Seasonal changes in biom ass of macrophytes on shaded and unshaded sections of the River Lambourn, England

Abstract

SUMMARY. Monthly changes in the biomass of Ranunculus, Berula and Callitriche were recorded on two 50‐m sites on the River Lambourn at Bagnor between March 1971 and October 1973. On the unshaded site. Ranunculus was the dominant macrophyte and characteristically its biomass changed from 20–40 g dry wt m‐2 in March to around 400 g dry wt m‐2 at the end of the growing season. On the shaded site, where Berula was the dominant macrophyte. the biomass of Ranunculus was lower than on the unshaded site. There was no significant difference between the mean biomasses of Berula on these two sites but Callitriche had a signifieantly higher biomass on the shaded site. Estimates of the total biomass of macrophyte on each site were calculated and the biomass of macrophyte removed during cutting operations each summer was also assessed.