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Carbon allocation to root exudates is maintained in mature temperate tree species under drought
Author(s) -
Brunn Melanie,
Hafner Benjamin D.,
Zwetsloot Marie J.,
Weikl Fabian,
Pritsch Karin,
Hikino Kyohsuke,
Ruehr Nadine K.,
Sayer Emma J.,
Bauerle Taryn L.
Publication year - 2022
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.18157
Subject(s) - fagus sylvatica , picea abies , biology , rhizosphere , exudate , botany , abies alba , root system , agronomy , beech , genetics , bacteria
Summary Carbon (C) exuded via roots is proposed to increase under drought and facilitate important ecosystem functions. However, it is unknown how exudate quantities relate to the total C budget of a drought‐stressed tree, that is, how much of net‐C assimilation is allocated to exudation at the tree level. We calculated the proportion of daily C assimilation allocated to root exudation during early summer by collecting root exudates from mature Fagus sylvatica and Picea abies exposed to experimental drought, and combining above‐ and belowground C fluxes with leaf, stem and fine‐root surface area. Exudation from individual roots increased exponentially with decreasing soil moisture, with the highest increase at the wilting point. Despite c . 50% reduced C assimilation under drought, exudation from fine‐root systems was maintained and trees exuded 1.0% ( F. sylvatica ) to 2.5% ( P. abies ) of net C into the rhizosphere, increasing the proportion of C allocation to exudates two‐ to three‐fold. Water‐limited P. abies released two‐thirds of its exudate C into the surface soil, whereas in droughted F. sylvatica it was only one‐third. Across the entire root system, droughted trees maintained exudation similar to controls, suggesting drought‐imposed belowground C investment, which could be beneficial for ecosystem resilience.