Phytolith transport in soil: A field study using fluorescent labelling Olga Fishkis a, ⁎, Joachim Ingwersen a , Marc Lamers a , Dmytro Denysenko b , Thilo Streck a a University of Hohenheim, Institute of Soil Science and Land Evaluation, Biogeophysics, D-70593 Stuttgart, Germany b University of Hohenheim, Institute for Chemistry, Bioinorganic Chemistry, D-70593 Stuttgart, Germany abstract article info Article history: Received 30 April 2009 Received in revised form 26 February 2010 Accepted 14 March 2010 Keywords: Phytoliths Phytolith transport Cambisol Luvisol Plant silica Silt illuviation Soil phytoliths have been widely applied to reconstruct vegetational history. To date, however, the transport behaviour of phytoliths in soil is poorly understood, causing uncertainties in the interpretation of phytolith data. The present study was therefore designed: (1) to determine transport rates of phytoliths in loamy and sandy soils under field conditions and (2) to elucidate the effect of phytolith size and shape on their transport behaviour in sandy and loamy soils. For this purpose, we adopted a fluorescent labelling technique from veterinary science. The phytoliths were extracted from common reed (Phragmites australis), labelled with the fluorescent dye fluorescein isothiocyanate, and applied to a loamy sand soil (Haplic Cambisol) and a silty loam soil (Stagnic Luvisol) in southern Germany. One year after application, the soils were sampled to analyse phytolith distribution with soil depth. The weighted mean transport distance of phytoliths after one year was 3.99 ± 1.21 cm for the Cambisol and 3.86 ± 0.56 cm for the Luvisol. Phytolith size significantly affected transport behaviour, indicating a preferential translocation of small-sized phytoliths. Our study provides direct evidence for a significant downward mobility of phytoliths in sandy and loamy soils under natural conditions. This should be taken into account when using phytoliths as palaeoenvironmental tracers. Quantifying phytoliths in soil with fluorescent labelling makes it possible to identify artificially applied phytoliths without using the conventional extraction method. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Phytoliths are amorphous silicon dioxide minerals (opal A; SiO 2 ·nH 2 O), formed in living plants through silicification of cell walls, cell lumina or intercellular spaces (Jones and Handreck, 1967; Rovner, 1983; Piperno, 2006a,b). After litter decomposition, phyto- liths are released and become mineral constituents of soils, also termed plant silica or biogenic opal. Many phytoliths possess a specific morphology and can therefore be attributed to taxonomic groups at least on a family level (Rovner, 1983; Piperno and Pearsall, 1998; Piperno, 2006a,b). This diagnostic feature is widely applied to reconstruct the palaeovegetation. During the last decade many studies on vegetation dynamics during the Holocene and/or Pleisto- cene have been conducted based on the analysis of phytoliths extracted from buried soils, lake deposits, archaeological sediments, and recent soils (Fisher et al., 1995; Gol`yeva et al., 1995; Piperno and Becker, 1996; Blecker et al., 1997; Alexandre et al., 1999; Gol'eva and Aleksandrovskij, 1999; Horrocks et al., 2000; Blinnikov et al., 2002; Delhon et al., 2003; Piperno and Jones, 2003; Gallego et al., 2004; Piperno, 2006a,b, Barczi et al., 2009). In recent soils the procedure for reconstructing palaeovegetation commonly involves extracting phy- toliths from different soil depths, the frequency counting of phytolith morphotypes in each depth, and interpreting the phytolith records by relating variations in phytolith morphology to past changes in the vegetation cover (Fisher et al., 1995; Gol`yeva et al., 1995; Piperno and Becker, 1996; Gallego et al., 2004). The transport behaviour of phytoliths in soil, however, is poorly understood, complicating the interpretation of the phytolith records. The possibility of phytolith translocation by bioturbation is widely recognised (Hart and Hum- phreys, 1997; Runge, 1999; Humphreys et al., 2003; Farmer et al., 2005), but the extent of this process and its relevance for palaeor- econstruction remain to be clarified. Even less clear is the extent of translocation with seeping water. While some authors believe this process to be relevant (Alexandre et al., 1997; Hart and Humphreys, 1997; Alexandre et al., 1999; Hart and Humphreys, 2003; Humphreys et al., 2003), others consider phytoliths to be immobile (Rovner, 1983; Fisher et al., 1995). Alexandre et al. (1997) reported translocation to a depth of 2.2 m in a ferrallitic soil, with a slight accumulation in an impermeable clay layer at 1.3–1.4 m. Humphreys et al. (2003) attributed the distribution pattern in Podzol mainly to translocation with percolating water. In contrast, Piperno (2006a,b) pointed out that the magnitude of transport is probably minimal because phytoliths occur commonly only in the upper part of recent soils and their concentration usually decreases in B horizons. Fisher et al. (1995) considered phytolith mobility to be negligible due to their large sizes. Indeed, the diameter of phytoliths used for palaeoreconstruction Geoderma 157 (2010) 27–36 ⁎ Corresponding author. Tel.: +49 71145922466. E-mail address: ofishkis@uni-hohenheim.de (O. Fishkis). 0016-7061/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.geoderma.2010.03.012 Contents lists available at ScienceDirect Geoderma journal homepage: www.elsevier.com/locate/geoderma