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Dryad

Temperature drives the coordination between aboveground nutrient conservation and belowground nutrient acquisition in alpine coniferous forests

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Oct 03, 2023 version files 5 KB

Abstract

Aboveground nutrient conservation via resorption processes and belowground nutrient acquisition from soils are two important mechanisms for plants to maintain nutrition and ecosystem functions. However, the mechanism by which plants coordinate these two nutrient strategies, especially for ectomycorrhizal (ECM)-dominated conifers in alpine forests, remains unclear.

We investigated the relationships between aboveground nutrient conservation and belowground nutrient acquisition and their environmental drivers by measuring leaf nutrient (i.e., nitrogen [N] and phosphorous [P]) resorption efficiency, resource foraging- and uptake-related root morphological (root diameter [RD], specific root length [SRL]/area [SRA]) and physiological (root tissue density [RTD], root N and P concentration) traits, mycorrhizal colonization rate (MCR), rhizosphere effect on soil N and P cycling, and environmental factors of 40 ECM coniferous populations on the eastern Tibetan Plateau, China.

Our results show that with increasing leaf nutrient (N and P) resorption efficiency, conifers shifted from depending on the ‘outsourcing’ strategy by mycorrhizal fungi (high MCR) to relying on the ‘do-it-yourself’ strategy of root mining (high rhizosphere effect on N- and P-mining-related enzyme activities) rather than on root foraging (high SRL and SRA) and preferred more conservative roots (high RTD and low root N and P concentrations). Temperature was the main factor driving a negative relationship of ECM fungi foraging, root uptake and a positive relationship of root mining with leaf nutrient resorption, while precipitation resulted in a decoupled relationship between root foraging and leaf nutrient resorption.

Our findings demonstrate temperature-driven and diverse collaborations (e.g., tradeoff or synergy) between belowground nutrient acquisition and aboveground nutrient conservation strategies in alpine ECM conifers and highlight that the preference for belowground nutrient acquisition strategies could influence the aboveground nutrient utilization strategy. This is insightful for a holistic understanding of the adaptation and responses of alpine forests to climatic change.