Hi Jason, Kruckeberg depicts the location of the "Sitka Spruce Zone" (where Sitka spruce is a widespread dominant species in forest ecosystems), not the distribution of the species, Picea sitchensis. The range of Sitka spruce goes well beyond the Sitka Spruce Zone, including lowland areas of Puget Sound and well into the Cascade Mountains (up to about 2,000 feet asl in Washington's Central Cascades). It's quite common in the "western hemlock/Douglas-fir" zone and can be a dominant species under certain conditions. Also, the species' current distribution has been significantly influenced (reduced) by extensive clearcutting of forest ecosystems in western Washington and Oregon, and the selective removal of Sitka spruce to manufacture airplanes during the World Wars.
Regards, Clay Antieau Botanist/Ecologist Seattle, WA -----Original Message----- From: Ecological Society of America: grants, jobs, news [mailto:ECOLOG-L@LISTSERV.UMD.EDU] On Behalf Of Jason Hernandez Sent: Wednesday, January 25, 2012 9:09 AM To: ECOLOG-L@LISTSERV.UMD.EDU Subject: [ECOLOG-L] Isolated populations of Sitka spruce Sitka spruce (Picea sitchensis) is a characteristic tree of the coastal "fog belt" of the Pacific Northwest. Arthur Kruckeberg, in _Natural History of the Puget Sound Country_, shows a nice map of the "Sitka spruce" zone's extent relative to the "western hemlock/Douglas-fir" zone in Washington State. Essentially, the Sitka spruce zone extends in a belt approximately 20 miles wide along the coast and the Strait of Juan de Fuca, but ends at the Olympic rain shadow at the San Juan archipelago; it does not extend south through the inland waterways of Puget Sound. The explanation given is that this species lacks the ability to regulate transpiration, and so requires the high humidity of the fog belt. However, in my years of observations, I have found at least three populations of Sitka spruce in central and southern Puget Sound, far outside the regular "Sitka spruce zone." These populations are small in extent, with the species absent from the rest of the central and southern Puget Sound basin. I have been curious about what factors have allowed these populations to establish and persist outside the fog belt, but I struggle to formulate any workable hypotheses. Has anyone else worked with any similar phenomena? Jason Hernandez
