How element translocation by plants may stabilize illitic clays in the surface of temperate soils

Abstract

It has been described several times that plant activity enriches the upper part of soil profiles in the inorganic elements they use for their growth (Si, K, Ca, Mg…). This phenomenon called “nutrient uplift” or “element translocation” can counteract element loss via leaching in surface soils and may therefore impact clay mineral stability in upper soil horizons. However, apart from some studies in tropical ecosystems, the link between element translocation and clay mineral stability has been poorly investigated yet. The present work explores the consequences of element translocation on clay mineral stability in temperate grassland soils through the use of a geochemical model. Initially, studies indicating that silicon and potassium translocation stabilizes 2:1 clay minerals and especially illitic clay minerals in surface soil were compiled. Using this analysis as a basis, we propose a simple biogeochemical model linking plant primary productivity and clay mineral thermodynamic stability that allowed explaining how plant activity may stabilize clay minerals in the upper part of temperate grassland soils. The influence of various parameters such as rainfall, primary production, elemental composition of plants or acidifying activity of roots was also investigated using the model. The outputs of the model suggested that plant activity under certain conditions may well stabilize illitic clay in surface soils which opens wide perspectives for modellers and experimentalists.