**Proposed Plan of Work for**

#### TREE ISLAND RESEARCH v1.1

Arnold van der Valk and Fred H. Sklar

with

> Dale Gawlik, Mike Korvela, Sue Newman, Chris McVoy, Yegang Wu, Steve
> Krupa, and Shili Miao

South Florida Water Management District

and

Daniel Mason, and Paul Wetzel

Florida Center for Environmental Studies

1.0 INTRODUCTION

1.1 Statement of problem

1.2 Background Information

1.3 Objectives

1.4 Tree Island Selection

2.0 PROPOSED STUDIES

2.1 Collecting and Synthesizing Available Information

(a) Literature review

```{=html}
<!-- -->
```
1.  Zaffke data

2.  Historical changes in abundance of tree islands

3.  Symposium

2.2 Tree Island Origin and Vegetation

2.2.1 Island topography and peat depth

2.2.2 Peat stratigraphy

> 2.2.3 Vegetation composition

2.2.4 Delineating tree island boundaries

2.2.5 Plant colonization and persistence

> 2.2.5 a Seed rain composition

4.  b Seed bank composition

> 2.2.5 c Seed dispersal by birds

2.3 Tree Island Development and Persistence

> 2.3.1 Peat accumulation rates

2.3.2 Tree growth

> 2.3.3 a Tree cores

5.  b Tree growth bands

2.3.3 Nutrient input by birds

2.3.4 Nutrient plume studies

> 2.3.4 a Nutrients in ground water
>
> 2.3.4 b Soil and plant and nutrient concentrations
>
> 2.3.4 c Groundwater and surfacewater flows

2.4 Tree Island Creation and Restoration

4.  Creation of tree islands

```{=html}
<!-- -->
```
4.  Restoration of tree islands

5.  Enhancing seed dispersal and plant establishment

> 2.4.3 a Attracting seed dispersing birds
>
> 2.4.3 b Deer grazing and plant recruitment

2.4.4 Seed germination and seedling growth

> 2.4.4 a Seed longevity of major tree species
>
> 2.4.4 b Seed germination
>
> 2.4.4 c Water depth tolerances of seedlings and saplings

2.5 Tree Island Model Development

2.6 Exotic Plant Spread

3.0 LOGISTICS

1.  TIME LINE

5.0 REFERENCES CITED

6.0 TREE ISLAND REFERENCES

April 2, 1998

**1.0 INTRODUCTION**

**1.1 Statement of problem**

Within the matrix of wetland types that makes up most of the greater
Everglades are small topographical highs, tree islands, which
historically have provided suitable habitat for a wide variety of
terrestrial plants and animals. For example, Gawlik and Rocque (1998)
found that tree islands support more species of birds than any other
habitat in the central Everglades. Because the maximum elevations of the
highest tree islands are only slightly above mean annual maximum water
levels, tree islands with their less flood tolerant vegetation are the
most sensitive component of the Everglades to changes in hydrology.

Flood control and water management measures 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 of problems caused by
modified water management practices have been changes in the physical
and biological character of tree islands. In the early 1960s, the number
of tree islands in portions of WCA-2A and the northern and southern
portions of WCA-3A declined significantly (Shortemeyer 1980). In WCA-2A
(Map 1) and the southern section of WCA-3A, tree islands were lost
because prolonged high water levels caused the death of tree species on
these islands. As illustrated in Map 1, most of the tree islands in
WCA-2A lost their trees and shrubs between 1950 and 1970 because of
prolonged high water levels. Prolonged low water levels in the northern
section of WCA-3A resulted in tree island destruction because peat fires
removed as much as 25 cm of their peat, and this resulted in water
depths too great for shrub and tree recolonization when these former
islands were flooded. Therefore, tree islands may provide the best and
surest measure of the overall health of the Everglades. And, if so, the
maintenance of healthy functioning tree islands should be a primary
consideration for determining appropriate water flows and levels in the
future for the Everglades.

A review of the literature has provided little insight into what
constitutes a healthy tree island. Studies on tree islands in the Water
Conservation Areas have been restricted almost exclusively to
descriptions of their vegetation (Davis 1943, Loveless 1959, Alexander
and Crook 1974, McPherson 1973, Zaffke 1983). How tree islands develop
and the ecological processes associated with their persistence were
summarized by Loveless (1959). Almost no studies have been done,
however, to test the various hypotheses of tree island development that
Loveless outlined.

Assuming that tree islands are important and given their potential use
as indicators of appropriate water management, it is imperative that a
comprehensive research program be initiated to study this crucial
component of the Everglades. All our hypotheses for this research
program are grounded in the belief that the health of tree islands is
the best indicator of the overall condition of the Everglades. Tree
islands are the first to suffer during droughts and are the least
tolerant to above normal water levels. By monitoring the health of tree
islands, it will be feasible to adjust the hydrology of the Everglades
through adaptive management and thus to ensure their persistence and
restoration. Data collected and models developed as part of this plan of
work are directly applicable to the Florida Everglades Forever Act of
1993 and mandated research on Minimum Flows and Levels and the US Corps
of Engineers' Comprehensive C&F Restudy. The work proposed will also
provide the information needed about how best to implement the
hydrologic regimes for various sections of the Everglades proposed by
the Natural System Model (NSM) so that any threats to tree islands are
minimized.

**1.2 Background Information**

Only two conceptual models of tree island formation in the greater
Everglades have been proposed for which there is any compelling
evidence: the floating tree island model and the fixed tree island model
(Davis, 1943, Loveless 1959; Gleason et al. 1977; Gleason et al. 1980).
Available evidence suggests that both types of tree islands are found.
Floating tree islands are also referred to as pop-up islands and battery
islands. Floating tree islands are common in the Loxahatchee National
Wildlife Refuge (Gleason et al. 1980) and possibly in other areas with
deep peats. Fixed tree islands are also referred to as pinnacle tree
islands or strands. Fixed tree islands seem to be the norm in most of
WCA-2A, WCA-3A, WCA-3B and Everglades National Park.

Gleason et al. (1974, 1975, 1977, 1980) described the development of
floating tree islands (Figure 1). Floating tree islands originate when a
large piece of peat, known as a battery, detaches from the bottom during
a period of high water and floats to the surface. This proto-tree-island
eventually becomes lodged on vegetation or other debris and colonized by
a variety of plant species, such as shrubs and trees, that are not able
to survive permanent inundation. Studies of the peat stratigraphy of
these islands show that the upper peat is derived from tree and fern
roots and tree leaf litter. The underlying peat is derived from water
lilly, sawgrass or arrowhead peats. Floating tree islands in various
sizes and stages of succession are found at any given time because they
are continuously being formed. These islands generally do not have
"heads" (taller clumps of trees at the north end of the island). Instead
they have relatively uniform vegetation over the entire island. These
islands also generally do not have the characteristic tear-drop shape of
fixed tree islands. Gleason et al. (1975) have suggested that floating
tree islands may subside or sink. Why these tree islands would subside,
however, is not known. If Gleason's theory is correct, then floating
tree islands are dynamic with continual production of new islands as
well as continual loss of old islands.

Fixed tree islands have three characteristic features: (1) they are tear
shaped and their long-axis is parallel to surface-water flows; (2) the
tallest trees and shrubs are found at the upstream end of the island,
the head, which is typically the widest part of the island; and (3)
behind the head there is an elongated v-shaped area, the tail, with a
lower elevation than the head . The vegetation of the tail is dominated
by shrubs or marsh species (e.g., sawgrass or typha) or a combination of
the two. There seems to be no published account of the formation of
fixed tree islands. In fact, Loveless (1959), who outlined various
proposed models of tree island formation in the Everglades, did not
propose a fixed tree island model. The following description of fixed
tree island formation has been developed from a variety of unpublished
reports and personal communications.

Fixed tree islands seem to be associated with topographic highs in the
bedrock underlying the Everglades. These topographic highs are believed
to be under the "heads" that characterize this type of tree island.
Field observations suggest that the trees on most tree islands are
rooted in the limestone bedrock of the heads. How and when shrubs and
trees become established on these heads is unknown. One possibility is
that shrubs and trees can become established during prolonged periods of
low water when these topographic highs are above water for a number of
years. Another possibility is that peat deposition on these topographic
highs eventually raises them above the mean maximum water level so that
they are high enough to allow them to be invaded by shrub and tree
species that cannot tolerate long-term inundation. It is conceivable
that both can occur depending on the maximum elevation of the limestone
underlying a head and that this might result in different types of
vegetation on these types of tree islands. Islands with low heads may
only be able to support shrub vegetation, i.e., willows and Myrica,
while islands with high heads may support various kinds of trees, i.e.,
Bays, Maples, and other tropical hammock tree species. If this is the
case, peat accumulation on low heads is of much greater significance
than on high heads, and fire is much more of a threat to islands with
low heads.

Regardless of how the shrubs and trees become established, the
characteristic tear shape of these tree islands is believed to be due to
the development of a "tail" behind the head (Figure 2). This tail seems
to be the result of the accumulation of peat in the lee of the head.
Thus fixed tree islands can grow in length with age, but their heads are
always found at the upstream end of the island. Because fixed islands
are associated with topographic highs in the bedrock, there are only a
limited number of this type of island possible in the Everglades. Two
different hypotheses have been suggested to explain the formation of
tails, the hydrodynamic and chemo-hydrodynamic.

According to the hydrodynamic hypothesis, the tail develops due to
litter from the head being deposited in the lee of the head by water
currents. There are two variants of the hydrodynamic hypothesis, the
catastrophic and the continuous. The catastrophic variant proposes that
movement of litter occurs only after major storms when high flow rates
scours litter from the heads and deposits it in their lee (Parker 1974).
The continuous variant proposes that normal flow rates erode litter from
the heads and deposits it in their lee. If either of these variants of
the hydrodynamic hypotheses is correct, the peat accumulating within the
tail should be at least partly of tree origin. For the catastrophic
variant, the peat in the tail should be composed of alternating layers
of marsh and tree peat (Figure 2) . For the continuous variant, the peat
in the tail should be a mix of marsh and tree peat (Figure 2).

The chemo-hydrodynamic hypothesis postulates that the organic matter
accumulating behind the head is not due to the movement of litter from
the head. According to this hypothesis, the tail develops due to the
release of nutrients from decomposing plant material on the head that
leach into the shallow groundwater and move downstream of the head due
to prevailing groundwater movement. This plume of

![](media/image1.pct){width="6.0in" height="5.582638888888889in"}

nutrients behind the island results in greater plant growth and the
build up of peat in the plume area when compared to nearby areas outside
the plume. Cattails are sometimes found growing in the tail behind these
islands. As the peat in the plume area builds up, shrubs and trees may
become established. If this chemo-hydrodynamic hypothesis is correct,
peat in the tail should all be of marsh origin

Why should there be higher nutrient concentrations behind fixed tree
islands? There are many factors that may be directly or indirectly
involved. The total mass of available nutrients on the head may increase
with time due to the growth of shrubs and trees and the build up of a
peat layer. Nutrients may be extracted from the limestone in which the
shrubs and trees are rooted. Nutrients, such as phosphorus, can be
released from the limestone by enzymes associated with plant roots and
by dissolution of the limestone by organic acids released by decomposing
plant litter. It is likely that tree islands accumulate nutrients during
the dry season and that they lose them due to leaching during the wet
season. Another possible reason for nutrient inputs on tree island heads
are birds. Birds may transport nutrients to the island and enrich them
relative to the surrounding areas. Birds are also believed to be the
major dispersal agents of seeds of many of the shrub and tree species on
these islands. Thus, birds may play a crucial role in both the
successional patterns on these islands as well as the extent and rate of
island growth. It is also possible that tree islands receive more dry
deposition of nutrients than surrounding marshes because of the height
of their vegetation (Redfield 1998). This could result in dry deposition
being a major component of nutrient budget of tree islands. Whether a
steady state condition develops eventually as annual nutrients losses
due to leaching from the heads begins to equal nutrient inputs into the
heads is unknown. If this is the case, there could be a limit to the
maximum depth of peat accumulation, i.e., the maximum height of an
island, and the length of the tail can develop behind the head.

Fire and prolonged periods of high water seem to be the two major
threats to fixed tree islands. Fire during dry periods can remove
significant amounts of peat from these islands and kill their shrub and
tree populations (Zaffke 1983). Prolonged droughts may also adversely
affect tree islands by increasing the rate of peat decomposition on the
islands. Prolonged periods of high water can also drown out tree
islands. Peat accumulation is the only mechanism that fixed islands have
to cope with a permanent increase in mean water level. It is not know
whether tree islands can continue to accumulate peat with age and hence
continue to increase in mean elevation or whether they reach a steady
state condition where annual litter inputs are balanced by litter
decomposition and erosion. Although both fire and abnormally high water
levels are known to have destroyed tree islands in the Everglades, the
overall magnitude and frequency of these disturbances is not known.
Whether and how fast fixed tree islands can become re-established after
they have been destroyed by fire or flood is also not know.

Changes in hydrology are not the only threat to the health of tree
islands. Tree islands have also been invaded by a number of exotic
species, including, *Melaleuca quinquenervia*, *Schinus
terebinthefolius* and most recently *Lygodium microphyllum*. The latter
is a climbing fern that has been spreading rapidly in recent years from
tree island to tree island in the Loxahatchee National Wildlife Refuge
(WCA-1). Once established on an island, this fern grows very rapidly and
it quickly can cover the entire tree canopy. Observations suggest that
this can kill the canopy trees as well as understory shrubs and herbs.
In 1989 and 1990, there was a fire in the Loxahatchee National Wildlife
Refuge which burned approximately 50,000 acres. Following this fire
*Lygodium microphyllum* was observed on tree islands in the burnt area.
Two years ago, an informal survey indicated that tree islands in a
17,000 acre area in the Loxahatchee National Wildlife Refuge were
infected with *L. microphyllum* (personal communication, Su Jewell).
Very little is know about the biology of this species or how to control
its spread. To date, it has not been reported on tree islands in WCA-2
or WCA-3, but there is nothing to prevent it from invading these
islands. By contrast, a considerable amount of work on the basic biology
and control of *Melaleuca* and *Schinus* has been done, and *Melaleuca*
has been eradicated from many tree islands,

**1.3 Objectives**

The studies proposed in this five-year work plan will focus on fixed
tree islands. We focus on fixed tree islands because there is very
little published information about them and their development. This
island type also appears to be the most common in water conservation
areas 2A, 3A, and 3B as well as Everglades National Park. The following
studies, proposed over the next five years, will provide essential
information needed about the development, persistence, restoration, and
creation of fixed tree islands:

1.  Literature Review and Symposium.

```{=html}
<!-- -->
```
(a) Tree Island Origin and Vegetation.

(b) Tree Island Development and Persistence.

(c) Tree Island Creation and Restoration

(d) Tree Island Model Development.

The overarching goal of these studies is to provide the information
needed to develop water management plans that will preserve existing
tree islands in the Everglades and to develop a strategy for restoring
tree islands destroyed by high water or fire. The information collected
will also be essential for developing models of tree island development
and fate in the Everglades Landscape Model and other similar models.

The proposed studies will be a cooperative effort involving personnel
from the South Florida Water Management District, Florida Center for
Environmental Studies, Florida Game and Fresh Water Fish Commission, US
Geological Survey, and various universities.

**1.4 Tree Island Selection**

Most of the proposed studies on the development and vegetation of fixed
tree islands (Table 1) will be done on 9 tree islands in WCA-3A and -3B
(Map 2). Specifically, two tree islands were selected in the northwest
section of WCA-3A (3AN1 and 3AN2) and two in WCA-3B (3BS1 and 3BS2). The
remaining five islands (3AS1 to 3AS5) were selected in the southern
portion of WCA-3A. All nine islands are approximately the same size.
Tree islands in these areas were chosen because there are a large number
of tree islands, particularly in the southern portion of WCA-3A, and
tree islands in the northwest section of WCA-3A and in WCA-3B will be
flooded more deeply and for longer periods of time according to NSM
projections. The latter islands will vary in the elevation of their
heads, i.e., in the vegetation on the heads, and collectively their head
elevations will encompass those of the other four islands. Elevation of
the head was chosen as the main variable to be examined because it is
believed to be the major determinant of the type of vegetation that
grows on them and how they will respond to changes in hydrological
regime. These 9 islands will be referred to as the core tree islands
throughout this plan of work. As much as feasible, tree islands that
have been previously studied were included in the core group, and all
information about specific tree islands from completed and ongoing
studies of tree islands in WCA-3A and -3B have been evaluated. The final
decision about which specific tree island to include in the core group
was made collectively by the investigators involved in the proposed
studies. Potential islands were first identified using aerial
photographs and maps. Some 30 islands were identified initially. Field
visits were made to all potential core islands, and the final selection
of the 9 islands was made on the basis of information collected during
the field visits. For some proposed studies, additional tree islands
will be sampled, and for studies of tree island restoration former tree
islands in WCA-2A will be selected.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Table 1. Proposed studies that will be carried out on all 9 core tree
islands. Long-term studies with repeated sampling will be done for five
years.

Task Number Task Description Sampling Frequency

2.2.1 Island topography and peat depth Once

2.2.4 Delineating tree island boundaries Once

> 2.2.5a Seed rain composition Bi-monthly

2.  b Seed bank composition Once

```{=html}
<!-- -->
```
2.  c Seed dispersal by birds Seasonally

> 2.3.1 Peat accumulation rates Bi-annually

3.  b Tree growth bands Annually

4.  b Soil and plant nutrient concentrations Once

> 2.4.3 b Deer grazing and plant recruitment Bi-annually

Map 2. Nine tree islands in WCA-3 (A&B) were selected as core study
islands. Two of these islands (3AS3 and 3BS1) were selected for
intensive study involving measurements of ground and surface water
movements, water and soil chemistry, seed banks, plant tissue analysis,
vegetation surveys, sedimentation rates, tree growth, and primary
productivity.

**2.0 PROPOSED STUDIES**

Four basic kinds of studies are proposed: (1) collection and synthesis
of all available information on tree islands; (2) studies on the origin,
geomorphological characteristics and vegetation; (3) studies of the
development and persistence of tree islands and their vegetation; and
(4) studies of the creation and restoration of tree islands.
Collectively, these studies will enable the development of realistic
models of tree islands that can be used to asses their health,
reconstruct lost tree islands, or mitigate for any tree islands lost to
changes in the hydrology of the Everglades.

Many of the proposed studies on the origin and development of tree
islands (see Table 1) will be done on 9 core tree islands. Unless noted
otherwise, on core islands, two sites, one on the head and the other on
the tail, will be selected for long-term studies on peat accumulation.
At these and all other permanent sites which will be sampled repeatedly
over a number of years, walkways will be built from the edge of the tree
island to the site. Walkways are needed to minimize investigator
disturbances to these sites.

**2.1 Collecting and Synthesizing Available Information**

Much of the available information on tree islands is in agency reports
and unpublished theses. Consequently, it is very difficult to get access
to it. There is also at least one major data set on the vegetation of
tree islands that has never been fully analyzed, a study of 7 tree
islands in WCA-3A by Michael Zaffke when he worked for the South Florida
Water Management District. An essential first step is to collect all
available information on tree islands and to synthesize it into a review
paper. Recently, a number of new studies on tree islands have been
initiated. In order to bring together the information in these ongoing
and recently completed studies, a symposium on tree islands will be
organized in the summer of 1998.

*2.1.1 Literature review*

A literature review on tree islands will be conducted. All published
papers and unpublished reports pertaining directly to tree islands will
be collected and synthesized. Individuals with knowledge of the history
of tree islands will be interviewed. The final product will be a
publishable review paper.

The topics to be covered in the literature review include:

Tree Island Formation

A.  Types of tree islands

1\. Soils

2\. Plant species

3\. Topography

> 4\. Hydrology

B Origin of tree islands

C Models of tree island development and persistence

Tree Island Disturbances

A Natural Disturbance

1\. fauna (deer, alligator, etc)

2\. hydrology

3 fire

B Invasion by exotic species

1\. *Melaleuca* *quinquenervia*

*2. Schinus terebinthefolius*

3 *Lygodium microphyllum*

## C Anthropogenic Disturbance 

1\. Native Americans

2\. Recreational

3\. Hydrology

4\. Fire

5\. Management e.g. *Melaleuca* control

6\. Climate

Life Histories and Water Depth Tolerances of Major Plant Species

A Trees

*1.* *Ilex cassine*

*2.* *Myrica cerifera*

*3.* *Persea borbonia*

*4.* *Salix caroliniana*

*5. Cephalanthus occidentalis*

6\. *Baccharis spp*

*7.* *Annona glabra*

B. Vines

*1.* *Mikania scandens*

*2.* *Sarcostemma clausa*

C. Forbs

*1. Aster carolinianus*

*2. Boehmeria cylindrica*

*3. Centella asiatica*

4\. *Eupatorium coelestinum*

*5. Polygonum hydropiperoides*

*6. Hydrocotyle umbellata*

*7. Ludwigia repens*

*8. Ludwigia alata*

D. Ferns

*1. Acrostichum danaeaefolium*

*2. Blechnum serrulatum*

3\. *Osmunda regalis*

4\. *Thelypteris palustris*

E. Grasses and Sedges

*1. Cladium jamaicense*

*2. Dichronema colorata*

*3. Eleocharis baldwinni*

*4. Panicum agrostoides*

*5. Panicum dichotomum*

Use of Tree Islands by Animals

A. Invertebrates

B. Reptiles and amphibians

C. Birds

D. Small mammals

E. Large mammals

Status and Future Trends of Tree Islands

*2.1.2 Zaffke data*

To gain an historical perspective on plant community change on tree
islands an unpublished data set collected by Michael Zaffke when he
worked for the South Florida Water Management District will be analyzed
and the islands where he had plots resampled. Zaffke established
permanent plots on 7 tree islands in WCA-3A. Species presence/absence
and limited cover class and tree density data are available from the
late 1970s and early 1980s from these plots. These data were collected
both before and after a fire that occurred at four of the sites in 1981.

The seven islands that were sampled have been relocated with Mike
Zaffke's help, but an attempt to find the permanent quadrats on them was
a complete failure. Although it will not be possible to resample the
permanent quadrates established by Zaffke, a general vegetation survey
of each of the 7 islands will be done to determine how they have changed
since Zaffke's study. This survey will compile a list of all species on
the islands and estimate the cover of each species on each island. (The
cover scale that will be used is outlined in section 2.2.4.) Results of
this general survey of the Zaffke islands will enable us to determine of
their overall species composition has changed, and, for the islands that
burned, if shrub and tree vegetation has become re-established.

*2.1.3 Historical changes in abundance of tree islands*

Losses of tree islands have been noted in WCA-2 and WCA-3 in various
reports, but the extent of these losses have never been adequately
documented. A comparison of archival aerial photography from each decade
from the 1940s to the 1990s will be done to try to quantify when tree
islands were lost or gained and the number and total area of islands
during each decade in selected areas. Three or four areas will be
selected in WCA-2 and WCA-3 in which changes of tree islands have been
reported. Comparable areas will also be selected in which changes in
tree islands have not been reported. In each area, the location and size
of each tree island will be measured and any distinguishable features of
the vegetation noted such as approximate height of trees and shrubs as
well as basic information about the geometry of the island (e.g.,
maximum width, maximum length, compass bearing of long axis). Tree
island data will be correlated with historical data on the hydrology of
each area and its fire history.

*2.1.4 Symposium*

A symposium on tree islands will be organized and held during the summer
of 1998 by Drs. Arnold van der Valk, Fred Sklar and Wiley Kitchens. All
researchers working on tree islands in the Everglades will be asked to
participate. The symposium will be designed to facilitate exchange of
information about ongoing and proposed projects and to help coordinate
future studies. Another major goal of this meeting will be to develop
conceptual models for tree island development and health that can be
incorporated into existing models of the Everglades such as the
Everglades Landscape Model. The proceedings of this symposium will be
published if papers presented are deemed to be of sufficient quality.

The symposium will be held in South Florida and will last two days.
Possible sites for this meeting are the Florida Center for Environmental
Studies, Florida Atlantic University, and the South Florida Water
Management District. The first day will be taken up with the
presentation of invited papers and will be open to the public. The
second day will be a workshop on tree islands to discuss conceptual
models of tree island and the evidence available for each of these
models. The proposed plan of work on tree islands will also be reviewed.

**2.2 Tree Island Origin and Vegetation**

How tree islands develop is largely undocumented. This information is
essential if meaningful guidelines for managing water levels in the
Everglades are to be developed that will ensure the persistence of tree
islands. Because so little is know about their origin and development,
the proposed studies will focus exclusively on fixed tree islands.

*2.2.1 Island topography and peat depths*

It is hypothesized that fixed tree islands consist of a head that is
located on a topographic high in the limestone bedrock and a tail that
has built up downstream of the head due to the accumulation of peat.
Data to confirm that this is how these islands originated is essential
to confirm the validity of the proposed fixed island model.

*Methods*

Depth to bedrock and depth of peat overlying bedrock will be determined
by probing the peat with thin metal rods on all core islands. This will
be done along multiple transects perpendicular to the long-axis of tree
islands in conjunction with the vegetation sampling of core tree islands
outlined in the section 2.2.4 Delineating tree island boundaries.
Relative depths collected along transects will be converted to absolute
elevations by relating water level at the time the beginning and end of
each transect to water level data from the nearest permanent marsh
gauging station.

A benchmark will also be established on the head of each core island.
The absolute elevation of this benchmark will be determined using a
kinematic GPS. All relative elevations along transects will also be
transformed into absolute elevations relative to this benchmark by
finding the elevation of the water at the beginning and end of each
transect in relation to the benchmark. This will provide a check on
absolute elevations based on water level gauges and will probably
provide more accurate absolute elevations for tree islands that are not
near a water gauging station.

*2.2.2 Peat stratigraphy*

Peat stratigraphy done on *Persea*-fern and *Ilex*-fern dominated tree
islands in the northern Everglades was useful in developing the floating
tree island model (Gleason et al. 1977). Peat stratigraphy has not been
studied on fixed tree islands in the southern Everglades. An
investigation of peat stratigraphy on these islands should provide
essential information for understanding the development of fixed tree
islands. In theory, data on the stratigraphy of peats in the tails of
fixed tree islands can be used to determine which of the three
hypotheses of tail formation is correct (Figure 2). The actual
usefulness of peat stratigraphy data from fixed tree islands, however,
may be limited because of the high frequency of fires that removed
surface layers of peat. For this reason, an exploratory study of peat
stratigraphy is proposed for two core islands. This study will determine
whether peat types can be identified and if enough information about
past vegetation is still present to warrant further studies. If usable
cores can be obtained, it should be possible to determine whether the
hydrodynamic or chemo-dynamic model of the development of tree island
tails is correct. If so, the remaining core tree islands and possibly
other tree islands will be sampled.

If obtaining meaningful peat cores on fixed tree islands is feasible,
radiocarbon and lead 210 dating of replicate cores from core tree
islands would provide additional information about peat accumulation
rates that would be very useful. Ongoing studies of the age of tree
islands in Everglades National Park by Charles Holmes of the U.S.
Geological Survey should be extended to the core tree islands in WCA-3A
and WCA-3B.

*Methods*

Nine peat cores will be collected from a core island in the northern
section of WCA 3A or WCA-3B. Three cores will be taken from the head of
the island, three cores from the tail of the island, and three cores
from the area surrounding the island (reference cores). A second island
in southern WCA-3A will be sampled in the same manner. The cores will be
examined for major peat types. Major plant species and plant components
(leaves, twigs, sticks) in peat cores will also be identified to develop
a plant successional sequence. Indicators of fire, i.e., charcoal, will
also be noted..

*2.2.3 Vegetation composition*

Although some studies of the vegetation of tropical hammocks within
Everglades National Park have been done, vegetation studies of the
greater Everglades have tended to emphasize the wetland vegetation.
There have been a few studies, however, that have examined the
vegetation of some tree islands in WCA 2 and 3 (Davis 1943, Loveless
1959, Alexander and Crook 1974, McPherson 1973, Zaffke 1983).
Collectively, these studies examined only a very limited number of
islands and provide only rather superficial information about the
vegetation of tree islands.

A new quantitative study of the vegetation of tree islands has been
initiated by the Office of Environmental Services of the Florida Game
and Fresh Water Fish Commission. This study will collect data on the
vegetation and physical characteristics of 40 tree islands in WCA-2A,
-3B and three zones within -3A identified by Shortemeyer (1980). In each
area, eight 2 mi x 2 mi grid cells will be selected from the South
Florida Water Management Model (SFWMM) and one island sampled within
each cell. The most elevated island within each cell will be sampled.
These islands should provide the best opportunity for detecting the
relative flooding tolerances among tree species found on these tree
islands. Tree species found only at the highest elevations should be the
least tolerant of prolonged flooding.

Vegetation sampling will be done using quadrats laid along two
transects, one along the long axis of an island and the other
perpendicular to the long-axis transect. A ground water well will be
used to mark the intersection of the transects. In each quadrat, peat
depth, water depth if present, and percent cover of all species rooted
in the quadrat will be recorded. DBH of all trees with a diameter of 10
cm or more will be recorded. Island vegetation will be analyzed and
classified using standard multivariate techniques. Island vegetation
will be related to past hydrologic conditions using data from the
nearest water level gauge to each island.

Information on island size, shape, orientation will be obtained from
aerial photographs.

*2.2.4 Delineation of tree islands*

The objective of delineation is to better define tree island boundaries
by examining their plant communities. Boundaries of tree islands are
needed to define tree islands for photo-interpretation and other
classification purposes and for hydrologic threshold models that may be
developed to determine the minimum and maximum water levels needed to
maintain tree islands.

Plants are the primary indicator of the stage of development of a tree
island. Known plant community types may also provide aerial photograph
signatures, useful for answering landscape level questions. Plant
community measurements will provide an inventory of tree island species,
measurement of vertical community structure, and abundance estimates for
the most common species on tree islands.

# Methods

On each core tree island, multiple belt transects several meters wide
that will be oriented perpendicular to the long axis of the island will
be used to sample the vegetation. Transects will begin in the nearest
slough habitat and end in slough habitat on the other side of the
island. Transects will be selected using a stratified random sampling
design. The island will be divided into three major divisions; the head
(upstream), the middle, and the tail (downstream). Each division will be
visually divided into 20m segments. A sampling transect 5m wide will be
randomly selected in each segment.

Plant cover will be estimated in contiguous quadrats. Eight cover
classes will be used: trace, 0-5%, 6-10%, 11-25%, 26-50%, 51-75%, 76-95%
and 96-100%. For herbaceous vegetation, quadrats will be 2.5x1m in area
and for shrub species 5x5m. Vertical vegetation structure will be
estimated by placing species in one of four height categories:
vegetation 1m or less, 2-3m tall, 3-5m tall, and 5m or greater and total
cover and thickness or depth of each canopy layer estimated. The density
of shrubs and trees more than 3 m tall will be recorded.

*2.2.5 Plant colonization and persistence*

The objective of this series of studies is to determine the capacity of
tree island vegetation to return to a pre-existing state following a
disturbance. The vegetation of a tree island may change due to fire,
high water levels, herbivores, invasion by exotics and direct
anthropogenic removal. Colonization of the islands after disturbance
could result from recruitment from the seed bank or from dispersal of
propagules to the island.

Many of the woody species on fixed tree islands have fleshy fruits that
are eaten by birds. It is likely that the seeds of these species are
dispersed in the feces of birds. Plant community structure, especially
live and dead shrub or tree height, may be critical in the rate of
recovery of vegetation following a disturbance because of its role in
attracting frugivorous birds to the disturbed island. The potential for
plant recolonization of tree islands will be examined by examining the
size and composition of their seed bank and their seed rain, i.e.,
number of seeds reaching the island per unit area per unit time. The
importance of plant structure on an island for attracting seed eating
birds also will be tested.

2.2.5 a Seed rain composition

The seed rain on core islands will be measured. Seed present in litter
traps described under short-term peat accumulation rates (2.3.4 Nutrient
plume studies) will be separated from the litter, identified to species
and counted. All seeds identified to species and counted. Seeds will be
tested for germinability by attempting to germinate 25 to 50 seeds under
standard conditions (25/35 C alternating temperature in the light)
placed on moist filter paper in Petri dishes. All seeds of each species
collected on a given sampling date will be composited into one sample
for these germination tests. If large numbers of small seeds are
collected, a subsample of 50 to 100 seeds will be taken. Seeds that are
contained in fleshy fruits will be separated from their fruits
mechanically and then tested

2.2.5 b Seed bank composition

The seed banks of core islands will be examined. At the permanent
sampling site at both the head and tail, twelve random soil cores of
10cm diameter to a depth of 5 cm will be collected. Gross organic
material, wood pieces, rhizomes, leaves, will be removed, the soil
placed through a sieve and the twelve cores homogenized. Six subsamples
will be taken from the homogenized soil and placed in germination trays.
Three trays will be maintained under saturated conditions and three
trays will be submerged under 10 cm of water. Following germination,
seedlings will be identified to species, counted and removed from the
trays. Additional detailed information on the methodology that will be
used for the seed bank studies can be found in van der Valk and Rosburg
(1997).

2.2.5 c Seed dispersal by birds

To determine the extent of seed dispersal by birds, individuals of
common bird species will be captured with mist nets during spring,
summer and winter on the core tree islands. These birds will be placed
in a clean plastic box lined with tin foil for 5-15 minutes. This
technique was sufficient to obtain fecal material from over 80% of
captured birds in tropical forests (Loiselle and Blake 1990). Samples
will be weighed wet and seeds will be extracted manually from randomly
selected fecal samples for subsequent germination (see section 2.2.5 a).
Remaining samples will be dried and analyzed for nutrients (see section
2.3.3, Nutrient input by birds). To determine the vegetation
characteristics that are most attractive to seed dispersing birds, a
number of vegetation characteristics will be related to the density and
species richness of seed-dispersing birds. Vegetation characteristics
include vegetation volume, height, canopy coverage, and stem density of
various size classes of trees. These characteristics will be measured as
part of section 2.2.4 Delineation of tree island boundaries.

**2.3 Tree Island Development and Persistence**

It is hypothesized that fixed tree islands initially develop on a
topographic high in the bedrock, the head, and that subsequently a tail
develops downstream of the head due to increased primary production
caused by the movement of nutrients from the head downstream in shallow
groundwater. Shortemeyer (1980) suggests that the head represents only
about 5% of the total area of the average fixed tree island and that
most of the island consists of the tail area. Information on how much
peat has accumulated on the head and tail of tree islands and the annual
rate of peat accumulation is needed to understand how long it takes for
tree islands to form. Also, this information will provide insight into
potential of tree islands to recover from disturbances such as prolonged
deep water and fire.

*2.3.1 Peat accumulation rates*

Peat formation is a function primarily of annual litter production and
decomposition, hydrology, and fire disturbance. Peat accumulation rates
are needed to determine if the maximum height of the islands is fixed or
if they can increase with long-term rises in water level and to
determine how quickly peat can accumulate after a fire or other
disturbance. Both the long-term and short-term peat accumulation studies
will be established on core tree islands.

*Methods*

Long-term Peat Accumulation Rates. Clusters of seven pins will be
anchored in the bedrock along two transects running perpendicular to the
long-axis of islands, one across the head and the other across the tail.
Five pin clusters will be installed along each transect. Each pin will
be labeled or numbered and the distance from the top of the pin to the
soil surface will be measured bi-annually. These pin measurements of
wetland elevation will be coordinated with bi-annual measurements of
sediment accumulation rates using marker horizons (i.e., feldspar). This
technique involves spreading an inert white soil across the surface of
the peat and collecting cores in the same area after new sediments have
had a chance to accumulate on top of the white marker. The depth of
accumulated sediments is an indication of the production of new peat. If
this production is less than the oxidation and dewatering of existing
peats, then the pin data will indicate a net subsidence for the area.
Pins and cores with feldspar marker horizons are both needed to
calculate the true net rate of tree island accretion (Cahoon et al.
1995).

Short-term Peat Accumulation Rates. Elevated litter traps will be placed
at the permanent sampling site on the head and tail of each core island.
The traps will consist of a wooden frame 30x30x5cm with an 1mm
fiberglass mesh on the bottom. Three clusters (three traps per cluster)
will be positioned randomly at each site. Material in the traps will be
collected every two months. Organic material collected in the litter
traps will be sorted into major plant parts (branches, leaves, twigs,
and seed/fruits) and its volume calculated. Litter in the traps, except
seeds, will be oven dried and weighed.

*2.3.2 Tree growth studies*

One method for establishing the relationship between tree islands and
hydrology is to examine the growth of trees on tree islands. Most of the
trees on tree islands are poorly adapted to flooding. Their rate of
growth and age are unknown, and the effects of different water levels on
growth and recruitment needs to be studies. Tree cores will be used to
try to determine the age of trees on selected tree islands and the
growth of trees during prolonged periods of below and above normal water
levels. On core tree islands, trees growth bands will also be placed on
selected trees. Growth bands will enable annual growth increments to be
measured without damaging the trees. They will be part of the long-term
monitoring of core tree islands and will be used to detect the immediate
impacts of changes in hydrology on their growth. These data combined
with data from litter traps (see 2.3.1 Peat accumulation rates) will be
used to estimate annual net primary production. This can be done using
standard mathematical models of tree growth paramaterized for each tree
species banded.

2.3.2.a Tree Cores

Tree cores will be collected in WCA-2A and WCA-3A in February 1998. This
will be a preliminary study to determine if it is feasible to collect
tree cores and get interpretable results. The tropical tree species
growing on tree islands have never been cored and it may not be possible
to get usable tree cores from them. Tree cores will be collected from
islands and trees selected by the expert being hired to do this study
under the Expert Assistance Program. Trees of known age that were
planted by the Florida Game and Fresh Water Fish Commission on created
islands in WCA-3A will be utilized to see if tree cores can be reliably
used to date trees on tree islands.

If tree cores prove to provide useful data about the age of trees and
about the effects of hydrological conditions on growth, then tree cores
will be taken of suitable trees on the heads of core tree islands.

2.3.2.b Tree growth bands

Standard aluminum, spring-tension, tree-growth bands will be attached at
breast height to selected trees on each of the core tree islands. These
bands will be monitored bi-annually to determine if the trees are being
stressed by changes in hydrology. It is expected that 5 to 10 trees will
be banded on each island. When the trees are first banded, information
needed to paramaterize standard tree growth models (e.g., tree diameter,
height to first branch, number of primary branches, diameters of primary
branches, height of tree, etc.) also will be collected.

*2.3.3 Nutrient input by birds*

During the nesting season, wading birds gather food over large areas and
concentrate it at colonies. The resulting nutrient enrichment is a major
determinant of plant species composition of tree islands (Frederick and
Powell 1994) and submerged aquatic vegetation (Powell et al. 1991).
Although, not all tree islands in the Everglades support wading bird
colonies, those in the central Everglades support more species of birds
than in any other habitat (Gawlik and Rocque 1998). It is hypothesized
that many birds feed in the surrounding wetlands and bring food back to
the islands, thus concentrating nutrients there. Also, during migration
when birds are traveling among ecosystems, tree islands offer small
fragments of forest habitat in a vast marsh system and may therefore
concentrate nutrients from beyond that in the surrounding marsh. This is
a preliminary study to examine whether bird feces are a significant
source of nitrogen and phosphorus input for tree islands.

*Methods*

To determine avian community composition and species-specific density
estimates, point-count surveys will be conducted on islands during three
seasons (spring migration, summer, and winter) using the methodology in
Gawlik and Rocque (1998). Islands will be divided into subsections if
warranted, and five replicate surveys will be conducted in each zone
during each season. If sampling bias assumptions are met then counts
will be transformed to density estimates using the program DISTANCE.
Otherwise, bird counts will be used to as measures of relative
abundance. Additional surveys will be conducted on 7 islands that are
not being studied to test for effects of research activities on bird
abundance and species composition. Also, surveys will be conducted at 9
marsh sites to identify species that occur in both marsh and tree island
habitat.

Nutrient input will be determined by coupling bird density estimates
with species-specific rates of defecation. Defecation rates will be
obtained from the literature and from direct observations of birds.
Nutrient content of bird feces will taken primarily from the literature.
To verify and to supplement literature data on nutrient content of bird
feces, about 40 composited samples of feces collected during the seed
dispersal phase (section 2.2.5 c) will be sent out for chemical
analyses. How much of the material deposited as feces on tree islands
comes from the surrounding marshes and how much is material that
originated on tree islands needs to be determined. This will be done by
examining the types of seeds and other material found in the feces. The
total mass of feces estimated to be deposited on an island will be
partitioned among marsh and island sources. If preliminary results
suggest that birds are adding significant quantities of N and P to the
islands annually, further studies will be initiated to determine which
bird species are most important for tree island nutrient budgets.

*2.3.4 Nutrient plume studies*

The fixed island model hypothesizes that tree islands are composed of a
head and a tail. The tree island is believed to be initiated with the
establishment of terrestrial plants on peat covered bedrock ridges or
pedestals. The process responsible for the development of the island's
"tail" is unknown. One variant of the fixed tree island model, the
chemo-hydrodynamic, postulates that the island's tail results from
accelerated peat production in a nutrient plume behind the head. This
nutrient plume results from the transport of nutrients from the island's
head in either shallow ground water or surface water downstream. Two
studies will be conducted on core tree islands to try to establish the
existence and extent of a nutrient plume. The first is designed to
determine directly if nutrients from the heads are leaching into tail
areas. The second is designed to test if this has occurred by examining
the nutrient concentrations in the soils and plants growing in the tails
and for the same plants and soils in the surrounding marsh, i.e.,
outside the nutrient plume. If the chemo-hydrodynamic hypothesis is
correct, plants and soils in the marsh should have lower nutrient
concentrations than those from the tails.

2.3.4 a Nutrients in surface and groundwater

The concentration and movement of N and P in surficial groundwater will
be studied only on two of the core tree islands: one tree island will be
located in south-central WCA-3A, an area which should undergo little
change in water regime according to the NSM as a result of the proposed
hydrological restoration, the second will be located in WCA-3B, an area
projected by the NSM to have increased inundation as a result of
hydrologic restoration. It is likely the movement of nutrients from the
head to the tail occurs primarily after major rain storms. Whether
nutrients are carried primarily by surficial groundwater or by surface
flow is unknown. How quickly water moves from the head to the tail by
either path is unknown and some preliminary close interval sampling will
need to be done to determine how to adequately sample surface and
groundwater movement associated with these storms. Both a surficial
groundwater sampling network and a surface water sampling network will
be established on the two core islands. Measurements of ground water
head and surface water flow will be used to model litter and nutrient
movement from head to tail.

Prior to the installation of pore water nutrient sampling wells, a
network of piezometers will be established around and within two core
tree islands. Piezometers will be placed along three parallel transects
running from the head to near the middle of the tail. There will be four
piezometers in each transect. Piezometers will be inserted into the
upper 15 cm of bedrock. Sensitive pressure sensors will be used with
these piezometers to determine the height, direction, and amount of
groundwater flow. The height of the groundwater in each piezometer will
be recorded every hour in an electronic data recorder for seven straight
days during the wet and dry seasons, and after two major rain events. In
conjunction, flow meters will be used to measure currents around the
head of the two intensive core islands during quarterly porewater
collections. More frequent measurements, of both surface water flow and
groundwater may be necessary if major storm events are discovered to be
a significant contributor to the nutrient plume hypothesis.

Two of the nine core tree islands will be studied intensively. On each
of these intensive islands, a total of 30 pore water nutrient sampling
wells (15 at 10 cm; 15 at 40 cm), located at regular intervals along the
direction of flow, will be sampled six times (quarterly and after two
major rain events). Pore water wells will be constructed of PVC pipe
with a slotted well screen located to isolate the surface 10-30 cm and
50-60 cm soil depths. A circular PVC disk encircling the well at the
soil surface will minimize potential for contamination from surface
water. The end of the well that enters the soil will be capped with a
pointed PVC fitting, while the sampling end will be sealed with a rubber
stopper. A clear acrylic (or similar) tube will extend through the
stopper to the base of the well. The well be closed to the atmosphere by
the attachment of a short length of impermeable tubing that will be
closed with a stopper. The impermeable tubing will be the point of
attachment of the peristaltic pump upon evacuation sampling. All wells
will be sampled at least quarterly. Samples will be collected with the
peristaltic pump directly into sample bottles, through an in-line 0.45
µm filter. Prior to sampling, the well will be evacuated and water
allowed to recharge. Samples will be acidified and analyzed for total
dissolved P and total dissolved Kjeldahl N. If funds are available,
samples will also be collected and analyzed for Ca, Mg,Fe, NO~x~-N and
NH~4~-N.

Throughout the year, more frequent measurements will be made using an
autosampler. Three autosamplers will be installed on both intensively
studied islands to sample surface water along the central well transect
in the head, halfway down the tail, and in the slough habitat upstream
of the head. Samples will be analyzed for TN and TP, and collected as
daily composites of 8-hr samples.

The heads of many tree islands are flooded during the wet season. It is
possible that nutrients , either in dissolved or particulate form, are
carried by surface flow from the head to the tail during these flooding
events. To develop an accurate spatial picture of nutrient flows,
surface water samples will be collected along the piezometer network at
each piezometer site that has standing water. Measurements of water
currents will also be made using high sensitivity flow meters at each
piezometer site whenever a water sample is taken. A full suite of
surface water quality parameters will be measured twice during the wet
season and after two major storm events, along with flow rates. The
possibility of lateral surface flow of water from the tree islands will
also be investigated. If this occurs regularly or after storm events,
water samples will be taken along both sides of the heads to determine
if nutrients are being carried to the tails by this flow path. Surface
water samples will be filtered to determine the proportion of dissolved
and particulate nutrients.

Various hydrodynamic and erosion models, to simulate the erosion of peat
and litter from the head and deposition of litter to create a tail, will
be evaluated for incorporation into a spatial tree island succession
model (see Sec. 2.5). Likewise, groundwater models will be developed to
simulate the movement of nutrients from the head to the tail.

To determine wet and dry deposition of atmospheric nutrients, standard
rain gauges will be placed on two core tree island heads and on two
adjacent marsh/slough areas free of any overhanging plant canopy. The
difference between the wet deposition under the canopy and in the marsh,
after a correction for foliar leaching from the canopy, will be an
estimate of the sum of all dry deposition on the tree island (Lindberg
et al. 1986). .

2.3.4 b Soil and plant and nutrient concentrations

If a nutrient plume is present and contributes to island formation due
to increased primary production, then soil and plants on the tail of
islands should have higher concentrations of nutrients and higher
standing crops in areas upstream of the island's head. The positive
effect of nutrient additions on both soil nutrient concentrations and
plant growth has already been demonstrated in the Everglades in WCA-2A
(see Davis 1994). Sawgrass (*Cladium jamaicense*) will be used to test
this hypothesis. Sawgrass is a species which grows well under low
nutrient conditions and which responds by increased growth to
fertilization (Stewart and Ornes 1983, Davis 1991).

When feasible, a 20X20 m plot will be established in areas dominated by
sawgrass upstream of each of the core tree islands and within the tail
of each island. On some core tree islands, there may not be sawgrass
stands upstream for the head or in the tail. In these cases, nearby tree
islands will be selected which do. In any case, 9 islands will be
sampled as part of this study. Within the plot, ten 0.5 x 0.5m plots
will be selected at random. In each plot, the maximum height of sawgrass
vegetative and flowering culms will be measured, and all aboveground
plant material in the subplot will be harvested. The sawgrass will be
separated from other macrophytes, dried at 65^o^ C and weighed. Sawgrass
foliage from each plot will be analyzed for phosphorus and nitrogen
concentrations using standard plant tissue analytical procedures.

Soil cores will be taken with thin-walled aluminum tubes (10 cm i.d.) to
a depth of 30 cm within each of the ten subplots in the 20X20 m plot
after the plants have been harvested. The cores will be divided into 10
cm sections. At each sampling site, all core sections from the same
depth will be composited. Each core section composite sample will be
analyzed for TN and TP using standard methods.

Soil samples also will be collected, as outlined above, on the head of
each island at which sawgrass samples are collected and at each sampling
point along the piezometer network on the two tree islands on which
groundwater studies will be done (see section 2.3.4 a).

Soil cores will be collected by driving a thin-walled aluminum coring
tube (10 cm i.d.) into the soil and extracting the tube with the core
intact. The cores will be extruded in the field and sectioned into 10 cm
depth increments, placed in sealed plastic bags, and stored at 4°C prior
to analyses. Soil samples will be dried and analyzed for percent dry
weight, water content, bulk density, TP and TN. A sub-sample will be
ashed and percent ash content determined.

2.3.4 c Groundwater and surfacewater flows

One of the hypotheses to be tested in this study is that the formation
of tree island tails is due to the movement of a plume of above and/or
below ground nutrients derived from the elevated head of the island.
Movement of the plume through the surficial groundwater of the island is
thought to be driven by a combination of rainfall and the flow vectors
in the surface water surrounding the tree island.

[Groundwater Flow:]{.underline} Groundwater flow generally cannot be
measured directly. Instead it is inferred by mapping the driving force,
hydraulic head (pressure), in three dimensions. Flow occurs down
gradient, i.e., in the direction of decreasing head. Changes in the
mapped head over time, particularly in response to transient events such
as rain storms, are used to confirm the mapped flow patterns.
Identification of the patterns of water flow on a tree island requires a
grid of synoptic measurements to create reliable contour maps of the
hydraulic head. A network of instrumented piezometers, monitored by
datalogger, will be used to gather the synoptic measurements, as well as
to collect time series information during and after storm events. The
instrumented network will be in place through the course of at least one
dry and wet season. Sampling frequency can easily be adjusted; 15
minutes is a likely interval.

Measurements by Steve Krupa (Sr. Sci., WRE) in WCA 2 suggests that the
bedrock floor of the Everglades is not in fact impervious, and that
there may be significant interaction between regional groundwater and
the surface waters of the Everglades. It is recommended therefore that
the network of surficial groundwater measurements described above be
supplemented with a drilled well, screened at multiple depths. This well
would be instrumented with pressure transducers and used to determine
the vertical gradient in hydraulic head.

To determine the direction of surficial groundwater flow and the
response to rainfall, each shallow piezometer will be outfitted with a
very low drift, temperature-compensated pressure transducer, and linked
either by cable or telemetry/cell phone to the central data station.
This station would house a datalogger, multiplexor, battery, solar panel
and telemetry link to the District. The logger should have inputs for a
tipping bucket raingage, air and soil temperature measurements, and a
measure of solar radiation. An instrumented weather station connected to
the datalogger would be preferable to permit continuous calculation of a
tree island water budget (particularly evapotranspiration). Differences
in head will be small on tree islands, so elevations of the instrumented
piezometers must be measured precisely and accurately by initial
surveying.

[Surface Water Flow:]{.underline} Present and historical field
observations indicate that although the heads of strand tree islands may
be above water, the tails may be inundated during a substantial portion
of the year. During such times, nutrients from the head may be carried
to the tail by surface water rather than groundwater flow. This will be
tested using a pulse-release dye tracing study. A temporary artificial
plume would be created to mimic the release of nutrients from the edge
of the head of the island; the shape of the plume would be monitored
over time (1 to 10 days) to map its movement. A conservative, non-toxic,
non-sorbing dye detectable by fluorimetry at ppb levels would be used.
Rhodamine WT may be a possibility, but would have to be tested for
interaction with dissolved and suspended organic carbon. A pulse release
would be created by encircling the head of the island with a perforated
tube, supplied by laterals from a central tank of dye on the middle of
the head of the island. Arrival and passage of the plume front will be
monitored by a network of autosamplers. Sampling frequency and start of
sampling will be determined from preliminary flow velocity measurements
and a pilot dye release. Some flow velocity measurements are available
in the literature. Disturbance of the flow field by airboats should be
avoided during the experiment; helicopter or prefereably canoes could be
used to replenish the autosamplers if needed. To determine dye
concentrations in the field during the course of the experiment, a
portable laboratory fluorimeter will be used.

**2.4 Tree Island Creation and Restoration**

Many tree islands have been lost due to fires and prolonged flooding of
some sections of the Water Conservation Areas. How to restore tree
islands in the Everglades that have been destroyed has never been
investigated. It is possible that mitigation for tree island losses due
to changes in hydrology will be needed. The studies proposed in this
section are designed to establish the potential for restoring damaged
tree islands and for creating new tree islands.

Four facets of tree island creation and restoration will be examined:

(1) establishing new topographic high or heads, i.e., creating new fixed
    tree islands;

(2) raising the surface elevation by the addition of peat on parts of
    former islands lost due to fire or high water;

(3) accelerating dispersal and establishment of suitable plant species
    on created and restored islands; and

(4) establishing seed germination requirements and water depth
    tolerances of seedlings of the most common shrub and tree species
    found on tree islands.

On both restored and created tree islands, it is possible that deer
herbivory may have a significant effect on success of recruitment of
tree species, especially during the wet season. To evaluate the impact
of deer on tree recruitment, deer exclosures will be established on
restored and created tree islands.

2.4.1 Creation of tree islands

To create or establish a fixed tree island will require constructing a
suitable new platform or head. In the past, small tree islands have been
constructed in WCA-3A by pilling up material excavated from nearby
areas. This technique creates islands that have deep water areas
adjacent to them that are heavily used by alligators, and, consequently,
the islands are unsuitable as habitat for many other animals, including
deer. In order to avoid the problem of having alligator holes associated
with tree islands, it will be necessary to create tree island by some
method other than excavation.

One promising method for creating new fixed tree island heads is to
construct heads using concrete modules and then to allow their tails to
develop naturally. If these artificial heads are built using
standardized modules that can be linked together, artificial tree island
heads of different sizes, heights and shapes could be built as needed.
An exploratory study is proposed to investigate the feasibility of
constructing tree island heads from inexpensive concrete modules.
Conceptually, what is being proposed is similar to research that has
been done to construct artificial reefs for fish from concrete modules.
Many questions, however, need to be answered concerning the feasibility
of constructing tree island heads, both economically and ecologically,
including:

(b) What is the ideal cement formulation for these modules? The cement
    formulation used needs to result in modules that resemble real heads
    in chemical composition, surface relief (roughness), and hardness
    and porosity.

(c) What is the ideal shape, thickness and size of a module? The modules
    need to be easily and cheaply transportable to suitable sites. One
    way to reduce the weight of the modules would be to make them hollow
    and capable of floating and then filling them with water to sink
    them once they are in place.

(d) How would modules be transported into place? The modules need to be
    of a size and weight that they could be transported in the
    Everglades either by being towed behind in an air boat or carried by
    a helicopter.

(e) What is the fastest way to establish tree and shrub species on
    artificial heads? Constructing modules with surface depressions that
    could be filed with peat and planting small seedlings in them might
    be the best and fastest way to get shrubs and trees established.
    Establishing artificial perches for birds on the newly built heads
    will also be tried to accelerate natural seed dispersal to the
    created tree islands (see section 2.4.2 a).

(f) Will deer use restored and created tree islands? If so, deer could
    have a significant impact on tree recruitment. To evaluate whether
    deer are using restored and created islands, deer exclosures will be
    built.

(g) Will tails begin to develop behind these heads? If so, why?
    Monitoring tail development behind artificial heads would be the
    ultimate test of the three hypothesis of tail development (Figure
    2). Experimental studies of tail development could also be done. For
    example, artificial heads could be fertilized to determine if this
    would result in a faster development of a tail as is predicted by
    the chemo-hydrodynamic hypothesis.

Once the practical problems associated with constructing modules and
heads have been solved, enough modules will be built to establish
several small tree islands of 900 to 1,000 m^2^ within the WCA's. They
will need to be monitored for a number of years to determine if plants
will survive and grow on them, if a peat layer begins to develop on
them, and if a tail develops in their lee.

> Initially created tree islands should be built in WCA-2A. Little is
> known about how to construct, transport and hook together the modules
> needed to build such an island. To reduce the logistical problems
> associated with their construction, it is preferable to build the
> first tree islands in WCA-2A rather than in WCA-3A. This will minimize
> any damage to natural areas that would inevitably occur as part of the
> process of learning to build these islands. Adding tree islands to the
> WCA's will help return them to a more natural condition and make them
> better wildlife habitat, especially for deer and birds. It might even
> improve them as phosphorus sinks since tree islands seem to be acting
> as long-term storage systems for nutrients in the Everglades.

2.4.2 Restoration of tree islands

Many tree islands have been lost due to removal of peat by fires and by
prolonged periods of high water. To test to see if the restoration of
these islands is feasible, surface elevations of sections of several
former tree islands in northern WCA-3A will be raised by adding peat.
Northern WCA-3A was chosen as a study site because estimates of peat
loss due to fire for this area are available in Shortemeyer (1980).
Several potential sources of peat will be explored, including
commercially available peat and compost material from nearby cities and
counties. On-going construction activities on canals and dikes in the
Everglade also may provide a source of peat. Peat will be transported to
the study site during the dry season using large, rubber-tired all
terrain vehicles or by airboat.

The size and number of the peat enhanced plots and the final elevation
of the peat in these plots will depend on the available peat supplies
and cost of transporting the peat. It is expected that the minimum size
of these plots will be between 10 x 10 m and 20 m x 20 m is size and
that at least three plots will be established. To keep this peat in
place, it will be necessary to build some kind of a frame. This frame
will be built out of PVC pipes and heavy plastic, weather-resistant
netting such as the kind used to contain sediment around construction
sites or used for snow fencing. Half of each plot will be fenced off to
create a deer exclosure. Peat enhanced plots will be set up on a minimum
of three tree islands. If more than three plots are feasible, planting
or sowing suitable shrub or tree species will be considered on one or
more plots.

*Methods*

Samples of the peat used to establish peat enhanced plots will be tested
to see if the peat used contains viable seeds using the same technique
described in section 2.2.5 b Seed banks.

The peat enhanced plots on these islands will be monitored for
establishment and growth of plants. The plots will be divided into 1 x 1
m subplots, and, for each plot, 30 to 50 permanent subplots will be
chosen at random, half of these plots will be in the deer exclosure.
Subplots along the periphery of the peat enhanced plot will be excluded.
The vegetation in these permanent subplots will be sampled every two
months. The cover of each species in a subplot will be estimated and the
density and height of all tree seedlings measured. All species in the
fenced and unfenced half of the plot not found in sampled subplots also
will be recorded when the subplots are sampled.

*2.4.3 Enhancing seed dispersal and plant establishment*

Studies on enhancing plant establishment will focus on the development
of techniques that will provide guidelines for reestablishment of woody
vegetation on tree islands impacted by fire or high water levels.
Emphasis will be placed on attracting seed dispersing birds,
establishing suitable woody vegetation from seed, and protecting tree
and shrub seedlings from herbivores.

2.4.3 a Attracting seed dispersing birds

An experiment will be developed to test whether increased use by
seed-dispersing birds enhances the establishment of trees on newly
created or restored tree islands (see section 2.4.2). This study will
also examine which of two methods is most effective and which provides
the greatest cost benefit, tree saplings or artificial perches.
Treatments will be perch type (tree sapling, artificial perch, no perch)
and island type (created or restored). Artificial perches will be
constructed of PVC pole and wood (e.g., Powell et al. 1991) and will be
the same height as the saplings. Saplings will be trees obtained from
local stock at nearby nurseries. On each peat enhanced plot (see section
2.4.2) subplots not used as part of the vegetation monitoring will be
divided into three groups and treatments will be randomly assigned to
each subplot until there are 10 replicates of each treatment, 5 within
deer exclosures and 5 without. Bird use will be surveyed using methods
similar to section 2.2.5 c for whole islands. The effectiveness of
perches for attracting seed dispersing birds will be evaluating by
monitoring the vegetation that develops in subplots with and without
perches. Vegetation surveys, conducted every two months, will estimate
the cover of all species and the density of tree seedlings. With time,
if no species become established on plots with perches or saplings
different from those on control plots, feces will be collected under
perches and saplings and examined for viable seeds as described in
section 2.2.5c; Seed dispersal by birds.

Sapling trees and perches will also be used on created tree islands to
see if they accelerate seed dispersal by birds on the tree islands. On
created tree islands, depressions in the surface of these islands filled
with peat will either be planted with a tree sapling, have an artificial
perch placed in them or have neither (controls). Treatments will be
assigned randomly with half of each treatment in the deer exclosure. As
on restored islands, the vegetation in these depressions will be sampled
every two month to determine which species are becoming established.

2.4.3 b Deer grazing and plant recruitment

Field observations suggest that grazing by deer is widespread on tree
islands and could be suppressing the recruitment and growth of some
plant species on tree islands. The effect of grazing may be accentuated
seasonally and in certain years because of high water conditions that
concentrate deer on the highest elevations. Differences in elevation
among islands may lead to spatial differences in grazing pressure within
years because high elevation islands may serve as upland refugia during
especially high water conditions.

On each of the 9 tree islands, two plots 2m x 2m in size with similar
vegetation composition will be established. One plot will be randomly
assigned as a treatment and will be enclosed with wire mesh around a PVC
frame 2m in height with an open top and bottom. Two sides of the wire
mesh will be raised approximately 15 cm above the ground to allow small
animals to move through the plot. The other plot will serve as a control
and will receive PVC poles at each corner without a wire mesh exclosure.
Each plot will be divided into four 1m x 1m subplots. In each subplot,
the number of seedlings and saplings of all tree species will be counted
and the percent cover of all herbaceous and woody plants \< 1 m in
height will be estimated once per year at the end of the wet season.

*2.4.4 Seed germination and seedling growth*

Establishment of natural vegetation is dependent on many factors,
including production of seeds in excess of those consumed by pre- and
post-dispersal predators; dispersal of seeds to sites suitable for
germination; and seeds remaining viable long enough so that they
encounter conditions suitable for germination. Sites suitable for the
establishment of woody species from seed must have the right combination
of soil moisture and light conditions to allow the seeds to germinate
(Fenner 1985). Species growing in the same general area often differ in
their specific seed germination requirements. This alone can result in
the establishment of different species from place to place or in the
same place from year to year. Information on the seed germination
requirements of dominant tree species on tree islands in WCA-2A and
WCA-3A is needed both to understand the development of and distribution
of vegetation on tree islands and how it will be affected by changes in
water levels. It is also essential information for the restoration and
creation of tree islands.

Environmental conditions required for plant establishment often differ
from conditions under which adult plants can live. Generally water depth
tolerances of seedlings and juveniles are narrower than for adults.
Therefore, water depths associated with adult plants may not reflect
optimal water depths for earlier life stages. Information on plant
growth and mortality of seedlings and juveniles of the most important
tree species at various water depths is needed to ensure that water
levels are managed correctly during periods when recruitment is
occurring on tree islands or when tree islands are being restored or
created..

#  The specific objectives of three studies proposed are to determine for selected tree and shrub species the longevity of their seeds, optimal seed germination conditions, and growth of their seedling at different water depths. It is anticipated that these studies will be done on at least 7 of the most common species on tree islands in WCA-2A and WCA-3A, including Ilex cassine, Myrica cerifea, Persea borbonia, Salix caroliniana, Cephalanthus occidentalis, Baccharis spp., and Annona glabra

2.4.4 a Seed longevity of common tree and shrub species

Seeds of the selected species will be harvested by hand from several
shrubs or trees on several tree islands in WCA-3A when the seeds are
mature. Seeds of a given species from all islands sampled will be
pooled. Nine hundred healthy seeds of each species, selected on the
basis of their hardness and exterior appearance (color, texture) and
size/mass, will be divided into 18 lots of 50 seeds and placed in mesh
bags. Six mesh bags will be buried on each of three tree islands on
which the species grows. Every two months, one bag from each island will
be retrieved and the number of intact seeds recorded. Intact seeds in
each bag will be divided into two equal groups. For one group, seed
viability will be determined using the tetrazolium dye test (Grabe
1970). Seeds in the other group will be tested for germinability using
standard seed germination techniques: 25/35 C in the light on moist
filter paper in Petri dishes. If more than 50% of the seed in a
retrieved bag is no longer intact, then only the tetrazolium test will
be conducted on all the seeds..

2.4.4 b Optimal conditions for seed germination

Seed for germination experiments will come from the same seed batches
that were collected for the seed longevity studies in the previous
section. Seeds will be germinated along a water potential gradient using
a technique adapted from Evans and Etherington (1990, 1991). This
gradient will be established by determining the relationship between
water potential and gravimetric water content of the test soil using a
pressure plate extractor technique. A peat soil will be used since this
is the type of soil found on tree islands. Using the generated curve,
water will be added to batches of air dried, sterile soil to produce a
specific water potential. Soil water potential treatments that
correspond to about 5%, 25%, 50%, and 100% of field capacity will be
used. Two additional flooding treatments will be set up in which the
soil is flooded to a depth of 1cm and 10cm.

The seed germination tests will be done in open containers filled with
soil at a specific water potential with the seeds (25 to 50) placed on
the surface. The seeds will be sterilized with a dilute bleach solution
to reduce problems with fungal growth. The closed Petri dishes will be
placed under three greenhouse light conditions: (1) 100% light, (2) 50%
light and (3) 0% light. The 50% light treatment will be established
using shade cloth. All Petri dishes will be placed in suitable
temperature conditions for germination. The two flooding treatments will
be done using open Petri dishes placed in plastic boxes (crispers) with
the soil surface covered with 1 or 10 cm of water. Each treatment will
be replicated at least three times. The number of replicates will be
established from preliminary tests of the seed germination protocols.
Seed germination will be determined by counting the number of seedlings
in each petri dish after a predetermined amount of time that will also
be established from the preliminary trails.

2.4.4 c Water depth tolerances of seedlings and juveniles

Seedlings will be started in a greenhouse using seeds from the seed lots
collected as part of the seed longevity study. Small seedlings (\<15 cm
in height) will be grown at soil moisture levels of 50% field capacity
and 100% field capacity and at water depths of 1cm, 15cm, and 30 cm.
Large seedlings (juveniles) (\> 15 cm in height) will also be grown at
50% and 100% field capacity and at water depths of 1cm, 15cm, 30cm, and
45 cm. The 50% and 100% field capacity soil moisture treatments will be
maintained as described in section 2.4.3 Seed germination and seedling
growth. Large containers will be used and water added as needed to
maintain the specified soil water potential or flooding depth. Plants
will be monitored biweekly with maximum shoot (leaf) length and number
of shoots and leaves measured. Measurements of net photosynthesis,
stomatal conductance, and transpiration will be made periodically.
Photosynthesis-light response curves will be developed for seedlings and
juveniles of each species. The number of replicates of each treatment
will be established from preliminary tests, but at a minimum there will
be five replicates of each treatment. The length of time the experiment
will be run will be established from the preliminary trials. At the end
of the study, plants will be harvested and their above and below ground
biomass determined. Relative growth rates of above- and belowground
biomass will be calculated and above- and belowground biomass allocation
will be determined for seedlings and juveniles of each species.

Roots of shrub and tree species are the most susceptible plant organs to
stress caused by prolonged flooding. A preliminary experiment will be
set up to examine the feasibility of identifying indices that can be
used in the field to determine if the roots of a common tree and shrub
species are showing signs of flooding stress. These indices could
include easily observed changes in root color or texture or might
involve inexpensive measurements of selected compounds in the roots that
are products of anaerobic metabolism (e.g., its alcohol content). These
experiments will be carried out in a home-made, small rhizotron, a
multi-chambered structure designed for observing root growth and
designed to facilitate root sampling. Individual chambers in the
rhizotron will be large enough to accommodate the root system of small
trees and shrubs. Two sides of each rhizotron chamber will have acrylic
plastic sides to allow inspection of the root system. The preliminary
experiment will involve growing individuals of one or two shrub or tree
species most susceptible to flooding in chambers flooded for different
lengths of time. Periodic measurements to establish the level of stress
of the plant (stomatal resistance, evapotranspiration rate) and value of
the various root indicators (color, texture, alcohol concentration,
etc.)of flooding stress being examined will be made as well as
simultaneous measurements of the indicators of stress being examined. If
the preliminary results warrant it, additional species will be examined
in the rhizotron, and field studies of the applicability of indicators
of flooding stress that have been identified will be initiated.

**2.5 Tree Island Model Development**

Two modeling approaches will be explored as part of this research plan.
One will be based upon standard tree growth models used by lumber
companies and foresters to simulate the growth of above-ground woody
structure such as, trunk size, branching format, height, etc. This
approach will be validated against band data and tree ring data of
representative individual trees on core islands. This approach will
explore our ability to duplicate species-specific intrinsic growth as a
function of age, hydrology, and climate. A conceptual model of this
approach (Figure 3) highlights the basic parameters. This model will
simulate the production, viability and germination of species-specific
seed stocks as a function of water depth, light and fire. Recruitment of
the seedlings from this seed stock into adults is then a function of
light, climate, soil fertility, and soil moisture. If conditions are
suitable for seedling growth and herbivory is negligible, then the
overall biomass of the species will increase as a function of
photosynthesis. Once a critical biomass and age is reached, the species
can flower, and the life-cycle process is completed.

The second modeling approach will be based upon dynamic ecosystem models
used by Sklar et al. (1985), Costanza et al. (1990), Fitz et al. (1996),
and Wu et al. (1997) to simulate the spatial interactions of soil
fertility, hydrology, and organic matter production in wetlands. This
approach will be validated against peat accumulation rates, litter fall
data, nutrient plume data, and tree island community composition. This
will be a multi-species model that incorporates the standard tree growth
model for each species into a successional model. This approach will
allow us to predict tree island sustainability as a function of water
depth and hydroperiod. A conceptual model of this landscape approach
(Figure 4) highlights the basic state variables. This model incorporates
all of the flowering, germination, and growth dynamics shown in Figure 3
into a single growth state variable shown in Figure 4. The growth state
variables in Figure 4 for marsh and tree species 1 and 2 represent
entire life cycles. The growth of all species are combined to produce
the biomass needed for peat accretion and peat export downstream. This
biomass also influences the pore water and soil chemistry (Peat Nutrient
Content). Peat elevation and peat fertility have a feedback role on the
growth and recruitment of trees. These peat variables, when combined
with inputs from birds, climate, fire and hydrology, create the habitat
conditions for tree island succession. This model will grow each species
as a function of competitive

interactions for light (shown as "Light 1 vs. 2") and each species'
physiological response to local ecology (shown as "Habitat Suitability
Sp. x"). This model is designed to be the basic tree island module of a
larger

landscape model. That is why it includes inflows and outflows of biomass
and nutrients. Data from five of the nine core tree islands will be used
to calibrate this model. Data from the other four islands will be used
to validate it.

This landscape approach will be effective at synthesizing data from
multiple spatial and temporal scales. Like most holistic approaches to
an ecosystem problem, this tree island research plan will gather data
from a wide variety of scales (e.g., short-term seed germination and
long-term peat accumulation). Linking information across disparate
scales (e.g., tree growth/day vs. tree island growth/decade) has always
been a problem for modelers. This problem is minimized by our ability to
structure code hierarchically. Short-term processes are nested within
long-term processes. Small scale structures are nested within larger
scales. Each nested module can be calibrated and validated separately.
Any code needed to link one scale to the next becomes an important
emergent property of the system. This is important because emergent
properties can be explored

Fig 3

Fig 4

computationally via sensitivity analyses and empirically via statistical
models and new experiments in the field or greenhouse.

**2.6 Exotic Plant Spread**

*Lygodium microphyllum* been found on many tree islands in the
Loxahatchee National Wildlife Refuge and has also been found in many
other moist areas along the southeastern coast of Florida. At present
most research, largely funded by the SFWMD's Land Management Unit and
Jonathan Dickinson State Park, has focused on eradication methodologies
(herbicides, fire, root raking and flooding (personal communication Amy
Ferriter, SFWMD and Dick Roberts, Jonathan Dickinson State Park)). In
addition the SFWMD has begun to fund the development of a bio-control
program. The latter work is being conducted by Dr. Robert Pemberton of
the USDA's Agriculture Research Service, Aquatic Weed Research branch,
Davie, Florida. Invasion of tree islands in WCA-2 and WCA-3 by exotic
plant species is the major known threat to the health of these islands,
other than hydrological changes.

The native distribution of *Lygodium microphyllum* is from West Africa
to Tahiti, Although it widely distributed, there is little known about
its life history, i.e., spore dispersal, germination, sporophyte growth
rates, etc. For example it is thought that the fern gametophytes
developing from spores dispersal for long distances may be self
compatible while gametophytes from spores dispersed for short distances
may be self incompatible (personal communication Robert Pemberton).
Nothing is known about how *Lygodium microphyllum* became established on
tree islands in the Loxahatchee National Wildlife Refuge, except that it
became widespread after a major fire. Because of its potential impact on
the tree islands in other WCAs, how *Lygodium* *microphyllum* is
dispersed and becomes established needs to be investigated.

***Method**s*

Spore trapping devices will be positioned on selected tree islands in
WCA-1, WCA-2A and WCA-3A at an increasing distance from known *Lygodium*
infestations. The traps will be serviced once a month. Spores collected
will be identified and enumerated.

Germination requirements of spores collected will be examined using a
5x3x2 factorial experiment with 5 soil moisture treatments; (25%, 50%,
100% of soil field capacity, 1cm and 10 cm inundation), 3 light
treatments; 100%, 50% and 0% light, and 2 nutrient treatments (high and
low N and P). The water potential/water depth treatments with be set up
as outlined in section 2.4.4 b Seed germination.

New sporophytes will be potted in sterile potting soil and their growth
monitored under the same treatments as will be used in the spore
germination study, except that three inundation treatments will be used,
a 20cm treatment will be added. Plant growth will be monitored every two
weeks. Maximum shoot length will be measured and the number of leaves
will be counted. This study is expected to run for about 6 months. At
the end of the study, plants will be harvested and their above and below
ground biomass determined. The number of replicates of each treatment
will be established from preliminary tests, but at a minimum there will
be five replicates of each treatment.

3.0 LOGISTICS

This section covers only work proposed in 1998. Because of very limited
practical experience working on tree islands, these personnel and
airboat needs are preliminary estimates and will undoubtedly need to be
adjusted in some cases. Detailed personnel and airboat needs will be
developed for subsequent years on the basis of practical experience
gained during 1998.

Person Person

Task Hours Days

2.1.1 Literature Review --

Searching data bases for scientific publications 40

Acquisition of scientific publications 40

Locating and acquisition of government reports 40

Unpublished data sets 40

Personal communications 40

Assimilation of Information 120

Synthesis of Information 120

Draft of Review Paper 120

**Total 560 70.0**

Air boat days 0

2.1.2 Zaffke data (7 tree islands)

Review of data 80

Location of zaffke's tree islands \*

Location of Zaffke's transect markers \*\*

Sampling of Zaffke's transects 112

Data entry and analyses 40

Report 40

**Total 272 34.0**

Airboat days 7

\* Completed

\*\* Completed. It was not possible to relocate the transects

5.  Symposium

Organization 80

Symposium 8

Symposium proceedings 384

**Total 472 59**

Airboat days 0

2.2.1 & 2.2.4 Delineating tree islands-topography, peat depth,
vegetation

(9 tree islands)

Field work 432

Data entry 40

Data analyses 40

Report 40

**Total 552 69.0**

Air boat days 27

2.2.2 Peat Stratigraphy

Collection of peat samples 32

Sample analyses 72

Report 32

**Total 136 17.0**

Air boat days 2

2.25 Plant colonization and persistence

2.2.5 a Seed rain

Sorting seeds from litter samples 324

2.2.5 b Seed Banks

(9 islands)

Collection of samples 72

Processing samples 32

Greenhouse work 120

Data entry and analyses 40

Report 40

**Total 628 78.5**

Air boat days 4.5

6.  c Seed dispersal by birds

**Total**

Air boat days

2.3.1 Peat accumulation rates

(9 islands)

Installation of pins and first reading 144

Second reading of pins 24

Installing feldspar marker horizons 40

Marker horizon measurements in field 40

Building litter traps 108

Putting out litter traps 144

Collecting litter traps (6 times) 168

Processing litter traps 64

Report 40

**Total 772 96.5**

Air boat days 23

5.  Nutrient plume studies

(6 islands)

Installation of monitoring wells 96

Collection of water samples (4 time periods) 192

Collection of standing crop 96

Preparation and processing of samples 72

Data entry and analyses 40

Report 32

**Total 528 66.0**

Air boat days 17

2.4.3 b Deer grazing and plant recruitment

(9 islands)

Installation exclosures 144

Monitoring of exclosures 36

**Total 180 22.5**

Air boat days 13.5

**Grand total**

**Person hours/days 4,100 512.5**

**Air boat days 94**

2.  TIME LINE

### TIMETABLE A. Work to be completed over the five year period. 

Task 1998 1999 2000 2001 2002

**2.2 Tree Island Origin and Vegetation**

2.2.1 Island topography and peat depth Jan-June Jan-Jun Jan-Jun Jan-Jun
Jan-Jun

2.2 Peat stratigraphy: collection and analysis Jan-Jul

2.2.4 Delineating tree island boundaries

field sampling May-Sept

data analyses and report writing Sept-Nov

2.2.5 Plant colonization and persistence

2.2.5a Seed bank Mar-Sept Mar-Sept

2.2.5b Seed rain Jun & Dec Jun & Dec Jun & Dec Jun & Dec

2.2.5c Bird dispersal of seeds

**2.3 Tree Island Development and Persistence**

2.3.1 Peat Accumulation Rates

pin installation and measurement Jun & Dec Jun & Dec Jun & Dec Jun & Dec
Jun

litter trap installation and retrieval Jun & Dec Jun & Dec Jun & Dec Jun
& Dec Jun

2.3.2 Tree Growth Mar Mar Mar Mar Mar

2.3.3 Nutrient input by birds Jan-Dec Jan-Dec Jan-Dec Jan-Dec

2.3.4 Nutrient Plume Studies

2.3.4a Nutrients in groundwater Quarterly Quarterly Quarterly Quarterly
Quarterly

2.3.4b Soil and plant nutrients Aug-Sept

### TIMETABLE A Continued

Task 1998 1999 2000 2001 2002

**2.4 Tree Island Creation and Restoration**

2.4.1 Artificial tree islands

design of island modules Mar-Jun

building and testing prototypes Jan-Dec

construction of island modules Jan-Dec

monitoring of island modules Jan-Dec

3.  Restoration of tree islands Jan-July

monitoring restored tree islands Aug-Dec Jan-Dec Jan-Dec Jan-Dec

2.4.3 Enhancing seed dispersal and plant establishment

2.4.3 a Attracting seed dispersing birds Jan-Dec Jan-Dec Jan-Dec

2.4.3 b Deer grazing/plant recruitment Mar/Sept Jan-Dec Jan-Dec Jan-Dec
Jan-Dec

2.4.4 Seed germination and seedling growth

2.4.4 a Seed longevity of major tree species Jan-Dec Jan-Dec Jan-Dec

2.4.4 b Seed germination Jan-Dec Jan-Dec Jan-Dec

2.4.4 c Water depth tolerances Jan-Dec Jan-Dec Jan-Dec

**2.5 Tree Island Model Development** Jan-Dec Jan-Dec Jan-Dec Jan-Dec
Jan-Dec

**2.6 Exotic Plant Spread** Jan-Dec Jan-Dec Jan-Dec Jan-Dec

5.0 REFERENCES CITED

Alexander, T.R. and Crook, A.G. 1974. Recent vegetational changes in
southern Florida. In: P.J. Gleason, (ed.) Environmental of South
Florida: Present and Past. Miami Geological Society, Memoir 2:61-72

Cahoon, D.R., D.J. Reed and J. W. Day, Jr. 1995. Estimating shallow
subsidence in microtidal salt marshes of the southeastern United States:
Kaye and Barghoorn revisited. Marine Geology. 128:1-9.

Costanza, R., F.H. Sklar and M. White. 1990. Modeling coastal landscape
dynamics. Bioscience. 40(2):91‑107.

Davis, J. H. 1943. The natural history of South Florida. Florida
Geological Survey Bulletin No. 25.

Davis, S. M. 1991. Growth, decomposition, and nutrient retention of
*Cladium jamaicense* Crantz and *Typha domingensis* Pers. In the Florida
Everglades. Aquatic Botany 40:2-3-224.

Davis, S. M. 1994. Phosphorus inputs and vegetation sensitivity in the
Everglades. pp. 357-378. In S. M. davis and J. C. Ogden (eds.)
Everglades: The Ecosystem and Its Restoration. St. Lucie Press, Delray
Beach, FL.826pp.

Fenner, M. 1985. Seed Ecology. Chapman and Hall, London.

Evans, C.E. and J.R. Etherington. 1990. The effect of soil water
potential on seed germination of some British plants. New Phytologist
115:539-548.

Evans, C.E. and J.R. Etherington. 1991. The effect of soil water
potential on seedling growth of some British plants. New Phytologist
118:571-579.

Fitz, H.C., E.B. DeBellevue, R. Costanza, R. Boumans, T. Maxwell, L.
Wainger and F.H. Sklar. 1996. Development of a general ecosystem model
for a range of scales and ecosystems. Ecol. Modelling. 88:263-295.

Frederick, P. C. and G. V. N Powell,. 1994. Nutrient transport by wading
birds in the Everglades. Pp 571-584 in Everglades: the ecosystem and its
restoration. (S. M. Davis and J. C. Odgen, eds.) St. Lucie Press, Delray
Beach, Florida.

Gawlik, D. E. and D. A. Rocque. 1998. Avian communities in bayheads,
willowheads, and sawgrass marshes of the central Everglades. Wilson
Bulletin 110:45-55.

Gleason, P. J., A. D. Cohen, H. K. Brooks, P. S. Stone, R. Goodwick, W.
G. Smith and W. Spackman, Jr. 1974. The environmental significance of
holocene sediments from the Everglades and saline tidal plain. IN: P. J.
Gleason (ed.) Environments of South Florida: Present and Past. Miami
Geological Society Memoir 2:287-341.

Gleason, P.J., R.H. Hofstetter, A.D. Cohen, and P.A. Stone. 1977.
Characteristics and peat stratigraphy of tree islands in certain wetland
environments. In, Interdisciplinary Studies of Peat and Coal Origins. A
Symposium. Edited by P.H. Given and A.D. Cohen. Geological Society of
America, Microform Publication No. 7.

Gleason, P.J., D. Piepgras, P.A. Stone, and J. Stipp. 1980. Radiometric
evidence for involvement of floating islands in the formation of Florida
Everglades tree islands. Geology 8:195-199.

Gleason, P.J., Stone, P.A., Goodrick, R., Guerin, G. and Harris, L.
1975. The significance of paleofloral studies an ecological aspects of
floating peat islands to water management in the everglades Conservation
Areas of Central and Southern Florida Flood Control District. Unpub.
Report, Central and Southern Florida Flood Control District. 176 pp.

Grabe, D.F. 1970. Tetrazolium testing handbook for agricultural seeds.
Contribution number 29 to the handbook on seed testing. Tetrazolium
testing committee of the Association of Seed Analysts.

Lindberg, S. E., G. M. Lovett, D. D. Richter, and D. W. Johnson. 1986.
Atmospheric deposition and canopy interactions of major ions in a
forest. Science 1410145.

Loiselle, B. A. and J. G. Blake. 1990. Diets of understory fuit-eating
birds in Costa Rica: seasonality and resource abundance. Studies in
Avian Biology 13:91-103.

Loveless, C.M. 1959. A study of the vegetation of the Florida
Everglades. Ecology 40:1-9.

McPherson, B.F. 1973. Vegetation in relation to water depth in
conservation Area 3, Florida. USGS Open file report #73025

Parker, G. G. 1974. Hydrology of the pre-drainage system of the
Everglades in southern Florida. pp. 18-23. In P. J. Gleason (ed.)
Environments of South Florida. Memoir 2. Miami Geological Society,
Miami, FL.

Powell, G. V. N., J. W. Fourqurean, W. J. Kenworthy, and J. C. Zieman.
1991. Bird colonies cause seagrass enrichment in a subtropical estuary:
observational and experimental evidence. Estuarine, Coastal and Shelf
Science 32:567-579.

Redfield, G. W. 1998. A conceptual basis for quantifying atmospheric
deposition of phosphorus to the South Florida Ecosystem. Unpublished
manuscript.

Schortemeyer, J.L. 1980. An evaluation of water management practices for
optimum wildlife benefits in conservation Area 3A. Florida Game and
Fresh Water Fish Commission.

Sklar, F.H., R. Costanza and J.W. Day, Jr. 1985. Dynamic spatial
simulation modeling of coastal wetland habitat succession. Ecological
Modeling. 29:261‑281.

Stewart, K. K. and W. H. Ornes. 1983. Mineral nutrition of sawgrass
(*Cladium jamaicense* Crantz) in relation to nutrient supply. Aquatic
Botany 16:349-359.

van der Valk, A. G. and T. R. Rosburg. 1997. Seed bank composition along
a phoshorus gradient in the northern Florida Everglades. Wetlands
17:228-236.

Wu, Y., F.H. Sklar and K. Rutchey. 1997. Analysis and simulations of
fragmentation patterns in the Everglades. Ecological. Applications.
7(1):268-276.

Zaffke, M. 1983. Plant communities of water conservation are 3A:
base-line documentation prior to the operation of S-339 and S-340.
Technical Memorandum DRE-164. South Florida Water Management District,
West Palm Beach, FL.

6.0 TREE ISLAND REFERENCES

Central and southern Florida Flood control District. 1971. Some aspects
of the hydrology of conservation area 3A. Staff report. Department of
Engineering

Alexander, T.R. and Crook, A.G. 1974. Recent vegetational changes in
southern Florida. In: Environmental of South Florida: Present and Past
(P.J. Gleason, ed.) Miami Geological Society, Memoir 2:61-72

Davis, J.H. 1943. The natural features of southern Florida. Florida
Geological Bulletin #25. Florida Department of Conservation, Florida
Geological Survey Tallahassee: 311 pp.

Dineen, J.W. 1972. Life in the tenacious Everglades. Central and
Southern Florida Flood Control District. In Depth Report. Vol 1, #5 ,
112pp.

Dineen, J.W. 1974. Examination of water management alternatives in
conservation Area 2A. Central and Southern Florida Flood Control
District. In Depth Report. Vol. 2(3) 11 pp.

Federico, A.C., Milleson, J.F., Millar, P.S. and Rosen, M. 1978.
Environmental Studies in the chandler slough watershed. South Florida
Water Management Tech. Pub. 78-2:120 pp.

Forthman, C.A. 1973. Effects of prescribed burning on sawgrass. MS
Thesis. University of Miami, Caral Gables, Florida.

Gleason, P.J. (ed.) 1974. Environments of south Florida: Present and
past. Miami Geological Society, Memoir 2, Miami

Gleason, P.J., Stone, P.A., Goodrick, R., Guerin, G. and Harris, L.
1975. The significance of paleofloral studies an ecological aspects of
floating peat islands to water management in the everglades Conservation
Areas of Central and Southern Florida Flood Control District. Unpub.
Report, Central and Southern Florida Flood Control District. 176 pp.

Goodrick, R.L. 1984. The wet prairies of the northern Everglades. Pages
185-189 in: Environments of south Florida, Present and past, P.J.
Gleason, ed. Miami Geological Society Caral Gables.

Gunderson, L.H. 1989. Historical hydropatterns in wetland communities of
Everglades national Park. Pages 1099-111 in: Freshwater Wetlands and
Wildlife, DOE Symposium Series No. 61, R.R. Sharitz and J.W. Gibbons,
eds. WSDOE Office of Scientific and Techinical Information, Oak Ridge.

Harms, W.R., Hooks, D.D., Brown, C.L., Kormani, P.P., Schultz, R.P.,
White, E.H. an Schrender, H.T. 1974. Examination of the trees in Rodman
Reservoir during October-November 1972. Final Environmental Statement
proposal for Oklawaha River, Ocala National Forest, Florida. U.S.
Department Agricultural an Forestry Service. EIS-FL-73-0075-F-1:pp 33-78

Harshberger, J.W. 1914. The vegetation of south Florida, south of 27,31'
north, exclusive of the Florida Keys. Transactions, Wagner Free
Institute of Science.

Higer, A.L. and M.C. Kolipinski. 1990. Changes of vegetation in Shark
River slough, Everglades National Park, 1940-64. Wetlands Symposium,
INIREB, Tabasco, Mexico.

Hilsenbeck, C.E., R.H. Hofstetter, and T.R. Alexander, 1979. Preliminary
synopsis of major plant communities in the East Everglades area:
vegetation map supplement. Unpublished Department of Biology, University
of Miami, Coral Gables, Florida

Hofstetter, R.H. 1973. South Florida ecological study. Appendix K.
Effects of fire in the ecosystem of southern Florida. An ecological
study of the effects of fire on the wet prairie, sawgrass glades and
pineland communities. U.S. Department Interior, National Park Service
Report No. DI-SFEP-74-09. 145pp.

Hofstetter, R.H. 1974. The ecological role of fire in southern Florida.
Florida naturalist 47:2-9

Leach, S.D., Klein, S.D. and Hampton, E.R. 1972. Hydrologic effects of
water control an management of southeastern Florida. United States
Department of Interior, Geological Survey, Water Resources Division,
Tallahassee, Florida, Report Investigations #60 pp. 1-115

Lin, S., Love, J., and Marban, J. 1984. Meteorological and hydrological
analysis of the 1980-1982 drought. Tech. Publication 84-7, June 1984.
South Florida Water management District

Loveless, C.M. 1959. A study of the vegetation in the florida
Everglades. Ecology, Vol 40, #1

Lowe. E.F. 1986. The relationship between hydrology and vegetational
pattern within the floodplain marsh of a subtropical, Florida lake.
Florida Scientist 49(4):213-233.

McPherson, B.F. 1973. Vegetation in relation to water depth in
conservation Area 3, Florida. USGS Open file report #73025

Parker, G.G. 1974. Hydrology of the pre-drainage system of the
Everglades in southern Florida. Pages 18-27 in Environments of South
Florida: Present and Past, P.J. Gleason, ed. Miami Geological Society
Memoir 2, Miami.

Robertson, W.B. 1954. Everglades fires, past, present, and future.
Everglades Natural History 1:9-16

Schomer, N.S. and R.D. Drew. 1982. An ecological characterization of the
Lower Everglades, Florida Bay and Florid Keys. U.S. fish and Wildlife
Service, Office of Biological Services, Washington, D.C. FWS/OBS-82/58.1
246 pp.

Stewart, K.K. 1974. Physiological edaphic an environmental
characteristics of Everglades sawgrass communities in environments of
south Florida Present and Past, Mem. 2, Miami Geological Society Miami
Florida.

Steward, K.K. and Ornes, W.H. 1975. The autecology of sawgrass in the
Florida Everglades. Ecology 56:162-171.

Stone, P.A. 1978. Floating islands - Biogeomorphic features of Hillsboro
Marsh, Northeastern Everglades, Florida. M.A. Thesis, Florida Atlantic
University, Boca Raton, Florida.

Thomas, T.M. 1974. A detailed analysis of climatological and
hydrological records of south Florida with reference to man's influence
upon ecosystem evolution. Pages 82-122 in Environments of south Florida:
Present and past, P.J. Gleason ed. Miami Geological Society Memoir 2,
Miami.

VanArman, J. and Goodrick, R. 1979. Effects of fire on a Kissimmee River
Marsh. Florida Scientist, vol. 42, No. 4. Pg. 183-195.