Search for: All records

Here we provide percent contribution of mineral associated (i.e., heavy fraction - HF) and relatively more labile (i.e., light fraction - LF) organic matter through soil profiles and along hillslope catena within sites in the Critical Zone Network (CZNet) Geomicrobiology cluster. Each sample is separated into a HF an a LF utilizing a 1.85 g cm-3 sodium polytungstate (3Na2WO4·9WO3·H2O or Na6 [H2W12O40]) solution. The resultant fractions are run for percent carbon (C) and nitrogen (N) and their associated stable isotopes (δ13C and δ15N) to offer novel insights in soil organic matter processes. Samples that were either too small for analytical analysis or below instrument detection limit are labeled with BDL. 

Enhanced rock weathering (ERW) is proposed as a carbon dioxide removal (CDR) strategy that sequesters carbon through the carbonic acid-promoted dissolution of ground silicate rocks. Studies have explored the efficacy of ERW through geochemical models and bench-scale reactors, but field-scale experimentation is limited. A year- long, replicated study was conducted at the Landscape Evolution Observatory (LEO) at Biosphere 2 to quantify basaltic CDR at the hillslope scale. LEO comprises three mesoscale surfaces (each 330 m2) with 1 m depth of granular basalt. We subjected these structures to three 30 d irrigation events followed by progressively lengthened dry periods. Aqueous discharge was collected bihourly for major and trace chemistry, and subsurface interactions were observed at 15 min intervals through distributed sensors enabling continuous monitoring of PCO2, volumetric water content, and total hillslope mass. This approach enabled closing of the carbon and water mass balance of the system for the duration of the experiment. CDR was quantified through direct monitoring of bicarbonate (HCO3) concentrations as validated through the charge balance of non-hydrolyzing cations and strong-acid anions. Concentration-discharge relations for HCO3 showed dilution trends with clockwise hysteresis, while a decrease in CO2 uptake occurred with increased hillslope water saturation (Shydro). The CDR rate, normalized to the specific surface area of the basalt, was -13.45 log10 moles C m 2 s 1, while other studies report CDR rates from -14 to -10 log10 moles m 2 s 1. We found that basalt CDR rates were impacted by depletions of PCO2 upon hydrologic infiltration, variable Shydro, and incongruent dissolution. 

This resource provides accompanying discharge and hydrologic data (silicon, sodium, silicon stable isotopes, and discharge and irrigation fluxes) presented in 'Stable Silicon Isotope Fractionation Reflects the Routing of Water Through a Mesoscale Hillslope', Earth and Planetary Letters, https://doi.org/10.1016/j.epsl.2024.119098 This dataset was collected at the Landscape Evolution Observatory (LEO) in Tucson, Arizona from 2022-2023. Discharge chemistry and flux are reported for each of the three LEO hillslopes. Files are provided in ".csv" format. 

This data is an on-going collection of soil temperature, soil moisture, soil CO2 concentration, and soil O2 concentration starting in October 2021. We have installed sensors and probes at different soil depths across landscapes in five of the former Critical Zone Observatory locations (see the document named "sensor location"). Soil temperature and moisture are measured using Acclima SDI-12 sensors. Soil CO2 concentrations are measured using Eosense CO2 probes (switching to Vaisala GMP343 and GMP251 in 2023). Soil O2 concentrations are measured using Apogee SO-110-L-10 soil oxygen sensors. This dataset, along with our measurements of soil geomicrobiology and biogeochemistry (available in EarthChem), will help us understand the role of microbes as drivers of Critical Zone biogeochemistry and soil formation. 

ABSTRACT The importance of biota to soil formation and landscape development is widely recognized. As biotic complexity increases during early succession via colonization by soil microbes followed by vascular plants, effects of biota on mineral weathering and soil formation become more complex. Knowledge of the interactions among groups of organisms and environmental conditions will enable us to better understand landscape evolution. Here, we used experimental columns of unweathered granular basalt to investigate how early successional soil microbes, vascular plants (alfalfa;Medicago sativa), and soil moisture interact to affect both plant performance and mineral weathering. We found that the presence of soil microbes reduced plant growth rates, total biomass, and survival, which suggests that plants and microbes were competing for nutrients in this environment. However, we also found considerable genotype‐specific variation in plant–microbial interactions, which underscores the importance of within‐species genetic variation on biotic interactions. We also found that the presence of vascular plants reduced variability in pH and electrical conductivity, suggesting that plants may homogenize weathering reactions across the soil column. We also show that there is heterogeneity in the abiotic conditions in which microbes, plants, or their combination have the strongest effect on weathering, and that many of these relationships are sensitive to soil moisture. Our findings highlight the importance of interdependent effects of environmental and biotic factors on weathering during initial landscape formation.