Competition between <i>Artemisia frigida</i> and <i>Cleistogenes squarrosa</i> under different clipping intensities in replacement series mixtures at different nitrogen levels

Abstract

Abstract The relative competitive ability of Artemisia frigida Willd. (C 3 , semi‐shrub) and Cleistogenes squarrosa (Trin.) Keng (C 4 , perennial bunchgrass), grown in a greenhouse, was studied under three nitrogen fertilizer levels, three defoliation intensities and five competitive replacement series in a factorial arrangement. Relative yield total and the respective crowding coefficients for each species were calculated with reference to aboveground, below‐ground and total biomass. The index of aggressivity was also determined relative to total biomass. Cleistogenes squarrosa was a consistently weak competitor at all nitrogen fertilizer and clipping levels compared with A. frigida . Artemesia frigida had a higher relative yield when grown in mixtures with C. squarrosa than in monocultures, whereas the yield of C. squarrosa was lower in mixtures with A. frigida than in monocultures. The relative competitive ability of A. frigida over C. squarrosa declined significantly at different clipping intensities with increasing nitrogen fertilizer. The interaction of nitrogen fertilizer with clipping was significant, although the clipping effect on aggressivity was not significant.