Does soil erosion rejuvenate the soil phosphorus inventory?

Andre Eger, Kyungsoo Yoo, Peter C. Almond, Gustavo Boitt, Isaac J. Larsen, Leo M. Condron, Xiang Wang, Simon M. Mudd

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Abstract

Phosphorus (P) is an essential nutrient for life. Deficits in soil P reduce primary production and alter biodiversity. A soil P paradigm based on studies of soils that form on flat topography, where erosion rates are minimal, indicates P is supplied to soil mainly as apatite from the underlying parent material and over time is lost via weathering or transformed into labile and less-bioavailable secondary forms. However, little is systematically known about P transformation and bioavailability on eroding hillslopes, which make up the majority of Earth's surface. By linking soil residence time to P fractions in soils and parent material, we show that the traditional concept of P transformation as a function of time has limited applicability to hillslope soils of the western Southern Alps (New Zealand) and Northern Sierra Nevada (USA). Instead, the P inventory of eroding soils at these sites is dominated by secondary P forms across a range of soil residence times, an observation consistent with previously published soil P data. The findings for hillslope soils contrast with those from minimally eroding soils used in chronosequence studies, where the soil P paradigm originated, because chronosequences are often located on landforms where parent materials are less chemically altered and therefore richer in apatite P compared to soils on hillslopes, which are generally underlain by pre-weathered parent material (e.g., saprolite). The geomorphic history of the soil parent material is the likely cause of soil P inventory differences for eroding hillslope soils versus geomorphically stable chronosequence soils. Additionally, plants and dust seem to play an important role in vertically redistributing P in hillslope soils. Given the dominance of secondary soil P in hillslope soils, limits to ecosystem development caused by an undersupply of bio-available P may be more relevant to hillslopes than previously thought.

Original languageEnglish (US)
Pages (from-to)45-59
Number of pages15
JournalGeoderma
Volume332
DOIs
StatePublished - Dec 15 2018

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Keywords

  • Hillslopes
  • Phosphorus fractionation
  • Soil age
  • Soil chronosequences
  • Soil erosion
  • Soil parent material
  • Soil phosphorus
  • Soil residence time

Cite this

Eger, A., Yoo, K., Almond, P. C., Boitt, G., Larsen, I. J., Condron, L. M., Wang, X., & Mudd, S. M. (2018). Does soil erosion rejuvenate the soil phosphorus inventory? Geoderma, 332, 45-59. https://doi.org/10.1016/j.geoderma.2018.06.021