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

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

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

Bibliographical note

Funding Information:
We thank the Department of Conservation for granting permission to sample soils in New Zealand. AE, KY and PCA had the conceptual idea for the research, GB performed the majority of the P laboratory analysis, XW prepared the samples and data from Feather River, AE and KY lead the data interpretation and write-up with contributions of all co-authors. KY and SM designed and conducted sampling at Feather River. IL and AE collected the New Zealand samples with support from NSF (OISE-1015454 to IL). AE was partially supported through a Landcare Research Capability Fund grant. KY thanks NSF (EAR-1253198) for supporting his portion of this work. KY and SM appreciate help in the field from Beth Weinman, Martin Hurst, Manny Gabet, and Tony Dosseto. IL and AE are grateful to Brendon Malcolm for help in the field.

Publisher Copyright:
© 2018 Elsevier B.V.

Keywords

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

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