Results of Rooftop study

Common Mosses on Nine Rooftops
in the Willamette Valley, Oregon

 Species found Abundance *  Occurrence
Dicranoweisia cirrata Very abundant 45%
Bryum capillare Abundant 33%
Racomitrium canescens Abundant 11%
Tortula princeps Abundant 33%
Rhytidiopsis robusta Abundant 11%
Antitrichia californica Sparse 22%
Ceratodon purpureus Sparse 56%
Scleropodium cespitans Sparse 22%
Tortula latifolia Sparse 11%
Bryum argenteum Rare 11%

*Abundance Code:   
   Average percent cover of a moss species on all rooftops sampled

    Very abundant = >40%
    Abundant = 10-40%
    Sparse = 1-10%
    Rare = <1%

Only one roof sampled was of cedar shakes, the rest were of asphalt shingles. Only Dicranoweisia cirrata and Bryum capillare were found on the cedar shakes. However, all the species found were present on asphalt shingles. On most rooftops sampled, there were typically fewer than 4 species present. Of these, the most common and abundant were Dicranoweisia cirrata, Bryum capillare, Tortula princeps. These species tend to form dense mats that cover large areas of the roof (see Part 1 of rooftop photos).

Racomitrium canescens var. ericoides (see Part 2 of rooftop photos) and Homalothecium aeneum were abundant, but occurred infrequently.  These species also have the ability to form large mats. Ceratodon purpureus was very commonly found on rooftops, but was in low abundance. This species is commonly found on many substrates and in many habitats. The remaining species were found infrequently, and in low abundance.  Antitrichia californica was found growing in heavily shaded areas of the roofs, while the other species were found in both exposed and shaded areas. This may suggest that different moss species grow in areas shaded by trees.

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