Classification of ultracontinental boreal forests in central Yakutia

Using the Braun-Blanquet approach, five associations of boreal forests were distinguished in central Yakutia, the most continental part of eastern Siberia. Ecological features of the syntaxa were explained with the use of the DCA ordination of 50 relevés. All available data from eastern Siberia were involved in the study for syntaxonomic analysis. Central Yakutian boreal forests were classified into two classes:Rhytidio-Laricetea sibiricae Korotkov etErmakov 1999 — ultracontinental light coniferous hemiboreal forests, andVaccinio-Piceetea Br.-Bl. inBr.-Bl. et al. 1939 — typical coniferous taiga forests of northern Eurasia. A new concept of higher syntaxonomic units of the classVaccinio-Piceetea in eastern Siberia has been developed. Three orders represent the diversity of taiga forests: (1)Cladonio-Vaccinietalia Kielland-Lund 1967 (with alliancesHieracio umbellati-Pinion sylvestris Anenkhonov etChytry 1998 andSaxifrago bronchialis-Pinion sylvestris all. nov.) — light coniferous boreal forests occurring in dry and moderately dry oligotrophic sites in various climatic sectors of Northern Eurasia; (2)Lathyro humilis-Laricetalia cajanderi ord. nov. (with alliancesAulacomnio acuminati-Laricion cajanderi all. nov. andRhododendro daurici-Laricion gmelinii all. nov.) — zonal boreal forests with xeric elements, which are typical of regions of northern Asia with cold, dry ultracontinental climate; (3)Ledo-Laricetalia cajanderi ord. prov. (with allianceLedo-Laricion cajanderi prov.) — North Eurasian boreal forests occurring in cold sites with excessive soil moisture, sometimes water-logged. Phytogeography and ecology of these orders are discussed in comparison with other regions of northern Asia.