Bryophytes on IsolatedQuercus garryanaTrunks in Urban and Agricultural Settings in the Willamette Valley, Oregon

Abstract

The bark of isolated Oregon white oaks (Quercus garryana Dougl.) supports a distinctive bryophyte flora. Savannah oaks are now rare, but isolated oaks remain in urban and agricultural areas. I documented the bryophyte flora and searched for Syntrichia laevipila var meridionalis, previously considered rare in the Pacific Northwest, on isolated oaks in urban and agricultural areas throughout the Willamette Valley. Most bryophytes on the wet sides of trunks were pleurocarpous mat-formers, while most on the dry sides were acrocarpous cushion- or turf-formers. Isolated oaks and their distinctive bryophyte community occurred to 201 m elevation, but S. laevipila var meridionalis was present only at or below 100 m elevation, never without the variety laevipila. Dry bark bryophytes were often heavily grazed, possibly by springtails or slugs. Gemmipary, present among several oak-dwelling species, may be a response to grazing or exhaust fumes.