 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.plant-soil.com J. Plant Nutr. Soil Sci. 2011, 174, 799–808 DOI: 10.1002/jpln.201000369 799 Effects of beech and ash on small-scale variation of soil acidity and nutrient stocks in a mixed deciduous forest Frédéric M. Holzwarth 1,2 *, Max Daenner 1 , and Heiner Flessa 3,4 1 Department for Ecoinformatics, Biometrics, and Forest Growth, Büsgen Institute, Georg-August-Universität Göttingen, Büsgenweg 4, 37077 Göttingen, Germany 2 present address: Department for Systematic Botany and Functional Biodiversity Research, Institute of Biology, Universität Leipzig, Johannisallee 21, 04103 Leipzig, Germany 3 Soil Science of Temperate and Boreal Ecosystems, Büsgen Institute, Georg-August-Universität Göttingen, Büsgenweg 2, 37077 Göttingen, Germany 4 present address: Institute of Agricultural Climate Research, Johann Heinrich von Thünen-Institut, Federal Research Institute for Rural Areas, Forestry and Fisheries, Bundesallee 50, 38116 Braunschweig, Germany Abstract Trees interact in a complex manner with soils: they recycle and redistribute nutrients via many ecolo- gical pathways. Nutrient distribution via leaf litter is assumed to be of major importance. Beech is commonly known to have lower nutrient concentrations in its litter than other hardwood tree species occurring in Central Europe. We examined the influences of distribution of beech (Fagus sylvatica L.), ash (Fraxinus excelsior L.), lime (Tilia cordata Mill. and T. platyphyllos Scop.), maple (Acer spp. L.), and clay content on small-scale variability of pH and exchangeable Ca and Mg stocks in the mineral soil and of organic-C stocks in the forest floor in a near-natural, mature mixed deciduous forest in Central Germany. The soil is a Luvisol developed in loess over limestone. We found a positive effect of the proportion of beech on the organic-C stocks in the forest floor and a negative effect on soil pH and exchangeable Ca and Mg in the upper mineral soil (0 to 10 cm). The proportion of ash had a similar effect in the opposite direction, the other species did not show any such effect. The ecological impact of beech and ash on soil properties at a sample point was explained best by their respective proportion within a radius of 9 to 11 m. The propor- tion of the species based on tree volume within this radius was the best proxy to explain species effects. The clay content had a significant positive influence on soil pH and exchangeable Ca and Mg with similar effect sizes. Our results indicate that beech, in comparison to other co-occurring deciduous tree species, mainly ash, increased acidification at our site. This effect occurred on a small spatial scale and was probably driven by species-related differences in nutrient cycling via leaf litter. The distribu- tion of beech and ash resulted not only in aboveground diversity of stand structures but also induced a distinct belowground diversity of the soil habitat. Key words: tree–soil interaction / species-specific effect / leaf litter / deciduous-tree species / forest floor / exchangeable cations Accepted March 29, 2011 1 Introduction Tree species differ in their influence on the acidification and the redistribution of nutrients in soils (see reviews by Binkley and Giardina, 1998; Augusto et al., 2002). Many studies have analyzed the differences between conifer and broadleaved species (e.g., Sanborn, 2001; Rothe et al., 2002; Binkley , 2003; Rothe et al., 2003). A smaller number have investi- gated broadleaf species (e.g., Nordén, 1994a, b; Finzi et al., 1998a, b; Neyrinck et al., 2000; Hagen-Thorn et al., 2004; Oostra et al., 2006), and only very few studies have studied species effects along a gradient of species mixture (Klemmedson, 1991; Rothe, 1997; Sanborn, 2001; Rothe et al., 2002). One approach for treating small-scale heterogeneity and establishing a gradient of species admixtures is garden experiments (Challinor , 1968; Binkley and Valentine, 1991; Scherer-Lorenzen et al., 2007). However, studying estab- lished forests may also reveal and describe mechanisms of tree–soil interactions in detail. Although near-natural forests might contain greater noise in the data, they are more repre- sentative of natural ecosystems and also cover long-term effects (Binkley and Menyailo, 2005; Leuschner et al., 2009). Although a multitude of pathways on how trees interact with soils has been described, litterfall is commonly thought to be of major importance (Ovington, 1953; Challinor , 1968; Finzi et al., 1998a, b; Washburn and Arthur , 2003). Other factors, which were found to contribute to differences in deciduous tree species, are, e.g., canopy interception (throughfall), canopy–precipitation interaction, stem flow, rooting patterns, * Correspondence: F. M. Holzwarth; e-mail: frederic.holzwarth@uni-leipzig.de