Potential environmental factors that influence the nitrogen concentration and d 15 N values in the moss Hypnum cupressiforme collected inside and outside canopy drip lines Mitja Skudnik a, * , Zvonka Jeran b , Franc Bati  c c , Primo  z Simon  ci  c d , Damijana Kastelec e a Slovenian Forestry Institute, Department of Forest and Landscape Planning and Monitoring, Ve cna pot 2, 1000 Ljubljana, Slovenia b Jo zef Stefan Institute, Department of Environmental Sciences, Jamova 39, 1000 Ljubljana, Slovenia c University of Ljubljana, Biotechnical Faculty, Department of Agronomy, Jamnikarjeva 101,1000 Ljubljana, Slovenia d Slovenian Forestry Institute, Department of Forest Ecology, Ve cna pot 2, 1000 Ljubljana, Slovenia e University of Ljubljana, Biotechnical Faculty, Department of Agronomy Jamnikarjeva 101,1000 Ljubljana, Slovenia article info Article history: Received 30 October 2014 Received in revised form 19 December 2014 Accepted 22 December 2014 Available online Keywords: Biomonitoring Moss survey Nitrogen N isotope Canopy drip Linear models Correction factors Environmental characteristics abstract Samples of the moss Hypnum cupressiforme were collected at 103 locations in forests of Slovenia. At each location, samples were taken at two types of sites: under tree canopies and in adjacent forest openings. The results show that the moss collected in the forest openings reflects the surrounding land-use characteristics and, consequently, the main N emission sources. For moss sampled under canopies, the characteristics of the forest at the moss-sampling locations are more important than the main emission sources outside the forest. A regression model was used to provide the nitrogen (N) concentration in moss from the forest openings in relation to the N concentration in moss under canopies and other environmental variables. The spatial distribution of the locations of the N concentrations and d 15 N values in moss collected in the forest openings and under the canopies in relation to main N deposition sources is discussed. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Increased concentrations of nitrogen (N) compounds have recently been identified as a critical load for the environment on a global scale (Krupa, 2003). Monitoring pollutants is essential to document the current status of and changes in the environment (Paoletti et al., 2010). Using moss as a biomonitor was first pro- posed in the late sixties (Rühling and Tyler, 1968), when it was used to monitor the atmospheric deposition of trace elements. Bio- monitoring is methodologically easier and cheaper than moni- toring precipitation or conducting air analyses; consequently, a much higher sampling density can be achieved (Harmens et al., 2011). In 1990, the European moss biomonitoring network was established. Initially, the aim was to determine the spatial patterns of the atmospheric deposition of trace elements (Rühling, 1994). Since 2005e2006, N concentrations have also been determined (Harmens et al., 2008). Reduced and oxidized N compounds have different 15 N isotope signatures (d 15 N). Based on the d 15 N values in moss, the N emission sources can be hypothesized (Pearson et al., 2000). If the d 15 N value in moss is low (more negative), then N is mainly derived from agricultural sources (NH x ). If the d 15 N value is high (less negative), then N originates from combustion processes (NO x )(Gerdol et al., 2014; Heaton, 1986; Larsen et al., 2007). The general suitability of moss for monitoring atmospheric N deposition has been shown in numerous studies (Harmens et al., 2014 and references therein). Apart from atmospheric deposition, other environmental factors also contribute to the variation in N concentrations in moss (Harmens et al., 2011; Schr€ oder et al., 2010). Schr€ oder et al. (2014) noted that the influential factors could differ among landscapes with different ecological characteristics. * Corresponding author. E-mail addresses: mitja.skudnik@gozdis.si (M. Skudnik), zvonka.jeran@ijs.si (Z. Jeran), franc.batic@bf.uni-lj.si (F. Bati c), primoz.simoncic@gozdis.si (P. Simon ci c), damijana.kastelec@bf.uni-lj.si (D. Kastelec). Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol http://dx.doi.org/10.1016/j.envpol.2014.12.032 0269-7491/© 2014 Elsevier Ltd. All rights reserved. Environmental Pollution 198 (2015) 78e85