Demise of the Dogwood?
July 17, 2012
Knoxville, TN — Populations of the flowering dogwood tree (Cornus florida) in 30 states declined by 49 percent over the past 25 years, according to a U.S. Forest Service study published in the Open Journal of Forestry this April.
Cherished for their showy spring flowers, dogwoods are valuable members of forest communities, shuttling calcium from far below ground to leaves, which enrich topsoil when they fall and decompose on forest floors. Dogwood fruits are also an important food for many birds and mammals.
Once common throughout the eastern United States, especially in the understory of hardwood forests, dogwood populations have decreased in 17 out of 30 states studied, and dogwood biomass declined in 20 out of 30 states. Declines were centered in the Appalachian Mountains and surrounding areas.
"This is the first study of dogwood’s decline across its entire natural range," said Christopher Oswalt, Forest Service Southern Research Station (SRS) researcher and lead author of the paper. "We believe this may largely be due to dogwood anthracnose, a fungal disease caused by Discula destructiva. That said, our data do not point to a single causal agent. "
The origins of the fungus are unclear, but it was introduced to the United States in the late 1970s. Several smaller studies have reported local losses of dogwood after infection with the Discula destructiva. While the pathogen has killed many dogwood trees, the ultimate causes of the species’ decline are more complex and include competition, defoliating pests, and a lack of management or restoration of the species.
Researchers compared dogwood populations over 2 time periods, the first (1983 to1995) representing the early days of D. destructiva's identification as a cause of dogwood anthracnose. The second time period spanned the years 2005 to 2007. Data were collected by the SRS Forest Inventory and Analysis program.
"Across much of its range, dogwood populations have really dwindled," says Oswalt. "Our results highlight the need to investigate what's happening to dogwoods on local and regional levels, and the need for proactive restoration, so we can save this classic American tree."
Access the full text of the study: http://www.srs.fs.usda.gov/pubs/40552