SL is the Discharge Slope map component dominated by Lutz spruce (Picea X lutzii) forest.  It is the single most common and extensive wetland type in the project area.   It is the most common as a monomial unit, but it also frequently occurs in a complex with the the Barclay's willow-dominated Discharge Slope Ecosystem map component (SS).    SL occupies virtually all toeslope transitions from upland to wetland on late-Wisconsin surfaces south of Clam Gulch.  It is primarily found where southern Kenai Peninsula discharge slopes occur as gradual transitions to lakebeds or drainageways or at terrace toeslopes on heavy late-Wisconsin till.

The most common understory dominants are rusty menziezia (Menziesia ferruginea), thinleaf alder (Alnus incana ssp tenuifolia), Barclay's willow (Salix barclayi), and bluejoint grass (Calamagrostis canadensis).  The presence of field horsetail (Equisetum arvense) in the understory, along with any of the above plants, is a good evidence of the presence of a water table or redoximorphic features within 30 cm (one foot) of the surface, and therefore that the regulatory wetland criteria outlined in the 1987 Army Corps of Engineers Wetland delineation manual may be met.  Forested wetlands such as this were under-represented by the National Wetlands inventory mapping that took place on the Kenai Peninsula during the late 1970's. 

As SL is  found at the edge of many southern peninsula wetlands, during aerial photograph interpretation we assumed that most wetland toeslope edges occupied by spruce forest met regulatory criteria for wetlands.  Field checks revealed that about 15% of the time these forests were actually upland, the highest inaccuracy of this type for any map unit.  Some of this error is attributed to our inexperience on early Wisconsin surfaces, especially those mapped as 'Knik' on the southern peninsula by Karlstrom (1964).  Once we discovered that the glacial till on Knik surfaces was thin and discontinuous, and that those forested foot and toeslopes were often upland, our accuracy improved.  However, some areas proved to be unpredictable; the upland-wetland margin is where the most aerial photograph interpretation error should be expected.  Since SL is so widespread and extensive, particular care should be taken in interpreting this map unit, although probably 90% of the areas mapped as SL will meet regulatory criteria.

Since the later 1990's, the spruce bark beetle (Dendroctonus rufipennis) epidemic has killed most of the mature spruce trees on the southern Kenai Peninsula.  The epidemic has initiated substantial ecological change, especially where logging has taken place.  Stands that previously had moderate bluejoint grass cover, are now dominated by bluejoint.  Most stands contain abundant 'advanced regeneration', old, smaller, suppressed trees.  As has occurred elsewhere following stand replacing spruce bark beetle epidemics (Veblen, et. al., 1990), this advanced regeneration is now in release from suppression, and is rapidly occupying the new space available to it.  

In Homer, the name SLd refers to a wetland that was SL but is now disturbed.