Published online by Cambridge University Press: 05 June 2012
Key points
1. Ferns both respond to and impact ecosystem nutrient cycling.
2. Most ferns and lycophytes acquire nutrients through roots and generally in association with endomycorrhizal fungi. Ferns also acquire nutrients through direct absorption from decomposing litter and exceptionally through association with either ants or nitrogen-fixing cyanobacteria.
3. At a local scale, the vegetative cover and richness of ferns appears to be greatest on sites with high fertility. However, ferns probably make the greatest proportional contribution to total plant biomass on infertile soils.
4. Nutrient levels of fern leaves span a wide range of nitrogen (N) and phosphorus (P) concentrations but ferns still have low N concentrations relative to seed plants. The decomposition rates of fern litter vary widely among species and habitats.
5. Ferns have low leaf calcium (Ca) concentrations relative to seed plants at any given site. Variation among sites in the amount of fern biomass will influence soil Ca cycling.
Introduction
Soil fertility and associated soil biodiversity are critical drivers of vegetation composition and function (Bardgett, 2005), even in human-modified ecosystems (Yaalon, 2007). Adaptations to persist and compete for nutrients on sites of varying fertility drive the development of variation among species and help to determine how species are distributed across the landscape (Grime, 2002; Callaway, 2007). Contrary to the popular notion that ferns are poorly adapted to current environmental conditions, they present a bewildering array of strategies and have radiated into the same habitats as seed plants.
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