Regrowth of understory epiphytic bryophytes 10 years after simulated commercial moss harvest

Abstract

Commercial moss harvest is the predominant disturbance for understory epiphytic bryophyte mats in the Pacific Northwest, yet the rate and dynamics of regrowth of this nontimber forest product are unknown. The first long-term evaluation of cover and species richness regrowth following simulated commercial moss harvest from understory vine maple (Acer circinatum Pursh) shrub stems is reported. Stems harvested of moss on six sites in the Oregon Coast Range in 1994 were examined for species composition and relative abundance of regrowth over the course of a decade. Percent cover increased 5.1%/year, averaging only 51% cover in year 10. Forty percent of the total cover in year 10 was attributable to encroachment from adjacent undisturbed mats and 14% to reestablished litterfall. Shortly after harvest, many taxa established on the newly available habitat, such that species richness surpassed preharvest levels by year 3. In the absence of competitive exclusion even by year 10, species richness continued to exceed preharvest levels by two taxa. Vegetative cover regrowth may require 20 years and volume recovery even longer. Commercial moss harvest should be managed on rotations of several decades, and patchy harvest methods should be encouraged over complete strip harvesting to ensure moss regeneration and promote bryophyte diversity.