Response of Calcareous Grassland Plant Species to Diffuse Competition: Results from a Removal Experiment

Abstract

1 A removal experiment was carried out in a species-rich limestone grassland in Derbyshire, England. Biodegradable herbicide was used to create eight sizes of gap around in situ ramets of five co-occurring plant species: Briza media, Carex caryophyllea, Lotus corniculatus, Plantago lanceolata and Sanguisorba minor. 2 For all species, plants in larger gaps had more leaves than control plants, although there was an associated decrease in mean leaf length. This morphological response was probably due to changes in light quality. 3 Total leaf length of the target plants remained similar between treatments despite changes in leaf morphology. Flower production was also unresponsive to gap size. The biomass of the three smallest species increased with increasing gap size, largely due to higher specific shoot weight. 4 Both the importance and intensity of competition (measured, respectively, as the variation explained and slope in regressions of above-ground biomass against gap size) were greatest for the three smallest species; the biomass of both Plantago and Sanguisorba was unaffected by diffuse competition over the range of gap sizes studied. 5 Morphological plant characteristics (leaf number and mean leaf length) were more sensitive to gap size than the traits more closely related to fitness (biomass, flowering and total leaf length) and as such may be buffering changes at this higher level.