Impact of Oak Wilt on Vegetation and Structure of a Degraded Barrens
File(s)
Date
1998-05Author
Collada, Angela E.
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
Metadata
Show full item recordAbstract
This study investigated vegetational changes in oak wilt patches that occurred in late-successional
barrens at Necedah National Wildlife Refuge. Oak wilt, a vascular disease that is
usually fatal to members of the red oak subgenus (Erythrobalanus), is common on better
drained soils south of the tension zone in Wisconsin. Vegetation of oak wilt patches was
compared with that in the surrounding woods and to Old Barrens, a 226 ha barrens restored
by wildfire in 1936. Allelopathy of Carex pensylvanica, a species that dominates the herb
layer of degraded barrens, was examined experimentally to determine if it inhibits germination
of savanna species.
A significant majority of patches occurred on well-drained Plainfield-Friendship soils
compared with less well drained Meehan-Newson soils. Structure of vegetation within
patches, classified in terms of the presence of shrub or tree layers, and condition of the oldest
dead oaks were correlated with patch size. Total herb cover was significantly higher in oak
wilt patches on Plainfield-Friendship soils than woods on either soil association or Old
Barrens, and inversely correlated with total tree cover across all sites. Deciduous shrub cover
was higher in Old Barrens than in oak wilt patches. The mean number of species per IO m
segment in each sampling unit was significantly higher in Old Barrens than oak wilt patches on
Plainfield-Friendship soils but not significantly different between patches and woods.
Several species displayed distinct patterns in their distributions. Thirty-seven species
were significantly more abundant in Old Barrens than in oak wilt patches on the same soil type
and 10 species showed significant differences when oak wilt patches were compared to
woods. C. pensylvanica and Vaccinium angustifolium, patch size, soil, and shrub cover were
correlated with the presence/absence and abundance of the most common species.
Two experiments designed to test the impact of C. pensylvanica on germination of
savanna species had mixed results. Germination of Solidago juncea and a commercial lettuce
was inhibited by Carex leachate. Mean radicle length of Schizachyrium scoparius and the
lettuce was lower when treated with the leachate than with deionized water. The species water
interaction was also significant for the 2 species. A test of the effect of Carex leachate
and litter (burned, minced, and no litter) on seedbank germination was inconclusive.