Systematics and distribution of spruce species in the North-West of Russia

Norway spruce (Picea abies) and Siberian spruce (P. obovata) are among the most important forest-forming coniferous species in the boreal part of Eurasia. Despite numerous publications on the taxonomy of Norway spruce and closely related taxa (P. obovata Ledeb. and P. fennica (Regel) Kom.), the problem of their identification, as well as clarification of their taxonomic status, has not been solved so far. Species delimitation is particularly challenging when P. abies, P. obovata and P. fennica occur in sympatry. Our study aims to assess taxonomic value of proposed earlier and search for stable diagnostic characters of cones and their scales to distinguish Picea abies and its sympatric in the North-West of Russia P. fennica and P. obovata. In addition, we analyzed and updated information on geographical distribution and phytocenotic characteristics of the above-mentioned species in the North-West of the European part of Russia. We examined herbarium specimens and cones sampled from 88 trees from 22 Picea stands located throughout the study region. Each tree was represented on average by 5 cones, in total 415 cones were analyzed. Morphometric analyses included 16 morphological characters of cones and their scales selected based on our own observations and published data. Multivariate comparison had shown a large overlap between P. obovata and P. fennica, while individuals of P. abies formed a separate and less overlapping cluster. Among the six qualitative (discrete) characters, shape of seed scale and shape of its upper margin have non-overlapping frequency distributions and can separate P. abies and P. obovata. Several new diagnostic characters are proposed: morphology and size of bract scales and ratio of the size of seed scales and bract scales. Phytocenotic analysis showed that different spruce taxa occupy specific habitats, which in their turn connected with the latitudinal gradient: in normally drained habitats, Picea obovata is found mainly in poor shrubby-green-mossy forests, which are typical of the northern and middle parts of the Northern taiga; Picea abies - in richer green-mossy habitats (Vaccinioso-hylocomiosum, Oxalidoso-hylocomiosum, Hylocomiosum), which begin to occur already from the middle part of the Northern taiga. Picea fennica occupies both habitats.