pH-dependent silicon release from phytoliths of Norway spruce (Picea abies)

Abstract

Accurate evaluation of the preservation state of fossil phytoliths in glacial lake sediments is important, as these microfossils are often used in paleoecological and archaeological studies. The characteristic phytolith type of the Norway spruce (Picea abies [L.] Karst.) needle is a potential keystone in paleoecological studies. In this laboratory study, we investigated dissolution of Picea abies blocky type phytoliths, to simulate dissolution processes in sediments and soils and create reference material to compare with fossil phytoliths. Intact needles, needle ash, diatomite and silica gel were treated with Britton-Robinson buffer solutions at pH values from 2 to 12 for 22 days. Silicon was measured by microwave Z. Lisztes-Szabó (&) Á A

Well-preserved Norway spruce needle phytoliths in sediments can be a new paleoenvironmental indicator

“…The most crucial difference was that the aluminum content was under the detection limit in the recent phytoliths, but the fossil phytoliths contained an average of 2 atom% aluminum. This result supports the hypothesis that extraneous metal elements are incorporated into the silica structure during the dissolution processes and the higher element content is rather an effect of the partial dissolution (Lisztes-Szabó et al, 2020). It should be noted that aluminum is usually colocalized with Si in needle phytoliths in P. glauca (Hodson and Sangster, 1998) and P. abies (Godde et al, 1988, 1991).…”

“…Lisztes-Szabó et al (2020) reported, based on their experiment with spruce needles treated in solutions with different pH, that most dissolved silicon appeared to originate from the phytolith surfaces and the silica matrix of the apoplast in the tissues, and only a small extent from the complete dissolution of phytoliths. These treatments indicated that Picea-blocky phytoliths in Norway spruce needles might be well-preserved in some glacial lake sediments, as phytolith silicon content was preserved three times more effectively in needle tissue than in needle ash (Lisztes-Szabó et al, 2020). Picea-blocky type needle phytoliths have a globular ultrastructure on the surface (Lisztes-Szabó et al, 2020).…”

“…These treatments indicated that Picea-blocky phytoliths in Norway spruce needles might be well-preserved in some glacial lake sediments, as phytolith silicon content was preserved three times more effectively in needle tissue than in needle ash (Lisztes-Szabó et al, 2020). Picea-blocky type needle phytoliths have a globular ultrastructure on the surface (Lisztes-Szabó et al, 2020). The disappearance of the globular structure may help assess the intensity of destructive processes in sediments.…”

“…Furthermore, the preservation features of phytoliths are variable for different species and morphotypes (Cabanes and Shahack-Gross, 2015; Madella and Lancelotti, 2012; Shillito, 2011) and depend on many environmental medium effects (Piperno, 2006; Wilding, 1974), moreover, on the extraneous element content (Bartoli, 1985). Therefore, the dissolution of blocky-type phytoliths of the Picea abies needles was investigated in a laboratory experiment to learn more about their preservation and taphonomy (Lisztes-Szabó et al, 2020). Simulating dissolution processes in the experimental treatments indicated that the characteristic Picea -blocky phytoliths of needles can be well-preserved in sediments and soils (Lisztes-Szabó et al, 2020).…”

“…Therefore, the dissolution of blocky-type phytoliths of the Picea abies needles was investigated in a laboratory experiment to learn more about their preservation and taphonomy (Lisztes-Szabó et al, 2020). Simulating dissolution processes in the experimental treatments indicated that the characteristic Picea -blocky phytoliths of needles can be well-preserved in sediments and soils (Lisztes-Szabó et al, 2020). Since there are phytoliths in spruce needles that can be studied well and their preservation was sufficient experimentally, the question arises if blocky phytoliths can be found in fossil needles or not.…”