The physical resistance of grass patches to invasion

One of the important factors determining success in plant competition is the ability of a plant to extend laminae in order to capture resources. To do this in mixed swards the laminae of one plant must first grow into the volume that contains laminae of another. The ability of laminae to overcome the resistance presented by a neighbour, and the ability to resist this ingress, was examined for the grasses Agrostis capillaris, Festuca rubra, Holcus lanatus, Lolium perenne and Poa trivialis that were subject to 3 cm and 6 cm cutting treatments. These abilities were inferred from the behaviour of 'indicator' leaves as they were pushed into monoculture target patches of each species. The 3 cm treatment resisted ingress significantly more than the 6 cm. Species patches differed significantly both in their ability to resist the ingress by the indicator species and in the ability of different indicator species to penetrate the target swards. These effects were still present when differences in leaf density (leaves cm 2) had been taken into account. The results suggest that grasses can vary in the physical resistance that they present to the leaves of an invading neighbour.