1. Does soil erosion rejuvenate the soil phosphorus inventory?
- Author
-
Peter C. Almond, Isaac J. Larsen, Gustavo Boitt, Kyungsoo Yoo, Xiang Wang, Leo M. Condron, Simon M. Mudd, and Andre Eger
- Subjects
geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Landform ,Chronosequence ,Parent material ,Soil Science ,Soil science ,Weathering ,04 agricultural and veterinary sciences ,Saprolite ,01 natural sciences ,Soil water ,040103 agronomy & agriculture ,Erosion ,0401 agriculture, forestry, and fisheries ,Environmental science ,Dominance (ecology) ,0105 earth and related environmental sciences - 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.
- Published
- 2018