Ecology of flowering dogwood (Cornus florida L.) in response to anthracnose and fire in Great Smoky Mountains National Park, United States of America

Cornus florida L. (flowering dogwood), a common understory tree species in eastern forests, is currently threatened throughout its range by a fungus (Discula destructiva Redlin) that causes dogwood anthracnose. This disease rapidly kills C. florida trees and mortality has exceeded 90% in some forest types. The health and ecological integrity of forest ecosystems throughout the eastern United States are threatened by the decline of C. florida populations, but management techniques to control anthracnose have received little attention. Hence, the objectives of this project were to determine (1) the influence of past burning on C. florida density and health, (2) how nutrient levels influence the density and health of C. florida, and (3) the role of C. florida in calcium (Ca) cycling.; We examined C. florida populations in burned and unburned oak-hickory stands in Great Smoky Mountains National Park to determine if burning prior to anthracnose infection has reduced the impacts of the disease. Burned stands contained greater C. florida densities and lower disease severity than unburned stands.; Nutrient availability has been hypothesized as a factor that influences dogwood anthracnose severity on C. florida. We studied the influence of Ca, potassium (K), and magnesium (Mg) on C. florida density and resistance to dogwood anthracnose. We found positive correlations between soil Ca, K, and Mg saturation and C. florida density in oak-hickory forests. We also found that seedlings grown in soil with lower inputs of Ca and K cations exhibited higher disease severity earlier in the growing season than seedlings grown with greater inputs of Ca and K.; Cornus florida is thought to play an important role in the Ca cycle because of the high Ca concentration found in the foliage. We quantified the relationship of C. florida density on Ca mineralization in the mineral soil and forest floor. Calcium mineralization occurred primarily in the forest floor and was generally greatest in the high density C. florida plots.; Our research showed a positive correlation between C. florida density and soil Ca, K, and Mg saturation. Higher levels of soil Ca and K may alleviate disease severity in C. florida. Further, our results indicate that prescribed fire may provide an important management tool to reduce disease incidence and severity in oak-hickory forests. We also found that the loss of C. florida from eastern forests has reduced the rate of soil and forest floor Ca mineralization, which may have negative effects on many associated flora and fauna.