PARENT SESSION
Poster Session #32: Plant Ecology I.
Wednesday, August 8, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Effects of simulated herbivory and light on growth and reproductive allocation in Dirca palustris L. (Eastern leatherwood, Thymelaeaceae) in selectively managed forests of the Northwoods.

Gann, Valerie¹, Brunkow, Paul¹, Marriage, Tara¹, Kahl, Katie¹, Jones, Cindy¹, Schulz, Kurt¹, Zasada, John², ^{1 2}

ABSTRACT- D. palustris (Eastern leatherwood) is a 1-3 meter tall perennial shrub that grows in the understory of mesic hardwood/conifer forests of the northeastern US. Leatherwood also suffers annual herbivore damage by Leucanthiza dircella in selectively cut forests of the Upper Peninsula of Michigan. Since phenology and physiology determine both the timing and distribution of resources, leaf herbivores may affect plant reproductive output and growth in the face of limited resources. This study examined fruit production, fruit mass and growth, at the branch and inflorescence level, in response to leaf clipping in forest sites subjected to different cutting management regimes. We hypothesized that proportion of fruits produced, fruit mass and/or growth would be negatively affected by leaf clipping. Analysis of covariance showed that clipping had no effect on branches in terms of fruit set, fruit mass or growth in two managed sites. Conversely, clipping in an old growth, uncut forest had significant effects on fruit set and fruit mass, but not on growth. Although previous studies demonstrated clipping to have negative effects on plant reproduction, our results suggest that allocation of resources towards reproduction may be species and habitat specific. These data also suggest that forest management techniques may have a negative impact on reproduction of this understory species.

KEY WORDS: Dirca palustris, Herbivory, Resource allocation, Plant reproduction