Abstract
Abstract. Various studies have been performed to quantify silicon (Si) stocks in plant biomass and related Si fluxes in terrestrial biogeosystems. Most studies are deliberately designed on the plot scale to ensure low heterogeneity in soils and plant composition, hence similar environmental conditions. Due to the immanent spatial soil variability, the transferability of results to larger areas, such as catchments, is therefore limited. However, the emergence of new technical features and increasing knowledge on details in Si cycling lead to a more complex picture at landscape and catchment scales. Dynamic and static soil properties change along the soil continuum and might influence not only the species composition of natural vegetation but also its biomass distribution and related Si stocks. Maximum likelihood (ML) classification was applied to multispectral imagery captured by an unmanned aerial system (UAS) aiming at the identification of land cover classes (LCCs). Subsequently, the normalized difference vegetation index (NDVI) and ground-based measurements of biomass were used to quantify aboveground Si stocks in two Si-accumulating plants (Calamagrostis epigejos and Phragmites australis) in a heterogeneous catchment and related corresponding spatial patterns of these stocks to soil properties. We found aboveground Si stocks of C. epigejos and P. australis to be surprisingly high (maxima of Si stocks reach values up to 98 g Si m−2), i.e. comparable to or markedly exceeding reported values for the Si storage in aboveground vegetation of various terrestrial ecosystems. We further found spatial patterns of plant aboveground Si stocks to reflect spatial heterogeneities in soil properties. From our results, we concluded that (i) aboveground biomass of plants seems to be the main factor of corresponding phytogenic Si stock quantities, and (ii) a detection of biomass heterogeneities via UAS-based remote sensing represents a promising tool for the quantification of lifelike phytogenic Si pools at landscape scales.
Highlights
Biogenic silicon (BSi), i.e. silica precipitates (SiO2 · nH2O) synthesized by various organisms, has been recognized as a key factor controlling Si fluxes from terrestrial to aquatic ecosystems (Dürr et al, 2011; Street-Perrott and Barker, 2008; Struyf and Conley, 2012), which mainly results from its pool size and a larger solubility compared to silicate minerals (e.g. Cornelis and Delvaux, 2016)
While open water and shadow showed the lowest digital numbers (DN) over all spectral bands, the highest DNs in the visible range were characteristic for sandy soil (Stoner and Baumgardner, 1981)
We found mean aboveground Si stocks of P. australis and C. epigejos to be comparable to or even distinctly higher than reported values for the Si storage in aboveground vegetation of different terrestrial biogeosystems
Summary
Biogenic silicon (BSi), i.e. silica precipitates (SiO2 · nH2O) synthesized by various organisms, has been recognized as a key factor controlling Si fluxes from terrestrial to aquatic ecosystems (Dürr et al, 2011; Street-Perrott and Barker, 2008; Struyf and Conley, 2012), which mainly results from its pool size and a larger solubility compared to silicate minerals (e.g. Cornelis and Delvaux, 2016). In most terrestrial ecosystems phytogenic Si, i.e. BSi synthesized by plants, generally represents the largest BSi pool in soil–plant systems, exerting the strongest influence on Si fluxes into soils (reviewed by Schaller et al, 2021). In agricultural soil–plant systems the recycling of phytogenic Si has been found to boost the biological Si feedback loop and to compensate for Si losses by crop harvest (Alexandre et al, 1997; Blecker et al, 2006; Cornelis et al, 2010; Yang et al, 2020; Li et al, 2020; Puppe et al, 2021)
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