Xylem traits in European beech (Fagus sylvatica L.) display a large plasticity in response to canopy release

Abstract

& Key message The position of trees in the canopy impacts xylem structure and its inter-annual variation. After canopy release, the increase in the hydraulic conductivity of growth rings was driven byanincreasein radialgrowthin largetrees,andbybothan increase in radial growth and changes in xylem structure in saplings. & Context Forest canopies are frequently subjected to disturbances that allow understory trees to access the upper canopy. The effect of canopy release on xylem anatomy has been assessed in juvenile trees and saplings, while the potential acclimation of larger trees remains poorly documented. & Aims We estimated the potential hydraulic conductivity of growth rings in large understory trees compared to overstory trees, and evaluated the responses to canopy release in large trees and in saplings. & Methods We recorded radial growth, wood density, and vessel structure in beech trees according to their position within the canopy and their size. Xylem traits were followed during 6 years after canopy release for large trees, and during 2 years for saplings. Vessel diameter and frequency as well as ring area were used to compute the potential annual ring hydraulic conductivity. & Results Large understory trees displayed lower radial growth increments and lower potential annual ring hydraulic conductivity than overstory trees. After canopy release, potential annual ring hydraulic conductivity increased in large trees, due exclusively to increased radial growth without any change in specific hydraulic conductivity. It increased in saplings due to both increased radial growth and increased specific conductivity. & Conclusion Tree size impacted xylem structure and resulted in plasticity of the potential hydraulic conductivity of the annual tree ring following canopy release.

Hydraulic safety margins and air‐seeding thresholds in roots, trunks, branches and petioles of four northern hardwood trees

“…b). Fagus grandifolia is shade‐tolerant with rapid stomatal responses times as a sapling (Woods & Turner, ) and may adopt a different hydraulic strategy once it reaches full sun, similar to findings for Fagus sylvatica (Cochard et al ., ; Noyer et al ., ). The similar air‐seeding thresholds in current‐year and multi‐year stems also is partially supported by data from Cochard et al .…”

Biomechanical control of beech pole verticality (Fagus sylvatica) before and after thinning: theoretical modelling and ground‐truth data using terrestrial LiDAR

“…Sample trees met the following criteria: breast height trunk diameter was 7.5 to 17.5 cm, stems were unforked, stem lean was less than 11°, fewer than 25 epicormic branches (sensu Colin et al., ) along the lowest 4 m of stem, and no visible injury, spiral grain, canker, or top dieback. The sample was split into two groups with similar mean values for diameter, height, and relative vertical crown length (see Noyer et al., for more details). In winter 2007–2008, one group was released by thinning that removed all competing trees within a 12‐m radius around each target tree (hereafter referred to as “thinned” poles) and the other group of trees was left unreleased (“control” poles) (Ningre et al., ).…”

Does acclimation in cavitation resistance due to mechanical perturbation support the pit area or conduit reinforcement hypotheses in Phaseolus vulgaris?

“…In a study by Christensen‐Dalsgaard and Ennos () only one of three species studied exhibited changes in WD due to drought. Wood density did not change dramatically in response to canopy release (Noyer et al ). One study that did observe changes in WD was able to show variation in response to a number of environmental factors including drought, nitrogen fertilization and shade treatments in Poplar (Plavcová and Hacke ).…”

“…Even if the effect is indirect, environmental factors that decrease conduit size, could have the potential to increase cavitation resistance if the smaller conduits also resulted in less pitted wall area and a smaller probability of a more vulnerable pit membrane pore. Plasticity in conduit size has been documented in a number of studies in response to environmental factors such as canopy release (Noyer et al ), low phosphorus concentration (Holste et al ), irradiance (Matzner et al ) or reduced moisture (Holste et al ). In addition, cavitation resistance typically changes in predictable ways in response to various environmental factors (Fichot et al ) but relatively few studies have specifically looked at whether the changes in conduit size resulted in altered cavitation resistance.…”