ARTICLE Different effects of earthworms and ants on soil properties of paddy fields in North-East Thailand Pascal Jouquet Æ Christian Hartmann Æ Chutinan Choosai Æ Yupa Hanboonsong Æ Didier Brunet Æ Jean-Pierre Montoroi Received: 25 September 2007 / Accepted: 29 July 2008 / Published online: 12 August 2008 Ó Springer-Verlag 2008 Abstract As soil engineers, earthworms and ants play major roles in soil functioning, especially in modifying soil physical and chemical properties. This study was con- ducted in a very constraining environment, i.e., paddy fields which have anoxic conditions (approximately four months per year), and which are affected by soil salinisa- tion during the dry period (approximately eight months per year). This study points out that despite those very adverse conditions, soil invertebrates must be taken into account in the dynamic of soil organic and mineral properties in paddy fields. The effects of one earthworm species, Glyphodrillus sp., and an ant species, Epelysidris sp., on soil physical and chemical properties were determined through elemental soil physical and chemical properties (texture, pH, con- ductivity, C and N contents) and near infrared reflectance spectroscopy (NIRS) in order to evaluate their ability to influence soil organic matter quality. PCA processed with NIRS data clearly showed that biogenic structures (ant sheetings and earthworm casts) were separated from the control surrounding soil. Earthworms and ants affected differently soil properties. Glyphodrillus sp. increased the SOM content and decreased the pH on the surface of the soil. These effects were attributed to an increase in fine particle content (clay). Conversely, Epelysidris sp. only increased the content of coarse particles (sand) and did not influence either soil pH or SOM content. Soil conductivity was found to be very variable but was not significantly affected by soil invertebrates. These results show the potential of soil macro-fauna to create heterogeneity at small spatial scale and to modify the quality of surface soils even under adverse conditions like saline paddy fields. Keywords Earthworms Á Ants Á Casts Á Paddy fields Á Soil properties Á NIRS Introduction Earthworms and ants are called ecosystem engineers (Jones et al. 1994; Jouquet et al. 2006) due to their strong influ- ence on soil properties. At the heart of the soil engineering concept is the ability of these soil invertebrates to produce organo-mineral structures, usually called biogenic struc- tures, where the dynamics of soil organic matter (SOM) and nutrients are modified (Lavelle 1997). While a lot of P. Jouquet (&) IRD, IMWI, SFRI, UMR 137 BIOSOL, Dong Ngac, Tu Liem, Hanoi, Vietnam e-mail: pascal.jouquet@ird.fr C. Hartmann IRD, UR176 SOLUTIONS, Land Development Department, Office of Science for Land Development, Paholyothin Road, Chatuchak, Bangkok 10900, Thailand e-mail: hartmann@ksc.th.com C. Choosai Á Y. Hanboonsong Faculty of Agriculture, Department of Plant Science and Agricultural Resources, Khon Kaen University, Khon Kaen 40002, Thailand e-mail: nuchchutinan@yahoo.com Y. Hanboonsong e-mail: yupa_han@kku.ac.th D. Brunet IRD, UR SEQBIO, Montpellier, France e-mail: didier.brunet@ird.fr J.-P. Montoroi IRD, UR 176 SOLUTIONS, Bondy, France e-mail: Jean-Pierre.Montoroi@bondy.ird.fr 123 Paddy Water Environ (2008) 6:381–386 DOI 10.1007/s10333-008-0134-x