The Nivolet CZ Ecosystem Observatory reveals rapid soil development in recently deglaciated alpine environments: Biotic weathering is the likely culprit

Soils are a critical component of the Earth system in regulating many ecological processes that provide fundamental ecosystem services (Adhikari and Hartemink, 2016). Soil formation factors may be operating at faster timescales than is typically considered in recently deglaciated alpine environments, yielding important implications for critical zone services (e.g., water retention, the preservation of carbon (C) and nutrients, and chemical weathering fluxes). It remains unclear how variation in these properties are linked to soil development and soil organic C pools and fluxes, in part because sites varying in these characteristics also typically vary in vegetation and climate.

Here we leveraged the high-altitude alpine pastures of the Nivolet Critical Zone and Ecosystem Observatory, Gran Paradiso National Park (Italy) to examine biotic and abiotic dynamics and controlling factors of organic C and weathering under different topographic positions and geologic substrates in a small localized mountainous region. Soil profiles were sampled across a range of parent materials deposited after the Last Glacial Maximum, including gneiss glacial till, carbonate and calcschist/gneiss colluvium, and gneiss/carbonate/calcschist alluvium across ridgetop, midslope and footslope topographic positions. Organic C, C stable isotopes, major and trace element content, particle size distribution, and pH reveal how parent material and landscape position govern soil C storage and development. Even under the cold climate, limited season with liquid water, young-age deglaciated context, soils have developed incipient spodic horizons and calcschist clasts appears completely weathered in place.

Alkali and alkaline earth elements exhibit chemical depletion throughout the profiles, whereas in some profiles phosphorus concentrations reflects nutrient uplift processes (i.e., accumulating at the top of the profile and depleted in mid-horizons) likely driven by “biotic” cycling. Phosphorus is relatively high in uppermost horizons at carbonate and glacial sites, but is quite low in gneiss, even though TOC is relatively high, suggesting that plants underlain by gneiss are able to generate organic compounds with lower P availability. Though rooting depth distributions exhibit linear declines with depth, contrary the typically observed exponential decay behavior, our data suggest that roots serve as important biotic weathering agents prompting rapid soil development. All profiles have high organic carbon content at the surface, but

are twice as high in the footslope Gneiss profile as in the midslope Glacier and Carbonate profiles and in the floodplain Alluvial profile.

These data, in conjunction with microbial analysis and geochemical variation, suggest that biota are key agents promoting the observed high degree of soil development in these high altitude ecosystems. We demonstrate how in the early stages of soil development abiotic and biotic factors influence soil weathering and C storage across different parent material and topography.

 

Adhikari, K. and Hartemink, A. E.: Linking soils to ecosystem services – A global review, Geoderma, 262, 101–111, 2016

How to cite: Baneschi, I., Dere, A., Aronson, E., Balint, R., Billings, S., Giamberini, S., Magnani, M., Mosca, P., Pennisi, M., Provenzale, A., Raco, B., Sullivan, P. L., and White, T.: The Nivolet CZ Ecosystem Observatory reveals rapid soil development in recently deglaciated alpine environments: Biotic weathering is the likely culprit, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16387, https://doi.org/10.5194/egusphere-egu2020-16387, 2020