Functional adjustments of xylem anatomy to climatic variability: insights from long-termIlex aquifoliumtree-ring series

Abstract

The present study assessed the effects of climatic conditions on radial growth and functional anatomical traits, including ring width, vessel size, vessel frequency and derived variables, i.e., potential hydraulic conductivity and xylem vulnerability to cavitation in Ilex aquifolium L. trees using long-term tree-ring time series obtained at two climatically contrasting sites, one mesic site in Switzerland (CH) and one drought-prone site in Italy (ITA). Relationships were explored by examining different xylem traits, and point pattern analysis was applied to investigate vessel clustering. We also used generalized additive models and bootstrap correlation functions to describe temperature and precipitation effects. Results indicated modified radial growth and xylem anatomy in trees over the last century; in particular, vessel frequency increased markedly at both sites in recent years, and all xylem traits examined, with the exception of xylem cavitation vulnerability, were higher at the CH mesic compared with the ITA drought site. A significant vessel clustering was observed at the ITA site, which could contribute to an enhanced tolerance to drought-induced embolism. Flat and negative relationships between vessel size and ring width were observed, suggesting carbon was not allocated to radial growth under conditions which favored stem water conduction. Finally, in most cases results indicated that climatic conditions influenced functional anatomical traits more substantially than tree radial growth, suggesting a crucial role of functional xylem anatomy in plant acclimation to future climatic conditions.

Drought Effects on Vessel Plasticity of Two Endemic <em>Magnolia</em> Species in the Tropical Montane Cloud Forests of Eastern Mexico

“…We argue that such disparities in the present modifications to the vessel traits are due to species-specific physiological plasticity in response to DY. Several studies suggest that recent ENSO events (from 1929 to 2016) pushed the TMCFs' tree species to their anatomical and physiological limits [11,24,61]. Our results demonstrate that the Magnolia's vessel traits show a perceptible trend to become less in number and smaller in size during drought periods (Figure 3).…”

“…We deduce that drought induces increased hydraulic conductance with the consequence of high construction costs but reduced hydric transport efficiency and lower TRW growth rates (Figure 3 and 4) [13,24]. species maintain their water transport functioning during the growing season [13,25,27,64,71,72].…”

“…Our study confirms that at the anatomical level, these types of analyses allow us to interpret the vulnerability of the Magnolia species. As such, we suggest that dendroecological and anatomic methods are useful to assess the effect of drought events on Magnolia species worldwide and to evaluate their vulnerability of certain trees to climatic stress [9,24,35,58,60,61]. On the hindsight, evaluating just these characteristics can not explain in its entirety the differences observed in TMCFs' trees' hydraulic conducting patterns and vessel functions [4,19,22].…”

Influence of Cambial Age and Axial Height on the Spatial Patterns of Xylem Traits in Catalpa bungei, a Ring-Porous Tree Species Native to China

“…However, the effect of both axial height and cambial age on vessel lumen diameter and other vessel-related traits has not been fully emphasized so far. Specifically, radial patterns of vessel-related traits, as well as the effect of cambial age on these traits, have mainly been addressed in dendrochronological studies [12,13]. Previous studies commonly included wood anatomical traits of different cambial ages at the stem level [14][15][16][17], and analyses of vertical patterns of wood anatomical traits have mainly been restricted to the outer growth rings [18,19].…”

“…Previous studies commonly included wood anatomical traits of different cambial ages at the stem level [14][15][16][17], and analyses of vertical patterns of wood anatomical traits have mainly been restricted to the outer growth rings [18,19]. Accordingly, within-tree variation, i.e., axial or radial variation in xylem traits, has frequently been documented [12,13,19]; however, reports on both axial and radial variation in wood anatomical traits, as well as their functional implications, are limited to a few species so far [20][21][22][23][24][25][26][27][28][29]. As a consequence, the simultaneous effect of axial height and cambial age, which both might affect vascular differentiation, has not been well investigated.…”