Black poplar forests of the Ob River floodplain on the north of the Tomsk oblast (Western Siberia, Russia)

We characterized natural black poplar (Populus nigra L.) forests of the Ob River floodplain within the limits of Aleksandrovsky district of Tomsk oblast, Western Siberia, Russia. The northern limit of Aleksandrovsky district crosses the Ob channel at the coordinates 60°42' N, 77°04' E and the southern one - at the coordinates 59°30' N, 77°04' E. The study area is located in middle taiga subzone. We collected data in the vicinities of Larino (61°31' N, 74°40' E), Aleksandrovskoye (60°26' N, 77°22' E) and Novonikolskoye (59°46' N, 79°12' E) villages in 1986-1989. According to Braun-Blanquet classification, black poplar forests of Aleksandrovsky floodplain area belong to the association Anemonidio dichotomi-Populetum nigrae Taran 1993, alliance Equiseto hyemalis-Populion nigrae Taran 1997, order Salicetalia purpureae Moor 1958 and class Salicetea purpureae Moor 1958. The association diagnostic species are Populus nigra (dominant), Anemonidium dichotomum, Lathyrus palustris, Lathyrus pilosus, Ptarmica cartilaginea. 15 original releves of poplar forests, from 30 years old to stage of timber stand decomposition, are presented. Standard plot area of the releves is 100 m. The average timber stand height in the releves varies from 14 to 27 m, the average chest high diameter is from 15 to 80 cm, the total projective cover of timber stand is from 8 to 60%, the total projective cover of shrub layer is from + to 8%. The average total projective cover (TPC) of herbage is 40%; herbs (TPC 23%) and grasses (TPC 16%) prevail in it, participation of legumes and sedges is insignificant (TPC 0.9% and 0.3% consequently). In the black poplar forests, 76 vascular plant species are noted including 4 species of trees (Populus nigra, Salix alba, Betula pubescens, Pinus sylvestris), 4 bushy trees (Salix dasyclados, Salix viminalis, Padus avium, Sorbus sibirica), 5 shrubs (Swida alba, Ribes nigrum, Rosa majalis, Viburnum opulus, Salix rosmarinifolia), 2 subshrubs (Solanum kitagawae, Rubus caesius), one dwarf subshrub (Comarum palustre) and 60 species of herbs. The average species saturation of the poplar stands with vascular plants is 32.8 species per 100 m. We characterized black poplar initial stage (poplar seedlings age is from 1 to 3 summers) on low river banks basing on one releve. We showed that in their species composition, juvenile poplar coenoses differ sharply from subsequent stages of their development. Initial stage specificity is due to a high constancy of wetland ephemers and other annuals (Filaginella pilularis, Limosella aquatica, Physcomitrella patens, Riccia frostii, Alopecurus aequalis, Bidens radiata, B. tripartita, Chenopodium rubrum, Ch. suecicum, Persicaria scabra, Rumex maritimus, R. ucranicus). We noted 31 species of vascular plants and 2 species of bryophyta on a plot of 100 m. According to our estimates, the total black poplar forests area within the limits of Aleksandrovsky district of Tomsk oblast is 53 km.

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