and only the vessel-grouping index (the ratio of the total number of vessels to the total number of vessel groupings) was dependent on the interactive effect of the treatment and canopy position. Our results indicate that the increasing Atmospheric Humidity predicted for high latitudes will result in moderate changes in the structure and functioning of the hybrid aspen xylem.
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Responses of sap flow, leaf gas exchange and growth of hybrid aspen to elevated Atmospheric Humidity under field conditions
AoB PLANTS, 2014Co-Authors: Aigar Niglas, Priit Kupper, Arvo Tullus, Arne SellinAbstract:An increase in average air temperature and frequency of rain events is predicted for higher latitudes by the end of the 21st century, accompanied by a probable rise in air Humidity. We currently lack knowledge on how forest trees acclimate to rising air Humidity in temperate climates. We analysed the leaf gas exchange, sap flow and growth characteristics of hybrid aspen (Populus tremula × P. tremuloides) trees growing at ambient and artificially elevated air Humidity in an experimental forest plantation situated in the hemiboreal vegetation zone. Humidification manipulation did not affect the photosynthetic capacity of plants, but did affect stomatal responses: trees growing at elevated air Humidity had higher stomatal conductance at saturating photosynthetically active radiation (gs sat) and lower intrinsic water-use efficiency (IWUE). Reduced stomatal limitation of photosynthesis in trees grown at elevated air Humidity allowed slightly higher net photosynthesis and relative current-year height increments than in trees at ambient air Humidity. Tree responses suggest a mitigating effect of higher air Humidity on trees under mild water stress. At the same time, trees at higher air Humidity demonstrated a reduced sensitivity of IWUE to factors inducing stomatal closure and a steeper decline in canopy conductance in response to water deficit, implying higher dehydration risk. Despite the mitigating impact of increased air Humidity under moderate drought, a future rise in Atmospheric Humidity at high latitudes may be disadvantageous for trees during weather extremes and represents a potential threat in hemiboreal forest ecosystems.