Stem Trait Spectra Underpin Multiple Functions of Temperate Tree Species.

Shanshan Yang,Mariet Hefting,Richard S P Van Logtestijn,Lourens Poorter,Juan Zuo,Ute Sass-Klaassen,Frank J Sterck,J Hans C Cornelissen,Leo Goudzwaard

doi:10.3389/fpls.2022.769551

Abstract

A central paradigm in comparative ecology is that species sort out along a slow-fast resource economy spectrum of plant strategies, but this has been rarely tested for a comprehensive set of stem traits and compartments. We tested how stem traits vary across wood and bark of temperate tree species, whether a slow-fast strategy spectrum exists, and what traits make up this plant strategy spectrum. For 14 temperate tree species, 20 anatomical, chemical, and morphological traits belonging to six key stem functions were measured for three stem compartments (inner wood, outer wood, and bark). The trait variation was explained by major taxa (38%), stem compartments (24%), and species within major taxa (19%). A continuous plant strategy gradient was found across and within taxa, running from hydraulic safe gymnosperms to conductive angiosperms. Both groups showed a second strategy gradient related to chemical defense. Gymnosperms strongly converged in their trait strategies because of their uniform tracheids. Angiosperms strongly diverged because of their different vessel arrangement and tissue types. The bark had higher concentrations of nutrients and phenolics whereas the wood had stronger physical defense. The gymnosperms have a conservative strategy associated with strong hydraulic safety and physical defense, and a narrow, specialized range of trait values, which allow them to grow well in drier and unproductive habitats. The angiosperm species show a wider trait variation in all stem compartments, which makes them successful in marginal- and in mesic, productive habitats. The associations between multiple wood and bark traits collectively define a slow-fast stem strategy spectrum as is seen also for each stem compartment.

Highlights

The unique feature that sets trees apart from other life forms is their tall and lignified stem
We addressed the question how stem traits differ among 14 temperate tree species and what trait trade-offs and plant strategies prevail
Gymnosperms had a higher lignin concentration but a lower wood density (0.42 g cm−3) than angiosperms (0.53 g cm−3). These two major taxa hardly differed in other physical strength traits, neither in any of the traits related to metabolism or chemical defense

Summary

Introduction

The unique feature that sets trees apart from other life forms is their tall and lignified stem. The stems provide multiple functions (Sterck et al, 2005; Chave et al, 2009), which can be broadly grouped into transport and storage of resources and assimilates, mechanical support, and defense. These functions are partly delivered by different. The bark fulfills multiple functions, such as storage, transportation, photosynthesis, and protection (Franceschi et al, 2005; Rosell et al, 2014; Tuo et al, 2021). The inner bark and outer bark have different traits and show little coordination because they fulfill different functions. The large stem trait variation across species indicates that tree species coordinate their traits and functions in different ways (Hacke and Sperry, 2001), with important implications for species performance (Poorter et al, 2010), species distribution within forests and across climatic regions (Sterck et al, 2011, 2014), and species responses to global change (Cornwell et al, 2009)

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Conclusion