Abstract
Abstract. Soil studies commonly comprise the uppermost meter for tracing, e.g., soil development. However, the maximum rooting depth of various plants significantly exceeds this depth. We hypothesized that deeper parts of the soil, soil parent material and especially paleosols provide beneficial conditions in terms of, e.g., nutrient contents, thus supporting their utilization and exploitation by deep roots. We aimed to decipher the different phases of soil formation in Dutch drift sands and cover sands. The study site is located at Bedafse Bergen (southeastern Netherlands) in a 200-year-old oak stand. A recent Podzol developed on drift sand covering a Plaggic Anthrosol that was piled up on a relict Podzol on Late Glacial eolian cover sand. Root-free soil and sediment samples, collected in 10–15 cm depth increments, were subjected to a multi-proxy physical and geochemical approach. The Plaggic Anthrosol revealed low bulk density and high phosphorous and organic carbon contents, whereas the relict Podzol was characterized by high iron and aluminum contents. Frequencies of fine (diameter ≤ 2 mm) and medium roots (2–5 mm) were determined on horizontal levels and the profile wall for a detailed pseudo-three-dimensional insight. On horizontal levels, living roots were most abundant in the uppermost part of the relict Podzol with ca. 4450 and 220 m−2, significantly exceeding topsoil root abundances. Roots of oak trees thus benefited from the favorable growth conditions in the nutrient-rich Plaggic Anthrosol, whereas increased compactness and high aluminum contents of the relict Podzol caused a strong decrease of roots. The approach demonstrated the benefit of comprehensive root investigation to support interpretation of soil profiles, as fine roots can be significantly underestimated when quantified at the profile wall. The possible rooting of soil parent material and paleosols long after their burial confirmed recent studies on the potential influence of rooting to overprint sediment–(paleo)soil sequences of various ages, sedimentary and climatic settings. Potential consequences of deep rooting for terrestrial deep carbon stocks, located to a relevant part in paleosols, remain largely unknown and require further investigation.
Highlights
Paleosols that developed in Late Glacial eolian sediments like, e.g., loess, dune sands or cover sands are valuable archives to reconstruct paleovegetation, soil and land use history (e.g., Pye and Sherwin, 1999; Van Mourik et al, 2012; Wallinga et al, 2013), with the prerequisite that individual phases of soil formation and sedimentation are distinguishable from each other
Both living and ancient roots were present preferentially in paleosols, which leads to the question of how unique or common this phenomenon is, and whether it applies, e.g., to young (i.e., Holocene) soils with considerably higher nutrient stocks compared to Pleistocene sediments and paleosols
The current multi-proxy approach added by pseudo-threedimensional investigation of root abundances in the soil– sediment profile R2014 in southeastern Netherlands points to the significance of roots in pedogenic processes and paleoenvironmental assessment of buried soils
Summary
Paleosols that developed in Late Glacial eolian sediments like, e.g., loess, dune sands or cover sands are valuable archives to reconstruct paleovegetation, soil and land use history (e.g., Pye and Sherwin, 1999; Van Mourik et al, 2012; Wallinga et al, 2013), with the prerequisite that individual phases of soil formation and sedimentation are distinguishable from each other. Gocke et al (2014a) showed that ancient calcified roots of Holocene age were present throughout a European Late Pleistocene loess–paleosol sequence, penetrating several paleosols This was recently confirmed by other sequences in southeastern Europe and China (Újvári et al, 2014; Li et al, 2015). Roots appeared despite comparatively low contents of most nutritional elements in the loess deposits (Gocke et al, 2014a) Both living and ancient roots were present preferentially in paleosols, which leads to the question of how unique or common this phenomenon is, and whether it applies, e.g., to young (i.e., Holocene) soils with considerably higher nutrient stocks compared to Pleistocene sediments and paleosols. Evidence for modern root remains in buried micro-Podzols was found by Wallinga et al (2013)
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