This data layer is an element of the Oregon GIS Framework. Seed zones for Alaska Yellow Cedar, Cottonwood, Douglas Fir, Engelmann Spruce, Grand Fir, Incense Cedar, Jeffrey Pine, Lodgepole Pine, Noble Fir, Pacific Silver Fir, Pacific Yew, Ponderosa Pine, Port Orford Cedar, Red Alder, Sitka Spruce, Sugar Pine, Western Hemlock, Western Red Cedar, Western White Pine, and basic zones for other species in Oregon. Zones are based on genetic variation patterns obtained by evaluating genotypes of trees from locations in the region. Wherever possible, the zone lines follow natural boundaries such as crests of mountain ranges, ridge tops, rivers -or physical boundaries, such as highways and railroads, since it would be impossible for cone collectors to recognize any other type of boundary.