Phosphorus forms as affected by abandoned anthills (Formica polyctena Forster) in forest soils: sequential extraction and liquid-state P-31-NMR spectroscopy

Ants are known to concentrate phosphorus (P) inside their nests via collect ion of food and litter. To elucidate the possible effects on long-term avai lability of soil P, five anthills abandoned by Red wood ant (Formica polyct ena Forster) >5-20 years ago were characterized for soil P forms in a tempe rate Danish deciduous forest. Sequentially extracted P fractions and liquid -state P-31 nuclear magnetic resonance (NMR) spectra were obtained on surfa ce samples (0-10 cm) from abandoned anthills and adjacent topsoil; in addit ion one representative soil profile in an abandoned anthill was investigate d. The results show that different inorganic and all organic P fractions we re enriched by a factor of 2.0-3.3 inside anthills relative to die surround ing soil. The soil underneath the abandoned anthill had higher P contents u ntil 50-cm depth. Phosphorus composition was less affected by former anthil l construction. Only the younger anthills revealed a preferential accumulat ion of labile organic P forms such as Na-HCO3 extractable P or diester P. T he accumulation of the stable and moderate labile P forms, however, persist ed for greater than or equal to 20 years after abandonment. We concluded th at former ant activity enhanced long-term P availability of soil due to hig h local P inputs, whereas changes of the P form distribution lasted 5-10 ye ars after nest abandonment.