Study site
Our study was conducted in the Hoh rainforest in the Olympic National Park, a World Heritage Site and Biosphere reserve in Washington State, USA (47°50’08” N, 123°58’54” W). The climate is mild and extremely wet with an average annual temperature of 10°C (range = -11°C – 36°C) and annual rainfall of 3200 mm (Harmon & Franklin, 1989). These forests are characterized by large degrees of vertical and horizontal heterogeneity formed by large and tall trees (> 80 m) that are dominated by Picea sitchensis and Tsuga heterophylla , an abundance of large nurse logs (>1 m diameter), a luxurious cover of bryophytes and herbs on the forest floor, and an abundance of epiphytic bryophytes (Franklin et al., 2002; Harmon & Franklin, 1989).