The Alaska Vegetation Classification - Alaska Geobotany Center ...

Figure 314pen broadleaf forest ofbalsam poplar with a shrub layer of.Mix barclayi and Alnus crisp and anherbaceous layer of Calamagrosriscanadensis, Equissrum pratense. andHeracleum lanatum on the flood plainof a river in southwestern AlaskaDistribution and site characteristics-Black cottonwood stands are found onlyalong the southeastern and southern coasts of Alaska. Balsam poplar stands occurover the remainder of forested areas in Alaska. When the two species' ranges meet,as in the Cook Inlet area, hybrids between the two species occur, making it difficultto determine which species dominates in some stands (Viereck and Foote 1970).Open balsam poplar and black cottonwood communities often are found on floodplains, but they occasionally occur on slopes. Flood-plain communities usuallygrow on well-drained sands and gravels capped by a thin layer of silt and an evenshallower layer of organic material on the surface of the mineral soil. Stands onslopes usually occupy shallow, stony mineral soils over bedrock. Soils on bothupland and flood-plain sites either lack permafrost or have deep active layers(70 centimeters [28 in] or more).Successional status-Tree-line stands seem fairly stable. On flood plains, thesestands maintain themselves in the face of severe flooding disturbance, including siltdeposition and erosion. On such flood-plain sites, poplar or cottonwood is seral andwhite spruce or Sitka spruce is the eventual climax tree species.Closely related types-Open balsam poplar or black cottonwood communities aresimilar to closed balsam poplar communities and closed black cottonwood communitiesbut have less tree cover. They also are similar to balsam poplar woodlands buthave more tree cover.Photographs-Murray 1980, figure 2; figure 31, this publication.Primary references-Edwards and Dunwiddie 1985, Racine and Anderson 1979,Viereck 1979.Communities-Populus balsamifera/Salix spp.-Alnus spp./Ca/amagrostis spp.(Racine and Anderson 1979, Viereck 1979). Populus balsamiferdSalix hastata-Shepherdia candensis-Epilobium angustifo/ium/Hyocomium splendens-Pleuroziumschreberi (Edwards and Dunwiddie 1985). Popu/us balsamiferdAlnus tenUifOlia/Equisetum spp. (Viereck 1989).95