THE IMPACT OF CREOSOTE BUSH (LARREA TRIDENTATA) AND BIOLOGICAL SOIL CRUST ON CA DISTRIBUTION IN ARID SOILS OF THE MOJAVE DESERT, SOUTHERN NEVADA

Ca is an important nutrient that plays a role in membrane stability and cell repair in plant life. Previous studies have shown depletion of Ca beneath biological soil crusts (BSCs) in desert soils. This study examines the impact of creosote bush (Larrea tridentata) and biological soil crust on calcium cycling and distribution in desert soils in order to explore the use of Ca as a biosignature. Samples of creosote bush, biological soil crust and eolian dust were taken at each of the two lithologically distinct field areas in the Mojave Desert. The first site is located in Eldorado Valley, NV, a soil formed on a young (800-1200 years) alluvial fan deposit which may contain limestone clasts from nearby sedimentary deposits. The second site is located on a late Holocene-aged deposit of the Lucy Gray Mountain Range in Ivanpah Valley, NV, in which the alluvium is made up of granitic bedrock material. Both sites are dominated by creosote bush and contain biological soil crusts. Soil and dust samples are being subjected to three sequential extractions of BaCl₂, acetic acid, and HNO₃; creosote bush and biological soil crust are being digested with HNO₃, and all solutions will be analyzed for Ca content. Preliminary characterization of the soils show that soils in close proximity to the plant tend to have lower pH values (approximately 7.8-8.7), and higher electrical conductivity than samples in the plant interspaces farther from the root systems. Future analyses will help to further understand the effect of the creosote bush and BSC on the distribution of Ca in desert soils.