Phosphorus speciation by 31P NMR spectroscopy 1 in bracken 2 (Pteridium aquilinum (L.) Kuhn) and bluebell (Hyacinthoides non3 scripta (L.) Chouard ex Rothm.) dominated semi-natural upland soil

Access to P species is a driver for plant community composition based on nutrient acquisition. Here we investigated the distribution and accumulation of soil inorganic P (Pi) and organic P (Po) forms in a bracken and bluebell dominated upland soil for the period between bluebell above ground dominance until biomass is formed from half bluebells and half bracken. Chemical characterisation and 31P Nuclear Magnetic Resonance spectroscopy was used to determine the organic and inorganic P species. Total P concentration in soils was 0.87 g kg− 1, while in plants (above- and below-ground parts) total P ranged between 0.84–4.0 g kg− 1 and 0.14–2.0 g kg− 1 for bluebell and bracken, respectively. The P speciation in the plant samples was reflected in the surrounding soil. The main forms of inorganic P detected in the NaOH-EDTA soil extracts were orthophosphate (20.0–31.5%), pyrophosphate (0.6–2.5%) and polyphosphate (0.4–7.0%). Phytate (myo-IP6) was the most dominant organic P form (23.6–40.0%). Other major peaks were scyllo-IP6 and α- and β- glycerophosphate (glyP). In bluebells and bracken the main P form detected was orthophosphate ranging from (21.7–80.4%) and 68.5–81.1%, in above-ground and below-ground biomass, respectively. Other detected forms include α-glyP (4.5–14.4%) and β-glyP (0.9–7.7%) in bluebell, while in bracken they were detected only in stripe and blade in ranges of 2.5–5.5% and 4.4–9.6%, respectively. Pyrophosphate, polyphosphate, scyllo-IP6, phosphonates, found in soil samples, were not detected in any plant parts. In particular, the high abundance of phytate in the soil and in bluebell bulbs, may be related to a mechanism through which bluebells create a recalcitrant phosphorus store which form a key part of their adaptation to nutrient poor conditions.