Publications by authors named "Arne Sellin"

Scenarios for future climate predict an increase in precipitation amounts and frequency of rain events, resulting in higher air humidity and soil moisture at high latitudes, including in northern Europe. We analysed the effects of artificially elevated environmental humidity (air relative humidity and soil moisture) on leaf gas exchange, water relations, growth and phenology of silver birch (Betula pendula) trees growing at the Free Air Humidity Manipulation (FAHM) experimental site situated in the hemiboreal vegetation zone, in eastern Estonia, with no occurring water deficit to the trees. The environmental humidity manipulation did not significantly affect the water relations traits but did affect some leaf gas exchange parameters, growth and phenology of the trees.

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Greenhouse gas (GHG) fluxes from peatland soils are relatively well studied, whereas tree stem fluxes have received far less attention. Simultaneous year-long measurements of soil and tree stem GHG fluxes in northern peatland forests are scarce, as previous studies have primarily focused on the growing season. We determined the seasonal dynamics of tree stem and soil CH, NO and CO fluxes in a hemiboreal drained peatland forest.

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Article Synopsis
  • Aquaporin water channels (AQPs) are important transmembrane proteins that facilitate the movement of water and solutes across cell membranes, and their specific roles in silver birch are not well understood.
  • A genome analysis of silver birch identified 33 potential AQP genes organized into five distinct subfamilies, each with conserved structural features and varying functions.
  • Despite finding that 23 of these genes are actively transcribed, the study observed no significant expression changes in leaves under cold stress, suggesting that this species has unique adaptive mechanisms to environmental challenges.
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It is widely acknowledged that many plant species can keep stomata open during night. We examined how nocturnal stomatal conductance differs among potted saplings of nine temperate tree species from diverse native habitats in wet and dry soil conditions, and how it affects plant predawn water status. Nocturnal stomatal conductance in dry soil conditions was low in all the species (with a maximum value of 14.

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High relative air humidity (RH ≥ 85%) is frequent in controlled environments, and not uncommon in nature. In this review, we examine the high RH effects on plants with a special focus on stomatal characters. All aspects of stomatal physiology are attenuated by elevated RH during leaf expansion (long-term) in C species.

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Forest understory species have to acclimatize to highly heterogeneous light conditions inside forest canopies in order to utilize available resources efficiently. Light sensitivity and response speed of hydraulic conductance (K) of common hazel (Corylus avellana L.) to fast changes in irradiance was studied in leaves from three different growth light conditions-sun-exposed, moderate shade, and deep shade.

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Climate change scenarios predict an increase in air temperature and precipitation in northern temperate regions of Europe by the end of the century. Increasing atmospheric humidity inevitably resulting from more frequent rainfall events reduces water flux through vegetation, influencing plants' structure and functioning. We investigated the extent to which artificially elevated air humidity affects the anatomical structure of the vascular system and hydraulic conductance of leaves in Betula pendula.

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Climate models predict greater increases in the frequency than in the amount of precipitation and a consequent rise in atmospheric humidity at high latitudes by the end of the century. We investigated the responses of hydraulic and relevant anatomical traits of xylem to elevated relative humidity of air on a 1-yr-old coppice of hybrid aspen (Populus×wettsteinii) growing in the experimental stand at the Free Air Humidity Manipulation site in Eastern Estonia. The hydraulic conductivity of stems was measured with a high pressure flow meter; artificial cavitation in the stem segments was induced by the air injection method.

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Leaves have to acclimatize to heterogeneous radiation fields inside forest canopies in order to efficiently exploit diverse light conditions. Short-term effects of light quality on photosynthetic gas exchange, leaf water use and hydraulic traits were studied on Betula pendula Roth shoots cut from upper and lower thirds of the canopy of 39- to 35-year-old trees growing in natural forest stand, and illuminated with white, red or blue light in the laboratory. Photosynthetic machinery of the leaves developed in different spectral conditions acclimated differently with respect to incident light spectrum: the stimulating effect of complete visible spectrum (white light) on net photosynthesis is more pronounced in upper-canopy layers.

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Physiological processes taking place in plants are subject to diverse circadian patterns but some of them are poorly documented in natural conditions. The daily dynamics of physico-chemical properties of xylem sap and their covariation with tree hydraulic traits were investigated in hybrid aspen (Populus tremula L.×P.

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The interactive effects of climate variables and tree-tree competition are still insufficiently understood drivers of forest response to global climate change. Precipitation and air humidity are predicted to rise concurrently at high latitudes of the Northern Hemisphere. We investigated whether the growth response of deciduous trees to elevated air humidity varies with their competitive status.

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As changes in air temperature, precipitation, and air humidity are expected in the coming decades, studies on the impact of these environmental shifts on plant growth and functioning are of major importance. Greatly understudied aspects of climate change include consequences of increasing air humidity on forest ecosystems, predicted for high latitudes. The main objective of this study was to find a link between hydraulic acclimation and shifts in trees' resource allocation in silver birch (Betula pendula Roth) in response to elevated air relative humidity (RH).

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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.

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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.

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Light- and nitrogen-use change was examined along productivity gradients in natural grasslands at Laelatu, western Estonia, both at community level and in most abundant species. Aboveground biomass (M) ranged from 341 to 503 g m(-2) in wet (W) and from 248 to 682 g m(-2) in dry (D) community. Aboveground leaf area ratio (aLAR) decreased with rising M in D site, while it increased in W site.

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Background: Effects of water deficit on plant water status, gas exchange and hydraulic conductance were investigated in Betula pendula under artificially manipulated air humidity in Eastern Estonia. The study was aimed to broaden an understanding of the ability of trees to acclimate with the increasing atmospheric humidity predicted for northern Europe. Rapidly-induced water deficit was imposed by dehydrating cut branches in open-air conditions; long-term water deficit was generated by seasonal drought.

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Daily dynamics of leaf (K(L)) and soil-to-branch hydraulic conductance (KS-B) was investigated in silver birch (Betula pendula Roth.) using evaporative flux method in situ: water potential drop was measured with a pressure chamber and evaporative flux was estimated as sap flux density measured with sap flow gauges. Canopy position had a significant (P < 0.

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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.

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Responses of leaf and shoot hydraulic conductance to light quality were examined on shoots of silver birch (Betula pendula), cut from lower ('shade position') and upper thirds of the crowns ('sun position') of trees growing in a natural temperate forest stand. Hydraulic conductances of leaf blades (K(lb) ), petioles (K(P) ) and branches (i.e.

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It is a well-described phenomenon that plant leaves respond to changes in light intensity and duration by adjusting leaf hydraulic efficiency, and there is current consensus that up- or down-regulation of water channels (aquaporins) in the plasma membrane of the bundle sheath and mesophyll cells play a central role in the underlying mechanisms. Recently, experimental evidence has been provided also for light-mediated changes of stem hydraulic conductance (K(stem)) in field-grown laurel plants. This effect was attributed to differences in potassium ion concentration of xylem sap as a function of light conditions.

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Variation in leaf hydraulic conductance (K(L)) and distribution of resistance in response to light intensity and duration were examined in shoots of silver birch (Betula pendula Roth). K(L) was determined on detached shoots using the evaporative flux method (transpiration was measured with a porometer and water potential drop with a pressure chamber). Although K(L) depended on light duration per se, its dynamics was largely determined by leaf temperature (T(L)).

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Stomatal density and size were measured along the light gradient of a Betula pendula Roth. canopy in relation to microclimatic conditions. The theoretical stomatal conductance was calculated using stomatal density and dimensions to predict to what degree stomatal conductance is related to anatomical properties and relative stomatal opening.

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More than 5,000 measurements from 1,943 plant species were used to explore the scaling relationships among the foliar surface area and the dry, water, and nitrogen/phosphorus mass of mature individual leaves. Although they differed statistically, the exponents for the relationships among these variables were numerically similar among six species groups (ferns, graminoids, forbs, shrubs, trees, and vines) and within 19 individual species. In general, at least one among the many scaling exponents was <1.

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Response of whole-leaf hydraulic conductance (G(L)) in little-leaf linden (Tilia cordata Mill.) to temperature and photosynthetic photon flux (Q(P)) was estimated by the evaporative flux method under natural conditions in a mixed forest canopy. Mean midday G(L) in the lower- and upper-crown foliage was 1.

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Responses of leaf conductance (gL) to variation in photosynthetic photon flux density (QP), leaf-to-air vapour pressure difference (VPD), bulk leaf water potential (Psi(x)), and total hydraulic conductance (GT) were examined in silver birch (Betula pendula Roth) with respect to leaf position in the crown. To reduce limitations caused by insufficient water supply or low light availability, experiments were also performed with branchlets cut from two different canopy layers. The intact upper-canopy leaves demonstrated 1.

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