Expansion of Calamagrostis villosa in sub-alpine Nardus stricta grassland: Cessation of cutting management or high nitrogen deposition? Michal Hejcman a,b, *, Michaela Klaudisova ´ c , Pavla Hejcmanova ´ d , Vile ´ m Pavlu ˚ a,e , Martina Jones f a Department of Ecology and Environment, Czech University of Life Sciences, Kamy ´cka ´ 1176, CZ-165 21 Prague 6 – Suchdol, Czech Republic b Department of Plant Nutrition, Crop Research Institute, Drnovska ´ 507, CZ-161 06 Praha 6 – Ruzyneˇ, Czech Republic c Department of Dendrology and Tree Breeding, Czech University of Life Sciences, Kamy ´cka ´ 1176, CZ-165 21 Prague 6 – Suchdol, Czech Republic d Institute of Tropics and Subtropics, Czech University of Life Sciences, Kamy ´cka ´ 1176, CZ-165 21 Prague 6 – Suchdol, Czech Republic e Department of Plant Ecology and Weed Science, Crop Research Institute, Drnovska ´ 507, CZ-161 06 Praha 6 – Ruzyneˇ, Czech Republic f Department of Science, Basingstoke College of Technology, Worting Road, Basingstoke RG21 8TN, UK 1. Introduction In central Europe, mountain areas receive disproportionately larger amounts of atmospheric N deposition than lowland areas. For example, in 2004, the average annual N deposition ranged from 5 to 10 kg ha À1 in lowland areas. However, in the Sudetes (a chain of middle mountains in the border land between Poland, Czech Republic and Germany) the range was between 15 and 30 kg ha À1 (C ˇ HMU ´ , 2005). There is clear evidence that increased N deposition and the consequent higher availability of N forced changes in N-limited ecosystems toward the dominance of more productive species (Bobbink et al., 1998; Fabiszewski and Wojtun ´ , 2001; Bohlmann et al., 2005; Hardtle et al., 2006; Honsova ´ et al., 2007). Furthermore, in many areas exposed to high levels of N deposition, the shift in limiting nutrient from N to P and the consequent spread of species well adapted to low P availability occurred (Kirkham, 2001; Tomassen et al., 2004; Wassen et al., 2005; Hejcman et al., 2007a). In mountainous areas of central Europe, recent large-scale expansion of Calamagrostis villosa is frequently attributed to both the direct and indirect effects of air pollution. Direct effects consist of changes in soil chemical properties, particularly in regard to the increase in availability of N and soil acidification. The loss of tree needles and the consequent increase in the amount of light reaching the ground are considered the primary indirect effect in spruce forests (Pys ˇek, 1991, 1993; Malcova ´ et al., 1999; Vacek et al., 1999; Wild et al., 2004; Fiala et al., 2005; Dra ´ bek et al., 2007). C. villosa has recently spread in Nardus stricta-dominated sub-alpine grassland in the Giant Mts. (Krkonos ˇe, Karkonosze and Riesengebirge in Czech, Polish and German). Authors of Agriculture, Ecosystems and Environment 129 (2009) 91–96 ARTICLE INFO Article history: Received 23 January 2008 Received in revised form 23 June 2008 Accepted 15 July 2008 Available online 23 August 2008 Keywords: Long-term N fertiliser experiment Defoliation sensitivity Tiller density Flowering induction Krkonos ˇe/Karkonosze ABSTRACT Calamagrostis villosa has recently expanded in Nardus stricta-dominated sub-alpine grassland of the Giant Mountains (Krkonos ˇe/Karkonosze, the Czech Republic). To investigate whether this expansion has been promoted by high nitrogen deposition or by the cessation of agricultural management, grassland plots dominated by C. villosa were manipulated with four treatments: control (Con), fertilised (Fer), cut (Cut) and cut–fertilised (Cut–Fer). NH 4 NO 3 was used at the rate of 30 kg N ha À1 and fertilisation and cutting were performed once a year after data collection in late July between 2000 and 2006. Plant species composition (analysed by RDA) was significantly influenced by cutting but not by fertilisation. Cutting reduced the cover, biomass, sward height and tiller density of C. villosa. Seedlings of N. stricta and panicles of C. villosa were recorded only in plots with cutting management. To investigate the effect of treatments on the spread of C. villosa, grassland sods dominated by N. stricta were transplanted into the experimental plots. Six years later, the density and cover of C. villosa spreading into the N. stricta sods were highest in Fer treatment. C. villosa was recognised as a defoliation-sensitive species and this sensitivity cannot be overcome by an increase in N supply. Recent expansion of C. villosa in the sub-alpine grassland can by explained by a long-term succession after the cessation of agricultural management and an increase in the N availability in recent decades. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author at: Department of Ecology and Environment, Czech University of Life Sciences, Kamy ´ cka ´ 1176, CZ-165 21 Prague 6 – Suchdol, Czech Republic. Tel.: +420 224 382 129. E-mail address: hejcman@fzp.czu.cz (M. Hejcman). Contents lists available at ScienceDirect Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee 0167-8809/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2008.07.007