Prospects for dendroanatomy in paleoclimatology – a case study on Picea engelmannii from the Canadian Rockies

The continuous development of new proxies as well as a refinement of existing tools are key to advances in paleoclimate research and improvements in the accuracy of existing climate reconstructions. Herein, we build on recent methodological progress in dendroanatomy – the analyses of wood anatomical parameters in dated tree rings – and introduce the longest (1585–2014 CE) dendroanatomical dataset currently developed for North America. We explore the potential of dendroanatomy of high-elevation Engelmann spruce (Picea engelmannii) as a proxy of past temperatures by measuring anatomical cell dimensions of 15 living trees from the Columbia Icefield area. There, X-ray maximum latewood density (MXD) and its blue intensity counterpart (MXBI) have previously been measured, which allows comparing the different parameters. Our findings highlight anatomical MXD and maximum radial cell wall thickness as the two most promising wood anatomical proxy parameters for past temperatures, each explaining 46 % and 49 %, respectively, of instrumental, high-pass filtered, July–August maximum temperatures over the 1901–1994 period. While both parameters display comparable climatic imprinting at higher frequencies to X-ray derived MXD, the anatomical dataset distinguishes itself from its predecessors by providing the most temporally stable warm-season temperature signal. For the long-term secular trends, discrepancies between anatomical MXD and maximum radial cell wall thickness chronologies were observed, where the former more closely follow the long-term variations of the X-ray based MXD. Further studies, including samples from more diverse age cohorts and the adaptation of RCS-based standardizations, are needed to disentangle the ontogenetic and climatic components of long-term signals stored in the wood anatomical traits and to more comprehensively evaluate the potential contribution of this new dataset to paleoclimate research.

Tangential Youngs Modulus of Coniferous Early Wood Investigated Using Cell Models

Summary The relationship between the tangential Young's modulus and the transverse cell shape in coniferous early wood was investigated by using cell models constructed by power spectrum analysis. The calculated Young's moduli of the cell models explained qualitatively the change of the experimental Young's moduli with density as well as the difference in the experimental values among species. The calculated Young's moduli differed significantly among species depending on the cell model shapes when compared at the same density. With increasing element angle in the model, the Young's modulus greatly increased without a significant change in the density, especially at the larger ratios of the axial length of the tangential cell wall to that of the radial cell wall.

Biochemical and Cytochemical Cell Wall Changes Across the Cambial Zone

Parallel biochemical and cytochemical investigations on several hardwoods disclosed progressive changes in radial cell wall composition and structure across the cambial zone. Phloem derivatives were characterised by the early deposition of a microfibrillar skeleton and a low amount of xylans. In the radial walls of xylem derivatives, cellulose micro fibrils were few and, at least in some species, xylans were rather abundant. The content in acidic pectins and calcium ions increased from the phloem to the xylem side. The presence of cellulose microfibrils, the activity of enzymes such as xylan synthases or pectin methylesterases might be useful clues to recognise early stages of xylem or phloem determination in the first cambial derivatives.