THE IMPORTANCE OF DUST IN THE FORMATION OF SOIL INORGANIC CARBON IN DRYLANDS

Soil carbon, which is the third-largest global pool, includes approximately 40% as soil inorganic carbon (SIC or CaCO₃). The formation of SIC provides a natural pathway for carbon sequestration in dryland ecosystems and is, therefore, a possible solution for decreasing atmospheric CO₂. Very few studies, however, have considered sequestration of carbon as SIC. Calcium flux is one of the controlling factors in the formation and accumulation of SIC. Understanding the source (i.e. provenance), amount, and flux of calcium (Ca) can enhance the accuracy of climate and hydrological models and the relative roles of parent material, weathering, and other critical zone processes in the control of SIC formation. However, the provenance of Ca is not clear for many drylands. The aim of this study is to 1) find a chemical fingerprint of the dust and 2) quantify the amount of calcium that dust contributes to pedogenic carbonate and soil formation at both a native (Reynolds Creek Experimental Watershed, RCEW) and managed (Northwest Irrigation and Soils Research Lab, NWIS) site in southwestern Idaho, both with loess parent material.

Prior studies suggest that dust and weathered bedrocks are likely sources of Ca in RCEW, however, the relative contribution from each source was not determined. It is known from previous studies that the dust flux rate in RCEW for 2016 and 2017 is about 11±4.9 g/m²/year and results from climatic and geochemistry data indicate that possible sources for dust inputs are playa and alluvial surfaces in Oregon and California.

We installed 12 dust traps in Kimberly, Idaho (NWIS) to measure dust deposition rates and investigate the dust flux, comparing the concentration of nutrients and elements in the soil, bedrock, and dust. Ongoing and future research will involve using Inductively Coupled Plasma Mass Spectroscopy, and strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) to determine the composition and source of dust.