RESPONSE OF CALCAREOUS GRASSLAND PLANT-SPECIES TO DIFFUSE COMPETITION- RESULTS FROM A REMOVAL EXPERIMENT

1 A removal experiment was carried out in a species-rich limestone gra ssland in Derbyshire, England. Biodegradable herbicide was used to cre ate eight sizes of gap around in situ ramets of five co-occurring plan t species: Briza media, Carex caryo-phyllea, Lotus corniculatus, Plant ago lanceolata and Sanguisorba minor. 2 For all species, plants in lar ger gaps had more leaves than control plants, although there was an as sociated 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 l eaf morphology. Flower production was also unresponsive to gap size. T he biomass of the three smallest species increased with increasing gap size, largely due to higher specific shoot weight. 4 Both the importa nce and intensity of competition (measured, respectively, as the varia tion explained and slope in regressions of above-ground biomass agains t 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 characteri stics (leaf number and mean leaf length) were more sensitive to gap si ze than the traits more closely related to fitness (biomass, flowering and total leaf length) and as such may be buffering changes at this h igher level.