Epiphytic lichen diversity and biomass in low-elevation forests of the eastern Washington Cascade range, USA

Abstract

I used litterfall sampling to estimate the biomass, diversity, and community structure of epiphytic lichens in three dry forest cover types in the eastern Washington Cascade range. Cover types represented a temperature/moisture and stand structural complexity gradient. Lichen litterfall biomass increased with increasing stand complexity and moisture. Lichen litterfall biomass was 3.42 kg/ha in open pine stands, 7.51 kg/ha in young mixed-species stands, 8.55 kg/ha in mature mixed-species stands. Six species accounted for 63% of the total sample biomass: Bryoria capillaris (20.2%), Hypogymnia imshaugii (15.8%), Letharia vulpina (14.5%), B. fremontii (7.2%), Nodobryoria abbreviata (2.8%), and Alectoria sarmentosa (2.6%). Bryoria tortuosa, considered rare in most of its range, was relatively common in young forest. Epiphytic lichen species richness and dominance did not differ among the three forest cover types. Lichen associations differed, however, among cover types. The dominant lichen in open pine stands was L. vulpina, followed by Bryoria spp., H. imshaugii, and L. columbiana. Vulpicida canadensis and L. columbiana were weak indicator species. Young stands were dominated by H. imshaugii, a strong indicator species of young stands, followed by B. capillaris and L. vulpina. Cetraria platyphylla and C. pallidula also were strong indicator species of young stands. Mature stands were overwhelmingly dominated by Bryoria species, primarily B. capillaris and B. fremontii, both strong indicators of mature stands. A. sarmentosa, H. imshaugii, and L. vulpina were other moderately abundant species. Alectoria imshaugii was also a strong indicator species of mature forest. Impacts on epiphytic lichens of dry forest management options that reduce stand density in fire-suppressed stands might vary. Lichens associated with dry open conditions would presumably benefit. The impact on species associated with old or moist conditions, especially forage lichens, might be lessened by variable-density thinning and other practices that maintain open- and closed-canopy patchiness and large trees. That patchiness might be hard to maintain with a maintenance program of understory burning patterned after natural fire regimes. At landscape scales, however, long-term persistence of forage and other lichens associated with mature moist forest would be enhanced by restoration of stable fire regimes.