TAMM review: Continuous root forestry—Living roots sustain the belowground ecosystem and soil carbon in managed forests

Elsevier, Forest Ecology and Management, Volume 532, 15 March 2023, 120848
Cindy E. Prescott, Sue J. Grayston

An estimated half of the carbon fixed by trees is transported belowground, a portion of which is exuded into the soil where it fuels a complex belowground food web. The biological transformation of exudates into microbial metabolites and necromass is a major source of soil organic matter (SOM), including persistent mineral-associated organic matter (MAOM). Recent recognition of the fundamental importance of these inputs from living roots for sustaining life belowground and replenishing SOM demands a rethinking of how we harvest forests. By severing the lifeline of living roots, clearcut harvesting devastates much of the belowground biodiversity in forests, and prohibits a principal pathway through which SOM and C stocks are replenished. Retention harvesting retains the influence of living roots within retention patches and potentially throughout the harvested area, but only if inter-tree distances are 15 m or less. Retention trees sustain and support the re-establishment of belowground life and function following forest harvest and may mitigate post-harvest soil C losses. Sustaining the belowground ecosystem via inputs from living roots is an underappreciated benefit of continuous-cover and retention forestry.