Seasonal dynamics of biomass partitioning in a tall sedge, Carex acuta L.

Abstract

The demographic and production characteristics were investigated in Carex acuta L., a common dominant of temperate herbaceous wetlands. The seasonal courses of shoot density and biomass were followed in a model population using the method of successive harvests for eight years. Destructive and non-destructive types of measurement were combined in order to study the biomass turnover at the level of single shoots. Belowground biomass was estimated from soil blocks and related to shoot density. The seasonal maximum of total aboveground biomass varied from 400 to 750gm−2, of which C. acuta formed 25–90%. Vegetative shoots accounted for 90% of the total shoot density and 95% of the species’ aboveground biomass. They invested about 90% of their annual production to leaf blades; new leaves were produced from early spring to top summer and increased their dry weight until late autumn. The generative shoots allocated about 2/3 of their annual production to the stem with inflorescence. They grew fast in spring but died off soon after seed maturation in July. The annual production was 2.7g and less than 2.0g dry weight for vegetative and generative tillers, respectively. The turnover rates, reflecting the dry weight of leaves lost during the vegetation season, were 1.2–1.3 year−1 and 1.0–1.1 year−1 for vegetative and generative shoots, respectively. Leaves had a smaller dry weight and a smaller specific leaf mass after, than before their death. This difference, which was ascribed to the downward re-translocation of mobile materials, accounted for 20% dry weight of the leaves prior to dying out. Roots formed about 90% of the live belowground biomass. The average root dry weight was about 2g per shoot in spring and summer and increased to about 5g per shoot by the end of the vegetation season. The annual aboveground primary production of C. acuta can be underestimated by about 1/3 if the turnover rate and downward re-translocation are not considered.