Does soil erosion rejuvenate the soil phosphorus inventory?

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 sloping and 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 preweathered 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.

Tree survival and growth responses in the aftermath of a strong earthquake

“…Landslides are the most likely cause of differences in soil P among eroding hillslope soils (e.g. Peltzer et al, ; Eger et al, ). Mountain beech has well‐developed ectomycorrhizae that enhance uptake of P and other nutrients from infertile soils using a dense fine root network (Wardle, ).…”

“…Landslides alter soils through physical losses, gains and mixing as well as through chemical changes (Cheng, Yang, Yu, Li, & Zhang, ; Lin et al, ). Chemical weathering of minerals in freshly exposed rocks, particularly of apatite, can lead to greater concentrations of available phosphorus (P) in young soils (Eger et al, ; Peltzer et al, ). With time P is leached from soils or occluded into unavailable forms during soil development (Peltzer et al, ).…”

Soil phosphorus fractions vary with harvest intensity and vegetation control at two contrasting Douglas-fir sites in the Pacific northwest

“…Maintained or increased labile and moderately labile P at Matlock at the 30-60 cm depths in the BO harvest treatment might be attributed to the direct effect of debris on the amount of P removed during harvest, its indirect influence on belowground decomposition (Devine and Harrington, 2007;Sanchez et al, 2006), or the rate at which plants access P and translocate it to surface soils (Eger et al, 2018). The response may also be associated with the aforementioned Scotch broom effect because the BO treatment had a markedly lower amount of Scotch broom present at the Matlock site (Harrington and Schoenholtz, 2010;D.…”

Nutrient concentrations and trophic state of three Andean lakes from Junín, Perú

“…Vystavna et al (2017) reported a long-term variation of total phosphorus concentrations measured over 53 years in the Slapy Reservoir, Czechia, which ranged 10 to 118 µg/L. Soil erosion is considered a main contributor (especially during floods) of phosphorus to streams, lakes, or other water bodies (Eger et al, 2018). However, agricultural activities, organic wastes in sewage, industrial discharges, cattle manure, construction sites, and urban areas can also contribute phosphorus (Reid et al, 2018).…”