Radial growth anisotropy and temporality in fast-growing temperate conifers

Abstract

& Key message Radial growth in a group of Pinus radiata D. Don. trees varies in magnitude around the circumference and follows synchronous but arrhythmic dynamics. & Context Eccentric and irregular girth growth is typically associated to specific growth responses, but it is generally assumed to be small or absent during normal development. The dynamics by which excess growth is formed are unclear. & Aims The objective of this study is to determine if growth anisotropy is a commonly occurring phenomenon without apparent mechanical imbalance of the tree and to document the temporality of differential radial growth. & Methods Six mature P. radiata trees were equipped with point dendrometers at different circumferential positions. Growth rates and periods of activity were monitored over 4 months. & Results The highest growth differential on a single tree exceeded a factor of two. The direction of the highest growth varied between trees. In one case, that direction switched over time. The amount of anisotropy was explained by differences in the number of growing days and growth rate entropy. & Conclusion Tree stem formation in fast-growing softwoods is a biological process characterized by high spatial heterogeneity and intermittent temporal activity.

Why trees grow at night

“…Meanwhile, the zero‐growth approach has become widely accepted and applied (Dietrich & Kahmen, 2019 ; Schafer et␣al ., 2019 ; Eitel et␣al ., 2020 ; Güney et␣al ., 2020 ; Lamacque et␣al ., 2020 ; Pappas et␣al ., 2020 ; Sellier & Segura, 2020 ). Accordingly, growth is defined as the radial stem increase above a previously reached stem radial maximum (Fig.…”

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

“…However, this sink role becomes uncertain in the future due to unknown effects of climate change on stem growth (Pugh et al, 2018 ). Annual stem growth variation across years and sites is influenced by underlying seasonal growth responses (Forrest & Miller‐Rushing, 2010 ; Sellier & Ségura, 2020 ; Steppe et al, 2015 ) and possible legacy effects (Ogle et al, 2015 ; Zweifel et al, 2020 ; Zweifel & Sterck, 2018 ). Multiple studies have described a sigmoidal curve to model annual radial growth, being fastest at the beginning and slowest at the end of the growth period (Cruz‐García et al, 2019 ; Deslauriers et al, 2003 ; van der Maaten et al, 2018 ).…”

TreeNet–The Biological Drought and Growth Indicator Network

“…Uncertainty also remains with the assumption of the zero-growth concept that no growth takes place in the case of stem shrinkage, which means that the turgor necessary for growth is not achieved (Zweifel et al, 2016) and no cell expansion is possible under such conditions. Even though the underlying concept of Lockhart (1965) is theoretically sound and many recent papers have provided evidence for its usefulness (Dietrich and Kahmen, 2019;Schafer et al, 2019;Aryal et al, 2020;Eitel et al, 2020;Güney et al, 2020;Lamacque et al, 2020;Pappas et al, 2020;Sellier and Segura, 2020;Dukat et al, 2021;Meng et al, 2021;Nehemy et al, 2021;Pierrat et al, 2021;Zweifel et al, 2021), the separation of dendrometer data into GRO and TWD has not yet been tested with an independent method. The main reason for this lack of rigorous testing is that there is no alternative method capable of cross-checking hourly resolved dendrometer data in mature forest trees over a reasonable period of time (i.e., without excessive destructive sampling).…”