Report SFRC-86/09 

Long Term Recovery of I Experimental Of fmRoad Vehicle 

Impacts and Abandoned Old I Trails in the Big Cypress National Preserve 

Everglades National Park, South Florida Research Center, PO. Box 279, Homestead, Florida 33030 
LONG TERM RECOVERY OF 

EXPERIMENTAL OFF-ROAD VEHICLE IMPACTS 

AND ABANDONED OLD TRAILS IN THE 

BIG CYPRESS NATIONAL PRESERVE 

Report SFRC-86/09 

Michael J. Duever , Lawrence A. Riopel le , and Jean M. McCollom 

Ecosys tan Research Uni t 

National Audubon Society 

Route 6, Box 1877 

Naples, FL 33964 

NATIONAL PARK SERVICE 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Contract No. CX 5280-5-2106 
TABLE OF CONTENTS 

LIST OF TABLES ....................................................... ii 

LIST OF FIGURES ...................................................... iv 

ABSTRACT .............................................................. 1 

INTRODUCTION .. ....................*...... 1 

METHODS ................................................................ 3 

Field and Laboratory Methods ...................................... 4 

Data Analyses ..................................................... 5 

~efinition of Impact Levels ....................................... 6 

Experimental Lanes ............................................ 6 

Old Trails .................................................... 8 

RESULTS AND DISCUSSION . EXPERIMENTAL LANES .......................... 8 

Condition of ~xperimental Plots in 1985 ........................... 8 

Small Cypress ................................................. 8 

Wheeled Vehicle Marl Marsh .................................... 10 

Sand Marsh .................................................... 10 

Pine ......................,................................... 10 

Airboat and Track Vehicle Marl Marsh .......................... 10 

Airboat and Track Vehicle Peat Marsh. ......................... 11 

Camparison of Vehicle ~ypes ....................................... 11 

Ccmplete Recovery of Lanes ........................................ 13 

One Pass Impacts .............................................. 13 

Medium Impacts ................................................ 15 

Heavy Impacts ................................................. 15 

Interpretation of Complete Recovery ........................... 15 

Statistically Recovered Lanes ..................................... 18 

Late Winter 1979 .............................................. 18 

Fall 1979 ..................................................... 21 

Fall 1985 ..................................................... 21 

Interpretation of Statistical Recovery ........................ 23 

Analysis of ~axonomic Differences ................................. 23 

RESULTS AND DISCUSSION - OLD TRAILS ................................... 26 

Statistically Recovered Trails .................................... 32 

Percent Recovery of Trails ..................................... 34 

Analysis of Taxonomic Differences ................................. 38 

CONCLUSIONS ........................................................... 42 

Experimental . Lanes ................................................ 42 

Old Trails ...................................................... 45 

General Coanments .................................................. 45 

LITERATURE CITED ...................................................... 47 
LIST OF TABLES 

Table 

1. The total number of experimental lanes at each impact 

level in each habitat. These totals were the basis for 

determining the percentages of recovered lanes in 

Figures 1-6 and for all other analyses presented in this 

report. Appendix E can be consulted to see which 

treatments were excluded and why ............................... 9 

2. Number and percentage of parameter - habitat 

combinations when a particular wheeled vehicle type had 

a distinctly higher (+) or lower (-) number of replicate 

lanes that had recovered as compared to other wheeled 

vehicle types. The more positive the nwlber, the 

greater the recovery from impacts created by that 

vehicle type .................................................. .12 

3. Total number of lowst, second lowst, and third lowst 

ranked habitats according to their degree of recovery 

(i.e. smallest percentage of lanes not significantly 

different from controls) for each parameter during each 

sampling period at each impact level based on their 

relative position along the vertical bars in Figures 4-6.......24 

4. Total number (by sampling period) of the three lowst 

ranked habitats according to their degree of recovery 

(i.e. smallest percentage of lanes not significantly 

different from controls) for each parameter at each 

impact level 'based on their relative position along the 

vertical bars in Figures 4-6. This table is similar to 

Table 3 except (1) numbers of the three lowest ranked 

habitats are smed and (2) these numbers and the 

percentage each is of their total possible occurrences 

are shown by individual sampling peri od........................ 25 

5. Nwlber of sample plots in which each taxon was present 

during fall 1985 in the unrecovered lanes and associated 

controls at the small cypress experimental test sites..........27 

6. Number of sample plots in which each taxon was present 

during fall 1985 in the unrecovered lanes and associated 

controls at the wheeled vehicle marl marsh experimental 

test sites.. ...................,.,............................. 29 

7. Number of sample plots in which each taxon was present 

during fall 1985 in the unrecovered lanes and associated 

controls at the pine experimental test site .................... 30 
Table Page 

8. Number of sample plots in which each taxon was present 

during fall 1985 in the unrecovered lanes and associated 

controls at the airboat-track vehicle marl marsh and 

peat marsh experimental test sites.. .......................... .31 

9. Number of replicate old trail plots where the trail 

parameter values had statistically recovered (i.e. ere 

not significantly different from the control values) at 

0, 1, and 7 years after abandonment (Appendix D) ............... 33 

10. Minimum and maximm percent recovery for replicate old 

trail plots in each habitat at 0, 1, and 7 years after 

abandomnt (See Appendix D for the individual 

percentages). The control value would represent 100% 

reovery .......................................................37 

11. Number of sample plots in which each taxon was present 

during 1985 at the small cypress old trail sites............ ... 39 

12. Number of sample plots in which each taxon was present 

during 1985 at the marl marsh old trail sites..................40 

13. Number of sample plots in which each taxon was present 

during 1985 at the large cypress old trail sites.. ............. 40 

14. Number of sample plots in which each taxon was present 

during 1985 at the pine old trail sites........................41 

15. Number of sample plots in which each taxon was present 

during 1985 at the sand marsh old trail site...................43 

16. Number of sample plots in which each taxon was present 

during 1985 at the hamnock old trail sites........... .......... 43 
LIST OF FIGURES 

Figure 

1. Percent of experimental one pass lanes that had 

recovered ( i .e. were no longer visible) ....................... .14 

2. Percent of experimental medium impact lanes that had 

recovered (i .e. were no longer visible) ................... ,. .. .16 

3. Percent of experimental heavy impact lanes that had 

recovered (i .e. were no longer visible) ....................... .1.7 

4. Percentages of one pass experimental lanes in the 

different habitats that had recovered (i.e. were not 

significantly different from the controls) at 0, 1, and 

7 years after the lanes were created. Vertical bars 

indicate ranges of percentages of all habitats for which 

data are available for each sampling period. Dashes 

identify the percentage for each habitat. See Table 1 

for a key to the numbers used to identify each habitat.........l9 

5. Percentages of medium impact experimental lanes in the 

different habitats that had recovered (i.e. were not 

significantly different from the controls) at 0, 1, and 

7 pars after the lanes were created. Vertical bars 

indicate ranges of percentages of all habitats for which 

data are available for each sampling period. Dashes 

identify the percentage for each habitat. See Table 1 

for a key to the numbers used to identify each habitat.........20 

6. ' Percentages of heavy impact experimental lanes in the 

different habitats that had recovered (i.e. were not 

significantly different from the controls) at 0, 1, and 

7 years after the lanes were created. Vertical bars 

indicate ranges of percentages of all habitats for which 

data are available for each sampling period. Dashes 

identify the percentage for each habitat. See Table 1 

for a key to the numbers used to identify each habitat.........22 

7. Percents of old trail parameters showing recovery 

(i.e. not significantly different from controls) for all 

habitats combined.. ............................................ 35 

8. Percents of old trails recovered (i.e. not significantly 

different from controls) for all parameters combined...........36 
identical to those used in 1979. One major change was the number of 

replicate samples collected in each experimental lane, each old trail, 

and each set of site control samples. In 1985, measurements were taken 

at 10 locations for visual rating, rut depth, and ridge height, and in 6 

plots for soil compressive strength and the vegetation and litter 

parameters, as compared to 30 and 3 measurements, respectively, in 1979. 

Field and Laboratory Methods 

The visual rating system used in 1985 was the same as that used in fall 

1979. A "0" rating indicated we could not see any differences between 

the appearance of the test lane and adjacent habitat at that particular 

location. Thus, a lane could be visible, but still have all "O" ratings 

in the locations where we measured than. A "1" indicated the lane was 

visible but there was no soil disturbance and very little difference in 

the appearance of vegetation in the lane as compared to adjacent 

undisturbed habitat. A "2" indicated that up to one half of the 

vegetation was missing in the trail and there could be some soil 

disturbance. A "3" was used when more than one half the vegetation was 

missing and there was moderate soil disturbance. A "4" indicated no 

vegetation in the trail and moderate to severe soil disturbance. 

Three methods were used to measure rut depth and ridge height depending 

on water levels and wid,h of the lane. If there was standing water, the 

water surface was used as a level from which we measured the distance 

down to the undisturbed soil surface and the centers of the rut and 

ridge. Ridge height and rut depth were the differences between the 

distances to the undisturbed soil surface and the centers of the ridge 

and the rut, respectively. In the narrower lanes in tl~e test plots 

without standing water we placed a 1 m board horizontally across the 

ridge top and measured the distance to the rut and adjacent undisturbed 

habitat. We then used the distance to undisturbed soil as ridge height 

and subtracted that distance from the rut reading to arrive at rut depth. 

In the old trail plots and experimental test lanes that were too wide to 

lay a 1 m long board across, we used a 2.5 powr hand level, with a tape 

measure as a level rod, to measure relative elevations of the rut, ridge, 

and adjacent undisturbed habitat. 

Vegetation was sampled in six 10 by 100 an plots in each test lane and 

old trail. A total of six controls per site were sampled in adjoining 

undisturbed habitat. The individual plots were randomly selected and 

delimited by narrow boards held in place by removable pins at the 

corners. Average height of the vegetation was then measured, percent 

cover estimated, and all plant taxa noted. A rating system was used to 

indicate relative abundance of plant taxa. "Occasional" was used when 

one to just a few plants of a taxon were found in the plot. "Gammon" 

indicated that stecns of that taxon ere numerous but did not dominate the 

sample. "Abundant" was used when one or more taxa clearly dominated the 

sample. In addition, comn was restricted to plots with more than 10 

percent cover and abundant could be used only when percent cover was 

greater than 40 percent. Although some of the more distinctive plants 
could be identified to genus, the lack of key characters on many 

individuals frequently made identification to genus impossible. As a 

result, we developed a nomenclature designed to zllow us to pick out 

major differences in abundance ef taxa in 13ne or trail samples as 

compared to control samples. All live aboveground vegetation and 

standing litter were then removed and placed in separate bags which were 

dried for at least 24 hours at 105 C. The samples were then removed fran 

the oven, allow4 to stand for one half hour to stabilize moisture 

content, and then weighed. 

Soil compressive strength was measured with a Soil Test Inc. Model CL 700 

penetrometer in the same plots as the vegetation. It was necessary to 

use different methods in different habitats depending on their soil 

characteristics. In the small cypress and wheeled vehicle marl marsh 

sites we measured the force required to push a penetrometer rod to a soil 

depth just short of bedrock. This was possible because of a slight 

crunching feel to the rod just before bedrock was reached. In the pine 

and the airboat and track vehicle plots, bedrock was not consistently 

near enough to the surface to use this method, so we measured the force 

needed to push the penetrometer rod 6 an into the soil. In the pine this 

worked well, but in the very loose marl and peat of the airboat and track 

vehicle plots the rod sometimes went deeper than 6 cm from its own 

weight. AS an alternative, in these habitats we dropped a 91.5 an long, 

0.6 an diameter steel rod from approximately 1.7 m and measured its depth 

of penetration into the soil. Since interpretation of the results was 

based solely on differences or lack of differences between impacted and 

control lanes within each plot, the variations in the methods used at 

different sites did not affect the outccxne of our analyses. 

Data Analvses 

While conducting the fall 1985 data analyses, we became aware of a number 

of discrepancies between this data set and those from 1978-79. As a 

result we went back to our original field notes and identified a number 

of errors in the data included in the 1981 report. This was a particular 

problem with the rut depth data. Thus, we have incorporated in the 

appendices to this report all of the corrected 1978 and 1979 data, as 

well as the 1985 data. For the experimental plot data, these include 

average values (Appendix A), percent recovery (Appendix B), and Duncan's 

new multiple range test results (Apndix C). Appendix D provides 

similar data for the old trails. 

Statistical analyses of the experimental test plots utilized the Duncan's 

new multiple range test. The Duncan's analyses for the 1985 data were 

done using the SAS ANOVA procedure (SAS Institute Inc. 1985), while the 

Duncan's analyses of the earlier data were done using the SAS GLM 

procedure (SAS Institute Inc. 1979). These analyses allowed us to 

determine which vehicle type - impact level combinations were 

significantly more or less impactj.ny as compared to each of the other 

combinations. However, we only compared data from an individual sampling 

period for all vehicle types at all impact levels within a single 
replicate plot. No statistical comparisons were made of any vehicle type 

impact level combinations between either replicate plots or sampling 

periods . 

Statistical differences between the old trail samples and their adjacent 

controls were determined using the non-paired T-test. 

Probability levels were always 0.05 for both the Duncan's new multiple 

range test and the T-test analyses. 

Definition of ImDact Levels 

Experimental Lanes 

In our 1981 report, we included a figure showing the number of runs 

required to achieve medium and heavy levels of impact in the major Big 

Cypress National Preserve habitats by the different types of ORVs used in 

the preserve. The figure showed the number of runs on a logarithmic 

scale so that all of the data would fit on one figure. While this format 

was useful for 'showing the relative number of runs needed to create 

certain levels of impact by different vehicles in different habitats, it 

was difficult to precisely determine the actual number of passes required 

to create these impacts. This was a particular problem where only a 

smll number of passes were made. Because this information was so 

important to our data analyses, we have reproduced this figure with the 

number of runs on an arithmetic scale to make it easier to see the exact 

number of runsamade by each vehicle. This required dividing the original 

figure into seven separate figures, which are here included as 

Appendix E. 

One important aspect of these data was that some runs were not made or 

achieved for a variety of reasons (Appendix F). 

(1) Some vehicles became stuck where they could not maintain 

traction on slippery substrates, such as marl or organic soils. These 

conditions normally occurred where either rock or sand was not near the 

ground surface and there was only sparse vegetation. This was 

particularly true of the smooth-tire buggy in both small cypress and marl 

marsh habitats. Swanp buggies typically do not operate in the extensive 

Everglades peat marshes for these reasons, and the water there is 

frequently too deep for three wheel all terrain cycles (ATCs) to operate 

effectively. 

(2) Certain habitats are too destructive of vehicles or just too 

uncomfortable to drive through frequently. Pine rockland with a dense 

understory of palmetto is an example of a habitat through which vehicles 

can drive cross country, but which are normally traversed along 

established trails to avoid vehicle damage and an extremely rough ride. 

(3) Although attempted, some vehicles were not able to create heavy 

impacts in some habitats. These treatments are indicated in the 
Apndix E figures by the broken bars. ATCs were unable to create heavy 

impacts in two of the three marl marsh and sand marsh habitats, or in any 

of the pine plots. Swamp buggies were unable to create heavy impacts in 

two of the three sand marsh and pine habitats, and several buggies were 

unable to create heavy impacts in one marl marsh site. Airboats were 

unable to create heavy impacts in either marl or peat marshes. The 

reasons for an inability to create heavy impacts ere a function of lack 

of impacting ability of the vehicle in the case of the airboat and AX, 

and relative insensitivity of the substrate at certain sites, such as the 

rock substrate in the pineland and one marl marsh site and the sand 

substrate in the sand marsh. 

There were a variety of reasons for why different numbers of passes were 

attmpted when we were unable to achieve a heavy impact. At a minimum, 

we made twice as many passes as was required to produce a medium level of 

impact by the same vehicle in the same replicate plot. With the 

airboats, we made almost six tims as many passes because it was the 

first vehicle tested and we wanted to be very certain we were not going 

to be able to create a heavy impact. At one of the wheeled vehicle marl 

marsh sites, an ATC required 2.6 tims as many passes to make a heavy 

impact as it did to make a medium impact. At the other two marl marsh 

sites, we stopped making passes in the ATC heavy impact lanes at 2.5 

times the number required to make a medium impact. However, at this 

point we had made 100 passes in each lane and it still appeared to be far 

from heavily impact&. In thirteen of the other situations where heavy 

impacts were not achieved, we made 2.85 - 4 times as many passes as it 

took to make the medium impacts before we quit. Among the remaining 

three treatments, from 2 - 2.6 times as many passes were made as in the 

medium impact lanes. In these instances, we did not have sufficient tim 

to make additional passes with a rented buggy, and the lanes were still 

far from being heavily impacted. 

(4) Sane possible treatments were not made when the one pass 

treatment also turned out to represent the medium impact level. This was 

the case for three of the buggies in all three of the small cypress 

plots, for the light buggy in one of the small cypress plots, for the 

tractor buggy in two of the three marl marsh plots, and for the track 

vehicle in all of the marl marsh plots. 

Interpretation of the study results requires a clear understanding of how 

we defined the impact levels we actually achieved. The study design 

allowed us to compare relative impacts of and recovery £ran one pass by 

almost all vehicle types in all major preserve habitats. It was the only 

impact level involving an equal number of passes in each habitat. The 

study design also allowed us to assess the number of passes required to 

make a certain level of impact and the recovery from these impacts. 

Since the medium impact tests were stopped when severe vegetation damage 

was achieved, by definition we also have to include in our medium impact 

analyses those tests where a medium impact was achieved with only one 

pass. Similarly, where heavy impacts were never achieved, even though 

they were attempted, these attempts cannot fairly be included within the 

analysis of heavy impacts. Thus, our analyses discuss (1) all one pass 
treatments as one pass treatments; (2) all medium impact treatments, and 

some one pass treatments which caused severe vegetation damage but little 

or no soil disturbance, as medium impact treatments; and (3) only those 

'heavy impact treatments which actually caused severe soil disturbance as 

heavy impact treatments (Table 1). All of the analyses in this report 

are based on these definitions of impact levels. This includes the 

analyses of the 1979 data as well as the 1985 data. 

Old Trails 

The old trails we selected for the recovery study were characteristically 

the most impact4 examples of trails through each habitat. Howver, none 

were included which had been "improved" by the addition of fill. 

Unfortunately, there was no clear documentation on when, why, or how the 

old trails used in our study were originally created. Although all were 

used by ORV's at the ti= this study began, a number of them, and 

possibly all, were not simply a product of ORV use. Just as w did not 

attempt to create experimental lanes in more than sparsely forested 

habitats, it is unlikely that ORV's initiate old trails through the large 

and smll cypress forests, hardwood harrtnocks, and some pine forest sites. 

The origin of these types of trails has been associated with a variety of 

activities in the Big Cypress Swamp. These include providing access to 

camps, and comercial a,ztivities such as oil and gas exploration, 

logging, agriculture, and land surveys. Cut stumps along many of these 

trails clearly indicate that large trees had to be removed before ORV's 

were able to pass. In addition, bulldozers were used to clear trails 

through portions of the Big Cypress in the past. However, the old trails 

monitored for recovery in our study were specifically selected because 

they had not been creatsd with heavy equipment. 

RESULTS AND DISCUSSION - EXPERIMENTAL LANES 

Condition of Experimental Plots in 1985 

Small Cypress 

When the test lanes were initially established, compass bearings were 

recorded for the base line from which the lanes began and for each test 

lane. When searching for lanes in 1985, it was often possible to locate 

the more obvious sections of a lane by using the original ground photos 

and compass bearings. This technique was not possible in the smll 

cypress sites because of the need for test vehicles to maneuver around 

trees in the plots. The small cypress habitat also seems to be a 

favorite area for hogs, and their extensive rooting destroyed many 

sections of test lanes or the adjacent control areas. Howver, in some 

lanes there was still much less vegetation in the trail as compared to 

the adjacent control areas, and ruts were still obvious. 
Table 1. The total number of experimental lanes at each impact level in 

each habitat. These totals were the basis for determining the 

percentages of recovered lanes in Figures 1-6 and for all other 

analyses presented in this report. Amendix F can be consulted 

to see which treatments were excluded and why. 

Habitat Total Number of Lanes 

Code One Med i urn Heavy 

Number Habitat- Pass Impact impact 

1 Small Cypress 15 

2 wheeled Vehicle Marl Marsh 14 

3 Sand Marsh (1985) 18 (9) 

4 Pine 18 

5 Airboat Marl Marsh 3 

6 Airboat Peat Marsh 3 

7 Track Vehicle Marl Marsh 3 

8 Track Vehicle Peat Marsh 3 
Wheeled Vehicle Marl Marsh 

Marl Marsh 1 was completely recovered probably because it was the driest 

.site when the lanes were created and bedrock is at the surface over much 

of the site. The ridges and furrows which remained from farming during 

the 1950's are still evident in Marl Marsh 3, and during 1985 the test 

lanes were often more obvious in the lowsr and wetter furrows. Width of 

the tire on the various test vehicles influenced the visual ratings 

because, the narroer the tire and thus the lane, the more the adjacent 

vegetation was able to camouflage the track. 

Sand Marsh 

None of the three Sand Marsh plots were sampled in 1985. Two had been 

destroyed and one had completely recovered. Sand Marsh 1 had been 

heavily grazed which masked any potential vegetation differences, and the 

ground had been trampled which obliterated any ruts that might otherwise 

have been present. A new gate in the fence along the baseline of Sand 

Marsh 2 resulted in enough ORV traffic to destroy most of the test lanes 

at this site. Only two lanes, AX and tractor heavy, were relatively 

unimpacted and *no trace of either was found. Sand Marsh 3 was unimpacted 

but no lanes remained, possibly because this was the driest of the three 

sand marsh sites when the lanes were created. 

Pine 

Pine 1 and 2 had completely recovered by 1985, but four lanes in Pine 3 

were found. This was the wettest of the three sites when the lanes were 

originally created, and had the deepest ruts. No vegetation impacts were 

still present in three of the lanes which were located only because the 

rut was still visible. The chain buggy heavy impact lane was not found 

largely because most of the run was across palmettos which minimized 

impacts to the soil surface. The ATC heavy impact lane was found due to 

an almost total lack of small pines in the trail. At the time of the 

initial tests, there were numerous pine seedlings in the area and these 

were killed by the repeated passes made in our unsuccessful attempt to 

create an AX heavy impact. With the wide swath that an AX makes, the 

absence of these pines was more obvious here than in the buggy lanes. 

The remaining small pines in the plot were killed by a fire in the fall 

of 1984 so this effect will disappear shortly. The ATC heavy impact lane 

was not found in 1979, possibly because the pine seedlings were not yet 

tall enough to be obvious by their absence from the lane. 

Airboat and Track Vehicle Marl Marsh 

In 1985 we found only the track vehicle heavy impact lanes at these three 

sites. There were no obvious vegetation differences between the lanes 

and adjacent undisturbed habitat, but ruts were still evident along the 

entire length of the lanes. 
Airboat and Track Vehicle Peat Marsh 

The track vehicle heavy impact lane in Peat Marsh 2 was the only lane we 

found in this habitat during 1985. Searchinq for the test lanes was 

hampered by the tall, thick sawgrass that characterizes this habitat. 

One researcher walked along in the sawgrass perpendicular to the test 

lanes, while the other walked in the shorter vegetation along the 

baseline telling the first when they should both be in a test lane. The 

individual in the sawgrass would then check for any evidence of 

vegetation impacts or ruts well to either side of the lane center. It 

proved quite difficult to obtain accurate samples of standing litter in 

the peat marshes because the dead stems of the dominant vegetation, 

sawgrass, frequently broke off when we were setting up the sample plots. 

Comparison of Vehicle Types 

In conducting the recovery analyses we attempted several approaches to 

evaluate which of the vehicles had shown more or less recovery. A 

strictly quantitative comparison was impossible because of (1) the 

variability of environmental characteristics among the replicates of each 

habitat and between habitats; (2) the several months that it took to 

complete all of the tests; and (3) the inability of some vehicles to 

either operate in sane habitats or make the desired impacts. The 

following analysis comparing the types of wheeled vehicles, although not 

as rigorous as might be desired, does provide an objective comparison 

that sheds some light on the topic. 

The analysis involved first determining individually for each combination 

of paramter and habitat, the total number of recovered lanes among the 

three replicate plots for each type of wheeled vehicle at each impact 

level within each sampling period. These results were based on the 

Duncan's new multiple range test tables in Amndix C. The medium impact 

data in these tables were supplemented by data from the one pass 

treatments where a medium impact had been achieved with only one pass by 

that vehicle in that replicate plot (see Appendix F). For each parameter 

evaluated, recovered lanes included those which had completely recovered 

(R) and those for which the parameter values were not significantly 

different from the control values, i.e. they had statistically recovered. 

Next, we compared these total numbers of recovered lanes among the 

various vehicle types within each impact level and sampling period. If a 

particular vehicle type had a distinctly higher or lowr nlrmber of 

recovered replicate lanes relative to the other vehicles, we tallied a +1 

or -1, respectively, for that vehicle. This was done individually for 

each parameter in each habitat. Then within each impact level for each 

year, we totalled the number of +l's and the number of -1's for each 

vehicle type (Table 2). 

As we reported in 1981, recovery from ATC impacts was slightly better and 

recovery from the tractor buggy impacts was slightly poorer than was 

recovery from impacts made by any of the other wheeled vehicles (Table 

2). For the ATC, the relatively better recovery was more pronounced at 
Table 2. Number and percentage of parameter - habitat combinations when a particular wheeled vehicle 

type had a distinctly higher (+) or lowsr (-) number of replicate lanes that had recovered as 

compared to other wheeled vehicle types. The more positive the number, the greater the 

recovery from impacts created by that vehicle type. 

--- - 

Higher Number Lowr Number Number of Possible 

of Recovered of Recovered Parameter - Habitat Net Distinctly 

Replicates Rep1 i ca tes - Combinations Different 

Winter Fall Fall Winter Fall Fall Winter Fall Fall Total Number Percent 

1979 1979 1985 1979 1979 1985 1979 1979 1985 

One Pass 

ATC +2 +7 0 000 20 30 33 83 +9 11 

Light +1 0 0 000 20 30 33 83 +1 1 

Smooth 0 0 0 000 10 14 16 40 0 0 

P 

Chain 000 0 0 0 20 30 33 83 0 0 

w Tractor 000 -1 -3 0 20 30 33 83 -4 - 5 

Heavy 000 -1 0 0 20 30 33 83 -1 -1 

Medium Impact 

ATC +3 +5 0 000 20 30 33 83 +8 10 

Light +1 +1 0 000 15 23 24 62 +2 3 

S~moth 000 -2 -1 0 10 14 16 40 -3 -8 

Chain +1 0 0 -1 0 0 20 30 33 83 0 0 

Tractor +1 0 0 -1 -2 0 15 23 24 62 -2 -3 

Heavy 000 0 -2 0 15 23 24 62 -2 -3 

Heavy Impact 

ATC 0 0 +1 000 15 23 24 62 +1 2 

Light 000 0 0 -1 15 23 24 62 -1 i2 

Srrrooth 000 000 10 14 16 40 0 0 

Chain +1 0 +2 -1 -3 0 20 30 33 83 -1 -1 

Tractor 000 -1 -3 0 15 23 24 62 - 4 -6 

Heavy 000 0 0 -2 15 23 24 62 -2 -3 
the one pass and medium levels of impact. This was at least partially 

because this vehicle was only able to create heavy impacts in 5 of the 12 

possible lanes, and it was difficult to detect distinctly better recovery 

with only one replicate plot in a habitat type. There was little 

difference among impact levels in the relatively poorer recovery of the 

tractor buggy lanes. None of these differences were associated with any 

particular parameter or habitat. However, they were most pronounced one 

year after, and least pronounced seven years after the impacts were made. 

Considering the large n-r of possible instances when a vehicle could 

have been distinctly more or less impacting than the other wheeled 

vehicles, the smll number of instances we found in this analysis 

suggests that there are only relatively minor differences in recovery 

rates of impacts produced by the various types of wheeled vehicles (Table 

2). 

Because of differences in habitat characteristics between the wheeled 

vehicle and airboat - track vehicle test sites, it was impossible to make 

any realistic comparisons of impact recovery between airboats or track 

vehicles and any of the individual types of wheeled vehicles. However, 

the following analyses do compare recovery from airboat and track vehicle 

impacts with that from the wheeled vehicles as a group. 

Complete Recovery of Lanes 

The clearest statement about recovery of an experimental test lane could 

be made when we knew exactly where the lane was and still could not find 

any trace of it. Using this criterion, we analyzed the 1978-79 and 1985 

data (Appendix A) separately for the one pass, medium impact, and heavy 

impact levels. 

One Pass Impacts 

Wng the one pass lanes, only the airboat impacts had completely 

disappeared between when they were made in fall 1978 and the first 

sampling period in late winter 1979 (Figure 1) . None of the track 

vehicle one pass lanes had disappeared within this same period. The only 

wheeled vehicle habitat where all of the one pass lanes were still 

visible in late winter 1979 was the smll cypress, although almost all of 

them were still visible at this time in the marl marsh and pine plots. 

Of the habitats where wheeled vehicles were tested, the sand marsh shod 

the highest percentage of completely recovered one pass lanes. 

In addition to the airboat one pass lanes, at the end of one full year 

following the creation of the experimental lanes, the sand marsh, pine, 

and track vehicle peat marsh one pass lanes had disappeared. All of the 

track vehicle marl marsh one pass lanes were still visible. 

Awroximately 40 to 50 percent of the smll cypress and wheeled vehicle 

marl marsh one pass lanes had completely recovered by this ti=. 

By fall 1985 all one pass lanes, except for one in the small cypress, had 

disappeared. 
WHEELED VEHICLES AIRBOAT TRACK VEHICLE 

SMALL MARL SAND MARL PEAT MARL PEAT 

CYPRESS MARSH MARSH PINE MARSH MARSH MARSH MARSH 

0 17 01 7 01 7 01 7 017 017 017 01 7 

YEARS SINCE IMPACTS 

Figure 1. Percent of experimental one pass lanes that had recovered (i.e. no longer visible). 
Medium Impacts 

Among the medium impact lanes, the airboat marl marsh lanes had 

disappeared by late winter 1979, but all others were visible (Figure 2). 

In fall 1979 all of the track vehicle marl and peat marsh and the wheeled 

vehicle marl marsh lanes were still visible. Only 20 percent of the 

small cypress lanes had disappeared within one year, but in sand marsh, 

pine, and airboat peat marsh habitats between 40 and 70 percent of the 

lanes had completely recovered within this period. 

By fall 1985 all of the medium impact lanes in the airboat and track 

vehicle habitats had disappeared, while a few lanes were still visible in 

most of the wheeled vehicle habitats. The sand marsh data indicated that 

all lanes in this habitat had disappeared. However, one of the sand 

marsh replicate plots had been completely and another partially destroyed 

since 1979, and it is possible that a few of the lanes in the destroyed 

plots might have been found in 1985. This possibility is enhanced by the 

fact that the plot which was destroyed was originally the most impacted 

and the one which remained was the least impacted of the sand marsh 

sites. 

Heavy Impacts 

Few of the heavy impact lanes in any habitat had disappeared during this 

study, even by fall 1985 (Figure 3). It seems clear that once severe 

soil disturbance occurs, it takes a very long time for those tracks to 

disappear. These impacts are most likely to be a major management 

problem in the small cypress and marl marsh habitats where heavy impacts 

were created with a variety of vehicle types, some with a relatively 

srnall number of passes. The problem of heavy impacts in pine, sand 

marsh, and peat marsh habitats appears to be less significant, since we 

found it difficult to create severe soil disturbance in several of their 

replicate plots or a fairly large number of passes was required to create 

them. However, ruts can obviously be created in these habitats with 

sufficiently frequent use as evidenced by the existence of old trails in 

these habitats. 

Interpretation of Complete Recovery 

Airboat lanes recovered more quickly than those produced by any other 

vehicle type. This is because during normal operation airboats are not 

in contact with the ground, and frequently are in water deep enough so 

that the vegetation is merely bent over and shortly thereafter pops back 

up again, particularly in one pass lanes. In the medium impact tests the 

number of runs was sufficient to severely batter the vegetation and 

eliminate the associated litter in the peat marsh. These impacts were 

visible for over a year following the creation of the impacts. In the 

marl marsh habitat the vegetation was sparse and short enough that the 

airboats were unable to produce any lasting impacts. We never were able 

to produce severe soil disturbance with an airboat. Nevertheless, 

existing airboat old trails do show evidence of ruts. This is probably 
WHEELED VEHICLES AIRBOAT TRACK VEHICLE 

0 17 01 7 01 7 017 017 017 017 01 7 

YEARS SINCE IMPACTS 

Figure 2. Percent of experimental medium impact lanes that had recovered (i.e. no longer visible). 
WHEELED VEHICLES AIRBOAT TRACK VEHICLE 

SMALL MARL SAND MARL PEAT MARL PEAT 

CYPRESS MARSH MARSH PINE MARSH MARSH MARSH MARSH 

& 

B 

z 60.- 

W 

U 

P; 

40'- PI 

20 -- 

H AAA AAA 

YEARS SINCE IMPACTS 

A Airboats could not achieve heavy impacts in these habitats. 

H Plot one was destroyed by heavy grazing and we were never able 

to produce heavy impacts in plots two and three. 

Figure 3. Percent of experimental heavy impact lanes that had recovered (i.e. no longer visible), 
associated with vehicles operating at tims of the year when water levels 

were considerably shallower than they were when we conducted our test 

runs. 

The other vehicles all ran directly on the ground surface. As a vehicle 

passed along a lane, vegetation in the wheel tracks was generally bent 

over and pushed onto or, where water levels were above or near the ground 

surface, into the surface soils. AS a result, the vegetation was 

normally at least bruised and the brittle litter broken up as a vehicle 

ran over it. Within a short time after a one pass or medium impact lane 

was created, it tended to appear as a pair of relatively "green" paths 

through the plot due to recovery and regrowth of vegetation and the 

absence of the brownish litter. In the heavy impact lanes the disturbed 

soil generally supportd a much reduced plant community, at least during 

the first year following the creation of the impacts. In the fall 1985 

sampling period, some of these lanes were difficult to see, not because 

of recovery within them, but because vegetation rooted adjacent to the 

lanes had overgrown them. Hobever, others were still obvious due to 

water being present only in the lane ruts or differences in amount, 

height, or taxonomic composition of vegetation in and adjacent to the 

lanes. 

Statistically Recovered Lanes 

While disappearance of an experimental ORV lane represented the clearest 

case of recovery, another way of looking at it is on the basis of when 

lane parameterso had statistically recovered (i .e. were not significantly 

different from control values) in a replicate plot (Appendix C). Thus, 

the trail may still be visible, but some environmental paramters may not 

be significantly different from conditions on an adjacent undisturbed 

site. This allowed us to make an assessment of which aspects of the 

environment were and remained more impacted by an ORV track. Hobever, 

even if a parameter is not significantly different from the controls, it 

is ,possible that there were real differences which our techniques simply 

were not sensitive enough to identify. One place this situation may have 

occurred was with our increasing the lane sample size from three in 1979 

to six in 1985. This change increased our ability to detect real 

differences 'between lane and control plots. Despite this increased 

ability to detect impacted lanes in 1985, the percentage of statistically 

recovered lanes had increased substantially since 1979 (Figures 4-6). 

Late Winter 1979 

The ranges in the percentage of lanes that were statistically recovered 

in late winter 1979 varied from 0 to 100 percent among the live 

vegetation paramters in the one pass (Figure 4) and medium impact 

(Figure 5) lanes. All soil parameter percentages indicated at least 75 

percent recovery in these same lanes. 
SO1 I, LIVE VEGETATION 

VISUAL RUT RIDGE PENETRO- LIVE - PERCENT STANDING 

RATINGS DEPTH HEIGHT METER BIOMRSS COVER IIEIGHT LITTER 

017 017 017 017 0 17 0 17 017 017 . . . . 

Figure 4. Percentages of one pass experimental lanes in the different habitats that had recovered (i .e. 

were not significantly different from the controls) at 0, 1, and 7 years after the lanes were 

created. Vertical bars indicate ranges of percentages of all habitats for which data are 

available for each sampling period. Dashes identify the percentage for each habitat. See 

Table 1 for a key to the numbers used to identify each habitat. 
SOIL LIVE VEGETATION 

VISUAL RUT RIDGE PENETRO- LIVE PERCENT STktJDI NG 

RATINGS DEPTH HEIGHT METER BIOKASS COVER tiEIGHT LITTER 

017 017 017 0 17 0 17 0 17 0 17 017 

Figure 5. Percentages of mdium impact experimental lanes in the different habitats that had recovered 

(i.e. were not significantly different from the controls) at 0, 1, and 7 years after the lanes 

were created. Vertical bars indicate ranges of percentages of all habitats for which data are 

available for each sampling period. Dashes identify the percentage for each habitat. See 

Table 1 for a key to the n-rs used to identify each habitat. 
In the heavy impact lanes the only parameter that ranged up to 100 

percent recovery at this tire was ridge height, and most parameters were 

below 35 percent (Figure 6). 

Standing litter had consistently shown no recovery in all habitats and at 

all impact levels because this brittle material had all been knocked down 

and broken up during the test runs (Figures 4-6). No data were available 

on visual ratings in late winter 1979. 

Fall 1979 

In the one pass and medium impact lanes, soil parameters had shown little 

or no additional recovery at the end of the first year after the impacts 

had been created (Figures 4-5). Visual ratings and standing litter 

ranged from 0 to 100 prcent. All of the live vegetation parameters in 

these lanes still showed a wide range of percent recovery, but none of 

them had less than 14 percent of the lanes recovered in any habitat. 

In the heavy impact lanes, for the rut depth, standing litter, and live 

vegetation parameters recovery ranged from 0 to 100 percent, while for 

the visual ratings it was less than 20 percent (Figure 6). Penetrometer 

measurements of compressive strength indicated little recovery for this 

,parameter in the heavy impact lanes of the two habitats where it was 

evaluated. 

Fall 1985 

By fall 1985, the live vegetation, standing litter, and'soil compressive 

strength (penetrometer) parameters had completely recovered in all one 

pass lanes (Figure 4). Among the visual rating and remaining soil 

parameters, only one lane in the small cypress was all that had not 

recovered. 

Among the medium impact lanes, at least 80 percent of the lanes in all 

habitats for all paramters had recovered (Figure 5). The small cypress, 

wheeled vehicle marl marsh, and pine were the only habitats which had not 

recovered completely. 

Percentages of recovered heavy impact lanes in the various habitats 

varied from 0 to 100 percent for the different parameters (Figure 6). 

Live biomass and vegetation height were the parameters which showed the 

greatest recovery. Wheeled vehicle marl marsh had not completely 

recovered for any parameter, while small cypress and pine had recovered 

completely in only two of eight parameters. The lack of recovery 

suggested for the pine habitat was somewhat misleading since only two of 

the nine attempts at creating a heavy impact there =re even successful. 

~lso, rut depth, percent cover, and standing litter in both pine heavy 

impact lanes were statistically recovered in fall 1979, but neither was 

statistically recovered in fall 1985. This discrepancy was solely a 

function of the increased sample size in 1985. Apendix Tables A 10, A 

29, and A 39 clearly show that at least some recovery has occurred for 

these parameters between 1979 and 1985. 
SO1 L LIVE VEGETATION 

VISUAL RUT RIDGE PENETRO- LIVE PERCENT sT:'::nT rIG 

RATINGS DEPTH HEIGHT METER EIOMASS COVER IIEIGI!'I' I.ITTEI1 

017 017 017 017 0 17 0 17 017 017 

1 

Figure 6. Percentages of heavy impact experimental lanes in the different habitats that had recovered 

(i.e. were not significantly different from the controls) at 0, 1, and 7 years after the lanes 

were created. Vertical bars indicate ranges of percentages of all habitats for which data 

are available for each sampling perid. Dashes identify the percentage for each habita.t. See 

Table 1 for a key to the numbers used to identify each habitat. 
Interpretation of Statistical Recovery 

In contrast to the visual rating, live vegetation, and standing litter 

parameters, rut depth and ridge height generally showed little recovery 

over the seven years since the impacts were initially evaluated. At the 

one pass and medium impact levels, while only a few lanes in some 

habitats were significantly impacted initially, some of these had not yet 

cmpletely recovered. In the heavy impact lanes, where severe soil 

disturbance had occurred, fewer than 70 percent of the lanes had 

recovered in terms of rut depth and ridge height even after seven years. 

We ranked all of the habitats on the basis of which had shown the 

smallest percentage of lanes which had statistically recovered for each 

parameter at each impact level during each sampling period to determine 

which habitats were exhibiting the least recovery for all of these 

combinations (Table 3). We then ranked the second lowest and the third 

lowst. This approach allowed a relatively objective analysis of which 

habitats were exhibiting the slowest recovery from the impacts made in 

1978. As in the previous analyses, the small cypress had recovered least 

and the marl marshes the next least. The airboat habitats had by far the 

highest ranking because this vehicle type produced the fewest initial 

impacts and recovered most quickly from those it did make. 

These same habitat ranking patterns were exhibited in the individual 0, 

1, and 7 year data sumnaries, with the exception of the track vehicle 

lanes (Table 4) . During the 0 and 1 year sampling period, recovery of 

the track vehicle marl and peat marsh lanes was comparable to the poor 

recovery seen in the small cypress and marl marsh wheeled vehicle lanes. 

However, after 7 years almost all of the track vehicle lanes had 

statistically recovered. 

Analvsis of Taxonomic Differences 

The difficulty involved in identifying many of the imnature plants 

encountered in the plots forced us to discuss them in terms of taxa, 

rather than species or genera. Also, not being trained botanists, none 

of the authors would stoutly defend all of our identifications, although 

some of the more distinctive forms are accurately identified. More 

importantly, by identifying the various taxa at a consistent level of 

taxonomic detail within each replicate plot, we were able to make 

statements about differences in taxonomic composition between the test 

lanes and adjacent undisturbed habitats that are relevant to recovery 

from ORV impacts. We have made no attempt to compare the 1985 taxonomic 

analysis with that done in 1979, The personnel involved in making 

taxonmic decisions were completely different at these times, and the 

relative ability and effort put into this aspect of the study were also 

different, so that comparisons are more likely to be misleading than 

helpful. However, the personnel and methodologies were consistent within 

each sampl i ng per i od . 
Table 3. Total number of lowest, second lowst, and third lowest ranked habitats according to their 

degree of recovery (i.e. smallest percentage of lanes not significantly different from controls) 

for each parameter during each sampling period at each impact level based'on their relative 

position along the vertical bars in Figures 4-6. 

Wheeled Vehicle Airboat Track Vehicle 

Small Marl Sand Marl Peat Marl Peat 

Ranking Cypress Marsh Marsh Pine Marsh Marsh Marsh Marsh 

(1) Lowest 26 15 3 14 0 2 17 14 

(2) Second Lowest 18 19 5 3 0 0 4 3 

(3) mird Lowest 7 9 3 3 0 1 5 3 

(4) Total 53 43 11 20 0 3 26 20 

(5) Total Nunher of Possible Comparisons * 56 56 45 53 28 28 41 4 1 

(6) Percent (4)/(5) 95 77 24 38 0 11 63 49 

* mere all of the habitats were neither 0% recovered (year 0) nor 100% recovered (year 7) for a 

particular parameter during a particular year at a particular level of impact. 
Table 4. Total number (by sampling period) of the three lowest ranked habitats according to their degree 

of recovery (i.e. mllest percentage of lanes not significantly different from controls) for 

each parameter at each impact level based on their relative position along the vertical bars in 

Figures 4-6. This table is similar to Table 3 except (1) nLrmbers of the three lowest ranked 

habitats are summed and (2) these numbers and the percentage each is of their total possible 

occurrences are shown by individual sampling period. 

Wheeled Vehicle Airboat Track Vehicle 

Small Mar1 Sand Marl Peat Marl Peat 

Year Cypress Marsh Marsh Pine Marsh Marsh Marsh Marsh 

0 Years 

Number of Occurrences 13 10 6 7 

Percent of Possible Occurrences* 93 71 4 3 50 0 10 88 8 8 

1 Year 

Number of Occurrences 24 20 5 3 0 2 18 13 

Percent of Possible Occurrences* 100 83 24 14 0 17 100 72 

7 Years 

Number of Occurrences 16 13 0 10 0 0 1 0 

Percent of Possible Occurrences* 89 72 0 56 0 0 7 0 

* Were all of the habitats were neither 0% recovered (year 0) nor 100% recovered (year 7) for a 

particular parameter at a particular level of impact. 
The analyses of total number of taxa per sample plot in fall 1985 

indicated significant differences between lanes and controls in only a 

few heavy impact lanes in small cypress and wheeled vehicle marl marsh 

.habitats (Appendix Table C 41). In all these cases there were fewsr taxa 

in the lanes. 

We subsequently analyzed each taxon individually in each habitat 

replicate to see if it occurred more frequently in either control or lane 

plots and how many times it was listed as being comon or abundant within 

individual control or lane plots. Tables 5-8 list those taxa which were 

of more than sporadic occurrence and which we feel had been consistently 

identified at a replicate site. 

In the small cypress both Dichromena and Rhynchospora were distinctly 

more frequent in the control samples at one or more replicate plots, 

while Bacopa, Eleocharis, two forms of Panicum, and Utricularia were more 

frequently found in the lanes (Table 5) . The occurrence of Bacopa and 

Utricularia in the lanes is not surprising since the ruts provide a 

wetter habitat more suitable to these genera. We are unable to explain 

why the other s,wcies were more comn in either the lane or control 

plots. ~oever', it was interesting that Dichromena and Rhynchospora were 

also more frequent in the old trail control plots, as were Bacopa and 

Eleocharis in the old trails themselves. 

The only taxon which was more frequent in one or the other of the wheeled 

vehicle marl marsh plots was Centella, and it was found more often in the 

test lanes (Table 6) . . Pluchea and yet another form of Panicum were more frequent in the pine 

control plots, while Hypericum, Ludwigia, and Xyris were more frequent in 

the lanes, (Table 7). Ludwigia was also found more often in the large 

cypress old trails. 

In the track vehicle ,peat marsh sites (Table 8) , the only taxon which was 

more frequent in one or the other of the plots was Cladium, and it was 

inore frequent in the controls. Cladium does not appear to tolerate 

severe soil disturbance as it was also distinctly more frequent in the 

control plots at the old trail small cypress, marl marsh, and pine sites. 

Taxa at the track vehicle marl marsh sites were similarly distributed in 

both the lane and control sample plots. 

RESULTS AND DISCUSSION - OLD TRAILS 

Most of the old trails study sites established in 1979 ere still visible 

from the air in February 1985 and on the ground in fall 1985. Airboat 

old trail plots in marl and peat marsh habitats were established at the 

beginning of the study in 1979, but airboats continued to use them and 

they were dropped from our study shortly thereafter. Two of the sand 

marsh sites had been heavily used between 1979 and 1985, and as a result 

were not included in the 1985 sampling. One of the hamnock old trails 
rlmm 

mmm 

mmm 

rlmm 

rlmm 

m m m 

mrlm 

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rlmm 

rlcVm 

tu 'a 

-4 

u 

rn 

2 

mrlm 

mmrl 

mmrl 

mcvm 

mmrl 

m m m 

mmm 

m m 

mmm 

rlwm 

mmm 

Nmm 

mmm 

4mrl 

4CVm 

mmm 

mem 

mmm 

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rlcum 

rlwm 

mwrl 

mmmwe 

rlmm 

(Vmm 

mmm 

mmm 

mem 

dcvm 

4 m e3 

m m m 

mmm 

mmm 

mmm 

(Vmm 

m(Vm 

Nmm 

mrlm 

rl~m 

curlm m m 

rlmm 

mrlm 

mmm 

m m m 

mwm 

(Vcnm 

mmm 

rlNM 

rlmm 

mmm 

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m m m 

rlm m 

mcncn 

cnmm 

mmcn 

dem 

rlwm 

emm 

mmrn 

mcnrl 

rlmw 

rlwm 

19 cn cn 

mwe 

r-l cn cn 

C\Ir-lm 

rlmm 
Table 5. Continued. 

plot Control 1 Pass Medium Heavy 

Taxon No Tractor ATC Light ATC Light Chain Tractor Heavy 

Muhlenbergia 1 2 3 S 2 2 3 4 1 1 

2 5+ S 4 S 0 5+ S 3 6 

3 5+ S 6+ S 4 4 5+ 5 4 

Panicum 1 1 0 2 S 1 3 0 0 1 1 

2 0 S 1 S 10 S 0 0 

3 0 S 0 S 0 0 0 0 0 

Panicum 2 1 6+ 5 S 6 5+ 3 6 5 5 

2 2 S 4 S 6+ 0 S 4 0 

3 0 S 0 S 0 0 0 0 0 

Rhynchospora 1 5 3 S 5 4 4 2 2 1 

2 6 S 5 S 4 0 S 3 0 

3 0 S 1 S 0 0 2 0 0 

Sagittaria 1 0 0 S 0 0 0 0 0 0 

2 2 S 3 S 3 0 S 2 0 

3 0 S 0 S 0 0 0 1 0 

Utricularia 1 

2 

S No data available 

+ Comnon or abundant in at least half of the six lane or control plots 
Table 6. Nwlber of sample plots in which each taxon was present during fall 1985 in the unrecovered lanes 

and associated controls at the wheeled vehicle marl marsh experimental test sites. 

Plot Control Medium Heavy 

Taxon No Light AK Light Chain Tractor Heavy 

Centella 

Cladium 2 4 S S 6 5 4 S 

3 5+ 6+ 6+ 5 6+ 5 4t 

Ludwig ia 

Muhlenbergia 2 

3 

S No data available 

+ Comnon or abundant in at least half of the six lane or control plots 
Table 7. Number of sample plots in which each taxon was present during 

fall 1985 in the unrecovered lanes and associated controls at 

the pine experimental test site. 

Plot Control Medium Heavy 

Taxon No Smooth ATC Smooth Chain 

Centella 3 2 5 3 5 2 

Cladium 3 3 2 4 3 3 

Cuscuta 3 4 4 5 4 3 

Flaveria 3 2 0 5 2 2 

Hypericum 1 3 2 2 2 4 4 

Hypericum 2 3, 2 2 0 3 1 

Ludwigia 3 2 

Muhlenbergia 3 2 

Panicum 1 3 3 

Panicum 3 . 3 4 

Pl uchea 3 3 

Rhynchospora 3 1 

Xyris 3 0 1 3 1 4 

* Comnon or abundant in at least half of the six lane or control plots 
Table 8. Number of sample plots in which each taxon was present during 

fall 1985 in the unrecovered lanes and associated controls at 

the airboat-track vehicle marl marsh and peat marsh 

experimental test sites. 

Marl Marsh Peat Marsh 

Plot Control Heavy Control Hea 

Taxon No Track Vehicle Track Vzicl; 

Bacopa 

Eleocharis 1 

2 

Proserpinaca 1 0 0 S S 

2 0 0 2 0 

3 0 0 S S 

Utricularia 1 

2 

- 

S No data available 

+ Ccrmnon or abundant in at least half of the six lane or control plots 
was originally located in a dense stand of shrubby growth on the edge of 

a hamnock. We were able to relocate the position of the plot on the 

ground, but the dense regrowth,which had occurred since 1979 made it 

impossible to find the trail. This was the only old trail which we 

considered to have recovered on the basis no longer being visible. 

As we discussed in our earlier report (Duever et al. 1981), the 

characteristics of old trails in hardwood hamnocks were so different from 

those in adjacent undisturbed habitat that we developed a separate 

sampling strategy for them to supplement our regular measurements. These 

trails were typically open to the sky so that understory growth was 

frequently quite dense in the trail as opposed to the adjacent forest 

floor which was in deep shade. We felt that recovery of this habitat 

would be evidenced more by regrowth of the woody taxa which characterize 

the hamnock than by developnt of a dense herbaceous understory. Thus 

in this habitat, we also counted numbers of the various taxa of woody 

plants growing in 1 by 5 m plots in the trail and adjacent habitat. The 

results of these supplementary samples are included below in the 

discussion of taxonomic characteristics of the old trail sites. All of 

the hanmocks studied were on irregular rocky surfaces where ruts occurred 

only in scattered depressions. One old trail, where we had been able to 

measure rut depths in 1979, had since recovered and ruts were no longer 

visible. Howver, at another site we were able to measure rut depths in 

1985, where ruts had not previously been noted (Table D 2). Except for 

the one hamnock old trail which was no longer visible, the visual ratings 

for the hamnock sites were still significantly different from the 

adjacent control plots in 1985 (Table D 1). . Statistically Recovered Trails 

Little recovery for most parameters in most habitats was found in 1985 

when we evaluated it on the basis of whether individual trail parameters 

had statistically recovered (i.e. were not significantly different from 

control values). Visual ratings indicated recovery in only one pine plot 

in 1985, so it appears that these trails will be visually apparent for 

many years (Table 9). Rut depths also shod recovery in only one 

habitat, the sand marsh plots in 1979. However, in 1985 we were able to 

measure significantly different rut depths in the one remaining sand 

marsh plot which had not been destroyed. This suggests that ruts were 

present in all of the sand marsh sites in 1979, but were not detected by 

the methods we were using then. Also we did not report the presence of 

ridges in 1979 in any habitat, but in 1985 found ridges which were 

significantly different from controls at two of three marl marsh sites. 

Among the live vegetation and standing litter parameters, with the 

exception of the pine sites, no habitat had more than two trails 

recovered. All of the pine old trails had recovered in terms of biomass, 

vegetation height, and number of plant taxa, and in two of the three 

trails percent cover and standing litter had also recovered. 

When the data in Table 9 =re combined for all habitats, the visual 

rating, live vegetation, and standing litter parameters indicated a 
Table 9. N&r of replicate old trail plots where the trail parameter 

values had statistically recovered (i.e. were not significantly 

different from the control values) at 0, 1, and 7 years after 

abandonment ( Amndix D) . 

Large Small Marl Sand 

cyp;ess Cypress - Marsh Marsh - Pine 

017 017 017 017 017 

Visual Rating 0 0 0 000 000 000 001 

Soils 

Rut Depths 000 000 000 330 000 

Ridge Heights S S 3 SS3 SS1 SS1 SS3 

Live Vegetation 

Biomass 311 002 002 101 213 

Percent Cover 310 001 001 001 102 

Height 323 012 011 111 323 

Number of Taxa S S 2 SS1 SS2 SS1 SS3 

Standing Litter S 3 2 S12 S01 S11 S12 

Sample Size 3 3 3 333 333 331 333 

S No data available 
greater percentage of statistically recovered trails in 1985 than in 1979 

(Figure 7). Rut depth recovery had occurred in 20% of the trails in 

1979, but in 08 of the trails,in 1985 because two of the sand marsh sites 

had been destroyed, and the methods used in 1985 clearly showed the 

presence of ruts in the remaining sand marsh site. 

When the data in Table 9 ere combined for all parameters (except number 

of taxa, for which we only have data in 1985, and ridge height), most 

habitats also indicated that more trails had recovered in 1985 ampared 

to 1979 (Figure 8). The only exception was the large cypress, where the 

data indicated recovery has been declining since the first measurements 

were taken in late winter 1979. This pattern was most evidenced by the 

biomass and percent cover data (Table 9). The reasons for this were 

similar to those described above for the hamnock sites. A dense growth 

of herbaceous vegetation has developed in the trails which are more open 

to the sky than is the adjacent deeply shaded forest. Deeper water in 

the trail also contributed to the develo~nt of a very different 

cmunity from that which exists in the adjacent forest. Although 

several of the other habitats also have a woody overstory, their 

undisturbed canopies are relatively open and the resultant trail - 

control comparisons were much more appropriate than they were in either 

the hamnock or large cypress sites. 

Thus, while there has hn recovery for same parameters in some old 

trails, they all have a number of years to go before they could be 

considered to be statistically, much less completely, recovered. 

. Percent Recovery of Trails 

In order to obtain a better idea of how quickly recovery was progressing 

for each parameter in each habitat, we calculated their percent recovery 

in each replicate plot for individual sampling periods (Appendix D) , and 

sumnarized them as ranges by habitat (Table 10). For visual rating and 

rut depth, percent recovery was calculated as the difference between the 

initial average values rneasured in March 1979 and the October 1979 and 

October 1985 average values, respectively, divided by the initial March 

1979 values. For the other parameters, percent recovery was calculated 

by dividing each average trail parameter value by each respective control 

parameter value. The control value would represent 100% recovery. 

Maximum percent recovery for visual ratings in 1985 =re all less than 70 

percent and minimum values ranged from 19 to 38 percent of our original 

measurements made during late winter 1979 (Table 10). Over the same 

period, maximum percent recovery of rut depths were from 56 to 96 

percent, but minimum percent recovery was only between -4 and 38 percent. 

As discussed above, the data for the large cypress old trails were not 

really comparable to those £ram the adjacent control plots. The 

extremely high percent recovery for all of the large cypress vegetation 

parameters, except standing litter, clearly indicate the large amount of 
LIVE VEGETATION 

VISUAL RUT PERCENT NUMBER STANDING 

RATING DEPTH BIOMASS COVER HEIGHT OF TAXA LITTER 

100 i 

01 7 017 017 017 017 017 0 1. 7 

YEARS SINCE ABANDONMENT 

Figure 7. Percents of old trail paramters showing recovery (i.e. not statistically different from 

controls) for all habitats combined. 

Table 10. Minimum and mximum percent recovery for replicate old trail plots in each habitat at 0, 1, and 

7 years after abandonment (See Asendix D for the individual percentages). The control value 

would represent 100% recovery. 

Live Vegetation 

Visual Rut Percent Nunher Standing Number 

Habitat Rating Depths Biomass Cover Height of Taxa Litter of Plots 

Large Cypress 

0 S S 0 0 0 S S 3 

1 0-3 -8-11 0-1 0-10 0-43 S 0 3 

7 38-63 27-56 37-995 252-978 40-200 100-200 3-27 3 

Small Cypress 

0 S S 0 0 0 S S 3 

1 8-18 0- 16 1-21 1-30 20-96 S 0- 21 3 

W 

-1 7 25-38 38-66 44-74 11-48 49-109 37-62 9-27 3 

Marl Marsh 

0 S S 0 0 0 S S 3 

1 3-33 13-22 1-27 0-43 0-47 S 0 3 

7 25-45 -4-96 57-90 23-96 89-162 64-133 36-69 3 

Sand Marsh 

0 S S 0-3 0-9 0-9 S S 3 

1 -20-45 S 5-26 4-28 25 -;8 5 S 0- 9 3 

7 28 P 96 121 8 0 118 46 1 

Pine 

0 S S 1-5 1-23 6-13 S S 3 

1 6-20 -18-36 3-12 5-15 55-58 S 0-34 3 

7 19-68 20-58 81-141 28-62 100-139 63-80 34-92 3 

S No data available 

P ~uts found in 1985, but recorded as 0 during 1979 field work 
understory vegetation in at least some of the old trails as compared to 

that found in the nearby undisturbed forest. 

'~uring 1985, with few exceptions the maximum percent recovery for most of 

the live vegetation and standing litter parameters in most of the 

remaining habitats (other than large cypress) fluctuated within + 41 

percent of the control values (100%). With the exception of percent 

cover and standing litter, most of their minimum percent recoveries were 

within + 63 percent of the control values (100%). Minimum percent 

recovery for percent cover and standing litter for these same sites both 

ranged from 9 to 46 percent of the control values (100%). Thus, while 

some parameters have essentially recovered in some trails in the seven 

years since abandonment, in all of the habitats at least one trail is 

less than 40 percent recovered in terms of visual rating, rut depth, 

percent cover, and/or standing litter. 

Analysis of Taxonomic Differences 

As in the experimental lane sites, we analyzed each taxon in each habitat 

replicate to see if it occurred more frequently in either control or 

trail plots and how many tims it was listed as being cannon or abundant 

within individual control or lane plots. Tables 11-16 list those taxa 

which were of more than sporadic occurrence and which we feel had been 

consistently identified at all replicate sites of each habitat. 

Seven taxa were identified as being distinctly more frequent in the smll 

cypress old trail control plots (Table 11). These included Cladium, 

~ichromena, Ipomoea , Muhlenbergia, one form of Panicum, Rhynchospora, and 

Taxodium, while l3acop and Eleocharis were the only taxa more frequently 

found in the old trails themselves. As mentioned above in the discussion 

of the experimental lanes, Bacopa, Dichromena, Eleocharis, and 

Rhynchospora were also similarly distributed in those small cypress 

plots. In addition to being more frequent in the control plots, 

Muhlenbergia was listed as being comnon or abundant in at least half of 

the control plots at two of the three sites. 

Cladium was the only taxon which was found more often in control plots at 

the marl marsh sites, while Eragrostis was the only species found more 

comnonly in the trail plots at these sites (Table 12). 

At the large cypress sites, Blechnum and Hyptis were found more often in 

the control plots, while Bacopa, Diodia, and Ludwigia were more frequent 

in the old trails (Table 13). Bacopa and Ludwigia *re also listed as 

beinq comnon or abundant in at least half of the trail plots at all three 

sites. Although cypress seedlings were not present in any of the old 

trail plots, they were absent from the control plots as well. 

Six taxa were inore frequent in the old trail pine control plots (Table 

14). These included Aristida, Cladium, Cuscuta, Dichromena, 

Muhlenbergia, and a form of Panicum, while Eragrostis and an unidentified 

forb were more frequent in the old trails. 
Table 11. Number of sample plots in which each taxon was present during 

1985 at the small cypress old trail sites. 

Site 1 Site 2 Site 3 

Taxon control trail control trail control trail 

Bacopa 1 4 1 5 

Cladiun 4 0 2 0 

D ichr omena 4 0 2 0 

Diodia 1 0 1 2 0 0 

Eleocharis 0 0 0 2 1 6+ 

Eragrostis 1 2 2 2 1 0 

Flaver ia 0 0 0 0 4 0 

I pomoea 2 0 2 0 1 0 

Muhlenbergia 5+ 0 5+ 0 6 0 

Panicum 2 5+ 1 1 0 5 0 

Rhynchospora 5 0 6+ 3 3 1 

Taxod i urn 5 0 4 0 0 0 

+ Camnon or abundant in at least half of the six trail or control plots 
Table 12. Number of sample plots in which each taxon was present during 

1985 at the marl marsh old trail sites. 

Site 1 Site 2 Site 3 

Taxon control trail control trail control trail 

Centella 1 4 2 1 0 0 

Cladium 4+ 2 4 4 

Dichromena 1 2 3 0 

Diodia 1 2 1 0 

Eragrostis 0 1 0 0 0 5+ 

Muhlenberaia 6+ 6+ 2 4 6+ 6 

Rhynchospord 2 4 5+ 2 1 3 

Sedge 1 1 2 1 0 1 1 

--- 

+ Comnon or abundant in at least half of the six trail or control plots 

Table 13. Nutnber of sample plots in which each taxon was present during 

1985 at the large cypress old trail sites. 

-- --- 

Site 1 Site 2 Site 3 

Taxon control trail control trail control trail 

Blechnum 

Ludwigia 

Proserpinaca 2 5+ 3 1 3 5 

Sagittaria 2 0 1 0 0 2 

+ Conmon or abundant in at least half of the six trail or control plots 
Table 14. Number of sample plots in which each taxon was present during 

1985 at the pine old trail sites. 

Site 1 Site 2 Site 3 

Taxon control trail control trail control trail 

And r opogon 1 0 1 1 4 4 

Aristida 1 0 1 1 4+ 2 

Centella 1 0 1 1 4 4 

Cladium 4+ 0 4 1 2 0 

Cuscuta 4 2 2 0 2 0 

D i chr arena 

Eragrostis 

Forb 

Ludwigia 

~uhlenbergia 

Panicum 2 

Rhynchospora 2 3 4 2 6+ 5 

- + Cmn or abundant in at least half of the six trail or'control plots 
In the one sand marsh old trail which had not been destroyed, Spartina 

was the only taxon which was more frequent in the control plots and 

Eragrostis the only taxon more frequent in the old trails (Table 15). 

The replacement of Spartina by Eragrostis was one of the primary reasons 

the trail was visible in the field. 

In the hamnock sites, Myrsine, Toxicodendron, and Psychotria were more 

comnon in the undisturbed hmck plots as was Baccharis in the old 

trails (Table 16). 

In general, there were a rimer of differences between taxa occurring in 

old trail or control plots. A few taxa clearly prefer the deeper water 

and/or less shaded conditions of some of the trails (Bacopa, Diodia, 

Eleocharisl or the ureater shade of some of the control sites (Blechnum). 

Cladium was more frequent in the control plots of the old trail -11 . 

cypress, marl marsh, and pine habitats and the experimental lane peat 

marsh. It ap,oears to be strongly selected against by disturbance. 

Alternately, at the three driest sites Eragrostis occurred more cmnly 

in the trails, suggesting that it is more successful and persistent on 

previously disturbed sites. Homver, with most of the taxa it is 

difficult to say for certain what the primary reasons were for their 

distribution at the old trail sites seven years after abandonment. 

The purpose of this study was to evaluate the long term recovery of ORV 

impacts. To this end we measured a variety of paramters in 

experimentally created lanes and abandoned old trails at sites which had 

been recovering for seven years. In terms of some biological processes 

seven years is a long time. Homver, in terms of soil processes and 

growth of forest trees, it is a very short period. Thus, the recovery 

which has occurred during this ,period could be described as good for 

certain impact levels and environmental parameters, but poor for others. 

Emrimental Lanes 

As described in our 1981 report, the crux of creating significant ORV 

impacts is soil disturbance. Soil disturbance increases as a site gets 

wetter, either along a moisture gradient or at different times of the 

year. If water levels are at or above the soil surface, impacts are much 

greater than if they are well below ground. So habitats or portions of a 

habitat which are wet more of the time are inore likely to be impacted and 

will take longer to recover. They also tend to have substrate and 

vegetative characteristics which make them more susceptible to impacts. 

The other major management consideration relating to ORV impacts is the 

length of time required for recovery. Anything over one year becomes a 

cumulative impact, since that is the interval between heavy use periods. 
Table 15. Nunher of sample plots in which each taxon was present during 

1985 at the sand marsh old trail site. 

Site 2 

Taxon control trail 

Eragrostis 2 64- 

Spartina 4+ 0 

+ Conmon or abundant in at least half of the six trail or control plots 

Table 16. Nder of sample plots in which each taxon was present during 

1985 at the hamock old trail sites. 

Site 2 Site 3 

Taxon control trai 1 control trai 1 

Bacchar is 2 3 1 3 

Myrsine 

Parthenocissus 2 1 0 1 

Psychotria 

Toxicodendron 4 1 1 0 
If one criterion (A) for recovery was the disappearance within one year 

of any track produced by a single pass in any habitat where a vehicle 

type normally operates, then clearly the only vehicles which meet 

'criterion A are the ATC and airboat. All of the swamp buggies also meet 

criterion A in the sand marsh and pine habitats, and the track vehicle in 

the peat marsh. As the allowable ncnnber of passes, and therefore the 

level of impact, increases to the point where the vegetation is severely 

damaged but the lane still disappears within one year (criterion B), the 

airboat is still acceptable in the marl marsh but not in the peat marsh 

habitats. The ATC also still meets criterion (B), but now only in the 

sand mrsh and pine habitats. Thus, these are the only types of vehicles 

which could still be allowed in the preserve and the only habitats they 

could operate in, if tracks which completely disappear within one year 

(criteria A or B) were considered the only acceptable levels of impact. 

Another possible criterion (C) for an acceptable level of recovery would 

be to allow the tracks to be visible for more than one year, as long as 

any remaining impacts were not statistically significant. Examination of 

the Tables in Appendix C indicates that if the visual rating parameter 

were considered, on this basis, then not surprisingly, we obtain 

essentially the same grouping of allomble vehicles and habitats as by 

criteria A or B. 

If criterion C is applied to the presence of significant,ruts and ridges 

one year after the impacts were made, then most of the wheeled vehicles 

could make one pass through all habitats. The exceptions would be the 

tractor buggy @ich would not be allowed in either small cypress or marl 

marsh habitats and the heavy buggy which would not be allowed in the 

smll cypress. The ATC could operate in any habitat at any level of 

activity on the basis of criterion C as applied to rut and ridge impacts. 

If criterion C were applied to vegetation impacts, we again find that on 

the basis of biomass, most of the wheeled vehicles could make one pass in 

any habitat. Again the tractor buggy is an exception, but now it would 

only be excluded from the small cypress. On the basis of height, one 

pass impacts would be acceptable from most wheeled vehicles in all 

habitats except the small cypress. The tractor buggy would be excluded 

from the marl marsh as well. Height impacts would also be acceptable at 

medium impact levels for all vehicles in the sand marsh and pine. 

Standing litter did not statistically recover at any sites and percent 

cover at only a few where the trail was still visible one year after they 

were made. Thus, if percent cover or standing litter were the basis for 

criterion C, the allowable vehicles and the habitats they could use would 

be the same as for the complete disappearance of trails (criteria A or 

B) . 

The results of our 1985 sampling showed that virtually all of the one 

pass lanes had completely disappeared. This was also the case with most 

of the medium impact lanes. The small cypress was the only habitat where 

a number of medium impact lanes were still visible, but only a few of 

these had not statistically recovered for most parameters. Where we were 
able to create heavy impacts, very few had disappeared, and a large 

percentage of lanes in a number of habitats had not statistically 

recovered for many of the parameters, Thus, these data clearly indicate 

that once a vehicle has severely disturbed the soil, recovery of that 

track takes a very long time. It also follows that the types of vehicles 

(ATC, airboat) with which we had the hardest tirrre creating heavy impacts 

would be the ones least likely to impact the soil. And the habitats 

(sand marsh, pine) where we had the hardest time creating heavy impacts 

would be the areas most resistant to ORV impacts. 

Old Trails 

The 1985 old trail data indicated that there had been substantial 

recovery since 1979 for a variety of paramters. However, many 

parameters in many lanes still had a long way to go before they would be 

statistically recovered, much less the trail no longer visible. In 

particular, there were very few lanes which had statistically recovered 

in terms of visual rating and rut depth. At only one site had the trail 

completely disappeared. The pine was the habitat showing the most 

recovery, with the distinct exception of the visual rating and rut depth 

parameters. 

General Comments 

One question that kept coming up in the course of our data analyses was, 

why are there visibly rutted trails through habitats where we were unable 

to create "heavy impacts"? Besides those trails not originally created 

by ORV1s, we are aware of several reasons for this discrepancy. Airboat 

trails are more easily rutted during periods when water levels are closer 

to the ground surface than when they are high, as was the situation when 

we created our experimental lanes. For the other vehicles which always 

run in contact with the ground surface, the most likely explanation 

involves the temporal distribution of impacts. Most Big Cypress National 

Preserve ORV trails are impacted over a two month period each year, which 

is associated with the November - December hunting season. However, our 

experimental impacts were created within a few hours. The difference in 

the temporal distribution of our experimntal impacts and those normally 

created in the Big Cypress National Preserve could result in 

significantly different affects on vegetation recovery. Vegetation which 

is impacted by a passing vehicle is frequently not killed outright, and 

will resprout and continue to grow. Hoever, if after resprouting it is 

again impacted, its ability to resprout and grow is further diminished. 

Subsequent repeated impacts on these plants will eventually kill them, 

whereas the same total number of passes in a few hours may only be 

comparable to a single pass as far as recovery is concerned. Once the 

plant has been killed its ability to bind the soil will also be 

diminished, and further passes will then begin to create a rutted trail, 

whereas an equal or greater number of passes over a short period of time 

might not even begin to create a rut. 
While standing litter may seem to be a relatively minor aspect of BCNP 

habitats, we were particularly interested in this component of the system 

because it is the major source of fuel controlling the spread of natural . fires. All South Florida ecosystems exist as a function of a specific 

fire regime. Prior to man's recent efforts to reshape the South Florida 

landscape, the major types of plant and animal cornnunities were 

distributed primarily according to the influences of each site's 

hydrologic characteristics, which in turn influenced the frequency and 

severity of fires. During the past 100 years, man's activities have 

altered many of the factors which control the occurrence and spread of 

fires in South Florida. ORV trails represent one of these factors, since 

they have created extensive networks of trails which can function as 

firebreaks in otherwise undisturbed habitats. These trails may be 

swathes of bare ground, which are rutted and therefore frequently wetter 

than the surrounding habitat. Howver, less impacted trails where the 

vegetation is merely bent over and the brittle standing litter eliminated 

are a much more widespread type of ORV trail. These latter trails may 

not affect the spread of hot, fast moving fires, but they may 

sufficiently impede slow backing fires, so that certain areas may over 

the long run bprn less frequently than they should, and ultimately change 

the character of portions of the Big Cypress National Preserve. Standing 

litter was one of the parameters which showed the slowst recovery from 

ORV impacts, and this combined with its importance to the maintenance of 

a natural fire regime w;thin the Big Cypress National Preserve, must be 

kept in mind when managment decisions are being made about the use of 

ORV's in this area. 

It must be kept in mind that the paramters which we monitored relate 

primarily to the aesthetic, soil, and understory plant comnunity 

characteristics of the study sites. Within the time frame available to 

us for this study, it was necessary to concentrate on components of the 

system which we could reasonably expect to see changes in within a 

relatively short time. We were aware that woody components of the 

forested Big Cypress Swamp cormunities are much sloer growing than the 

herbaceous components, and that we would not be able to quantitatively 

measure their long term recovery from impacts. However, despite the lack 

of quantitative data, it can safely be said that 50 to 300 year old trees 

which have been killed.in the course of ORV use or trail construction 

cannot be expected to recover by regrowth in less than 50 to 300 years. 
LITERATURE CITED 

Duever, M.J., J.E. Carlson, and L.A. Riopelle. 1981. Off-road 

vehicles and their impacts in the Big Cypress National 

Preserve. Report T-614. South Florida Research Center, 

National Park Service, Homestead, Florida. 214 w. 

SAS Institute Inc. 1979. SAS user's guide. SAS Institute Inc. 

Raleigh, North Carolina. 494 p. 

SAS Institute Inc. 1985. SAS user's guide: statistics. SAS 

Institute Inc. Cary, North Carolina. 956 pp. 

Apendices A-F (141 pages) to this report are available for inspection 

at: 

ECOS~S~~II'I Research Unit Big Cypress National Preserve 

~ational Audubon Society S. R. Box 110 

Rt. 6, Box 1877 Ochopee, FL 33943 

Naples, FL 33964 (813) 695-2000 

(813) 657-2531 

Copies may also be purchased for the cost of duplication.