The Pacific Northwest
is known for its moist temperate environment in which mosses
flourish, even in the most urban areas. Urban mosses are
of concern to homeowners because many people believe mosses damage
rooftops. For example, some people think that a thick mat of
moss may retain moisture that could potentially damage shingles
and shakes. On the other hand, some authors suggest that
mosses may be beneficial to roofs because they moderate the damaging
effects of the summer sun. (See Need for Control: Rooftops).
Knowing which mosses
are growing on rooftops is basic information that may ultimately
prove useful in evaluating their effects. We (a group of
students) identified the ten most common rooftop mosses in the
Corvallis and Eugene areas of western Oregon. Our climate is
moist and temperate, with wet winters and dry summers.
Rooftops were chosen for their generous
moss growth and accessibility. A total of nine rooftops
were sampled in Eugene and Corvallis, OR. The three most abundant
mosses on each roof were collected and evaluated for percent
cover. All roofs sampled had a mild slope and were predominately
north and west facing.
Mosses were identified in the lab
using Lawton (1971), Schofield
(1992), and McCune (2000).
Voucher specimens were deposited at the Oregon
State University Herbarium.
For results of this study, click here.