Original article Impact of ecologically different earthworm species on soil water characteristics Gregor Ernst a, * , Daniel Felten a , Michael Vohland b , Christoph Emmerling a a Universita ¨t Trier, FB VI, Bodenkunde, Campus II, Behringstraße, D-54286 Trier, Germany b Universita ¨t Trier, FB VI, Fernerkundung, Campus II, Behringstraße, D-54286 Trier, Germany article info Article history: Received 7 November 2008 Received in revised form 8 January 2009 Accepted 13 January 2009 Available online 5 February 2009 Handling editor: Stefan Schrader Keywords: Earthworms Functional groups Soil water Soil tension Infiltration abstract A laboratory experiment was performed to assess the impact of ecologically different earthworm species on soil water characteristics, such as soil tension, water content, and water infiltration rate. Three earthworm species (Lumbricus rubellus, Aporrectodea caliginosa, Lumbricus terrestris) were exposed in soil columns (diameter 30 cm, height 50 cm) for 100 days with a total fresh earthworm biomass of 22.7  0.4 g per column, each in duplicate. Each column was equipped with tensiometers at 10 and 40 cm and FD-probes at 10 cm depth, to continuously measure the temporal development of soil tension and soil moisture. Additionally, 30 g of sieved and rewetted horse manure was placed on the soil surface as a food source. Precipitation events (10 mm) were simulated at day 28 and day 64. At the end of the experiment the water infiltration rate and the runoff at 55 cm depth were determined. The results showed considerable evidence, that ecologically different earthworms modify soil water characteristics in different ways. The anecic L. terrestris and the endogeic A. caliginosa showed the tendency to enhance the drying of the topsoil and subsoil. Their intensive and deep burrowing activity might enhance the exchange of water vapor due to a better aeration in soil. In contrast, the epigeic L. rubellus tended to enhance the storage of soil moisture in the topsoil, which might be linked to lower rates of litter loss from soil surface and thus a thicker litter layer remaining. A. caliginosa led to considerable higher water infiltration rates and faster water discharges in the subsoil, relative to the other species, probably due to a high soil dwelling activity. Ó 2009 Elsevier Masson SAS. All rights reserved. 1. Introduction Earthworms play a major role in ecosystem functioning. They may be the dominant group of the decomposer community, enhancing the mineralization of soil organic matter by consump- tion, respiration and gut passage [14,24,26]. Their burrowing and feeding activity enlarge the surface of organic substances and contribute to transformation and vertical transport of organic matter in soils [33]. They may stimulate microbial activity and availability of nutrients in soil [7,36]. Due to their soil dwelling activity, the soil structure is modified by the production of stable macropores and aggregates [5,12,21] and thus, soil water charac- teristics are strongly influenced [4]. According to Aina [1], Bardgett et al. [4], Shipitalo and Butt [31], and Willoughby and Kladivko [35] earthworms contribute to an increase in water infiltration in soil. In contrast, Alegre et al. [3] observed a decrease in water infiltration rates when anecic earthworms (Lumbricus terrestris) were inocu- lated in an Amazonian soil. Furthermore, they observed a reduction in soil tension by an inoculation of Lumbricus terrestris in soil, probably due to a modification of the soil structure. In the study of Boyle et al. [10] earthworms affected higher water contents on different stages of soil tension. However, several studies showed evidence that the soil physical and chemical properties may vary, depending on the currently earthworm species present. Bastardie et al. [5], Capowiez et al. [12], and Je ´gou et al. [21] described qualitative differences in the bur- rowing system of various earthworm species. In general, anecic earthworms build larger, more vertical, and less sinuous burrows relative to endogeic species [5]. Soil macropores vary in volume, orientation and their vertical distribution due to species-specific differences in burrowing behavior [11,21,22,23,27]. Additionally, the varying feeding behavior of ecologically different earthworm species may affect soil organic matter turn- over, distribution, and mineralization in different ways [13]. Anecic earthworms particularly feed and decompose large organic mate- rial, which may lead to an efficient transfer of organic matter from * Corresponding author. Tel.: þ49 (0)651 201 2254; fax: þ49 (0)651 201 3809. E-mail address: gregor.ernst@uni-trier.de (G. Ernst). Contents lists available at ScienceDirect European Journal of Soil Biology journal homepage: http://www.elsevier.com/locate/ejsobi 1164-5563/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ejsobi.2009.01.001 European Journal of Soil Biology 45 (2009) 207–213