How does climate influence xylem morphogenesis over the growing season? Insights from long-term intra-ring anatomy inPicea abies

Abstract

Background and Aims During the growing season, the cambium of conifer trees produces successive rows of xylem cells, the tracheids, that sequentially pass through the phases of enlargement and secondary wall thickening before dying and becoming functional. Climate variability can strongly influence the kinetics of morphogenetic processes, eventually affecting tracheid shape and size. This study investigates xylem anatomical structure in the stem of Picea abies to retrospectively infer how, in the long term, climate affects the processes of cell enlargement and wall thickening.Methods Tracheid anatomical traits related to the phases of enlargement (diameter) and wall thickening (wall thickness) were innovatively inspected at the intra-ring level on 87-year-long tree-ring series in Picea abies trees along a 900 m elevation gradient in the Italian Alps. Anatomical traits in ten successive tree-ring sectors were related to daily temperature and precipitation data using running correlations.Key Results Close to the altitudinal tree limit, low early-summer temperature negatively affected cell enlargement. At lower elevation, water availability in early summer was positively related to cell diameter. The timing of these relationships shifted forward by about 20 (high elevation) to 40 (low elevation) d from the first to the last tracheids in the ring. Cell wall thickening was affected by climate in a different period in the season. In particular, wall thickness of late-formed tracheids was strongly positively related to August-September temperature at high elevation.Conclusions Morphogenesis of tracheids sequentially formed in the growing season is influenced by climate conditions in successive periods. The distinct climate impacts on cell enlargement and wall thickening indicate that different morphogenetic mechanisms are responsible for different tracheid traits. Our approach of long-term and highresolution analysis of xylem anatomy can support and extend short-term xylogenesis observations, and increase our understanding of climate control of tree growth and functioning under different environmental conditions.

Water potential control of turgor‐driven tracheid enlargement in Scots pine at its xeric distribution edge

“…Whereas temperature or photoperiod are often proposed to explain wood anatomical variations under temperate and cold climates (e.g. Jenkins et al ., ; Fonti et al ., ; Björklund et al ., ), our results are consistent with studies on conifers in water‐limited environments (Castagneri et al ., , ; Belokopytova et al ., ).…”

Moisture‐driven shift in the climate sensitivity of white spruce xylem anatomical traits is coupled to large‐scale oscillation patterns across northern treeline in northwest North America

“…cell growth features) have been increasingly and successfully used to investigate physiological and functional responses to inter-and intra-annually changing climate conditions over long periods (e.g. Carrer, Brunetti, & Castagneri, 2016;Fonti et al, 2013;Pellizzari et al, 2016) and across climatic gradients (Borghetti, Gentilesca, Leonardi, van Noije, & Rita, 2017;Castagneri et al, 2017;Kulmala et al, 2017;Pacheco, Camarero, & Carrer, 2018). However, only few studies have K E Y W O R D S boreal forest, climate change, divergence, drought, pacific decadal oscillation, Picea glauca, plasticity, tree-ring width, wood anatomy investigated long-term climate effects on wood anatomy of northern treeline conifers in general (e.g.…”

Xylogenesis of compression and opposite wood in mountain pine at a Mediterranean treeline

“…This period, in which wood formation occurs, is also the time window when xylem differentiates. Environmental conditions prior to or during this time window directly affect the number and properties of the cells formed (Castagneri et al 2017;Frankenstein et al 2005;Fonti et al 2010) and thus the functioning of the xylem. Inversely, several tree-ring characteristics can be used as proxy to reconstruct past environmental conditions (e.g., Solomon et al 2007).…”