Controls on the presence and storage of soil inorganic carbon in a semi-arid watershed

Authors: STANBERY, CHRISTOPHER - Boise State University; GHAHREMANI, ZAHRA - Boise State University; HUBER, DAVID - University Of Texas - El Paso; WILL, RYAN - Boise State University; BENNER, SHAWN - Boise State University; GLENN, NANCY - Boise State University; HANIF, TANZILA - Boise State University; SPAETE, LUCAS - Boise State University; TERHAAR, DANIELLE - Boise State University; LOHSE, KATHLEEN - Idaho State University; SEYFRIED, MARK - Retired ARS Employee; FREUTEL, WILLIAM - Boise State University; PIERCE, JENNIFER - Boise State University

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2023
Publication Date: 5/15/2023
Citation: Stanbery, C., Ghahremani, Z., Huber, D., Will, R., Benner, S., Glenn, N., Hanif, T., Spaete, L., Terhaar, D., Lohse, K., Seyfried, M., Freutel, W., Pierce, J. 2023. Controls on the presence and storage of soil inorganic carbon in a semi-arid watershed. Catena. 225. Article 106980. https://doi.org/10.1016/j.catena.2023.106980.
DOI: https://doi.org/10.1016/j.catena.2023.106980

Interpretive Summary: Soil inorganic carbon (SIC) constitutes approximately 40% of terrestrial soil carbon and is an integral part of the global carbon cycle. Whereas rainfall has been identified as the primary factor controlling SIC accumulation in arid and semi-arid regions, the hierarchy of local controls such as parent material and biota on SIC development on distribution and accumulation are poorly understood. The Reynolds Creek watershed in southwestern Idaho is an ideal location to study factors influencing SIC because it spans a wide range of precipitation 235 mm to 900 mm along an elevation gradient and it contains a wide variety of parent materials (granite, basalt, other volcanics, and alluvium). We collected soil samples to 1 m depth along this elevation gradient and focused on understanding the local controls on distribution of SIC at the lower SIC dominated elevations. We found that variations in precipitation governed the presence or absence of SIC, with a threshold for SIC accumulation at ~500 mm mean annual precipitation. Below this threshold, SIC pools varied substantially and significantly between sites. After precipitation, slope consistently ranked as the second most important predictor of SIC accumulation. Wind-blown dust was observed in most of the soil profiles at lower elevations, which likely contributed to SIC accumulation. Optically Stimulated Luminescence (OSL) ages from 1 and 1.9 m depths within a late Pleistocene alluvial fill terrace of Lower Reynolds Creek (~285 mm modern annual precipitation) yield ages of ~22 ± 3 ka and ~-30 ± 5 ka. These ages, combined with soil profile SIC total of 28.08 kg m-2 SIC yield an accumulation rate of ~1.25 kg SIC per 1000 years. This study provides an initial model predicting SIC distribution and accumulation in a shrub-dominated dryland watershed.

Technical Abstract: Soil inorganic carbon (SIC) constitutes approximately 40% of terrestrial soil carbon and is an integral part of the global carbon cycle. Whereas rainfall has been identified as the primary factor controlling SIC accumulation in arid and semi-arid regions, the hierarchy of local controls such as parent material and biota on SIC development on distribution and accumulation are poorly understood. The Reynolds Creek watershed in southwestern Idaho is an ideal location to study factors influencing SIC because it spans a wide range of precipitation 235 mm to 900 mm along an elevation gradient and it contains a wide variety of parent materials (granite, basalt, other volcanics, and alluvium). We collected soil samples to 1 m depth along this elevation gradient and focused on understanding the local controls on distribution of SIC at the lower SIC dominated elevations. We found that variations in precipitation governed the presence or absence of SIC, with a threshold for SIC accumulation at ~500 mm mean annual precipitation. Below this threshold, SIC pools varied substantially and significantly between sites. After precipitation, slope consistently ranked as the second most important predictor of SIC accumulation. Wind-blown dust was observed in most of the soil profiles at lower elevations, which likely contributed to SIC accumulation. Optically Stimulated Luminescence (OSL) ages from 1 and 1.9 m depths within a late Pleistocene alluvial fill terrace of Lower Reynolds Creek (~285 mm modern annual precipitation) yield ages of ~22 ± 3 ka and ~-30 ± 5 ka. These ages, combined with soil profile SIC total of 28.08 kg m-2 SIC yield an accumulation rate of ~1.25 kg SIC per 1000 years. This study provides an initial model predicting SIC distribution and accumulation in a shrub-dominated dryland watershed.