Remnant Trees and Canopy Lichen Communities in Western Oregon: A Retrospective Approach

Abstract

The “New Forestry” practice of green‐tree retention is becoming an important management tool for publicly owned lands, yet few data exist to demonstrate that this tool can succeed at enhancing biodiversity. We addressed this issue by using a retrospective approach to compare canopy lichen litter in adjacent, paired stands of rotation age (55–120 yr): one with and one without old‐growth (>300 yr) remnant trees. We sampled three functional groups of lichens in 17 stands in western Oregon: alectorioid lichens, cyanolichens, and green‐algal foliose lichens. Thirteen stands were low elevation (520–850 m) and four were mid‐elevation (1220–1340 m). Biomass of cyanolichen and green‐algal foliose lichen litter was greater in low‐elevation sites, whereas alectorioid lichen litter biomass was greater in mid‐elevation sites. Cyanolichens were absent from all mid‐elevation sites. Biomass of alectorioid lichen and cyanolichen litter was greater in low‐elevation sites with remnant trees than in those without remnant trees by 86% and 233%, respectively. The biomass of green‐algal foliose lichen litter was 80% greater in mid‐elevation sites without remnant trees than in those with remnant trees. Total lichen litter biomass was slightly, but not significantly, greater in stands with remnant trees at both low elevations (by 23%; ∼370 kg/ha standing biomass in remnant stands) and mid elevations (by 12%; ∼470 kg/ha standing biomass). Cyanolichen litter biomass was positively related to the number of remnant trees present; alectorioid and green‐algal lichen litter biomass were negatively correlated with the density of trees in the regeneration cohort. Because retaining live remnant trees will differentially affect these three functional groups of macrolichens, managers must be clear as to their objectives before using green‐tree retention as a tool to enhance biodiversity.

Distribution of epiphytic macrolichens in relation to remnant trees in a multiple-age Douglas-fir forest

“…Unfortunately, cyanolichen colonization of regenerating forests is a slow process; even a century after the last major fire, Lobaria oregana is still most abundant in the vicinity of remnant trees. The generality of this result from the Eagle Rock RS is supported by a recent study that found a similar pattern in thirteen Douglas-fir forest stands: cyanolichen biomass was 233% higher in stands with remnant trees than in those without remnant trees (Peck and McCune 1997). Lobaria oregana slowly invades regenerating forest canopies by dispersal from remnant tree crowns.…”

Sunscreening fungal pigments influence the vertical gradient of pendulous lichens in boreal forest canopies

“…The biomass of pendulous lichens peaks in old forests (Esseen et al 1996, Price andHochachka 2001), and conversion of old forests to managed stands with short rotations (,100 years) has dramatically decreased this epiphytic component Esseen 1998, 2003). Several species, such as Usnea longissima, are of concern for conservation (Rolstad et al 2013), as well as for ecosystem and wildlife management (Peck and McCune 1997).…”

Influence of stand size on pattern of live trees in mixedwood landscapes following wildfire

“…Research suggests that harvested areas with live residual trees contained bird communities more similar to old forest than did harvested areas with no residual trees (Westworth andTelfer 1993, Norton andSteventon et al 1998. Similar results were also found for arthropods (Schowalter 1995), small mammals (Steventon et al 1998), and some lichen groups (Peck and McCune 1997).…”