Schoenoplectus californicus (Cyperaceae) amorphous silica contribution to the silicon cycle in pampean shallow lakes: an analysis of spatio-temporal variation and silicon–lignin relations

Abstract

Context. Phytoliths constitute an important source of silicon in terrestrial and aquatic ecosystems. Schoenoplectus californicus (C.A.Mey.) Soják (Cyperaceae) is an important phytolith producer. Aims. We investigated the spatio-temporal variation in phytolith content of S. californicus in shallow lakes of the Pampean region, considering biomass and its relation to soil silicon content and lignin content. Methods. Calcination techniques were applied to quantify phytoliths. The biomass was estimated by destructive methods. Soil silicon concentration was determined through ultraviolet–visible spectrophotometry by means of the silicomolybdate method. For lignin determination, a fibre analyser and sulfuric acid were used. Key results. No significant differences were observed in the spatio-temporal analysis. There were no differences in the biomass estimation and in the phytolith per m2 contribution. Regarding soil silicon content, when the concentration was low, the phytolith production was low. Lignin content remained constant between sites. No correlation was observed between phytolith and lignin content. Conclusions. S. californicus is an accumulator of amorphous silica, generating a constant quantity of phytoliths over the years and between sites. The variation in some environmental conditions does not seem to be enough to be reflected in plant silica production. No relation between lignin and silica was found, perhaps due to their different roles in plant structure. Implications. The inclusion of other wetlands with more contrasting conditions may reveal the environmental constraints for the amorphous silica production. This study shows the importance of this community as a silicon source, and the implications of its displacement by other communities or urban development.