As time goes by—Spatiotemporal changes of biogenic Si pools in initial soils of an artificial catchment in NE Germany

Abstract

Accumulation and recycling of biogenic silicon (BSi) in terrestrial ecosystems influence fluxes of dissolved Si from the continents to the oceans, thus act as a filter in the global Si cycle. Although the biogenic control mechanism especially of phytogenic Si pools (phytoliths) has been generally recognized since decades quantitative information on other terrestrial BSi pools is surprisingly rare. For the first time terrestrial protophytic (diatom frustules), protozoic (testate amoeba shells) and zoogenic (sponge spicules) Si pools were quantified in soils of initial ecosystem states. We analyzed spatiotemporal changes of these Si pools in differently aged soils of the artificial catchment ‘Chicken Creek’ in NE Germany. Within a relatively short time span (<10 years) of ecosystem development protophytic, protozoic and zoogenic Si pool sizes increased markedly, whereat protozoic Si pools were the smallest ones with a maximum of 6.2mgm−2. Zoogenic Si pool size (max. 22.6mgm−2) is comparable to the one of protophytic Si pools (max. 30.5mgm−2) although only few sponge spicules (n=10) and spicule fragments (n=2) were found. Differences in quantities, dynamics and resistibility against dissolution of various BSi pools indicate their possibility to influence biogeochemical Si cycling relatively rapid (protophytic and protozoic Si pools) or slow (zoogenic Si pool). Spatiotemporal changes of protophytic and protozoic Si pools within the first decade of ecosystem development seem to be mainly controlled by (biotic) small-scale environmental conditions (e.g., vegetation, food sources).