Ecosystem Composition Controls the Early Fate of Rare Earth Elements during Incipient Soil Genesis

Abstract

We used a model rock-biota system to demonstrate that ecosystem composition (microbial and plant) regulates the fate of REE during early biota-rock interactions.Graphical abstract: word cloud with article keywords, Buffalograss, and X-ray diffractogram. Main Manuscript 2The rare earth elements (REE) are of increasing importance in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. Despite their great promise, REE fractionation in early plant-microbe-rock systems has largely remained elusive. We tested the hypothesis that REE mass-partitioning during the incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, plant, and arbuscular mycorrhiza.Pore-water element abundances reflected a rapid transition from abiotic to biotic weathering, the latter associated with lower aqueous loss and higher uptake. Abiotic dissolution contributed 38.6±19% to total denudation. Microbes incremented denudation, particularly in rhyolite, this effect associating with decreased bioavailable solid fractions in this rock. Total mobilization (aqueous+uptake) was ten times greater in planted treatments compared to abiotic control, REE masses in plant generally exceeding those in water. Plants of larger biomass further increased solid fractions, consistent with soil genesis. Mycorrhiza had a generally positive effect on total mobilization. The incipient REE weathering was dominated by inorganic dissolution enhanced by biotic respiration, the patterns of denudation largely dictated by mineralogy. A consistent biotic signature was observed in La:phosphate, mobilization:solid fraction in all rocks, as well as in the general pattern of denudation and uptake.The transformation of rock to soil supports Earth's terrestrial life. Soil genesis and evolution have been under scientific scrutiny for over a century. With recent advances in analytical chemistry, molecular/evolutionary biology, hydrology, ecology and remote sensing we are only now beginning to understand how different components of geosphere, hydrosphere, atmosphere, and biosphere work together at different scales to shape the surface of Earth and transform parent rock into soil that sustains the ecosystem 1,22,3,1,4,5 . Among the most reactive phases in the transformation of crustal rock are the earliest stages of mineral weathering when first microbial and plant communities interact with bedrock and spark the flow of energy and nutrients that feed into major biogeochemical cycles. The igneous rock-Earth's nutrient store, exhibits its largest thermodynamic disequilibrium at surface pressure and temperatures, where the oxic aqueous environment makes it highly susceptible to weathering. Rapid mineral transformations of crustal rock often accompany the earliest stages of weathering, and they are intensified under mineral colonization by microbiota and plant roots. Studying these early interactions in the natural soil-forming system has classically been focused on nutrients that Main Manuscript...

Controlled Experiments of Hillslope Coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological Change

“…In addition to water residence times, rock dissolution rates are also influenced by formation of secondary minerals [95]. Plants and microorganisms can also strongly influence weathering rates through production of organic acids and other complexing agents [72,96], through respiration and uptake of water and dissolving nutrients [97], and through enzymatic promotion of bicarbonate formation from CO 2 [98,99].…”