High-resolution densitometry and elemental analysis of tropical wood.

Peter Hietz,Ingeborg Lang,Michael Grabner,Thomas Prohaska,Monika Horsky

doi:10.1007/s00468-014-1126-7

Abstract

Key message Understanding the mobility and distribution of chemical elements in wood is necessary to apply dendrochemistry. Crystals are likely stable and could be used to analyze changes in nutrient supply. Dendrochemistry uses the variation in wood chemical composition to infer about past environmental conditions and possible effects on tree growth. Elemental or isotopic variation might also help to identify annual growth where tree rings are anatomically not distinct. However, most elements are—to a certain degree—mobile within wood and may be related to anatomical structures. Therefore, understanding what affects elemental distribution is important to make use of and critically assess the potential of dendrochemistry. We studied the variation of wood density and elements at high spatial resolution in wood of six species with anatomically distinct to rather indistinct tree rings from a Thai monsoon forest. Many elements had a higher concentration in parenchyma than in fiber cells, and the co-variation of elements differed strongly between elements and also between species. Strong wood density changes along the ring boundary were found only in Melia azedarach. In all species, the X-ray images showed crystals. EDX spectra showed that these consist of calcium or silicon (in Chukrasia tabularis) as major elemental components. A high concentration of heavy metals (Fe, Cu and Zn) was found in Vitex peduncularis. We conclude that at least for the species studied the radial variation of elemental concentration is unlikely to reveal annual rings that anatomy could not. However, if elements in crystals are more stable than in cell walls or living protoplasts, analyzing the distribution of elements present in crystals may show environmental conditions that, in turn, influence crystal formation and are little known.

Highlights

Wood represents an important archive, deposited during a tree’s life and reflecting tree physiology and environmental conditions that affect growth
The analysis of a highly resolved chemical variation can help to identify annual growth where annual rings are anatomically not distinct enough (Evans and Schrag 2004; Poussart et al 2006; Verheyden et al 2004). This approach has been made possible by instrument developments, in particular laser ablation (LA), which coupled with inductively coupled plasma mass spectrometry (ICP-MS; Hoffmann et al 1994; Prohaska et al 1998) or gas chromatography-isotope ratio mass spectrometry (GC-IRMS; Schulze et al 2004) can achieve a spatial resolution in the lm range
A basic assumption of dendrochemistry is the relation of wood chemical composition to the time the wood was produced, which requires the radial transport of elements to be minimal or that mobile fraction can be removed

Summary

Introduction

Wood represents an important archive, deposited during a tree’s life and reflecting tree physiology and environmental conditions that affect growth. The analysis of a highly resolved chemical variation can help to identify annual growth where annual rings are anatomically not distinct enough (Evans and Schrag 2004; Poussart et al 2006; Verheyden et al 2004). This approach has been made possible by instrument developments, in particular laser ablation (LA), which coupled with inductively coupled plasma mass spectrometry (ICP-MS; Hoffmann et al 1994; Prohaska et al 1998) or gas chromatography-isotope ratio mass spectrometry (GC-IRMS; Schulze et al 2004) can achieve a spatial resolution in the lm range

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