Leaves Fall Off and Decay, but What do Roots do?

© 2003 Eugene S. Takle

Forests offer attractive options for temporary sequestration of carbon by converting atmospheric carbon dioxide into plant carbon in the woody portion of the tree. Non-woody portions include leaves and fine roots. Leaves, like biomass from all non-woody plants, agricultural crops, etc., generally are considered to convert to soil carbon and then decay back to atmospheric carbon within a few years. But what about roots? It is frequently estimated that 33-67% of the annual net primary production (NPP) in a forest ecosystem occurs in roots, but these estimates assume that fine roots are produced, die, and are converted to soil organic matter in a period of one year. Matamala et al. (2003) provide measurements of the turnover times for carbon of fine roots for forests of pine and sweetgum and found such times to vary from 1.2 to 9 years depending on the root diameter. This longer time of turn-over will substantially reduce estimates of the contribution of roots to the global annual NPP of terrestrial ecosystems.


Reference

Matamala, R., M.A. Gonzalez-Meler, J.D. Jastrow, R.J. Norby, and W.H. Schlesinger, 2003: Impacts of fine root turnover on forest NPP and soil C sequestration potential. Science, 302, 1385-1387.