Functional relationships between morphology and respiration of fine roots in two Chinese temperate tree species

Abstract

Fine root morphology is closely linked with physiological functions. However, we have limited understanding of relationships between morphological traits and respiration of fine roots. In this study, we measured the fine root respiration rates of Tilia amurensis Rupr. and Pinus koraiensis Sieb. et Zucc with a simplified specially designed root-chamber system in the field. We found that mean diameter and specific root length (SRL) exhibited significant power relationships with fine root respiration in both species. Respiration rates of smaller fine roots (<0.5 mm for Tilia amurensis and <0.7 mm for Pinus koraiensis) in mean diameter were much higher and varied widely compared with those larger diameter class (0.6-1.8 mm for Tilia amurensis and 0.8-1.9 mm for Pinus koraiensis). Moreover, significant positive relationships existed between fine root nitrogen (N) concentration and respiration in both species. For Tilia amurensis, SRL explained more of the variability in respiration (84%) than diameter or N concentration, while for Pinus koraiensis, fine root N concentration explained more of the variability in respiration (79%) than diameter or SRL. Our results suggest that fine roots are composed of individual roots differing markedly in respiration and morphology, rather than identical units as traditionally assumed.

Impacts of morphological traits and temperature on fine root respiration during dormancy of Caragana korshinskii

“…Root respiration is strongly linked to morphological traits such as root diameter, tissue composition, and specific root length. Most studies of the relationships between root respiration and root morphology have been conducted during growth periods and have generally demonstrated similar results (Dannoura et al 2006;Marsden et al 2008;Sun and Mao 2011). For example, mean roo diameter, nitrogen concentration, and specific fine root length have different effects on R fr (Sun and Mao 2011).…”

“…Most studies of the relationships between root respiration and root morphology have been conducted during growth periods and have generally demonstrated similar results (Dannoura et al 2006;Marsden et al 2008;Sun and Mao 2011). For example, mean roo diameter, nitrogen concentration, and specific fine root length have different effects on R fr (Sun and Mao 2011). Specific root respiration and its relationship to mean root diameter, tissue density, and specific root length vary among species (Makita et al 2009(Makita et al , 2012.…”

“…Fine roots are generally defined as roots less than 2 mm in diameter (Hendrick and Pregitzer 1992); these tissues play a key role in belowground C cycling in ecosystems (Jackson et al 1997;George et al 2003). Like leaves, fine roots have high physiological activity (Burton et al 2008) and they show higher respiration rates than roots with larger diameters (Dannoura et al 2006;Marsden et al 2008;Makita et al 2009Makita et al , 2012Sun and Mao 2011). Fine root respiration (R fr ) is responsible for approximately 40 % of plant total C flux (Hamilton et al 2002;Drake et al 2008;Franck et al 2011), thus precise estimates of R fr are vital to ecological research.…”

“…The close relationships between root respiration and root morphology, chemistry, and anatomy in larch (Larix gmelinii) and ash (Fraxinus mandshurica) plantations have been explored by Jia et al (2013). However, few attempts have been made to understand the relationships between root morphology and R fr (Makita et al 2009;Sun and Mao 2011), which may be the result, in part, of the technical difficulties inherent in measuring R fr (Marsden et al 2008). Standard method and practice have not been established for measuring R fr and collection of field data is time-and labor-intensive.…”

Redefining fine roots improves understanding of below‐ground contributions to terrestrial biosphere processes

“…Importantly, many traits that vary among root orders are often considered to be important for terrestrial cycles of C, water, and nutrients. For example, root life span, diameter, and secondary development increase with root order (Pregitzer et al, 2002;Guo et al, 2008c;Valenzuela-Estrada et al, 2008;Espeleta et al, 2009;Xia et al, 2010;Rewald et al, 2012), while root turnover, respiration, nitrogen and metal content, and mycorrhizal colonization tend to decrease (Figs 3, 4) (Gill & Jackson, 2000;Guo et al, 2008bGuo et al, , 2013Valenzuela-Estrada et al, 2008;Helmisaari et al, 2009;Makita et al, 2009;Jia et al, 2011;Sun & Mao, 2011;Burton et al, 2012;Rewald et al, 2012;Ouimette et al, 2013). Root decomposition rates also differ strongly among root orders, probably in part because of differences in tissue substrate chemistry (Fan & Guo, 2010;Goebel et al, 2011;Xiong et al, 2013), although the specific factors have not been elucidated.…”