PARENT SESSION
Oral Session #6: Disturbance Ecology of Forests: Fire, Patterns. Presiding: R. DeFries.
Monday, August 6, 2001. 8:00 AM to 12:00 PM. Hall of Ideas F.

Indirect effects of forest disease on herbaceous plant diversity.

Hane, Elizabeth¹, ¹

ABSTRACT- The understory of the northern hardwood forest in the northeastern U.S. is undergoing restructuring following the introduction of beech bark disease, an exotic insect/pathogen complex from Europe. The disease affects adult beech (Fagus grandifolia) trees, and causes a large increase (in some places by a factor of 20) in the density of beech saplings in the understory of affected areas. This influx of understory beech affects the regeneration of other species (i.e. sugar maple) and is also affecting the herbaceous community on the forest floor. Removal experiments indicate that the and diversities of the herbaceous community are being affected by the increase in beech saplings. A shading experiment and soil-moisture measurements further indicate that the effects are likely due to increased shading. The diversity of herbs has increased significantly over the three-year study in beech-removal plots when compared to trends in untreated plots (p = 0.03). This indicates that the presence of beech saplings may be suppressing the diversity of herbaceous plants at the plot level. diversity, however, is increasing, due to the patchy nature of the sapling thickets that are a result of the disease. Thus one indirect effect of beech bark disease on herbaceous plants may be a spatially more coarsely grained population structure of herbaceous species.

KEY WORDS: herb diversity, exotic disease, Fagus grandifolia, Northern hardwood forest