Effects of future rainfall patterns on density and diversity of predatory mites (Gamasida) in characteristic agricultural soils of the Pannonian area Janet Wissuwa 1, Helene Berthold 2, Alexander Bruckner 1, Johann G. Zaller 1, Johannes Hösch 2, Andreas Baumgarten 2 Introduction Mesostigmata (Gamasida) are the dominant acarine soil predators in terms of abundance and diversity. They play an important role in many ecosystems by affecting processes like decomposition and nutrient cycling but are often overlooked. The effect of future changes in the seasonal occurrence and intensity of rainfall on predatory mites in agricultural ecosystems has not been studied. Yet, changes in rainfall patterns are expected to affect soil mites, which are influenced by soil moisture and temperature. Regional climate change scenarios for eastern Austria (Pannonian region) predict fewer but heavier rainfall during the vegetation period resulting in repeated drought stress for the soil fauna. This might reduce overall abundance and diversity and lead to a shift within the mite assemblage benefiting drought-tolerant species. The first year results from the study period 2011 to 2013 are presented here. Materials and Methods Study design The AGES lysimeter station consists of 18 3 m 2 lysimeters containing the three main soil types of the Marchfeld, which cover 80% of the agricultural area in this region. In 2011 the lysimeters were cultivated with field peas (Pisum sativum) according to good farming practice. Rainfall was manipulated during the vegetation period from May (start of the experiment) to November with two levels – current rainfall (30 year mean amount) vs. predicted rainfall patterns according to a regional climate scenario (CNRM ) derived from the latest IPCC 4 th Assessment Report Each factor was replicated three times. Soil sampling took place at the end of May (M), July (J) and September (S). Five random soil cores (Ø 5 cm, depth 10 cm) per lysimeter were pooled and extracted with Berlese- Tullgren funnel. The three main soil types of the region are: - sandy calcaric phaeozem (S) - gleyic phaeozem (F) - calcic chernozem (T) Statistics Abundance, diversity and species assemblage were analysed according to a full three-factorial design with rainfall treatment, soil type and month as fixed factors applying Permutational ANOVAs and Principal Coordinates Analysis using PRIMER v6. The species assemblage was analysed using a Hellinger-distance matrix. Results and Conclusions The rainfall treatment did not affect mite density, diversity and species assemblage. Mite density (Fig. 2A) and species richness (Fig. 2B) were significantly affected by soil type and month. The mite assemblage differed significantly between the three soil types (Fig. 2C) and three months (Fig. 2D). There was a significant soil type - month interaction in both directions i.e. soil type within each month (S<>F, S<>T) and month within each soil type (Fig. 2E). 1 Institute of Zoology, Univ. Natural Res. Life Sci. Vienna (BOKU), Austria – 2 Institute for Soil Health and Plant Nutrition, Austrian Agency for Health and Food Safety (AGES), Vienna, Austria Funded by the Austrian Climate and Energy Fund as a part of the program 'ACRP' Fig. 1. Layout of the lysimeter station at AGES Vienna Our results show that soil type and season affect predatory soil mites to far greater extent than changes in rainfall patterns. One vegetation period is not enough to reveal effects of climatic changes on mite abundance, diversity and community. Furthermore, soil mites might avoid drought stress by commuting deeper into the soil. Fig. 2. Mite density (A) and species richness (B) at three different soil types and sampling dates. Ordination of species assemblage for soil type (C), month (D) and the interaction between both factors (E), Means ± SD, n = 3 SFTSFT MJSMJS SxM FxM TxM SxJ FxJ TxJ SxS FxS TxS AB C E D