High-Resolution X-Ray Computed Tomography: A New Workflow for the Analysis of Xylogenesis and Intra-Seasonal Wood Biomass Production

Abstract

Understanding tree growth and carbon sequestration are of crucial interest to forecast the feedback of forests to climate change. To have a global understanding of the wood formation, it is necessary to develop new methodologies for xylogenesis measurements, valid across diverse wood structures and applicable to both angiosperms and gymnosperms. In this study, the authors present a new workflow to study xylogenesis using high-resolution X-ray computed tomography (HRXCT), which is generic and offers high potential for automatization. The HXRCT-based approach was benchmarked with the current classical approach (microtomy) on three tree species with contrasted wood anatomy (Pinus nigra, Fagus sylvatica, and Quercus robur). HRXCT proved to estimate the relevant xylogenesis parameters (timing, duration, and growth rates) across species with high accuracy. HRXCT showed to be an efficient avenue to investigate tree xylogenesis for a wide range of wood anatomies, structures, and species. HRXCT also showed its potential to provide quantification of intra-annual dynamics of biomass production through high-resolution 3D mapping of wood biomass within the forming growth ring.

Wood Formation Modeling – A Research Review and Future Perspectives

“…The monitoring of volume and mass variables only are potentially useful for parameterizing and verifying parsimonious wood formation models useful for regional-scale to global modeling, for example in new generations of DGVMs. Recently a new method called high-resolution X-ray computed tomography (HRXCT) is also capable of monitoring intraannual stem radial width (called “size growth” by the authors), and biomass dynamics and promises to create further such observations relevant to modeling wood formation (Lehnebach et al, 2021 ). However, whether or not all information content necessary for model validation can be retained by all these new types of observations remains unclear, as neither zone-width nor volume and mass- only data have so far been used to validate any wood formation models.…”

Number of growth days and not length of the growth period determines radial stem growth of temperate trees

“…Radial growth involves the production of new xylem and phloem cells by the cambium and the expansion of these cells (‘growth in size’) followed by cell wall formation or maturation (‘growth in biomass’; Cuny et al, 2015 ; Lehnebach et al, 2021 ; Rathgeber et al, 2016 ). The expansion of cells leads to irreversible increase in stem diameter and is considered ‘radial growth’ in this study.…”

Linking wood density records of common beech (Fagus sylvatica L.) with temperature and precipitation variability from a temperate lowland site.

“…WD can be considered as an integrator of ecophysiological activity, which may provide novel and additional information on climate-growth relationships of trees compared to radial growth data (Bouriaud et al, 2004;van der Maaten et al, 2012). WD is determined by wood anatomical characteristics (e.g.…”

“…WD is determined by wood anatomical characteristics (e.g. cell wall thickness or size and density of sap transporting vessels), which in turn are shaped by prevailing environmental conditions, and hence steered by climatic variables (van der Maaten et al, 2012). Especially for conifer trees, relationships between maximum latewood density (MXD) and summer temperature have been established and are (widely) used for climate reconstructions (Schweingruber et al, 1978;Briffa et al, 1998;Björklund et al, 2017Björklund et al, , 2019, even for periods that go back more than a thousand years in time (Esper et al, 2018;Klippel et al, 2019).…”

“…However, densitometric studies on European beech showed that climatic signals are recorded in MXD and may provide valuable information related to the climate response of beech trees (Bouriaud et al, 2004;Skomarkova et al, 2006;Meinardus et al, 2012). Despite these findings, our knowledge of MXD and intra-annual WD variations in hardwoods and beech in particular, is still limited (van der Maaten et al, 2012;Bontemps et al, 2013).…”