Stem radius changes and their relation to stored water in stems of young Norway spruce trees

Abstract

Changes in the stem radius of young Norway spruce [Picea abies (L.) Karst.] were related to changes in stem water content in order to investigate the relationship between diurnal stem size fluctuations and internally stored water. Experiments were performed on living trees and on cut stem segments. The defoliated stem segments were dried under room conditions and weight (W), volume (V), and xylem water potential (Ψ s ) were continuously monitored for 95 h. Additionally, photos of crosssections of fresh and air-dried stem segments were taken. For stem segments we found that the change in V was linearly correlated to the change in W as long as Ψ s was >-2.3±0.3 MPa (phase transition point). Stem contraction occurred almost solely in the elastic tissues of the bark (cambium, phloem, and parenchyma), and the stem radius changes were closely coupled to bark water content. For living trees, it is therefore possible to estimate the daily contribution of "bark water" to transpiration from knowledge of the stem size and continuous measurements of the stem radius fluctuations. When Ψ s reaches the phase-transition point, water is also withdrawn from the inelastic tissue of the stem (xylem), which -in the experiment with stem segments -was indicated by an increasing ratio between ∆V and ∆W. We assume that for Ψ s below the transition point, air is sucked into the tracheids (cavitation) and water is also withdrawn from the xylem. Due to the fact that in living P. abies Ψ s rarely falls below -2.3±0.3 MPa and the xylem size is almost unaffected by radius fluctuations, dendrometers are useful instruments with which to derive the diurnal changes in the bark water contents of Norway spruce trees.

Tree growth, wood and bark water content of 28 Amazonian tree species in response to variations in rainfall and wood density

“…On the other hand, the living components of the bark (phellogen, vascular cambium, phelloderm) may dilate in response to hydration due to the presence of osmotically-active compounds, such as sugars and amino acids. Thus, it seems plausible to conclude that most of the pole contraction occurs in the bark and associated living tissues, such as the sapwood parenchyma (Molz & Klepper 1973, Zweifel et al 2000, De Schepper et al 2012. Therefore, in this work, the rainfall effect on the stem water content could be attributed to a high transpiration rate of the forest canopy in the dry season.…”

“…Fluctuations in pole diameter are associated with diurnal and seasonal changes in the water content of stem, particularly with variation in the water content of the bark, and to a lesser extent, with sapwood swelling and contraction (Zweifel et al 2000, Remorini & Massai 2003.…”

“…Variations in the water content of poles reflect their water-storing capacity -tree capacitance (Goldstein et al 1998, Stratton et al 2000, Zweifel et al 2000, as the pole can store water to be used when the amount of water lost by transpiration exceeds the water uptake capacity of the tree (Cermak et al 2007). It occurs, for example, during the hottest period of the day or during the dry season of the year.…”

Periodicidade do crescimento de espécies arbóreas da Floresta Estacional Semidecidual no Sul do Brasil

“…Considerando-se que uma das funções da casca é o armazenamento de água (ROSELL et al, 2014), os valores negativos observados da taxa de incremento podem ser atribuídos ao uso dessa reserva hídrica pela planta durante o período mais desfavorável. Adicionalmente, a variação da umidade relativa do ar leva a oscilação da largura da casca, já que ela está em contato direto com o ambiente (ZWEIFEL et al, 2000;STAHL et al, 2010).…”

Above- and below-ground biomass, surface and volume, and stored water in a mature Scots pine stand

“…Sapwood water storage is a key feature that helps the tree to cope with diurnal peaks in water demand as well as with a longer drought stress. A considerable amount of water for the daily transpiration is supplied from the stored water (Č ermák et al 1982;Goldstein et al 1998;Zweifel et al 2000;Č ermák et al 2007;Urban et al 2013). Therefore, this paper also describes the amount of available water storage in the skeleton organs.…”