1. Faculty of Chemistry, University of Latvia, Jelgavas Street 1, LV-1004 Riga, Latvia
2. Latvian State Forest Research Institute ‘Silava’, 111 Rigas Street, LV-2169 Salaspils, Latvia
3. Faculty of Geography and Earth Sciences, University of Latvia, Jelgavas Street 1, LV-1004 Riga, Latvia