Gradient analysis of the distribution of a fungal disease of Cornus florida in the southern Appalachian Mountains, Tennessee

Abstract

Based on 115 samples collected throughout the western portion of Great Smoky Mountains National Park, southern Appalachian Mts., and on spatial data derived in a GIS (Geographical Information System), the distribution of the disease dogwood anthracnose affecting Cornus florida (flowering dogwood), caused by the fungus Discula destructiva in this portion of the Park was assessed, and factors contributing to the disease's severity were identified through correlation and multiple linear regression analysis. The degree of infection varies considerably locally, and is influenced by elevation, slope curvature, slope position, and potential soil moisture. However, the abundance of C. florida (stem density) alone explains 25 % of the variation in disease severity. Factors contributing to disease severity do not change significantly between disturbed and undisturbed sites. The highest mortality rates are restricted to dense stands in damp, sheltered sites at low slope positions, implying that surviving populations of flowering dogwood may represent a biased genetic subset of the original population.

Cornus florida L. Mortality and Understory Composition Changes in Western Great Smoky Mountains National Park

“…The two cove types were mostly in topographically protected areas with generally northerly aspects, and the alluvial stands were in sheltered bottoms adjacent to streams. Local topographic features and stand conditions that increase understory moisture, decrease light availability, and reduce the evaporative potential of leaf surfaces are associated with higher rates of dogwood anthracnose infection (Hibben and Daughtrey 1988;Chellemi and Britton 1992;Erbaugh et al 1995;Wilds 1997). In our study, the three forest types with the greatest overstory basal area in 1995-2000 (acid coves, typic coves, and alluvial areas) experienced the greatest mortality, likely as a result of increased shading and reduced evapotranspiration.…”

“…Infected individuals exhibit poor fruit production and thus reduced fecundity (Windham et al 1993). Mortality and reduced fecundity of infected trees may inevitably result in a loss of genetic and phenotypic variability within surviving population remnants (Wilds 1997). Management techniques to control dogwood anthracnose have received little attention, although methods that reduce shading offer some promise (Britton et al 1994).…”

“…Dogwood anthracnose was first identified in GSMNP in the late 1980s and has spread across a wide range of forest types in which C. jlorida is found. In the western half of GSMNP, Wilds (1997) observed anthracnose infection in 98% of plots established to assess the distribution and severity of the disease. As part of the long-term monitoring program of GSMNP, permanent vegetation plots established in the 1970s have been resampled to monitor changes in the Park's vegetation communities.…”

Analysis of genetic diversity in flowering dogwood natural stands using microsatellites: the effects of dogwood anthracnose

“…Two years later, an estimated 75% of the remaining trees had been eliminated (Windham et al 1995). In a study by Wilds (1997), dogwood anthracnose infection was as high as 98% in experimental, biodiversity plots located in the western part of the GSMNP. In the periods from 1977-1979to 1995, Jenkins and White (2002 collected flowering dogwood data from 86 permanent plots located in the western portion of GSMNP.…”

Distribution of fungal foliage and shoot pathogens in a natural Scots pine population in relation to environmental variables

“…The classification was based on exposure and slope, which affect solar insolation, air circulation, evaporation potential, and date of snow melt (Parker 1982;Wilds 1997). The four microhabitat types are (1) south or southwest-facing slope, (2) north or northeast-facing slope, (3) level ground in depression, and (4) level ground on hilltop.…”