Vegetative Changes in a Wetland in the Vicinity of a Well Field, Dade County,
Florida
Water-Resources Investigations Report 89-4155
By Ronald H. Hofstetter and
Roy S. Sonenshein
ABSTRACT
Plant communities
present in 1978 and 1986 were analyzed at 250 random points on stereoscopic
pairs of aerial photographs for four study sites in the vicinity of the
Northwest Well Field in Dade County, Florida. Sites NW and NE lie northwest
of the well field beyond the cone of depression. Site SW lies in the outer
part of the cone, and site SE lies within the cone of depression. Relative
frequency values for several plant types including herbs, shrubs-small trees,
and trees were analyzed by the Heterogeneity G-test to determine heterogeneity
among sites in 1978 and 1986.
In 1978, all four
sites were dominated by plant communities having herbs, shrubs, or a mixture
thereof. The communities at sites NW and NE were similar, and those at SE
and SW were somewhat similar. In 1986, sites NW, NE, and SE were dominated
by a mixture of shrubs and trees. Only at site SW was the relative frequency
of occurrence of herbaceous plants still high. At each site, there was a
decrease in herbaceous vegetation and an increase in woody vegetation during
this period, with the increase in trees being greatest at site SE.
Time between the
start of the well-field operation in May 1983 and the January 1986 photographs
was insufficient to allow determination of any direct effects of the well
field on the vegetation. Ground-level observations in 1987 and 1988 indicate
a trend toward continued increase in dominance of woody plants and a decrease
in herbaceous wetland vegetation. Development of a forest of the exotic
pest tree melaleuca is occurring at all four sites, but especially at site
SE. Vegetative changes between 1978 and 1986 are attributed to an invasion
of the exotic species melaleuca, a shortened hydroperiod, and natural succession
within the plant communities.
(The entire report is available
below.)
View
the PDF version of this report ( 891kb) (best
for printing)