Impact of farming practices on soil diatoms and testate amoebae: A pilot study in the DOK-trial at Therwil, Switzerland

Testate amoebae (Arcellinida and Euglyphida) and diatoms (Bacillariophyta) respond to different ecological gradients. These protists are useful tools for biomonitoring and paleoecological studies in aquatic and terrestrial ecosystems. However, little is known about the responses of these micro-eukaryotes to soil management practices. We analyzed the testate amoeba and diatom communities from the DOK-trial (D: biodynamic, O: bio-organic, K: german "konventionell" integrated conventional) agricultural experiment at Therwil, Switzerland. Soil samples were collected from biodynamic and conventional plots and subsequently incubated for four months in a growth chamber. The diatom diversity tended to be higher in the biodynamic than in the two conventional systems. Redundancy analysis (RDA) suggested that diatom community structure differed between organic and the two conventional systems. Testate amoeba abundance was about five times higher in biodynamic than in conventional systems (P < 0.05) but no significant differences in diversity were reported between treatments. Altogether, these data suggest that diatoms and testate amoebae are sensitive to farming systems. As direct analyses of soil samples are time-consuming, molecular tools would be very useful for further development of the use of protists in bioindication. Crown Copyright (C) 2011 Published by Elsevier Masson SAS. All rights reserved.