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

By M. L. McCormack, Ian A. DICKIE, D. Eissenstat, T. Fahey, Christopher W. Fernandez, Dali Guo, Heljä-Sisko Helmisaari, E. Hobbie, Colleen M. Iversen, R. B. Jackson and 7 more. New Phytologist, 2015

1,262 citations recorded by the source corpus.

Fine roots acquire essential soil resources and mediate biogeochemical cycling in terrestrial ecosystems. Estimates of carbon and nutrient allocation to build and maintain these structures remain uncertain because of the challenges of consistently measuring and interpreting fine-root systems. Traditionally, fine roots have been defined as all roots ≤ 2 mm in diameter, yet it is now recognized that this approach fails to capture the diversity of form and function observed among fine-root orders. Here, we demonstrate how order-based and functional classification frameworks improve our understanding of dynamic root processes in ecosystems dominated by perennial plants. In these frameworks, fine roots are either separated into individual root orders or functionally defined into a shorter-lived absorptive pool and a longer-lived transport fine-root pool. Using these frameworks, we estimate that fine-root production and turnover represent 22% of terrestrial net primary production globally - a c. 30% reduction from previous estimates assuming a single fine-root pool. Future work developing tools to rapidly differentiate functional fine-root classes, explicit incorporation of mycorrhizal fungi into fine-root studies, and wider adoption of a two-pool approach to model fine roots provide opportunities to better understand below-ground processes in the terrestrial biosphere.

Subfields: Global and Planetary Change, Mechanical Engineering, Soil Science

View Paper: https://www.semanticscholar.org/paper/acf37b9d7c7f43d459ef806726ef9d594186625e

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Citations in the corpus

Sampling roots to capture plant and soil functions (2017, methodology): “Functional Ecology © 2017 British Ecological Society, Functional Ecology, 31, 1506–1518 McCormack et al. 2015).”
Root traits are multidimensional: specific root length is independent from root tissue density and the plant economic spectrum (2016, background): “that some transport roots may have been included in some samples (McCormack et al. 2015).”
Root nutrient concentration and biomass allocation are more plastic than morphological traits in response to nutrient limitation (2017, background): “We avoided suberized root tissue, avoided structural or transport roots, and focused on absorptive roots, but we acknowledge that some transport roots may have been included in some samples (McCormack et al. 2015).”
Fine-root trait plasticity of beech (Fagus sylvatica) and spruce (Picea abies) forests on two contrasting soils (2017, background): “Possibly, root morphological plasticity is most relevant for the finest roots, which are assumingly most active in nutrient uptake (McCormack et al. 2015).”
Modeling plant–water interactions: an ecohydrological overview from the cell to the global scale (2016, background): “Fine roots are mostly composed of living tissues and are essential for the uptake of water and nutrients, while coarse roots serve as aggregated conduits for transport and structural stability of the plant.(135,136) Water flows into the roots because the water potential is typically larger in the so”
Climate and soil nutrients differentially drive multidimensional fine root traits in ectomycorrhizal‐dominated alpine coniferous forests (2020, background): “This RD size class usually consists of both absorptive and non-absorptive roots (Guo et al., 2008; McCormack et al., 2015), which may confound the patterns and drivers of root trait variation.”
Climate, soil and plant functional types as drivers of global fine‐root trait variation (2017, methodology): “While recent studies (e.g. McCormack et al. 2015) have advocated the use of more refined root sampling schemes, fine-roots ≤2 mm form the bulk of fine-root trait data available at present and show similar patterns to roots of the first three-orders only (Freschet & Roumet 2017).”