The Biomass and Productivity of Glyceria Maxima: I. Seasonal Changes in Biomass

Abstract

Biomass determinations were made in stands of Glyceria maxima regularly throughout a year. The greatest mean biomass found, in Sept. was 1.5 kg dry weight/m2. This was 21% of the fresh weight, contained 7.5% ash and included 0.66 kg/m2 of green shoots. The standing crop of shoots, and the dry matter and ash contents were similar to the general averages from other investigations. Allowing for the seasonal variations such dry matter and ash contents may therefore be used for conversions of biomass data for which they are unknown. Underground parts were usually over 40% of the biomass, and the considerable variability meant that assumed ratios would not convert standing crops to biomass accurately. The seasonal maximum was indistinct because old shoots died, while other parts continued growth, between July and Oct. The annual accumulation of dead organic matter, and hence the annual aerial yield, probably exceeded the seasonal maximum standing crop.