Elevated air humidity affects hydraulic traits and tree size but not biomass allocation in young silver birches (Betula pendula)

Abstract

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). A second question was whether the changes in hydraulic architecture depend on tree size. Two years of application of increased RH decreased the biomass accumulation in birch saplings, but the biomass partitioning among aboveground parts (leaves, branches, and stems) remained unaffected. Increased stem Huber values (xylem cross-sectional area to leaf area ratio) observed in trees under elevated RH did not entail changes in the ratio of non-photosynthetic to photosynthetic tissues. The reduction of stem–wood density is attributable to diminished mechanical load imposed on the stem, since humidified trees had relatively shorter crowns. Growing under higher RH caused hydraulic conductance of the root system (KR) to increase, while KR (expressed per unit leaf area) decreased and leaf hydraulic conductance increased with tree size. Saplings of silver birch acclimate to increasing air humidity by adjusting plant morphology (live crown length, slenderness, specific leaf area, and fine-root traits) and wood density rather than biomass distribution among aboveground organs. The treatment had a significant effect on several hydraulic properties of the trees, while the shifts were largely associated with changes in tree size but not in biomass allocation.

Artificially decreased vapour pressure deficit in field conditions modifies foliar metabolite profiles in birch and aspen

“…Trees were thereby generally N limited in the FAHM field regardless of the VPD condition, and N limitation was elicited by decreased VPD only in aspen. Sellin et al (2015) reported that the humidification treatment affected the leaf N and P concentrations most at the upper canopy level. Since we collected the samples from the middle of the canopy level, the difference in N and P concentrations may be less clear.…”

“…High starch content relative to soluble sugars indicates that carbon storage is favoured over transport, respiration, and growth in decreased VPD. Inhibited growth rate and foliage development implicate that trees were sink limited under decreased VPD ( Sellin et al , 2015 ). Levels of heptulose sugars, other than sedoheptulose, were higher in leaves exposed to decreased VPD than to ambient VPD.…”

The competitive status of trees determines their responsiveness to increasing atmospheric humidity – a climate trend predicted for northern latitudes

“…are less affected by waterlogging and soil hypoxia than high-light plants, apparently facing to photoinhibition (Wagner & Dreyer, 1997). In addition, decreasing hydraulic efficiency of the root system with increasing tree dimensions may impose relatively greater hydraulic limitations on advantaged trees under water deficit (Sellin et al, 2015). High precipitation in June 2010 ( Fig.…”

Consequences of different sample drying temperatures for accuracy of biomass inventories in forest ecosystems

“…nitrogen content. Thus, a brief literature review revealed that biomass components were dried at different temperatures, including 60 °C [19][20][21] , 65 °C [22][23][24] , 70 °C [25][26][27] , 75 °C 17,28,29 , 85 °C 30,31 and 105 °C [32][33][34] .…”