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THE VEGETATION OF ULAO
SWAMP By Jill Hewitt - UWM
Graduate Student
Because Ulao (YOU – LAY’ – OH) Swamp is large enough to
extend across section lines, it was described and mapped in the original
land surveyor notes. In 1835, the wetland vegetation was recorded as a
mixture of American beech, black and white ash, birch, white cedar, and
tamarack. Left undisturbed, these forest types typically are invaded by
white cedar, which once established, prevents further regeneration of shade
intolerant species. Gradually, the forest becomes dominated by white cedar,
almost to the total exclusion of all other species. The pre-settlement
upland forest surrounding Ulao Swamp consisted of American beech, sugar
maple, white ash, birch, bur oak, hickory, American elm, and
ironwood.
Since the Government Land Survey 167 years ago, the
tamarack population has disappeared, the beech population has been reduced
greatly, and only a small amount of cedar remains in the northern portion of
Ulao Swamp. The current vegetation is a mosaic of degraded hardwood swamp
(snags and damaged trees), southern wet-mesic forest, shrub-carr, alder
thicket, southern and northern sedge meadow, and southern cattail
marsh. Active and fallow agricultural fields, commercial development, and
private homes have largely replaced the pre-settlement beech-maple forest
surrounding the swamp.
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Forked Aster, a Wisconsin State
Threatened Species,
was found in the Ulao Swamp during the survey.
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I collected 231 vascular plant species in Ulao Swamp
during 2000 and 2001 when the wetland was examined. Of these, 97% are
native, and 92% are perennial. The wetland flora includes 24 tree, 36
shrub and woody vine, and 171 herbaceous species. Tree canopy in the
relic lowland forest varies from completely open to very dense. Depth of
surface water varies throughout the site; ranging from 0 to 100 cm.
Average pH measured in Ulao Swamp was 6.65 (neutral to slightly acidic).
I located an impressive population of forked aster, a
state threatened plant, on the west boundary of Ulao Swamp, just south
of Ulao Parkway. Seventeen species listed on SEWRPC’s “Uncommon Vascular
Plants of Southeastern Wisconsin” also are present in the wetland. |
Two herbaceous (reed canary grass and garlic
mustard) and three shrub (common buckthorn, glossy buckthorn, and
honeysuckle) exotic species considered invasive in our region were recorded
in the sampling units. Reed canary grass was located in 19 sample
points, while common buckthorn was found in 14. Glossy buckthorn,
honeysuckle, and garlic mustard were each identified in 2
sample points.
Using classification and ordination techniques as well as
aerial photo interpretation, I classified and mapped the vegetation data
into nine cover types: cattail marsh (19%), closed ash forest (22%), flooded
maple forest (15%), harvested forest (1%), open ash forest (25%), pond (1%),
reed canary grass (3%), sedge/shrub (13%), and wet meadow (1%). Vegetation
data and digital pictures of cover types are stored in a Geographic
Information System (GIS) developed for the swamp and surrounding watershed.
The GIS will enable future measurements of environmental parameters related
to vegetation distribution within Ulao Swamp as well as providing storage
and comparison of new data as they are collected during and after the
restoration period.
Due to the complexity of the wetland hydrologic regime as
well as impulsive anthropogenic influence on the area, it is difficult to
predict the future course of the Ulao Swamp vegetation. My data suggest that
ash and maple species may survive the flooding, and the wetland could
regenerate an ash-maple hardwood forest, these species are met. American elm
remains susceptible to disease and will not become a future dominant in
the swamp canopy. Recent plantings of tamarack and cedar seedlings may avoid
the high water levels by clinging to the numerous hummocks created by the
fallen trees and associated debris. Given the historical and present
disturbance regime of Ulao Swamp, future changes in the vegetation of the
lowland forest will be interesting to record. I would like to thank all the
landowners who eagerly provided access to the swamp and to the Ulao Creek
Partnership, which was instrumental in securing the funding for this
project. |
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Pre-settlement Vegetation of The Ulao Swamp
Trees recorded during the 1835 land survey and their historic location
with respect to the current Ulao Swamp boundaries and section lines. |
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