Forests Archives | JuneauNature

Conifer and deciduous forest types

I’ve spent most of my career studying forests throughout Southeast Alaska. As caretaker at Asx‘ée twisted tree (Eagle River), 1980-92, I studied forest succession on raised former tideland, and post-glacial succession in the valley of L’ux, milky (Herbert River). Later, kayaking took me to the great forests of the southern Tongass. From 1996 to 2005, I was field leader of the Landmark Trees Project, documenting the finest giant-tree stands of our region. And after that, with Bob Christensen, I switched to the Ground-truthing Project, more directly focused on timber issues.

Tall spruce on alluvium of Gaat Héeni, sockeye river (Gartina Creek) near Xuniyaa, lee of the north wind (Hoonah). Red alder grows closer to the channel on more active floodplain.

Well-drained soils eventually support medium to large-tree old-growth forest (left column) that varies mostly according to substrate character; this sequence represents increasingly well drained sites from cedar types to karst large-tree. The right-side column follows a successional series through postlogging and (lastly) post-blowdown development. For more on succession, see Nature>Ecology 101>Succession.

Southeast forests are at the well-drained end of a soil-moisture spectrum. dominating most of those surfaces below subalpine elevations. At the wet end of that spectrum are forests so soggy that delineators map them as jurisdictional wetlands, requiring special permits and mitigative measures. My habitats document, Summit to Sea, treats these communities along with other wetland types.

Even within the ‘dry’ spectrum of forest types, there’s considerable variation in soil drainage, which in turn influences nutrient availability, temperature and rooting depth for plants. Drainage is the principal environmental factor determining both overstory and understory species composition. Poorly-drained forested sites have open canopies, thus drainage indirectly exerts control on light penetration to the understory.