The global silicon (Si) cycle, which is intricately linked to global carbon cycling through a variety of avenues, is defined by dynamic processes occurring in both terrestrial and aquatic systems. The biologic controls on Si cycling have traditionally focused either on aquatic ecosystems where photosynthetic diatoms consume large amounts of Si, or Si uptake by terrestrial vegetation, as land plants consume and recycle large amounts of Si. However, little is known about non-plant terrestrial Si cycling. In this Perspective article we outline the knowledge gaps in terrestrial non-plant biological Si cycling, highlighting the need for studies exploring the unexplored biogenic silica (BSi) pools in soil represented by bacterial and fungal silica, sponge spicules and diatom frustules, protozoic silica platelets, and clay-sized phytoliths. We suggest specific research attention be given to how the proportions of different BSi pools in soil differ with land cover and climate. In this context, we call for specific method improvements to quantify different BSi pools in soil. In addition to quantifying these unexplored BSi pools, exploration of dissolution kinetics of various soil BSi structures is needed to assess their role in Si cycling. We are convinced that future research dealing with these aspects will substantially deepen our understanding of global Si dynamics. The corresponding results will certainly change our current view and introduce new key players in terrestrial biological Si cycling.
bacterial silicabiogenic silicaclay-sized phytolithsdiatom frustulesdissolved silicafungal silicasponge spiculestestate amoeba plateletsThe author(s) declared that financial support was received for this work and/or its publication. Publication of this article was financed via the ZALF publication fund. JCC was supported by the Debi and Andy Butler ('84) Term Chair at Babson College.section-at-acceptanceBiogeochemical DynamicsBackground
Silicon (Si) is a non-metallic element that is very reactive with oxygen (O) and water (H2O), which is why it is hardly ever found in its pure form under natural conditions. Thus, Si usually occurs as pure silica (SiO2, mainly in the form of quartz) or other silicate minerals like feldspars or clays in nature. Si compounds are very abundant in the Earth’s crust, which mainly (about 90% by volume) consists of silicate minerals. Silicate minerals can be found in crystalline, poorly crystalline, or amorphous forms, which exhibit relatively low, intermediate, and high solubility, respectively (Iler, 1979; Monger and Kelly, 2002).
Silicate mineral weathering represents the original source of dissolved silica (DSi) in terrestrial and marine ecosystems, where it mainly occurs as monomeric silicic acid (H4SiO4) at pH < 9 (Dietzel, 2000). During silicate mineral weathering carbon dioxide (CO2) is removed from the atmosphere, exerting control on the climate on geological time scales (Berner, 1992). Several marine organisms use H4SiO4 to build structures made of biogenic silica (BSi, SiO2 · nH2O), e.g., diatom frustules, sponge spicules in a process, which is called biosilicification. These BSi structures eventually sink to the seafloor forming new sediments that are buried, compacted, and transformed back into silicate rocks over a geological time scale. Moreover, marine diatoms link the Si cycle with the carbon (C) cycle on a global scale, because they represent up to 54% of the biomass in the oceans, and thus can fix large quantities of CO2 via photosynthesis (Tréguer and Pondaven, 2000).
In terrestrial ecosystems H4SiO4 is taken up by various organisms and precipitated in the form of BSi as well. As BSi is much more soluble compared to silicate minerals, BSi accumulation and dissolution is an important control on H4SiO4 cycling as it moves from the continents to the oceans (Dürr et al., 2011; Struyf and Conley, 2012). Consequently, biological Si re-cycling has attracted broad attention in Si cycling research. In this context, plants have been in the focus of BSi research for decades (Bartoli, 1983; Conley, 2002; Jones and Handreck, 1967; Yang et al., 2020). BSi precipitates in plants are known as phytoliths (phytogenic silica), which enter soil via litterfall. Phytoliths have been widely studied in the context of biogeochemical Si cycling, because they represent an important source of DSi in soil (Alexandre et al., 1997; Blecker et al., 2006; Sommer et al., 2013). Changes in the vegetation caused by, e.g., deforestation, have been found to substantially affect the riverine transport of H4SiO4 to the oceans, and thus Si cycling (Conley et al., 2008; Chen et al., 2014; Carey and Fulweiler, 2012a).
In agricultural landscapes, cereal crops are known to accumulate relatively high amounts of BSi in their biomass (Carey and Fulweiler, 2016), with Si contents of up to 10% of dry weight (Epstein, 1994). Perpetual and sustained harvest-related BSi exports have led to substantial Si losses in agricultural plant-soil systems (anthropogenic desilication), especially in temperate zones where the majority of research has focused (Clymans et al., 2011; Guntzer et al., 2012; Puppe et al., 2021). As the accumulation of BSi has been found to enhance biotic and abiotic stress resistance of cereal crops, such as wheat (Triticum aestivum) or rice (Oryza sativa) (Epstein, 2009), anthropogenic desilication potentially has negative impacts on food security (Carey and Fulweiler, 2016; Meunier et al., 2008; Tubana et al., 2016). Moreover, the conversion of more land for agricultural production could deplete soil BSi reserves over time with consequences for long-term fluxes of Si to coastal systems (Carey and Fulweiler, 2012b; Clymans et al., 2011).
While phytogenic silica and its significance for the Si cycle has been subject to a myriad of studies for decades, only recently has the BSi formed by organisms other than plants been recognized as potential driver of biogeochemical Si cycling (Figure 1) (Ikeda, 2021; Puppe, 2020; Zaman et al., 2025). In this Perspective article we discuss the (so far) unexplored BSi pools in terrestrial ecosystems and their potential contribution to Si cycling. Finally, corresponding knowledge gaps are identified and directions for future research are outlined. We hope that our Perspective article will stimulate research off the beaten track and thus foster our understanding of the role of different organisms in terrestrial ecosystems for Si cycling.
Overview of soil BSi pools in terrestrial ecosystems. The different box colors indicate the current state of research regarding pool quantity and significance for Si cycling: (i) Green, numerous studies, significance known; (ii) Yellow, only few studies, potential significance recognized; (iii) Red, no quantitative studies, potential significance hypothesized but yet unknown. Red font color indicates yet unquantified BSi pools. Figure modified from Puppe (2020).
Flowchart illustrating soil biogenic silica (BSi) pools in terrestrial ecosystems, categorized into bacterial, fungal, phytogenic, zoogenic, and protistic (protozoic and protophytic) silica with specific BSi forms listed under each category.Unexplored biogenic silica pools in soilBacterial and fungal silica
The literature has yet to reveal the intricacies regarding bacterial and fungal silica. Yet, what we know today is that specific bacteria and microfungi can accumulate BSi and enhance the dissolution of mineral silica in soil via acidic metabolites (Ehrlich et al., 2010). Already in the 1960s Heinen (1965) showed that the bacterium Proteus mirabilis accumulates BSi within its cells. In a more recent review article Ikeda (2021) summarized current knowledge on biosilicification in the bacterial genus Bacillus. In this context, 240 Bacillus strains were analyzed, of which 29 showed notable amounts of silicic acid uptake within 48 h after inoculation, whereby Bacillus cereus exhibited the highest silicic acid uptake rate (Hirota et al., 2010). Silica accumulation in B. cereus was found to be associated with the formation of spores, which showed an enhanced resistance against acids if Si is deposited in the spore coat. As bacteria including P. mirabilis and Bacillus spec. are common in soils worldwide, corresponding bacterial silica pools in soil might play a significant role in Si cycling. However, quantitative information on bacterial and microfungal Si pools are lacking so far. This is because there is no data on soil biomasses and Si contents of specific taxa of BSi accumulating bacteria and microfungi available yet, which is needed for the quantification of bacterial and microfungal Si pools in soil.
Regarding fungal silica, the formation of silica structures in macrofungi (i.e., fungi that produce visible fruiting bodies) has been recently discovered (Dar et al., 2025; Dar et al., 2024; Golokhvast et al., 2014). Due to their similarity to plant phytoliths, these silica structures formed in the fruiting bodies of fungi have been named mycoliths, a term that is derived from the Greek words “mykes” and “líthos” for mushroom and stone, respectively (Golokhvast et al., 2014). However, as is the case for bacterial and microfungal silica, there remains no data on mycolith Si pool quantities in soil. Until now only very few macrofungus species (e.g., Agaricus augustus, Inonotus hispidus, Lycoperdon perlatum, or Phyllotopsis nidulans) have been used for the extraction of mycoliths, and thus it is currently unknown if Si uptake and mycolith formation is a common feature in macrofungi. However, this knowledge along with information on species-specific fruiting body biomasses and corresponding Si contents is needed to reliably estimate mycolith Si pools in terrestrial ecosystems. As there are about 14,000 macrofungus species known (Hawksworth, 2001), the corresponding mycolith production potential of macrofungi can be assumed to be quite big.
Sponge spicules and diatom frustules
In most soils, especially in fluvial deposits, sponge spicules can be found, whereby the majority of spicules originate from freshwater sponge species (Clarke, 2003; Kaczorek et al., 2018). However, there are only very few studies that quantified corresponding zoogenic Si pools in soils of terrestrial ecosystems (Puppe et al., 2016; Puppe et al., 2017). These studies showed that the relatively large sponge spicules can significantly contribute to total biogenic Si pools in specific soils, although spicule abundance might be very low compared to other BSi structures like phytoliths or frustules of freshwater diatoms.
In terrestrial ecosystems diatoms can be found in different habitats like soil, lichens, or mosses (Yogeshwaran et al., 2025). As components of the microbial community diatoms might play an important ecological role in these terrestrial habitats. For example, diatoms have been found to represent important contributors to Si cycling in some terrestrial ecosystems (Creevy et al., 2016; Puppe et al., 2016; Puppe et al., 2017). Desplanques et al. (2006) identified diatoms in the irrigation water as a major input of BSi to a rice field in the Camargue, France. However, there are still no quantitative data on protophytic Si pools in agricultural soils yet.
Protozoic silica platelets
Protozoic silica in soil mainly originates from testate amoebae, unicellular eukaryotes (protists) that form a shell ranging between ∼5–300 μm in size. Currently almost all testate amoeba taxa are assigned to two orders, i.e., the Arcellinida and the Euglyphida. While the order Arcellinida includes testate amoebae with lobose pseudopodia and shells made by secretion (autogenous shells), agglutination of foreign material (xenogenous shells), or a combination of secretion and agglutination, the order Euglyphida includes testate amoebae with filose pseudopodia and shells that are usually made up of self-secreted silica platelets, the so-called idiosomes (Adl et al., 2019; Meisterfeld, 2002a; 2002b). Research on protozoic silica has been focused on testate amoebae in the order Euglyphida, which are usually characterized by siliceous shells made up of idiosomes. However, a few taxa (i.e., Lesquereusia, Netzelia, and Quadrulella) with autogenous siliceous shells can also be found in the order Arcellinida (Puppe, 2020). The idiosomes are formed in so-called silica deposition vesicles (SDVs) in the testate amoeba cell cytoplasm, subsequently deposited on the cell surface by exocytosis, and bound together by organic cement (Anderson, 1994; Ogden, 1991). A commonality among all protozoic Si pool studies to date is that they only consider intact testate amoeba shells for pool calculations. Thus, there is no data on protozoic Si pools represented by single silica platelets, the building blocks of idiosomic testate amoeba shells.
In temperate forests testate amoeba numbers can reach up to hundreds of thousands of individuals per gram soil (Ehrmann et al., 2012), which is why annual biosilicification rates of testate amoebae equal or even exceed reported annual Si uptake rates of trees in the ecosystems (Puppe et al., 2015). However, intact empty testate amoeba shells have been found to disappear (decompose) within several weeks in forest soil (Lousier and Parkinson, 1981). Against this background, we can reasonably assume that the non-organic building blocks of testate amoeba shells, i.e., the idiosomes, are quite abundant in soil. This assumption is corroborated by the following observations: (i) Sedimentary deposits are usually rich in idiosomes, which mainly originate from soil in the catchment areas (Douglas and Smol, 1987; Pienitz et al., 1995) and (ii) specific testate amoeba taxa (e.g., Schoenbornia or Heleopera) usually construct their shells from foreign materials (xenosomes) including idiosomes collected from the environment (Meisterfeld, 2002a; Schönborn et al., 1987), where these idiosomes must consequently occur in relatively high abundance. However, quantitative data on protozoic Si pools represented by idiosomes are still lacking. Moreover, there is no information on the stability of idiosome pools in specific soils, because dissolution kinetics of idiosomes have not been examined until now (Puppe, 2020).
Clay-sized phytoliths
Phytogenic Si (phytolith) pools in soil are usually quantified by extraction methods, i.e., destructive chemical (alkaline) or non-destructive physical (gravimetric) extraction. However, both methods exhibit shortcomings that hamper the interpretation of extraction results. Alkaline extractions, for example, unselectively extract Si from the different amorphous (and poorly crystalline) fractions present in a soil sample. This basically means that not only the targeted phytogenic Si, but also non-biogenic, i.e., minerogenic and pedogenic, Si fractions are extracted to a certain extent (Georgiadis et al., 2014; Li et al., 2019; Saccone et al., 2007). To correct for this uncertainty, the so-called DeMaster-method has been commonly used to quantify BSi/phytolith contents in a soil, although this technique has also been challenged recently (Kaczorek et al., 2019; Li et al., 2019; Meunier et al., 2014). Moreover, alkaline extractants also extract Si originating from other BSi structures like testate amoeba shells, diatom frustules, or sponge spicules, providing challenges to quantifying phytogenic Si pools. Consequently, quantifying specific components of soil BSi pools requires both microscopic analyses (testate amoeba shells, diatom frustules, sponge spicules) and gravimetric extractions (phytoliths) (Puppe et al., 2017), as there is no method to yet quantify the proportions of different BSi fractions in an extract.
Gravimetric phytolith extraction from soil samples is usually restricted to the silt fraction (2–63 μm) and consequently extracts are filtered at 2 or 5 µm to eliminate the clay fraction (<2 µm). Thus, phytolith analyses and corresponding phytogenic Si pool quantifications are restricted to the phytolith fraction >2 or >5 µm. However, as phytoliths >2 or >5 µm represent only a minor part in plant materials, it can be reasonably assumed that these Si pool qualifications substantially underestimate the total phytogenic Si pool in soil. In moso bamboo (Phyllostachys pubescens) leaves, for example, Umemura and Torii (2025) found about 36% of phytoliths to be smaller than 2 µm. In American beech (Fagus grandifolia) leaves about 72% of extractable phytoliths were reported to be smaller than 5 μm (Wilding and Drees, 1971). Puppe et al. (2017) found that extractable phytoliths >5 μm only represented about 16% of the total phytogenic Si content in Calamagrostis epigejos and Phragmites australis. Consequently, phytolith input into soil via plant debris seems to be dominated by small (clay-sized) phytoliths. Thus, it can be reasonably assumed that clay-sized phytoliths represent a relatively large fraction of the phytogenic Si pool in soil, which represents a vast assemblage of phytoliths of different size, age, and dissolution stage. As clay-sized phytoliths exhibit relatively high specific surface-areas, they represent a highly reactive fraction of this assemblage making clay-sized phytoliths potential key players in biogeochemical Si cycling (de Tombeur et al., 2024; Schaller et al., 2021). Moreover, clay-sized phytoliths might be important constituents of micro-aggregates, which have been found to store and protect phytoliths in soil (Li et al., 2020; Li et al., 2023).
In general, quantitative information on phytogenic Si pools in soil reported until now must be treated with caution. While alkaline extractions might overestimate phytogenic Si pools due to the untargeted dissolution of amorphous soil fractions, the gravimetric phytolith extraction does not cover phytoliths <2 or <5 µm and consequently underestimates the phytogenic Si pool. Kaczorek et al. (2019) used alkaline as well as gravimetric extractions to quantify BSi and phytolith contents in the soil horizons of four different sites, respectively (i.e., a deciduous forest, a coniferous forest, a grassland, and an arable land). They found gravimetrically extractable phytoliths >5 µm to represent 21%, 25%, and 72% of the total (alkaline) extractable BSi fraction in the uppermost soil horizons of the analyzed beech forest, grassland, and coniferous forest, respectively. It can be assumed that these uppermost organic horizons are mainly shaped by plant litter and corresponding phytogenic Si and that only negligible amounts of pedogenic/minerogenic soil fractions occur, which is why potential effects of these fractions on the alkaline extraction results can be ruled out. In contrast, the uppermost Ap horizon of the arable land showed gravimetrically extractable phytoliths >5 µm to represent only 11% of the total (alkaline) extractable BSi fraction. This is because the Ap horizon is regularly mixed by ploughing, which hinders continuous formation of an organic soil horizon. If we assume phytogenic Si to represent the main source of BSi in these soils, it can reasonably be assumed that clay-sized phytoliths represent a significant, yet under-reported, soil Si pool in terrestrial ecosystems.
Future directions
In our Perspective article we highlight the potential significance of unexplored BSi pools in terrestrial ecosystems for Si cycling. We encourage the scientific community to test our assumptions by conducting in-depth investigations of these unexplored BSi pools. In this context, future research should focus on the following aspects:
Collecting information on the quantity of the unexplored BSi pools in soil. As the proportions of different BSi pools in soil will most likely differ in different ecosystems under different climates, studies from all over the world are needed. The corresponding results will help us to better understand the contribution of each BSi pool to global Si fluxes and cycling.
Method improvements to expeditiously quantify different BSi pools in soil samples. (1.) Counting different BSi structures under the microscope is quite time-consuming and is restricted to specialized experts who can recognize and differentiate between these structures. In this context, artificial intelligence (AI) might be a promising tool for the detection and enumeration of specific BSi structures in microscopical images. The AI-based automation of detecting and enumerating BSi structures would allow a fast-speed screening of micrographs, and thus highly accelerate BSi pool quantification. To implement AI techniques in Si studies, large BSi image datasets for model training are required. (2.) Regarding phytogenic silica sequential filtering (i.e., using 5, 2, and 0.45 µm filters during phytolith extraction) represents a promising approach to gather information on the different phytolith fractions in a soil (i.e., phytoliths >5 µm, phytoliths >2 µm, and clay-sized (<2 µm) phytoliths).
Physicochemical analyses of the different BSi structures to understand how stable different BSi structures are under natural (soil) conditions. As BSi dissolution kinetics control Si fluxes, we need data regarding how soil properties affect the dissolution of different BSi structures, and the stability of different BSi structures in different ecosystems under different climates.
We believe that investigating these topics in future studies will greatly enhance our understanding of how the terrestrial BSi cycle shapes global Si dynamics. The findings are likely to revise our current perspective and reveal new, important contributors in biological Si cycling on land. A similar advancement is observable regarding marine ecosystems, where the reign of diatoms in Si cycling has been challenged recently (Churakova et al., 2023; Closset et al., 2025). The more accurately we can quantify biosilicification in terrestrial (as well as marine) ecosystems, the better we will understand biogeochemical Si cycling and its linkage to the C cycle and other ecological processes.
Data availability statement
The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.
Author contributions
DP: Writing – original draft, Writing – review and editing, Conceptualization, Visualization. ZL: Writing – original draft, Writing – review and editing. JC: Writing – original draft, Writing – review and editing.
Conflict of interest
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ReferencesAdlS. M.BassD.LaneC. E.LukesJ.SchochC. L.SmirnovA. (2019). Revisions to the classification, nomenclature, and diversity of eukaryotes. J. Eukaryot. Microbiol.66 (1), 4–119. 10.1111/jeu.1269130257078AlexandreA.MeunierJ.-D.ColinF.KoudJ.-M. (1997). Plant impact on the biogeochemical cycle of silicon and related weathering processes. Geochimica Cosmochimica Acta61 (3), 677–682. 10.1016/s0016-7037(97)00001-xAndersonO. (1994). Cytoplasmic origin and surface deposition of siliceous structures in sarcodina. Protoplasma181 (1), 61–77. 10.1007/BF01666389BartoliF. (1983). The biogeochemical cycle of silicon in two temperate forest ecosystems. Ecol. Bull., 469–476. Available online at: https://www.jstor.org/stable/20112881.BernerR. A. (1992). Weathering, plants, and the long-term carbon cycle. Geochimica Cosmochimica Acta56 (8), 3225–3231. 10.1016/0016-7037(92)90300-8BleckerS. W.McCulleyR. L.ChadwickO. A.KellyE. F. (2006). Biologic cycling of silica across a grassland bioclimosequence. Glob. Biogeochem. Cycles20 (3). 10.1029/2006gb002690CareyJ. C.FulweilerR. W. (2012a). Human activities directly alter watershed dissolved silica fluxes. Biogeochemistry111, 125–138. 10.1007/s10533-011-9671-2CareyJ. C.FulweilerR. W. (2012b). The terrestrial silica pump. PLoS One7 (12), e52932. 10.1371/journal.pone.005293223300825CareyJ. C.FulweilerR. W. (2016). Human appropriation of biogenic silicon–the increasing role of agriculture. Funct. Ecol.30 (8), 1331–1339. 10.1111/1365-2435.12544ChenN.WuY.WuJ.YanX.HongH. (2014). Natural and human influences on dissolved silica export from watershed to coast in Southeast China. J. Geophys. Res. Biogeosci. 119, 95–109. 10.1002/2013JG002429ChurakovaY.AguileraA.CharalampousE.ConleyD. J.LundinD.PinhassiJ. (2023). Biogenic silica accumulation in picoeukaryotes: novel players in the marine silica cycle. Environ. Microbiology Reports15 (4), 282–290. 10.1111/1758-2229.1314436992638ClarkeJ. (2003). The occurrence and significance of biogenic opal in the regolith. Earth-Science Rev.60 (3-4), 175–194. 10.1016/S0012-8252(02)00092-2ClossetI.BaronasJ. J.TorricellaF.De TombeurF.LiguoriB. T.PetruccianiA. (2025). Silicification in the ocean: from molecular pathways to silicifiers' ecology and biogeochemical cycles. Ocean Sci.21 (6), 3427–3470. 10.5194/os-21-3427-2025ClymansW.StruyfE.GoversG.VandevenneF.ConleyD. J. (2011). Anthropogenic impact on amorphous silica pools in temperate soils. Biogeosciences8 (8), 2281–2293. 10.5194/bg-8-2281-2011ConleyD. J. (2002). Terrestrial ecosystems and the global biogeochemical silica cycle. Glob. Biogeochem. Cycles16 (4), 61–68. 10.1029/2002gb001894ConleyD. J.LikensG. E.BusoD. C.SacconeL.BaileyS. W.JohnsonC. E. (2008). Deforestation causes increased dissolved silicate losses in the hubbard brook experimental forest. Glob. Change Biol.14 (11), 2548–2554. 10.1111/j.1365-2486.2008.01667.xCreevyA. L.FisherJ.PuppeD.WilkinsonD. M. (2016). Protist diversity on a nature reserve in NW england—with particular reference to their role in soil biogenic silicon pools. Pedobiologia59 (1-2), 51–59. 10.1016/j.pedobi.2016.02.001DarA. H.WaniA. H.TalieM. D.BhatM. Y.SheikhA. R. (2024). Nutritional composition and mycolith assessment of some wild mushrooms from southern region of kashmir himalaya, India. J. Food Compos. Analysis132, 106336. 10.1016/j.jfca.2024.106336DarA. H.WaniA. H.BhatM. Y.SheikhA. R.LoneS. A. (2025). Mycoliths (fungal-phytoliths) from some hymenomycetous macrofungi. Vegetos38 (4), 1569–1579. 10.1007/s42535-024-00936-xde TombeurF.HodsonM. J.SaundersM.ClodeP. L. (2024). How important is carbon sequestration in phytoliths within the soil?Plant Soil505 (1), 185–198. 10.1007/s11104-024-06700-zDesplanquesV.CaryL.MouretJ. C.TrolardF.BourriéG.GraubyO. (2006). Silicon transfers in a rice field in camargue (france). J. Geochem. Explor.88 (1-3), 190–193. 10.1016/j.gexplo.2005.08.036DietzelM. (2000). Dissolution of silicates and the stability of polysilicic acid. Geochimica Cosmochimica Acta64 (19), 3275–3281. 10.1016/s0016-7037(00)00426-9DouglasM. S.SmolJ. P. (1987). Siliceous protozoan plates in Lake sediments. Hydrobiologia154 (1), 13–23. 10.1007/bf00026827DürrH. H.MeybeckM.HartmannJ.LaruelleG. G.RoubeixV. (2011). Global spatial distribution of natural riverine silica inputs to the coastal zone. Biogeosciences8 (3), 597–620. 10.5194/bg-8-597-2011EhrlichH.DemadisK. D.PokrovskyO. S.KoutsoukosP. G. (2010). Modern views on desilicification: biosilica and abiotic silica dissolution in natural and artificial environments. Chem. Reviews110 (8), 4656–4689. 10.1021/cr900334y20441201EhrmannO.PuppeD.WannerM.KaczorekD.SommerM. (2012). Testate amoebae in 31 mature forest ecosystems--densities and micro-distribution in soils. Eur. J. Protistol.48 (3), 161–168. 10.1016/j.ejop.2012.01.00322342135EpsteinE. (1994). The anomaly of silicon in plant biology. Proc. Natl. Acad. Sci.91 (1), 11–17. 10.1073/pnas.91.1.1111607449EpsteinE. (2009). Silicon: its manifold roles in plants. Ann. Appl. Biol.155 (2), 155–160. 10.1111/j.1744-7348.2009.00343.xGeorgiadisA.SauerD.HerrmannL.BreuerJ.ZareiM.StahrK. (2014). Testing a new method for sequential silicon extraction on soils of a temperate–humid climate. Soil Res.52 (7), 645–657. 10.1071/sr14016GolokhvastK. S.ChaikaV. V.UgayS. M.SeryodkinI. V.GalkinaA. N.RomashkoR. V. (2014). Silicon microstructures (mycoliths) found in the Inonotus obliquus fungus. Biol. Med.6 (2 SI).GuntzerF.KellerC.PoultonP. R.McGrathS. P.MeunierJ.-D. (2012). Long-term removal of wheat straw decreases soil amorphous silica at broadbalk, rothamsted. Plant Soil352, 173–184. 10.1007/s11104-011-0987-4HawksworthD. L. (2001). Mushrooms: the extent of the unexplored potential. Int. Journal Medicinal Mushrooms3 (4), 1. 10.1615/intjmedmushr.v3.i2-3.60HeinenW. (1965). Siliciumstoffwechsel bei Mikroorganismen: VI. Mitteilung. Arch. für Mikrobiol.52 (1), 49–68. 10.1007/BF004090234287464HirotaR.HataY.IkedaT.IshidaT.KurodaA. (2010). The silicon layer supports acid resistance of bacillus cereus spores. J. Bacteriol.192 (1), 111–116. 10.1128/JB.00954-0919880606IkedaT. (2021). Bacterial biosilicification: a new insight into the global silicon cycle. Biosci. Biotechnol. Biochem.85 (6), 1324–1331. 10.1093/bbb/zbab06933877302IlerR. (1979). The chemistry of silica: solubility, polymerization, colloid and surface properties and biochemistry of silica. New York: Wiley-Interscience.JonesL.HandreckK. (1967). Silica in soils, plants, and animals. Adv. Agron.19, 107–149. 10.1016/S0065-2113(08)60734-8KaczorekD.VrydaghsL.DevosY.PetóÁ.EfflandW. R. (2018). “Biogenic siliceous features,” in Interpretation of micromorphological features of soils and regoliths (Elsevier), 157–176.KaczorekD.PuppeD.BusseJ.SommerM. (2019). Effects of phytolith distribution and characteristics on extractable silicon fractions in soils under different vegetation – an exploratory study on loess. Geoderma356, 113917. 10.1016/j.geoderma.2019.113917LiZ.Unzué-BelmonteD.CornelisJ.-T.LindenC. V.StruyfE.RonsseF. (2019). Effects of phytolithic rice-straw biochar, soil buffering capacity and pH on silicon bioavailability. Plant Soil438 (1-2), 187–203. 10.1007/s11104-019-04013-0LiZ.de TombeurF.LindenC. V.CornelisJ.-T.DelvauxB. (2020). Soil microaggregates Store phytoliths in a sandy loam. Geoderma360, 114037. 10.1016/j.geoderma.2019.114037LiZ.MeunierJ.-D.DelvauxB. (2023). Goethite affects phytolith dissolution through clay particle aggregation and pH regulation. Geochimica Cosmochimica Acta349, 11–22. 10.1016/j.gca.2023.03.021LousierJ. D.ParkinsonD. (1981). The disappearance of the empty tests of litter-and soil-testate amoebae (testacea, rhizopoda, protozoa). Arch. für Protistenkd.124 (3), 312–336. 10.1016/s0003-9365(81)80024-3MeisterfeldR. (2002a). Order Arcellinida Kent, 1880. Illustrated Guide Protozoa. Editors LeeJ. J.LeedaleG. F.BradburyP. (Lawrence, Kansas: Society of Protozoologists, Lawrence, Kansas) 2, 827–860.MeisterfeldR. (2002b). Testate amoebae with filopodia. Illustrated Guide Protozoa. Editors LeeJ. J.LeedaleG. F.BradburyP. (Lawrence, Kansas: Society of Protozoologists, Lawrence, Kansas) 2, 1054–1084.MeunierJ.GuntzerF.KirmanS.KellerC. (2008). Terrestrial plant-Si and environmental changes. Mineral. Mag.72 (1), 263–267. 10.1180/minmag.2008.072.1.263MeunierJ. D.KellerC.GuntzerF.RiotteJ.BraunJ. J.AnupamaK. (2014). Assessment of the 1% Na2CO3 technique to quantify the phytolith pool. Geoderma216, 30–35. 10.1016/j.geoderma.2013.10.014MongerH. C.KellyE. F. (2002). Silica minerals. Soil Mineralogy Environmental Applications7, 611–636. 10.2136/sssabookser7.c20OgdenC. (1991). Ultrastructure of the vegetative organisation and initial stages of silica plate deposition in the soil testate amoeba Corythion dubium. Protoplasma163 (2), 136–144. 10.1007/bf01323337PienitzR.DouglasM. S.SmolJ. P.HuttunenP.MeriläinenJ. (1995). Diatom, chrysophyte and protozoan distributions along a latitudinal transect in fennoscandia. Ecography18 (4), 429–439. 10.1111/j.1600-0587.1995.tb00146.xPuppeD. (2020). Review on protozoic silica and its role in silicon cycling. Geoderma365, 114224. 10.1016/j.geoderma.2020.114224PuppeD.EhrmannO.KaczorekD.WannerM.SommerM. (2015). The protozoic Si pool in temperate forest ecosystems — quantification, abiotic controls and interactions with earthworms. Geoderma243-244, 196–204. 10.1016/j.geoderma.2014.12.018PuppeD.HöhnA.KaczorekD.WannerM.SommerM. (2016). As time goes by—Spatiotemporal changes of biogenic Si pools in initial soils of an artificial catchment in NE Germany. Appl. Soil Ecol.105, 9–16. 10.1016/j.apsoil.2016.01.020PuppeD.HöhnA.KaczorekD.WannerM.WehrhanM.SommerM. (2017). 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. Biogeosciences14 (22), 5239–5252. 10.5194/bg-14-5239-2017PuppeD.KaczorekD.SchallerJ.BarkuskyD.SommerM. (2021). Crop straw recycling prevents anthropogenic desilication of agricultural soil–plant systems in the temperate zone–results from a long-term field experiment in NE Germany. Geoderma403, 115187. 10.1016/j.geoderma.2021.115187SacconeL.ConleyD. J.KoningE.SauerD.SommerM.KaczorekD. (2007). Assessing the extraction and quantification of amorphous silica in soils of forest and grassland ecosystems. Eur. J. Soil Sci.58 (6), 1446–1459. 10.1111/j.1365-2389.2007.00949.xSchallerJ.PuppeD.KaczorekD.EllerbrockR.SommerM. (2021). Silicon cycling in soils revisited. Plants10 (2), 295. 10.3390/plants1002029533557192SchönbornW.PetzW.WannerM.FoissnerW. (1987). Observations on the morphology and ecology of the soil-inhabiting testate amoeba schoenbornia humicola (schönborn, 1964) decloitre, 1964 (protozoa, rhizopoda). Arch. für Protistenkd.134 (4), 315–330. 10.1016/S0003-9365(87)80004-0SommerM.JochheimH.HöhnA.BreuerJ.ZagorskiZ.BusseJ. (2013). Si cycling in a forest biogeosystem – the importance of transient state biogenic Si pools. Biogeosciences10 (7), 4991–5007. 10.5194/bg-10-4991-2013StruyfE.ConleyD. J. (2012). Emerging understanding of the ecosystem silica filter. Biogeochemistry107, 9–18. 10.1007/s10533-011-9590-2TréguerP.PondavenP. (2000). Silica control of carbon dioxide. Nature406 (6794), 358–359. 10.1038/3501923610935620TubanaB. S.BabuT.DatnoffL. E. (2016). A review of silicon in soils and plants and its role in US agriculture. Soil Sci.181 (9/10), 393–411. 10.1097/ss.0000000000000179UmemuraM.ToriiA. (2025). Effects of a chemical dispersant on the dispersibility of moso bamboo phytoliths in a particle-size analysis. Soil Sci. Plant Nutr.71, 1–9. 10.1080/00380768.2025.2450407WildingL. P.DreesL. R. (1971). Biogenic opal in Ohio soils. Soil Sci. Soc. Am. J.35 (6), 1004–1010. 10.2136/sssaj1971.03615995003500060041xYangX.SongZ.YuC.DingF. (2020). Quantification of different silicon fractions in broadleaf and conifer forests of northern China and consequent implications for biogeochemical Si cycling. Geoderma361, 114036. 10.1016/j.geoderma.2019.114036YogeshwaranM.ThackerM.WadmareN.VigneshwaranA.RadhakrishnanC.PardhiS. (2025). Soil diatoms and their applications as an indicator of environmental changes. Appl. Soil Ecol.213, 106277. 10.1016/j.apsoil.2025.106277ZamanW.AyazA.PuppeD. (2025). Biogeochemical cycles in plant-soil systems: significance for agriculture, interconnections, and anthropogenic disruptions. Biology, 14(4), 433. 10.3390/biology1404043340282298
Edited by:Wei He, China University of Geosciences, China
Reviewed by:Dongdong Zhu, Ocean University of China, China