New Phytologist Editors' choice: June 2015, 206:4
Last updated: 8 May, 2015
Root biochemistry, root traits, and soil carbon – making the links
Wang J-J, Tharayil N, Chow AT, Suseela V, Zeng H. 2015. Phenolic profile within the fine root branching orders of an evergreen species highlights a disconnect in root tissue quality predicted by elemental- and molecular-level carbon composition. New Phytologist 206: 1261–1273.
A large fraction of the carbon that is sequestered in soil is derived from fine roots, but traditional indices of root decomposition (e.g., carbon-to-nitrogen ratio) have failed to adequately reflect the importance of fine roots to soil carbon. Phenolic compounds exert a disproportionate influence on root decomposition and recalcitrance, and in the latest issue of New Phytologist Wang et al. report on the linkage between macro-elemental and morphological traits of fine roots with the quantitative and qualitative profile of phenolic compounds.
Recognizing that fine roots cannot be treated as a homogenous carbon source, Wang et al. structured their investigation using the framework of variation of root traits within fine root architecture. They analyzed the seasonal dynamics of phenolic compounds in leaves and roots of Ardisia quinquegona, an important forest shrub species in South China and looked for correlations between phenolic content and a suite of root traits across root branching order. Free and bound phenols decreased with increasing root order, and seasonal variation was greater in lower order roots. Significantly, root traits such as specific root length and nitrogen content were decoupled from the phenolic profile, revealing the inadequacy of these more traditional indicators of carbon quality.
This paper is particularly noteworthy for making the critical links between detailed biochemical analyses, the higher order ecological implications of the phenolic profiles, and the value of the root trait framework to ecological modeling. Comprehensive and integrative perspectives such as this are needed for developing a predictive understanding of carbon, water, and nutrient cycling in terrestrial biosphere models.
Richard Norby, Editor New Phytologist
Oak Ridge, TN, USA
Originally posted 8th May 2015.