PETERSEN, RAYMOND L.* and LISA FUNDERBURK. Biology Department, Howard University, Washington, DC 20059. - A History of Ozone Pollution (1850-1990) in Eastern United States Based on the Use of Osmunda cinnamomea L. Herbarium Specimens.
Over 1,000 herbarium specimens of the cinnamon fern Osmunda
cinnamomea L. from Maryland, New Jersey, and Pennsylvania were
assessed for symptoms of foliar ozone injury – interveinal bronze
necrotic lesions of the pinnules. (Ozone-injury symptomology is based
on control-fumigation of live O. cinnamomea plants.) Herbarium
sheet inventory included: locale (State and County), collection date
(year and Julian day), presence or absence of ozone injury, and
percent area of pinnule damaged. (Morphometric analysis of two
pinnules sampled from each herbarium sheet was used to obtain
estimates of percent area of pinnule damage.) From these data two
measures of ozone injury were obtained: (1) % incidence of injury
(i.e. number of specimen with necrotic lesions/total number of
specimens/ local/decade) and (2) degree of ozone injury, expressed as
% area of pinnule damaged. Based on this assessment a decade-by-decade
history of ozone pollution from 1850-1990 is constructed. Herbarium
specimens from the 19th century show little to no signs of ozone
injury (i.e., both % incidence of injury and degree of ozone injury
are less than 1%). Thereafter, an irregular but overall progressive
increase in the % incidence of injury is detected. The pattern
generated is somewhat reflective of historic and economic events of
the 20th Century – the invention of the internal-combustion engine and
the automobile and the First World War, the Depression of the 1930’s,
the Second World War, the ending of the Second World War with the
un-rationing of gasoline, the economic and industrial expansion of the
1950s and 60s, and the Clean Air Acts of the 1960s and 70s. There is a
high positive regression correlation of percent area of pinnule-damage
as of function of the growing season and no correlation of % pinnule
area damage as a function of annual chronology (i.e., average %
pinnule area damage/specimen did not change over the years). These
findings demonstrate the value of herbarium specimens in the
construction of environmental histories.
Key words: environmental history, herbarium specimens, Osmunda cinnamomea, ozone pollution