How big is the influence of biogenic silicon pools on short-term changes in water-soluble silicon in soils? Implications from a study of a 10-year-old soil–plant system

Abstract

Abstract. The significance of biogenic silicon (BSi) pools as a key factor for the control of Si fluxes from terrestrial to aquatic ecosystems has been recognized for decades. However, while most research has been focused on phytogenic Si pools, knowledge of other BSi pools is still limited. We hypothesized that different BSi pools influence short-term changes in the water-soluble Si fraction in soils to different extents. To test our hypothesis we took plant (Calamagrostis epigejos, Phragmites australis) and soil samples in an artificial catchment in a post-mining landscape in the state of Brandenburg, Germany. We quantified phytogenic (phytoliths), protistic (diatom frustules and testate amoeba shells) and zoogenic (sponge spicules) Si pools as well as Tironextractable and water-soluble Si fractions in soils at the beginning (t 0 ) and after 10 years (t 10 ) of ecosystem development. As expected the results of Tiron extraction showed that there are no consistent changes in the amorphous Si pool at Chicken Creek (Hühnerwasser) as early as after 10 years. In contrast to t 0 we found increased water-soluble Si and BSi pools at t 10 ; thus we concluded that BSi pools are the main driver of short-term changes in water-soluble Si. However, because total BSi represents only small proportions of water-soluble Si at t 0 (< 2 %) and t 10 (2.8-4.3 %) we further concluded that smaller (< 5 µm) and/or fragile phytogenic Si structures have the biggest impact on short-term changes in water-soluble Si. In this context, extracted phytoliths (> 5 µm) only amounted to about 16 % of total Si contents of plant materials of C. epigejos and P. australis at t 10 ; thus about 84 % of small-scale and/or fragile phytogenic Si is not quantified by the used phytolith extraction method. Analyses of small-scale and fragile phytogenic Si structures are urgently needed in future work as they seem to represent the biggest and most reactive Si pool in soils. Thus they are the most important drivers of Si cycling in terrestrial biogeosystems.

Phytolith‐rich biochar: A potential Si fertilizer in desilicated soils

“…Several cultivated plants are high Si‐accumulators. In particular, monocotyledons, notably cereals and sugarcane, actively take up dissolved silica (Deshmukh & Bélanger, ) which precipitates in plant tissues as amorphous silica bodies named phytolith (McKeague & Cline, ), a phytogenic silica (PhSi; Cooke & Leishman, ; McKeague & Cline, ; Puppe et al, ; Sommer et al, ). Once deposited into soil within organic debris, phytoliths can dissolve and provide plant‐available Si (McKeague & Cline, ).…”

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

“…Silica in plants is an important component of the silicon geochemical cycle because it is more available than silicon originating from minerals (Derry et al 2005;Fraysse et al 2009;Puppe et al 2017). The influence of phytolith biogenic silica content on ecosystems was shown by several authors (Wang et al 2011;Ran et al 2018).…”

“…Few studies have reported on the dissolution behavior of phytoliths in plant tissues. Puppe et al (2017), however, reported that a silicon pool evolves through release of silicon in soils, because phytogenic Si in plant tissues is temporarily protected from dissolution. Studying dissolution of phytoliths in tissues may enable more accurate estimates of the amount of dissolved silicon from fossil and subfossil needles, and provide a better understanding of phytolith taphonomy.…”

The Role of Macrophytes in Biogenic Silica Storage in Ivory Coast Lagoons

“…a silica ring formed around the periphery of the cell, deposited on a dispersed organic matrix, or laid down as deposits within the cell wall or between the cellulose wall and the plasma membrane or in cortical intercellular spaces within the cell (Prychid et al, 2003). In general, these fragile phytogenic silica structures as well as very small phytoliths (<5 µm) are difficult to trace in sediments, but they potentially play an important role in silica cycling (Meunier et al, 2017;Puppe et al, 2017). Additionally, given the very large number of epiphytic diatoms on non-rinsed plant samples, it cannot be excluded that a fraction of plant-silica in our results is actually diatom-silica, even though plants were washed thoroughly before analysis, according to protocol.…”

“…Struyf et al, 2015). Alternatively, Puppe et al (2017) suggest the formation of a layer of coarse organic matter on top of sediments from which phytoliths cannot be released easily and hence are missing in underneath sediment layers. We have no arguments supporting either of these hypotheses, none of our sediment cores contained such a distinct organic top layer and samples were visually homogeneous organic rich (fine material) over the entire depth of the core (15 cm).…”