Abstract
The plant-available pools of calcium, magnesium and potassium are assumed to be stored in the soil as exchangeable cations adsorbed on the cation exchange complex. In numerous forest ecosystems, despite very low plant-available pools, elevated forest productivities are sustained. We hypothesize that trees access nutrient sources in the soil that are currently unaccounted by conventional soil analysis methods. We carried out an isotopic dilution assay to quantify the plant-available pools of calcium, magnesium and potassium and trace the soil phases that support these pools in 143 individual soil samples covering 3 climatic zones and 5 different soil types. For 81%, 87% and 90% of the soil samples (respectively for Ca, Mg and K), the plant-available pools measured by isotopic dilution were greater than the conventional exchangeable pool. This additional pool is most likely supported by secondary non-crystalline mineral phases in interaction with soil organic matter and represents in many cases (respectively 43%, 27% and 47% of the soil samples) a substantial amount of plant-available nutrient cations (50% greater than the conventional exchangeable pools) that is likely to play an essential role in the biogeochemical functioning of forest ecosystems, in particular when the resources of Ca, Mg and K are low.
Highlights
The plant-available pools of calcium, magnesium and potassium are assumed to be stored in the soil as exchangeable cations adsorbed on the cation exchange complex
Magnesium (Mg), calcium (Ca) and potassium (K) are three major and essential nutrients for p lants[1]. In forest ecosystems, their plant-available pools are assumed to be stored in the soil as dissolved cations in solution and as exchangeable cations adsorbed on the cation exchange c omplex[2,3]
The objectives of this study are twofold: (i) to test the hypothesis that nutrient cation pools other than the conventional exchangeable pool contribute to solid solution equilibrium in a variety of forest soils covering a wide range of climatic, edaphic, chemical fertility and tree species cover conditions; (ii) to characterize the variability of the isotopically exchangeable pools in relation to the physical and chemical properties of the soil in order to better describe the different soil phases that may act as a support for this additional plant-available pool
Summary
The plant-available pools of calcium, magnesium and potassium are assumed to be stored in the soil as exchangeable cations adsorbed on the cation exchange complex. Magnesium (Mg), calcium (Ca) and potassium (K) are three major and essential nutrients for p lants[1] In forest ecosystems, their plant-available pools are assumed to be stored in the soil as dissolved cations in solution and as exchangeable cations adsorbed on the cation exchange c omplex[2,3]. Over the last decade degradation of forest soil fertility have been reported worldwide and are expected to increase[6,15,16,17] It is not yet fully understood how trees cope with very low nutrient resources in the soil and sustain long term forest p roductivity[18]. Many studies have reported discrepancies between chemical fertility (exchangeable pools, nutrient fluxes), tree nutrition (foliar nutrient concentrations) and forest productivity indicators[21,22,23,24,25]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
