Effect of grazing intensity on clonal morphological plasticity and biomass allocation patterns of Artemisia frigida and Potentilla acaulis in the Inner Mongolia steppe

Morphological traits and biomass allocation patterns of Artemisia frigida and Potentilla acaulis under different grazing intensities were studied at the Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences (43 degrees 26 '-44 degrees 08 ' N, 116 degrees 04 '-117 degrees 05 ' E). The internode length, branching intensity and biomass allocation responded significantly to grazing intensities. Artemisia frigida had the longest and the shortest internode length under no grazing and moderate grazing respectively. Potentilla acaulis had the longest internode length under light grazing and its internodes shortened significantly under heavy grazing. Branching intensities of both species rose with increasing grazing intensity. Population total biomass in Artemisia frigida decreased while that in Potentilla acaulis decreased firstly and then increased with increasing grazing intensity. The aboveground biomass and root/shoot ratio in Artemisia frigida decreased significantly with increasing grazing intensity, while that of Potentilla acaulis increased. Biomass allocations to structural components of these two species were different. Differences in morphological plasticity and biomass allocation patterns of these two species indicated that they had different ecological strategies to grazing. Potentilla acaulis was more adapted to heavy grazing than Artemisia frigida. Communities of Leymus chinensis and Stipa grandis may finally converge to a Potentilla acaulis community under continuous overgrazing, and eventually turn to desert.