Effect of hydropattern changes on ecological and biological properties of
forested wetlands located in the Central Everglades: A Tree Island
Monitoring Program.
Coronado-Molina C., M. Korvela, L. Bauman, A. Gras, and F. Sklar
South Florida Water Management District, West Palm Beach, FL
Flood control and water management implemented by the Central and
Southern Florida Project in the late 40’s altered historic water patterns in
the Everglades National Park and the Water Conservation Areas (WCAs).
One of the most sensitive indicators caused by past water management
practices has been the change in the physical, ecological and biological
properties of tree islands. For instance, in the early 1960s, the number of
tree islands in portions of WCA-2A and WCA-3A significantly decreased
due to prolonged high water levels that caused the death of tree species on
these islands. In contrast, prolonged low water levels in the northern
section of WCA-3A resulted in tree island destruction because peat fires
removed the top 25 cm of their peat, resulting in water depths too great for
tree species colonization.
Since tree islands are ecologically important and given their potential use
as indicators of appropriate water management, the South Florida Water
Management District has implemented a comprehensive research program
to monitor this crucial component of the Everglades Landscape. By
monitoring the health of tree islands, it is feasible to adjust the
hydropattern in marsh areas of the Everglades through adaptive
management and thus to ensure tree island persistence and restoration. The
monitoring program includes monthly sampling of litterfall, bi-monthly
measurements of tree growth and annual vegetation surveys on nine tree
islands located on WCA-3A and 3B. Based on hydroperiod patterns, these
nine islands were grouped into two island types: wet (inundated less than 6
months and 10 cm of water level) and flooded (inundated more 6 months
and 30 cm of water level) islands. The main objectives of this monitoring
program are a) to characterize spatial and temporal long-term patterns of
litterfall production, tree growth, and species composition, and b)
determine the effects of water level fluctuations on below and
aboveground primary production on tree islands.
Preliminary results have shown that flooded tree islands have lower
litterfall production rates relative to wet tree islands. Over the study
period, litterfall production for the two island types has been 0.90
g/m2/day, and 1.65 g/m2/day for flooded and wet islands, respectively.
Salix caroliniana, Annona glabra, and Magnolia virginiana contributed
65% of the total litterfall production in flooded tree islands. In contrast,
Persea borbonia, Myrica cerifera, and Chrysoblanus icaco contributed 70
% of the total litterfall production in wet tree islands. The leaf fall
production pattern for these six tree species was related to their abundance
and distribution on each island type. Nonetheless, these results suggest
that tree islands subjected to shorter hydroperiod have higher litterfall
production than tree islands subjected to longer hydroperiod.
Tagged trees were grouped into two water level fluctuations, low and
high. Patterns of tree growth showed that Myrica cerifera, Annona glabra,
Persea borbonia, and Salix caroliniana had higher growth rates than
Chrysoblanus icaco, and Magnolia virginiana. Similarly, S. caroliniana
showed a strong seasonal growth, being higher during the dry season and
lower during the rainy season. In contrast, M. cerifera, P. borbonia, and A.
glabra showed higher growth during the rainy season relative to the dry
season. On the other hand, C. icaco and M. virginiana did not show any
strong seasonal growth. Water level fluctuations significantly affected the
growth patterns of only S. caroliniana which had higher growth rates on
tree islands subjected to short hydroperiod, growth rates of other tree
species were not significantly affected by water level fluctuations. The
relationship between hydrologic patterns and aboveground primary
production processes suggests that a single, simple hydrologic restoration
target is further complicated by how different environments are best suited
for these six different tree species.
Coronado-Molina, Carlos, South Florida Water Management District,
3301 Gun Club Road, West Palm Beach, FL, 33406
Phone: 561-686-8800 extension 4547, Fax 561-681-6310
ccoron@sfwmd.gov