Balsam poplar / Thinleaf alder
Populus balsamifera / Alnus incana ssp. tenuifolia
n = 6
I.B.1.c. Closed Balsam Poplar Forest
Ecosystem: Riparian

Balsam poplar / thinleaf alder has been described by many other Alaskan workers.  Viereck, et. al. (1992) cite at least eight other classifications that describe a type identical to the one found on the lowlands.  However, the most similar type documented in nearby Chugach National Forest is a black cottonwood (Populus trichocarpa) / Sitka alder (Alnus viridis ssp. sinuata) type with devil's club (Echinopanax horridum) and salmonberry (Rubus spectabilis) (DeVelice et. al., 1999; and Boggs, 2000).

Balsam poplar (Populus balsamifera) / thinleaf alder (Alnus incana ssp. tenuifolia) is found on the large floodplain of the Fox River, at the head of Kachemak Bay, where cattle grazing is common and probably affects the composition and structure of those stands.  This community is probably also present in a few places along the Anchor River, Deep Creek, Kasilof and Kenai Rivers. Another plot, near Nikiski, with Sitka alder (Alnus viridis ssp sinuata)  in lieu of thinleaf alder was included in this summary.

A closed poplar canopy shades a tall dense alder thicket, with an abundant tall bluejoint grass (Calamagrostis canadensis) layer.  Several forbs are present at low abundance: baneberry (Actea rubra), fireweed (Chamerion angustifolium), ladyfern (Athyrium felix-femina), and fragrant bedstraw (Galium triflorum), along with trace amounts of arctic starflower (Trientalis europea), red currant (Ribes triste), and monkshood (Aconitum delphinifolium).  The plot near Nikiski had a significant devil's club (Oplopanax horridus) component. 

The organic mat is thin, although the plot near Nikiski supported an organic layer nearly a meter thick, and the water table is deep.  When this community occurs on floodplains with occasional to frequent flooding it may qualify as a jurisdictional wetland.

Table 1. Frequency of soil series occurrence and hydric status at NRCS holes.

  Soil Series n

 Table 2Summary of plant frequency and average cover for plants occurring in more than 50% of plots.

        Wetland Indicator Status



 Average Cover

  Alaska National
tall Populus balsamifera 1.0 63.4 FACU FACU, FACW
Alnus incana2  ssp. tenuifolia   1.0 70.0 FAC FACU, FACW
Low shrubs
Ribes triste   1.0 0.5 FAC FAC. OBL
Rubus idaeus 0.6 4.7 FAC UPL, FAC
Calamagrostis canadensis   1.0 84.0 FAC FAC, OBL
Actaea rubra   1.0 5.3 FAC* UPL, FAC*
Chamerion angustifolium   1.0 4.9 FACU FACU, FAC
Athyrium filix-femina   1.0 3.7 FAC FAC, FAC+
Galium triflorum   1.0 2.4 FACU FACU, FACU+
Trientalis europaea 1.0 0.6 FAC FAC*, FAC
Aconitum delphiniifolium   1.0 0.5 FAC FAC
Equisetum arvense 0.8 14.4 FAC* FAC*, FACW-
Dryopteris expansa   0.6 0.5 FACU FACU, FACW
Heracleum maximum   0.6 0.5 FACU FACU-, OBL
Bare soil 0.8 0.5
2Plant with known physiological adaptation for occurrence in wetlands (USACE, 1987)


 Introduction and Key to Plant Communities  

Introduction and Key to Ecosystems

    Kenai Hydric Soils    Map Unit Summary    Methods    Glossary

Contact: Mike Gracz
Kenai Watershed Forum 
PO Box 15301
Fritz Creek, AK  99603
The Alaska Natural Heritage Program
Environment and Natural Resource Institute
University of Alaska, Anchorage
707 A Street, Suite 101
Anchorage, Alaska  99501

04 May 2007 09:54