Document: ROB-3-65-8

Forest understory spatial patterning in old-growth and managed northern hardwood forests in Wisconsin and Michigan.

SCHELLER, R.M.* and D.J.MLADENOFF

University of Wisconsin - Madison, Madison, WI 53706, USA ¹

Abstract:
As a forest stand matures, forest structure and resource availability become increasingly heterogeneous. Interspecific competition and dispersal processes also occur at multiple spatial and temporal scales. These processes are reflected in the spatial pattern of the landscape. We hypothesize that forest understory communities in northern Wisconsin exhibit smaller patch size and greater heterogeneity when resource heterogeneity is large and forest structure is more developed. The hypothesis was tested by comparing the spatial patterns of understory plant communities in three forest types: 1) old-growth forests, 2) second-growth, even-aged forests, and 3) uneven-aged forests with recent selective logging. A new method, the sociogram, was developed to measure the patch size and patch heterogeneity of ecological communities. The sociogram is modeled after the semivariogram and uses Srensen's coefficient to define community dissimilarity. The sociogram was applied at scales ranging from a single quadrat (4 m²) up to the extent of the forest stand. Results from 12 forest stands indicate that understory communities in old-growth and uneven-aged forests have smaller average patch sizes and greater community heterogeneity, when compared to even-aged forests. These results are independent of the alpha diversity found in the forest stands and reflect differences in resource heterogeneity and forest structure. The spatial patterning found in old-growth forests may enhance both ecological stability and biodiversity.

Keywords: landscape ecology, plant community ecology, spatial patterning, geostatistics, forest understory vegetation

This abstract is being presented at: 10:30 AM in session:
Oral Session #58: Landscape Ecology.