Study area
We conducted this study on federal forest
lands in the eastern portion of the central Oregon Coast Range
(44°30’0”N 123°30’0”W; Fig. 1). Vegetation consisted primarily of
Douglas-fir (Psuedotsuga menziesii ) and western hemlock
(Tsuga heterophylla ) forests typically growing on steep terrain
with numerous and deeply incised drainages. The climate was cool and wet
during winter (i.e., wet season; November 1 – March 31) with occasional
sub-freezing temperatures and snow, and warm and dry in the summer
(i.e., dry season; April 1 – October 31). Forest age was highly
correlated with management history, fire, and land ownership. Old
forests (>80 years old) were located primarily on federal
lands in relatively small patches in a matrix of young forests
(<80 years old) and non-forest (Kennedy & Spies, 2004;
Linnell, Davis, Lesmeister, & Swingle, 2017; Wimberly & Ohmann, 2004).
Young forests (22 – 44 years old) in this study were typical of the
region and were established as plantations, which resulted in stands
dominated by Douglas-fir trees with straight-boles, simple branches, few
cavities, and highly interconnected live crowns.