Bryoid Layer Response to Soil Disturbance by Fuel Reduction Treatments in a Dry Conifer Forest

Abstract

We investigated the response of the bryoid layer, bryophyte and lichen communities on the soil surface, three years after fuel reduction treatment (logging and burning) in the central Blue Mountains of eastern Oregon. Both treatment and control areas had been decimated by spruce budworm and drought before the fuel reduction treatments. Treatments reduced overstory and understory woody vegetation, litter, and coarse woody debris and disturbed the soil surface. In the untreated stands minor local disturbances had created bare mineral soil over about 1% of the ground area, about half of that was from burrowing rodents. Fuel reduction treatments disturbed an additional 23% of the ground area, beyond the 1% disturbed in untreated sites. Over half of the recently disturbed treatment areas had been colonized by pioneering short mosses. Bare soil from rodent disturbances covered about 10 times more area in treated sites than in untreated sites, increasing from 0.4% to 5.5% cover. The bryoid layer responded to the treatments by changes in species composition, rather than species richness. Treated areas had more cover of small acrocarpous pioneer bryophytes (i.e., Funaria hygrometrica, Ceratodon purpureus, and especially Bryum caespiticium), whereas cover of larger pleurocarps, such as Brachythecium and Rhytidiadelphus was reduced by soil disturbance. We infer that pioneer bryophytes perform a valuable ecosystem service in these dry forests by rapidly colonizing and stabilizing the soil surface, reducing its vulnerability to erosion by wind and water.