Dogwoods in Decline?

 

Each dogwood bloom is actually a cluster of tiny green flowers surrounded by four modified leaves called bracts. Photo by Wendy Evans, courtesy of Bugwood.org

Dogwood trees are cherished across the southeastern United States for their showy spring flowers. The small, deciduous trees are often found in the understory of hardwood forests, where they shuttle calcium from far below ground to leaves. Each fall, the calcium-rich leaves fall to the forest floor and decompose, enriching the topsoil with minerals. Dogwood fruits are also an important food for many birds and mammals.

Unfortunately, a new study suggests that dogwood populations are rapidly declining across the Southeast. “We found that the number of dogwood trees has fallen by almost 50 percent,” says Christopher Oswalt, Southern Research Station (SRS) researcher and lead author of a study published this April in the Open Journal of Forestry. “We saw decreases in 17 out of 30 states studied, and biomass declines in 20 out of 30 states, with the sharpest declines in Appalachia.”

The study is the first to look at dogwood populations across the species’ entire natural range. Several smaller studies have reported local losses of dogwood after infection with the introduced fungus, Discula destructiva. The fungus causes dogwood anthracnose, an important cause of dogwood decline. While the pathogen has killed many dogwood trees, the ultimate causes of the species’ decline are more far-reaching, and include competition, defoliating pests, and a lack of management or restoration of the species.

Oswalt and his team paired dogwood population data from two time periods, the first (1983 -1995) representing the early days of D. destructivas identification as a cause of dogwood anthracnose. The second time period spanned the years 2005 to 2007. The SRS Forest Inventory and Analysis program gathered data for each of the time periods.

“Across much of its range, dogwood populations have really dwindled,” says Oswalt. “Our results highlight the need to investigate whats happening to dogwoods on local and regional levels, and the need for proactive restoration, so we can save this classic American tree.”–Sarah Farmer

Access the full text of the study.

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