M. Laiviņš et al. Augu sugu socioloģisko grupu ekoloģija un ģeogrāfija Augu sugu socioloģisko grupu ekoloģija un ģeogrāfija Latvijas skujkoku mežos Ecology and Geography of the Plant Species Sociological Groups in Needle-Leaved Forests of Latvia Māris Laiviņš, Baiba Bambe Latvijas Valsts Mežzinātnes institūts „Silava” Latvian State Forestry Research Institute „Silava” e-mail:
[email protected];
[email protected] Solvita Rūsiņa, Dace Piliksere Latvijas Universitātes Ģeogrāfijas un Zemes zinātņu fakultāte Faculty of Geography and Earth sciences, University of Latvia e-mail:
[email protected];
[email protected] Vija Kreile Teiču Dabas rezervāta administrācija The Administration of Teichi Nature Reserve e-mail:
[email protected] Abstract. On the basis of 2332 vegetation relevés, 30 sociological species groups were developed for Latvian needle-leaved forests. All vascular plant, moss and lichen species were used in analysis. Phi coefficient (Φ) was used as a fidelity measure for calculation of sociological groups, and the threshold value was setΦ > 45.0. All 30 sociological groups were divided into three clusters according to their phytosociological characterization: 10 stable (constant) groups, 13 quasistable (semi-constant), and 7 serial groups. Analysis of Ellenberg indicator values revealed that the most important environmental factors explaining differences in species composition among groups are soil fertility (Ellenberg nitrogen value) and climate continentality (Ellenberg continentality value). Analysis of distribution of sociological species groups into different syntaxa confirmed that Latvian needle-leaved forest plant communities belong to three forest vegetation classes of Eurosiberian boreonemoral zone: Vaccinio-Piceetea, Pulsatillo-Pinetea, and Querco-Fagetea. Key words: needle-leaved forests, sociological group, dynamic categories, Latvia.