Silicon Mobilization in Soils: the Broader Impact of Land Use

Dissolved Si (DSi) provision from land systems triggers diatom growth and CO2 sequestration. Soils and ecosystems act as a Si “filter”, transforming DSi originated from mineral weathering into biogenic Si (BSi) after DSi uptake by plants, or into other pedogenic forms of Si (non-BSi). Land use changes the quantity of BSi and non-BSi pools along the soil profile. However, methods used to isolate Si pools include chemical extractions at high temperatures and alkaline environments and therefore are unable to provide information concerning the dissolution potential of BSi and non-BSi pools under normal conditions of temperature and pH. Here, we conducted a batch experiment where forest, pasture and cropland soil samples were mixed with water at 25 °C and pH 7. The soil samples were collected from a temperate land use gradient located in the Belgian Loess Belt. We measured dissolved Si and aluminium (Al) during 80 days. BSi and non-BSi pool contents along the soil profile were known, as they had been established previously through chemical extraction. Results show that BSi and non-BSi enriched samples present distinct Si and Al dissolution curves. While non-BSi pools contribute significantly with immediate availability of Si, BSi pools present an initial slow dissolution. Therefore, croplands that were depleted of phytoliths and had poorly organic horizons display higher concentrations of initial dissolved Si, while pastures and forests, where pedogenic pools dominate only at depths below 40 cm, have more limited initial Si release.info:eu-repo/semantics/publishedVersio

Towards a global arctic-alpine model for Near-infrared reflectance spectroscopy (NIRS) predictions of foliar nitrogen, phosphorus and carbon content

Source at https://doi.org/10.1038/s41598-019-44558-9. Near-infrared spectroscopy (NIRS) is a high-throughput technology with potential to infer nitrogen (N), phosphorus (P) and carbon (C) content of all vascular plants based on empirical calibrations with chemical analysis, but is currently limited to the sample populations upon which it is based. Here we provide a first step towards a global arctic-alpine NIRS model of foliar N, P and C content. We found calibration models to perform well (R2validation = 0.94 and RMSEP = 0.20% for N, R2validation = 0.76 and RMSEP = 0.05% for P and R2validation = 0.82 and RMSEP = 1.16% for C), integrating 97 species, nine functional groups, three levels of phenology, a range of habitats and two biogeographic regions (the Alps and Fennoscandia). Furthermore, when applied for predicting foliar N, P and C content in samples from a new biogeographic region (Svalbard), our arctic-alpine NIRS model performed well. The precision of the resulting NIRS method meet international requirements, indicating one NIRS measurement scan of a foliar sample will predict its N, P and C content with precision according to standard method performance. The modelling scripts for the prediction of foliar N, P and C content using NIRS along with the calibration models upon which the predictions are based are provided. The modelling scripts can be applied in other labs, and can easily be expanded with data from new biogeographic regions of interest, building the global arctic-alpine model

The effects of dunite fertilization on growth and elemental composition of barley and wheat differ with dunite grain size and rainfall regimes

Enhanced weathering (EW) of silicate rocks is a negative emission technology that captures CO2 from the atmosphere. Olivine (Mg2SiO4) is a fast weathering silicate mineral that can be used for EW and is abundant in dunite rock. In addition to CO2 sequestration, EW also has co-benefits in an agricultural context. Adding silicate minerals to soils can significantly improve crop health and growth as the weathering releases elements such as silicon (Si) that can stimulate crop growth and increase stress resistance, a co-benefit that is becoming increasingly important as global warming proceeds. However, dunite also contains heavy metals, especially nickel (Ni) and chromium (Cr), potentially limiting its use in an agricultural context. In this study, we investigate the influence of dunite addition on growth of barley and wheat in a mesocosm experiment. We amended the soil with the equivalent of 220 ton ha-1 dunite, using two grain sizes (p80 = 1020 µm and p80 = 43.5 µm), under two rainfall regimes (each receiving the same amount of 800 mm water y−1 but at daily versus weekly rainfall frequency). Our results indicate that the amendment of fine dunite increased leaf biomass but only with daily rainfall. Aboveground biomass was significantly reduced with weekly rainfall compared to daily rainfall, but this reduction was slightly alleviated by fine dunite application for wheat. This indicates a positive effect of dunite during drying-rewetting cycles. For barley the negative effect of reduced rainfall frequency was not counterbalanced by dunite application. Contrary to our expectations, calcium (Ca) and Si concentrations in crops decreased with fine dunite application, while, as expected, magnesium (Mg) concentration increased. Coarse dunite application did not significantly affect crop nutrient concentrations, most likely due to its lower weathering rate. In contrast to what was expected, plant Ni and Cr concentrations did not increase with dunite application. Hence, despite high dunite application in our experiment, plants did not accumulate these heavy metals, and only benefited from the released nutrients, albeit dependent on grain size and rainfall frequency

Sponge spicules as blueprints for the biofabrication of inorganic–organic composites and biomaterials

While most forms of multicellular life have developed a calcium-based skeleton, a few specialized organisms complement their body plan with silica. However, of all recent animals, only sponges (phylum Porifera) are able to polymerize silica enzymatically mediated in order to generate massive siliceous skeletal elements (spicules) during a unique reaction, at ambient temperature and pressure. During this biomineralization process (i.e., biosilicification) hydrated, amorphous silica is deposited within highly specialized sponge cells, ultimately resulting in structures that range in size from micrometers to meters. Spicules lend structural stability to the sponge body, deter predators, and transmit light similar to optic fibers. This peculiar phenomenon has been comprehensively studied in recent years and in several approaches, the molecular background was explored to create tools that might be employed for novel bioinspired biotechnological and biomedical applications. Thus, it was discovered that spiculogenesis is mediated by the enzyme silicatein and starts intracellularly. The resulting silica nanoparticles fuse and subsequently form concentric lamellar layers around a central protein filament, consisting of silicatein and the scaffold protein silintaphin-1. Once the growing spicule is extruded into the extracellular space, it obtains final size and shape. Again, this process is mediated by silicatein and silintaphin-1, in combination with other molecules such as galectin and collagen. The molecular toolbox generated so far allows the fabrication of novel micro- and nanostructured composites, contributing to the economical and sustainable synthesis of biomaterials with unique characteristics. In this context, first bioinspired approaches implement recombinant silicatein and silintaphin-1 for applications in the field of biomedicine (biosilica-mediated regeneration of tooth and bone defects) or micro-optics (in vitro synthesis of light waveguides) with promising results