Exploring the overflow tap theory: linking forest soil CO2 fluxes and individual mycorrhizosphere components to photosynthesis

The study analyzed soil CO2 efflux (Rs) in a south east England oak forest, finding that autotrophic respiration (Ra) contributes 56% of the total flux, with mycorrhizal hyphae (Rm) accounting for 18%. While soil temperature primarily drives daily Rs variation, root (Rr) and mycorrhizal (Rm) fluxes are linked to gross primary productivity (GPP), with Rm acting as a carbon "overflow tap" that may influence long-term soil organic carbon sequestration.

• In the studied temperate deciduous oak forest, the annual cumulative soil CO2 efflux (Rs) averaged 740 ± 43 g C m−2 yr−1. The components of this flux were distributed as 44% heterotrophic (Rh), 38% root (Rr), and 18% mycorrhizal hyphae (Rm), resulting in a total autotrophic (Ra) contribution of 56%.
• Soil temperature is the primary driver of daily Rs variation (R2 = 0.81), with the strongest response seen in heterotrophic fluxes (Rh, R2 = 0.65), followed by root fluxes (Rr, R2 = 0.41) and mycorrhizal hyphae (Rm, R2 = 0.18).
• Root and mycorrhizal fluxes are linked to gross primary productivity (GPP). While both respond to daily GPP changes, mycorrhizal hyphae (Rm) show a strong relationship with GPP over weekly to monthly periods, particularly when root fluxes (Rr) are low, suggesting Rm functions as a carbon "overflow tap" affecting soil organic carbon turnover.

APA

Stockholm Environment Institute (2012). Exploring the overflow tap theory: linking forest soil CO2 fluxes and individual mycorrhizosphere components to photosynthesis. https://www.sei.org/publications/exploring-the-overflow-tap-theory-linking-forest-soil-co2-fluxes-and-individual-mycorrhizosphere-components-to-photosynthesis/

Chicago

Stockholm Environment Institute. Exploring the overflow tap theory: linking forest soil CO2 fluxes and individual mycorrhizosphere components to photosynthesis. 2012. https://www.sei.org/publications/exploring-the-overflow-tap-theory-linking-forest-soil-co2-fluxes-and-individual-mycorrhizosphere-components-to-photosynthesis/.

Wikipedia

{{cite report |author=Stockholm Environment Institute |title=Exploring the overflow tap theory: linking forest soil CO2 fluxes and individual mycorrhizosphere components to photosynthesis |date=9 January 2012 |url=https://www.sei.org/publications/exploring-the-overflow-tap-theory-linking-forest-soil-co2-fluxes-and-individual-mycorrhizosphere-components-to-photosynthesis/ |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{stockholmenvironmentinstitute2012exploring, author = {{Stockholm Environment Institute}}, title = {{Exploring the overflow tap theory: linking forest soil CO2 fluxes and individual mycorrhizosphere components to photosynthesis}}, institution = {Stockholm Environment Institute}, year = {2012}, month = jan, url = {https://www.sei.org/publications/exploring-the-overflow-tap-theory-linking-forest-soil-co2-fluxes-and-individual-mycorrhizosphere-components-to-photosynthesis/}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }