Floor Vandevenne

Agricultural silica harvest: have humans created a new loop in the global silica cycle?

Silica (Si) is of great concern to agronomists because it has a beneficial effect on plant resistance to various stresses, enabling yield optimization in economically important crop species. Yet biogenic silica (BSi) cycling in soils controls a large part of the Si export fluxes to rivers and oceans. Despite the importance of agricultural-harvest-related Si removal, previous studies have not addressed this topic thoroughly. By performing a detailed quantification of agricultural Si export in Western Europes Scheldt River basin, we show that harvest not only disrupts BSi cycling but also introduces an agricultural Si pathway, with major export Si fluxes as compared with BSi production in climax forest communities and grasslands. Harvesting substantially changes terrestrial Si cycling because reconstitution of BSi to soils in litter fall is prevented. The agricultural Si loop clearly constitutes an important flow of BSi out of terrestrial ecosystems – one that is currently unrecognized in global biogeochem...

Silicon pools in human impacted soils of temperate zones

Besides well-known effects of climate and parent material on silicate weathering the role of land use change as a driver in the global silicon cycle is not well known. Changes in vegetation cover have altered reservoirs of silicon and carbon in plants and soils. This has potential consequences for plant-Si availability, agricultural yields, and coastal eutrophication, as Si is a beneficial element for many crop plants and an essential nutrient for diatom growth. We here examined the role of sustained and intensive land use and human disturbance on silicon (Si) pool distribution in soils with similar climatological and bulk mineralogical characteristics. We show that land use impacts both biogenic and nonbiogenic Si pools. While biogenic Si strongly decreases along the land use change gradient (from forest to croplands), pedogenic silica fractions (e.g. pedogenic clays) increase in topsoils with a long duration of cultivation and soil disturbance. Our results suggest that nonbiogenic Si pools might compensate for the loss of reactive biogenic silicon in temperate zones.

Landscape cultivation alters d30Si signature in terrestrial ecosystems

Despite increasing recognition of the relevance of biological cycling for Si cycling in ecosystems and for Si export from soils to fluvial systems, effects of human cultivation on the Si cycle are still relatively understudied. Here we examined stable Si isotope (δ30Si) signatures in soil water samples across a temperate land use gradient. We show that – independent of geological and climatological variation – there is a depletion in light isotopes in soil water of intensive croplands and managed grasslands relative to native forests. Furthermore, our data suggest a divergence in δ30Si signatures along the land use change gradient, highlighting the imprint of vegetation cover, human cultivation and intensity of disturbance on δ30Si patterns, on top of more conventionally acknowledged drivers (i.e. mineralogy and climate).

Grazers: biocatalysts of terrestrial silica cycling

Silica is well known for its role as inducible defence mechanism countering herbivore attack, mainly through precipitation of opaline, biogenic silica (BSi) bodies (phytoliths) in plant epidermal tissues. Even though grazing strongly interacts with other element cycles, its impact on terrestrial silica cycling has never been thoroughly considered. Here, BSi content of ingested grass, hay and faeces of large herbivores was quantified by performing multiple chemical extraction procedures for BSi, allowing the assessment of chemical reactivity. Dissolution experiments with grass and faeces were carried out to measure direct availability of BSi for dissolution. Average BSi and readily soluble silica numbers were higher in faeces as compared with grass or hay, and differences between herbivores could be related to distinct digestive strategies. Reactivity and dissolvability of BSi increases after digestion, mainly due to degradation of organic matrices, resulting in higher silica turnover rates and mobilization potential from terrestrial to aquatic ecosystems in non-grazed versus grazed pasture systems (2 versus 20 kg Si ha−1 y−1). Our results suggest a crucial yet currently unexplored role of herbivores in determining silica export from land to ocean, where its availability is linked to eutrophication events and carbon sequestration through C–Si diatom interactions.

Landscape cultivation alters delta Si-30 signature in terrestrial ecosystems

Despite increasing recognition of the relevance of biological cycling for Si cycling in ecosystems and for Si export from soils to fluvial systems, effects of human cultivation on the Si cycle are still relatively understudied. Here we examined stable Si isotope (δ30Si) signatures in soil water samples across a temperate land use gradient. We show that – independent of geological and climatological variation – there is a depletion in light isotopes in soil water of intensive croplands and managed grasslands relative to native forests. Furthermore, our data suggest a divergence in δ30Si signatures along the land use change gradient, highlighting the imprint of vegetation cover, human cultivation and intensity of disturbance on δ30Si patterns, on top of more conventionally acknowledged drivers (i.e. mineralogy and climate).

Transport of Dissolved Si from Soil to River: A Conceptual Mechanistic Model

This paper reviews the processes which determine the concentrations of dissolved silicon (DSi) in soil water and proposes a conceptual mechanistic model for understanding the transport of Si through soils to rivers. The net DSi present in natural waters originates from the dissolution of mineral and amorphous Si sources in the soil, as well as precipitation processes. Important controlling factors are soil composition (mineralogy and saturated porosity) and soil water chemistry (pH, concentrations of organic acids, CO2 and electrolytes). Together with production, polymerization and adsorption equations they constitute a mechanistic framework determining DSi concentrations. We discuss how key controls differ across soil horizons and how this can influence the DSi transport. A typical podzol soil profile in a temperate climate is used as an example, but the proposed model is transferrable to other soil types. Additionally, the impact of external forcing factors such as seasonal climatic variations and land use is evaluated. This blueprint for an integrated model is a first step to mechanistic modelling of Si transport processes in soils. Future implementation with numerical methods should validate the model with field measurements.

Soybean Trade: Balancing Environmental and Socio-Economic Impacts of an Intercontinental Market.

The trade in soybean, an important animal feed product, exemplifies the environmental and socio-economic impact of global markets and global agricultural policy. This paper analyses the impact of increasing production of soybean in the exporting countries (deforestation and grassland conversion) as well as in importing regions (decrease in permanent grassland by substitution of grass as feed). Ecosystem services monetary values were used to calculate the environmental and socio-economic impact of observed land use changes. This is balanced against the economic value of the global soybean trade. The results prove that consumption choices in one region have real effects on the supply of ecosystem services at a large spatial scale. Conclusively, solutions to make this global market more sustainable are discussed.

Erratum: CORRIGENDUM: Landscape cultivation alters δ30Si signature in terrestrial ecosystems

Scientific Reports 5, Article number: 7732 10.1038/srep07732 (2015); Published: January132015; Updated: March152015 Jean-Thomas Cornelis was included in the Acknowledgements but omitted from the author list in the original version of this Article. This has been corrected in the PDF and HTML versions of the Article and in the Supplementary Information. Acknowledgements “F.I.V. thanks Special Research Funding of the University of Antwerp (BOF-UA) for PhD fellowship funding and Patrick Frings, Ryan Taylor and Jean-Thomas Cornelis for proof-reading and editing the manuscript. We also acknowledge Flemish Science Foundation (FWO) for funding the project “Tracking the biological control on Si mobilisation in upland ecosystems” (project number G014609N).” Now reads “F.I.V. thanks Special Research Funding of the University of Antwerp (BOF-UA) for PhD fellowship funding and Patrick Frings and Ryan Taylor for editing the manuscript as native speakers. We also acknowledge Flemish Science Foundation (FWO) for funding the project “Tracking the biological control on Si mobilisation in upland ecosystems” (project number G014609N) and BELSPO for funding the project SOGLO.” Author contributions “F.I.V. collected the samples and wrote the first drafts. C.D. and H.H. optimised and developed the isotopic analytical method, analysed the samples, made the data processing, and co-developed the discussion. F.I.V., W.C., E.S., G.G. and B.R. were involved in site selection and/or installation of the land use gradient. B.R. and A.L.B. provided background data on clay analysis and Si fractions in the soil. P.M., E.S., L.A. and G.G. initialised and conceptualised the work on Si biogeochemistry in joint collaborations. All authors contributed to the writing and methodological development of the paper.” Now reads “F.I.V. collected the samples and wrote the first drafts. C.D. and H.H. optimised and developed the isotopic analytical method, analysed the samples, made the data processing, and C.D., H.H. and J-T C. co-developed the discussion. F.I.V., W.C., E.S., G.G. and B.R. were involved in site selection and/or installation of the land use gradient. B.R. and A.L.B. provided background data on clay analysis and Si fractions in the soil. P.M., E.S., L.A. and G.G. initialised and conceptualised the work on Si biogeochemistry in joint collaborations. All authors contributed to the writing and methodological development of the paper.” The original Article contained an error in the calculation of the weathering index Total Reserve in Bases (TRB) in figure 2b. The correct figure 2 appears below as Figure 1. Figure 1 (a) Scatterplot of biogenic silica (BSi) in mg g−1 dry soil in the soil profile, (b) Total Reserve in Bases (TRB = [Na] + [Mg] + [Ca] + [K]) weathering index calculated on dry soil, in cmol charge kg−1. Sites are represented by symbols: ...

CORRIGENDUM: Landscape cultivation alters δ30Si signature in terrestrial ecosystems

Scientific Reports 5, Article number: 7732 10.1038/srep07732 (2015); Published: January132015; Updated: March152015 Jean-Thomas Cornelis was included in the Acknowledgements but omitted from the author list in the original version of this Article. This has been corrected in the PDF and HTML versions of the Article and in the Supplementary Information. Acknowledgements “F.I.V. thanks Special Research Funding of the University of Antwerp (BOF-UA) for PhD fellowship funding and Patrick Frings, Ryan Taylor and Jean-Thomas Cornelis for proof-reading and editing the manuscript. We also acknowledge Flemish Science Foundation (FWO) for funding the project “Tracking the biological control on Si mobilisation in upland ecosystems” (project number G014609N).” Now reads “F.I.V. thanks Special Research Funding of the University of Antwerp (BOF-UA) for PhD fellowship funding and Patrick Frings and Ryan Taylor for editing the manuscript as native speakers. We also acknowledge Flemish Science Foundation (FWO) for funding the project “Tracking the biological control on Si mobilisation in upland ecosystems” (project number G014609N) and BELSPO for funding the project SOGLO.” Author contributions “F.I.V. collected the samples and wrote the first drafts. C.D. and H.H. optimised and developed the isotopic analytical method, analysed the samples, made the data processing, and co-developed the discussion. F.I.V., W.C., E.S., G.G. and B.R. were involved in site selection and/or installation of the land use gradient. B.R. and A.L.B. provided background data on clay analysis and Si fractions in the soil. P.M., E.S., L.A. and G.G. initialised and conceptualised the work on Si biogeochemistry in joint collaborations. All authors contributed to the writing and methodological development of the paper.” Now reads “F.I.V. collected the samples and wrote the first drafts. C.D. and H.H. optimised and developed the isotopic analytical method, analysed the samples, made the data processing, and C.D., H.H. and J-T C. co-developed the discussion. F.I.V., W.C., E.S., G.G. and B.R. were involved in site selection and/or installation of the land use gradient. B.R. and A.L.B. provided background data on clay analysis and Si fractions in the soil. P.M., E.S., L.A. and G.G. initialised and conceptualised the work on Si biogeochemistry in joint collaborations. All authors contributed to the writing and methodological development of the paper.” The original Article contained an error in the calculation of the weathering index Total Reserve in Bases (TRB) in figure 2b. The correct figure 2 appears below as Figure 1. Figure 1 (a) Scatterplot of biogenic silica (BSi) in mg g−1 dry soil in the soil profile, (b) Total Reserve in Bases (TRB = [Na] + [Mg] + [Ca] + [K]) weathering index calculated on dry soil, in cmol charge kg−1. Sites are represented by symbols: ...