Wood Cellular Dendroclimatology: Testing New Proxies in Great Basin Bristlecone Pine

Abstract

Dendroclimatic proxies can be generated from the analysis of wood cellular structures, allowing for a more complete understanding of the physiological mechanisms that control the climatic response of tree species. Century-long (1870–2013) time series of anatomical parameters were developed for Great Basin bristlecone pine (Pinus longaeva D.K. Bailey) by capturing strongly contrasted microscopic images through a Confocal Laser Scanning Microscope. Environmental information embedded in wood anatomical series was analyzed in comparison with ring-width series using measures of empirical signal strength. Response functions were calculated against monthly climatic variables to evaluate climate sensitivity of cellular features (e.g., lumen area; lumen diameter) for the period 1950–2013. Calibration-verification tests were used to determine the potential to generate long climate reconstructions from these anatomical proxies. A total of eight tree-ring parameters (two ring-width and six chronologies of xylem anatomical parameters) were analyzed. Synchronous variability among samples varied among tree-ring parameters, usually decreasing from ring-width to anatomical features. Cellular parameters linked to plant hydraulic performance (e.g., tracheid lumen area and radial lumen diameter) showed empirical signal strength similar to ring-width series, while noise was predominant in chronologies of lumen tangential width and cell wall thickness. Climatic signals were different between anatomical and ring-width chronologies, revealing a positive and temporally stable correlation of tracheid size (i.e., lumen and cell diameter) with monthly (i.e., March) and seasonal precipitation. In particular, tracheid lumen diameter emerged as a reliable moisture indicator and was then used to reconstruct total March–August precipitation from 1870 to 2013. Wood anatomy holds great potential to refine and expand dendroclimatic records by allowing estimates of plant physiological adaptations to external stressors. Integrating xylem cellular features with ring-width chronologies can widen our understanding of past climatic variability (including annual extreme events) and improve the evaluation of long-term plant response to drought, especially in connection with future warming scenarios.

An interpreted language implementation of the Vaganov–Shashkin tree-ring proxy system model

“…Addition of a cell growth module could produce cell anatomical simulations that could be compared to emerging observations (c.f. Fonti et al, 2010;Cuny et al, 2015;von Arx et al, 2016;Ziaco et al, 2016;Popkova et al, 2018). Finally, the model may also be ported to other open source languages, as has been done for the monthly resolution 'lite' version of the Vaganov-Shashkin model (VSL;Tolwinski-Ward et al, 2011 Vaganov et al (2011).…”

New frontiers in tree-ring research

“…Micro-wood anatomy research has expanded tree-ring studies into new geographical areas (see the ‘Nontraditional species’ section) to elucidate growth patterns and chronologies from tropical species from which conventional tree-ring data cannot be derived (Venegas-González et al, 2015). Furthermore, wood anatomical features allow us to distinguish independent climate signals at various geographic locations to characterize sensitivity gradients and how future shifts in climate may heterogeneously effect forest populations across the world (Castagneri et al, 2015; Ziaco et al, 2016). Our growing understanding of the physiological mechanisms of xylem vulnerability and the impacts of water stress enable us to improve models of drought, tree mortality, and carbon cycling (Adams et al, 2017; Anderegg et al, 2015; Levanič et al, 2011; Figure 6).…”

Linking dendroecology and association genetics in natural populations: Stress responses archived in tree rings associate with SNP genotypes in silver fir (Abies alba Mill.)

“…Likewise, while we focused on dendrophenotypes derived from tree-ring width, wood cores harbour many additional time-series traits that should be explored in future studies. These include anatomical features such as cell wall thickness or lumen area which are considered as proxy for physiological adaptations to external factors (Carrer, Brunetti, & Castagneri, 2016;Ziaco, Biondi, & Heinrich, 2016) as well as isotope measures, which, for example, can be used to characterize the water use efficiency of a tree (Seibt, Rajabi, Griffiths, & Berry, 2008). Microdensitometry can supplement ring width data with information of wood density and thereby provide a more complete picture of growth, for example, during extreme events (e.g., Martinez-Meier, Sanchez, Pastorino, Gallo, & Rozenberg, 2008).…”