Spatial and temporal variability of soil gas diffusivity, its scaling and relevance for soil respiration under different tillage Andreas Schwen a, ⁎, Eva Jeitler b , Jürgen Böttcher c a Institute of Hydraulics and Rural Water Management, University of Natural Resources and Life Sciences (BOKU), Muthgasse 18, 1190 Vienna, Austria b Austrian Agency for Health and Food Safety (AGES), Vienna, Austria c Institute for Soil Science, Leibniz University of Hannover, Hannover, Germany abstract article info Article history: Received 1 October 2014 Received in revised form 17 April 2015 Accepted 20 April 2015 Available online xxxx Keywords: Gas diffusivity Soil respiration Spatial and temporal variability Scaling Soil tillage Soils are an important source and sink for carbon. Soil management such as reduced or no-tillage management has been reported to increase soil organic matter budgets, probably due to a hampered microbial mineralization of organic components. While soil respiration is mainly controlled by temperature and soil moisture, it can be also limited by the soil pore system facilitating diffusive gas fluxes between the soil and the atmosphere. Howev- er, soil gas diffusivity as a controlling factor for soil respiration has not been assessed under different soil manage- ment. Moreover, no adequate methods have been developed yet that facilitate the description of spatial or temporal variations of the highly non-linear soil gas diffusivity functions. Therefore, the objectives of this study were to deduce and apply a scaling rule for gas diffusivity, and to observe and analyze spatio-temporal variations of soil respiration and gas diffusivity under conventional tillage (CT) and no-tillage (NT). We measured soil res- piration rates and gas diffusivities along a transect on an arable field in Hollabrunn (Lower Austria) within the 2014 vegetation period. We also determined the soil hydraulic properties and gas diffusivities as a function of air-filled porosity. By adopting the similar media approach of Miller and Miller we facilitated scaling of spatially variable gas diffusivity model functions. The scaling performed well to derive representative mean parameters while preserving the spatial variability in the scaling factors. The comparison of scaling factors for soil water re- tention, hydraulic conductivity, and gas diffusivity revealed that flow pathways were not the same for water and gases. This finding was explained by the continuity of pores that are accessible for water or gas movement. Compared to NT, the CT plot was characterized by greater soil respiration rates, gas diffusivities, total porosities, and unsaturated hydraulic conductivities, while soil water retention, observed volumetric water contents, and the spatial variability of these properties were smaller. Soil respiration rates were mainly changing with time as a result of soil temperature and soil water content. However, we also found that the diffusive soil properties slightly influenced CO 2 efflux rates. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Soil management practices affect the physical soil properties dy- namically in space and time with consequences for the storage and movement of water, nutrients and pollutants, and the gas exchange within the soil–plant–atmosphere continuum (Strudley et al., 2008). It is well known that for given climatic conditions and a particular soil– plant system, the soil management system considerably controls soil structure development (Messing and Jarvis, 1993). Consequently, the impacts of different soil management techniques (i.e. soil tillage methods) on soil physical and hydraulic properties have been frequent- ly studied in recent decades (e.g., Buczko et al., 2006; Sauer et al., 1990; Strudley et al., 2008). Despite a considerable spatial and temporal vari- ability, most publications reported averaged comparisons between dif- ferent tillage practices and did not account for spatio-temporal dynamics (Schwen et al., 2011; Strudley et al., 2008). Recently, a series of studies addressed both the temporal and management-induced changes in soil hydraulic properties (Alletto and Coquet, 2009; Bormann and Klaassen, 2008; Cameira et al., 2003; Daraghmeh et al., 2008; Hu et al., 2009; Moret and Arrue, 2007; Mubarak et al., 2009; Schwen et al., 2011). These studies helped to improve our understand- ing of the dynamic impacts of soil management on physical and hydrau- lic soil properties. Despite some site-specific differences, the above listed studies revealed controversial implications of no-tillage (NT) management practices on physical and hydraulic soil properties. Compared to conventionally tilled systems (CT), soils under NT tend to have a better developed macropore network and a temporally more stable soil structure. This results in an increased saturated hydraulic conductivity Geoderma xxx (2015) xxx–xxx Abbreviations: CT, conventional tillage; GHG, greenhouse gas; NT, no-tillage. ⁎ Corresponding author. E-mail address: andreas.schwen@boku.ac.at (A. Schwen). GEODER-11979; No of Pages 14 http://dx.doi.org/10.1016/j.geoderma.2015.04.020 0016-7061/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Geoderma journal homepage: www.elsevier.com/locate/geoderma Please cite this article as: Schwen, A., et al., Spatial and temporal variability of soil gas diffusivity, its scaling and relevance for soil respiration under different tillage, Geoderma (2015), http://dx.doi.org/10.1016/j.geoderma.2015.04.020