Snowpack driven changes in decadal soil evolution: insights from a 48-year snow manipulation experiment
Feldhaus, Aaron Michael
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Soil mantled landscapes are a critical interface that support biological life, weather geologic materials, and develop in response to changes in climate. Climate has long been considered a dynamic control on the evolution of Earth's landscapes. However, we have limited understanding regarding how soils respond to short-term perturbations of key climate variables like precipitation and moisture availability. Furthermore, the timescales over which diverse weathering processes feedback and measurably change soil character are still relatively uncertain, as well as how they respond to swift changes in climate. Here, we explore the role of precipitation in decadal soil evolution by utilizing a 48-year snowpack experiment located in the Greater Yellowstone Ecosystem (GYE) of SW Montana. In this unique field site, we compare soil development across experimental plots with enhanced snowpack, where snow has been doubled (2x) and quadrupled (4x) above ambient conditions for almost five decades. We find that decadal snowpack addition provides multiple pathways for enhancing soil weathering, both physically and chemically. Soils under enhanced snowpack generally contain higher amounts of fine-grained material (clay and silt) and are more acidic (lower soil pH) in nature. Significant (>85%) surface depletions of the fallout radionuclide 210 Pb and reduced surface horizon carbon and nitrogen content, along with reduced above and below ground vegetation biomass provide evidence of increased wind erosion of soils that experience enhanced winter snowpack. Modeling of diffusion-like mixing from 210 Pb profiles also indicates there is increased bioturbation intensity (soil mixing) under enhanced snowpack. We find that snowpack addition, through associated changes in plant communities and vegetation biomass, along with its effects on physical and chemical weathering processes, produces rapid and measurable changes in the weathered state of soils. Our results indicate that short-term, decadal perturbations in snowpack significantly alter weathering mechanisms in this landscape, which measurably overprint thousands of years of soil development. These findings provide novel insight into the fundamental role of climate on short-term soil evolution and have significant implications for how mountainous or snowpack-dominated systems may respond to perturbations in climate.