Sitka alder / Marsh horsetail
Alnus viridis ssp. sinuata / Equisetum palustre
IIB(1)b: Closed Tall Alder Shrub
Ecosystem:  Discharge SlopeRelict Lakebed

Variable Sitka alder (Alnus viridis ssp. sinuata) types are widespread in Alaska, but a marsh horsetail (Equisetum palustre) understory is not described in the literature.

Sitka Alder / marsh horsetail was found in a few flat areas along the eastern terraced margin of the large isostatically rebounded marine terrace between Kasilof and Kenai, adjacent to low-relief kame-like features.  It is characterized by a dense canopy of Sitka alder with a thick marsh horsetail understory over plentiful marsh fivefinger (Comarum palustre) and open water.  Scattered paper birch (Betula papyrifera) overtops the alder, and occasional arctic starflower (Trientalis europea) is found at all locales.  Numerous other plants are present in low numbers.  Two shrubs, high-bush cranberry (Viburnum edule) and prickly rose (Rosa acicularis), can be abundant. 

The water table was at 2 centimeters at all three locales, and the organic layer was 160 cm thick.  All plots measured qualify as jurisdictional wetlands.   

Table 1. Frequency of occurrence and hydric status of soil series named at NRCS holes.  Bold type indicates soils on the NRCS Alaska hydric soils list. 

  Soil Series n

Hydric Criteria Number


1, 2B2, 3

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

        Wetland Indicator Status


f  Average Cover   Alaska National
medium Betula papyrifera 1.0 1.3 FACU FACU, FAC+
regeneration Betula papyrifera 1.0 0.5 FACU FACU, FAC+
tall Picea glauca 0.7 2.8 FACU FACU, FAC*
Alnus viridis ssp sinuata 1.0 63.3 FAC FAC, FACW*
Rosa acicularis 0.7 17.8 FACU FACU
Viburnum edule 0.7 10.3 FACU FACU, FACW
Equisetum palustre 1.0 51.7 FACW FACW
Comarum palustre 1.0 48.3 OBL OBL
Trientalis europaea 1.0 0.5 FAC FAC*, FAC
Calamagrostis canadensis 0.7 7.8 FAC FAC, OBL
Equisetum arvense 0.7 7.8 FAC* FAC*, FACW-
Pyrola asarifolia 0.7 0.5 FAC FACU, FACW
Caltha palustris 0.7 0.5 OBL OBL
Linnaea borealis 0.7 0.5 FACU FACU-, FAC
Lichen 0.7 0.5
Moss 1.0 36.7
Open water 1.0 10.2
Bare soil 1.0 13.5      


 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 09:36