Competitive interactions between Nardus stricta L. and Calluna vulgaris (L.) Hull: the effect of fertilizer and defoliation on above- and below-ground performance

abonos abonos npk biomasa biomass biomasse calluna calluna vulgaris chemical composition composition chimique corte cutting engrais engrais npk fertilidad del suelo fertilizers mycorrhizae nardus nardus stricta npk fertilizers peat soils plant competition sandy soils soil fertility sol sableux sol tourbeux suelo arenoso suelo turboso