Effects of trampling and competition on plant growth and shoot morphology of Plantago, Eragrostis and Eleusine species

Plant growth and shoot morphological patterns of three weeds, Plantago asiatica, Eragrostis ferruginea and Eleusine indica, were compared between monoculture and multispecies mixed culture along a trampling gradient. Total dry weights of these species were markedly lower in mixed culture than those in monoculture at all trampling levels, indicating intense multispecies competition. Differences in the total dry weights between monoculture and mixed culture, however, decreased with increasing trampling intensity, suggesting that trampling reduces the intensity of competition from neighbours. Differences in sizes and numbers of shoots and leaves were significant between the target species but there were little differences in their responses to trampling and multispecies competition. In response to trampling in monoculture, the maximum lengths of leaves and shoots decreased but the numbers of leaves and tillers increased significantly as trampling intensity increased. In response to competition, both the lengths and numbers of leaves and tillers were significantly smaller in mixed culture than in monoculture. These results suggest that there is a trade-off relationship between trampling tolerance and competitive ability, and these species prefer less-competitive habitats resulting from trampling.