The ecological role of silicon in semi-arid rangelands: from the greenhouse to the field

• Applicant: Professor Dr. Jörg Schaller
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 455559377

Drylands i.e. arid, semiarid and dry subhumid ecosystems, cover approximately one quarter of the land mass, support 50% of the world’s livestock population and provide several ecosystem services. Plant communities in these areas are exposed to high water limitation, intensive human pressure in terms of cropland practices and livestock production, and periodic devastations by locusts. However, our understanding of plant community responses to biotic and abiotic factors and the underlying mechanisms of these responses is still limited for drylands. This applies especially to dryland ecosystems dominated by annual plant communities. Plant species responses to environmental conditions vary among plant taxa depending on their functional traits. One trait that has been shown to influence various functions in plants, which are relevant in the ecology of drylands, is the ability to take up and accumulate silicon. Silicon (Si) changes nutrient stoichiometry as well as alleviates biotic and abiotic stress. Silicon is assumed to influence plant-water relations by at least three pathways. Edaphically, the amount of amorphous Si (ASi) in soils has been identified to increase soil water holding capacity and plant available water. Physiologically, silicon influences stomata regulation and wilting behavior and anatomically it forms a layer below the cuticle that reduces water loss by transpiration. Therefore, Si might be crucial for species’ performance responses to drought. High foliar Si concentration can also decrease herbivory (mammalian and insects). The proposed project aims to establish a thorough understanding of the ecological relevance of silicon in annual species of semi-arid rangelands by exploring (a) the variability of foliar Si contents in plant species of three functional groups (forbs, legumes, grasses) under different environmental conditions, (b) the effects of Si availability on species’ nutrient stoichiometry, (c), the effects of Si availability on species’ responses to drought, and (d) effects of plant’s Si content on a model herbivore’s feeding preference. The relations will be studied in greenhouse and field experiments in 12 annual species to elucidate the underlying mechanisms and to assess their relevance under natural conditions. We will explicitly link Si content to species’ fitness responses to assess its predictive ability for species’ responses based on “foundation stones” of trait-based ecology. The proposed study will thus address the knowledge gap of the importance of Si in the ecology of semi-arid rangelands. Our findings will indicate whether Si variability offers possibilities to mitigate effects of drought or herbivory on species’ performance. The project will thus improve projections of consequences of global change with theoretical and applied implications.

• DFG Programme: Research Grants
• International Connection: Israel
• International Co-Applicant: Dr. Ofir Katz