Sub soil P status could explain the absence of resilience in plant species composition of subalpine grassland 63 years after the last fertilizer application

A unique grassland fertilizer experiment (the ‘Grass Garden’) was discovered on a podzol in the Giant (Krkonoše) Mts. in 2006. Sixty three years after having been fertilized with wood ash and manure for over 200 years, a 5 ha plot was dominated by Deschampsia cespitosa in the centre of the plot and Avenella flexuosa on the edge, whereas Nardus stricta was dominant in adjacent land which has never been fertilized. To explain these differences, soil (to three depths) and biomass samples were collected from three quadrants in Deschampsia, Avenella, and Nardus areas. Although the total and Olsen P appeared unaffected by the former fertilizer application in the surface humus layer, both P forms (plus soil solution P) were higher in the Grass Garden than outside for the eluvial and illuvial layers. Concentration and storage of P in green and senescent biomass was the lowest in Nardus and the highest in Deschampsia.It is suggested that these differences in P status may be responsible for the different dominant species between the areas, since Nardus is known to be very efficient in P recycling and has high P use efficiency. Long-term after-effects of fertilizer application must be evaluated over the whole soil profile since nutrients can move into the subsoil where the plants are able to acquire them.