Vegetation zonation and primary succession along the Porcupine River in interior Alaska
Farjon, Aljos; Bogaers, Pieter
Primary succession of vegetation on the floodplain of the Porcupine River in interior Alaska is discussed. The authors describe three different seres leading to the climax vegetation, i.e. a moss-rich Picea glauca forest. The seres are determined by conditions created by the meandering river, these conditions are summarized and interactions with the vegetation are discussed. Sere I occurs on broad sandbars, usually on inner curves of meanders, where there is rapid sedimentation and decreasing influence of the river. Populus balsamifera is present in a pioneer stage and dominates in a Balsam poplar wood, which is eventually invaded and replaced by White spruce (Picea glauca). Sere II occurs in both thermokarst and oxbow lakes and is little influenced by the river. An aquatic vegetation develops into riparian types which are also replaced by White spruce. Sere III occurs again on the banks of the river, here flooding is frequent and remains so through the sere. An open pioneer type is followed by a Salix interior facies and this in turn by a Salix alaxensis wood poor in species. Populus balsamifera is absent in this sere. The floristic and structural composition of the seres is given in Tables 1, 2 and 3. A new forest community, the Salix alaxensis/Calamagrostis spp.Equisetum arvense-community, is proposed for this region. White spruce does not occur in it as long as this community remains under the influence of the river.