ALBERT

Description: by Christoph Ptatscheck, Walter Traunspurger Objectives In this study we investigated the dynamics of meiofaunal and macrofaunal communities in artificial water-filled tree holes. The abundances and, for the first time, biomasses and secondary production rates of these communities were examined. The experimental set-up consisted of 300 brown plastic cups placed in temperate mixed forests and sampled five times over a period of 16 months to determine the impact of (i) seasonal events, (ii) physicochemical parameters, and (iii) food resources on the tree hole metazoans. Outcomes Metazoan organisms, especially the meiofauna (rotifers and nematodes) occupied nearly all of the cups (〉 99%) throughout the year. Between 55% and 99% of the metazoan community was represented by rotifers (max. 557,000 individuals 100 cm -2 ) and nematodes (max. 58,000 individuals 100 cm -2 ). Diptera taxa, particularly Dasyhelea sp. (max. 256 individuals 100 cm -2 ) dominated the macrofaunal community. Macrofauna accounted for the majority of the metazoan biomass, with a mean dry weight of 5,800 μg 100 cm -2 and an annual production rate of 20,400 μg C 100 cm -2 , whereas for meiofauna mean biomass and annual production were 100 μg 100 cm -2 and 5,300 μg C 100 cm -2 , respectively. The macrofaunal taxa tended to show more fluctuating population dynamic while the meiofaunal dynamic was rather low with partly asynchronous development. Seasonality (average temperature and rain intervals) had a significant impact on both meiofauna and macrofauna. Furthermore, bottom-up control (chlorophyll-a and organic carbon), mainly attributable to algae, was a significant factor that shaped the metazoan communities. In contrast, physicochemical water parameters had no evident influence. 23.7% of organism density distribution was explained by redundancy analysis (RDA) indicating a high dynamic and asynchrony of the systems.