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We hypothesized that at the very beginning of terrestrial ecosystem development, airborne testate amoebae play a pivotal role in facilitating organismic colonization and related soil processes. We, therefore, analyzed size and quantity of airborne testate amoebae and immigration and colonization success of airborne testate amoebae on a new land surface (experimental site “Chicken Creek”, artificial post-mining water catchment). Within an altogether 91-day exposure of 70 adhesive traps, 12 species of testate amoebae were identified to be of airborne origin. Phryganella acropodia (51% of all individuals found, diameter about 35–45 μm) and Centropyxis sphagnicola (23% of all individuals found, longest axis about 55–68 μm), occurred most frequently in the adhesive traps. We extrapolated an aerial amoeba deposition of 61 individuals d−1 m−2 (living and dead individuals combined). Although it would be necessary to have a longer sequence (some additional years), our analysis of the “target substrate” of aerial immigration (catchment site) may point to a shift from a stochastic (variable) beginning of community assembly to a more deterministic (stable) course. This shift was assigned to an age of seven years of initial soil development. Although experienced specialists are necessary to conduct these time-consuming studies, the presented data suggest that terrestrial amoebae are suitable indicators for initial ecosystem development and utilization.
The size and dynamics of biogenic silicon (BSi) pools influence silicon (Si) fluxes from terrestrial to aquatic
ecosystems. The research focus up to now was on the role of plants in Si cycling. In recent studies on old forests annual biosilicification rates of idiosomic testate amoebae (i.e. TA producing self-secreted silica shells) were shown to be of the order of Si uptake by trees. However, no comparable data exist for initial ecosystems. We analyzed the protozoic BSi pool (idiosomic TA), corresponding annual biosilicification rates and readily available and amorphous Si fractions along a 10-year chronosequence in a post-mining landscape in Brandenburg, Germany. Idiosomic Si pools ranged from 3 to 680 g Si ha−1 and were about 3–4 times higher at vegetated compared to uncovered spots. They increased significantly with age and were related to temporal development of soil chemical properties. The calculation of annual biosilicification resulted in maxima between 2 and 16 kg Si ha−1 with rates always higher at vegetated spots. Our results showed that the BSi pool of idiosomic TA is built up rapidly during the initial phases of ecosystem development and is strongly linked to plant growth. Furthermore, our findings highlight the importance of TA for Si cycling in young artificial ecosystems.
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 6.2 mg m−2. Zoogenic Si pool size (max. 22.6 mg m−2) is comparable to the one of protophytic Si pools (max. 30.5 mg m−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).
The comparison of multi model runs of the reference period 1979-1993 with different observational data sets for several climate parameters enables the quantification of the model uncertainties in representing present-day climate conditions for Central Europe. The quantification is based on a number of objective distance measures which detect differences in the spatial and temporal structures of the data sets being compared. Additional climate change simulations of two 30-year periods (control and scenario simulation) are performed for the SRES B2 global change scenario. They indicate a severe warming for Germany with values of up to 4 K in summer which is much higher than the quantified uncertainty range of the regional models for this climate parameter. For precipitation in Germany, a weak reduction during the summer months is overcompensated by an increase in winter and fall. However, the simulated changes are smaller than the quantified uncertainty range for the regional models so that in particular a significant reduction of the annual precipitation in Germany cannot be stated on basis of the current simulations for the B2 scenario. Aim of the research in the context of DEKLIM A reliable assessment of possible future climate developments requires an improved understanding of climate and its variability as well as a detailed knowledge of the uncertainties of climate simulations which provide the requested information about the potential degree of future changes. The project QUIRCS focuses on the climate patterns of Central Europe and investigates the quality of currently used regional climate models and regionalization techniques by a model inter-comparison, a substantial model evaluation, additional sensitivity studies and an extensive analysis of climate data. The major scientific aims are • to quantify the uncertainties of regional climate simulations and of observed climate data, • to provide a regional climate change scenario for Europe with a particular focus on Germany, • to assess the reliability of the produced climate change signals with respect to the Collapse.