CYPRESS WETLANDS F<R WATER MANAGElfENT,

RECYCLING AND CONSERVATION

Second Annual Report

to

National Science Foundation, Grant AEN 73-07823 AOI (Formerly GI-3872l), under the National Science Foundation's Program of Research

Applied to National Needs

and

The Rockefeller Foundation, Grant RF-73029

November 1, 1974 through October 31, 1975

A research project with participants from several divisions of the University of Florida, National

Audubon Society, and other organizations, coordinated through the Center for Wetlands

with the assistance of a Steering Committee of User Agencies

Howard T. Odum, Principal Investigator Katherine C. Ewe1, Co-Principal Investigator

.James lol. Ordway, Site Manager Margaret K. Johnston, Administrator of Center

Center for Wetlands Phelps Lab

University of Florida Gainesville, Florida 32611

December 15, 1975

' ..

PHASE 12. CORKSCREW SWN1P, A VIRGIN STRAND

IHchae1 J. Duever

ECOSYSTEM ANALYSES AT CORKSCREW SW~~*

Michael J. Duever. John E. Carlson and Lawrence A. Riopelle

~ationa1 :Audubon Society . *Subcontract to the Hationa1 Audubon Society from Center for Wetlands

For comparison with the cypress dome sites in Gainesville, and

to determine factors which control swamps on a regional basis, measurements

are being made of the Corkscrew S~"amp Strand including zones of virgin bald

cypress, pond cypress, and surrounding environments. Using models of

swamp function developed earlier to suggest what is important, measurements

are being nw.de of the hydrology, the soils, the major chemical cycles, the

resulting vegetation, and some indic:(~"3 of the animals. By comparing

the hydrologic and other factorS in the several wetlands environments in

Corkscrew SW3mp Sanctuary, inferences are being drawn as to the range of hydro-

period, fire, nutrients, and weather "i'hich r.laintain cypress swamps and

which factors may develop other ecosystem types. Water Budgets, chemical

budgets, and simulation models are being developed.

The study area is shown in Figure 1. Table 1 has the main transect: sites

being monitored. Weather stations from which data are being used are given

in Fig. 2. A summary of the measurements made or to be measured in the

final year is given in Table 2.

627

/

NAPLES (27 MI)

~

MARSH

IMMOKi\EE -_ (16 MI.)

I em ~ 450 m

• 4-•• • 4-• • •• .• • •• RD.• • •• • • • • • •

S

PINE PALMETTO OR MYRTLE PRAIRIE - t MARSH - -X...

.. POND" CYPRESS - •

"BALD" CYPRESS - 0 LOGGED CYPRESS-®

Fig. 01. Major habitats and study areas; Corkscrew Swamp Sanctuary.

628

TABLE 1. Corkscrew Swamp Sanctuary Study Sites.

Grapefruit Island Transect:

Little Corkscrew Island (LCI) ... myrtle pra1r1e (pine-palm) Mud Lake Marsh (MLM) - marsh (mixed vegetation) Grapefruit Island (GI) - hammock (palm-oak) Ruess Marsh (RM) - marsh (mixed vegetation) Ruess Island (RI) - myrtle prairie (pine-palm)

Orange Grove (OG) - ditch draining orange grove

Seven Culverts (7C) - marsh (mixed vegetation)

North Marsh Transect:

North Marsh Willow (NMW) - willow Maidencane (MC) - marsh (maidencane) Spartina (SP) - marsh "(Spartina) Buttonbush (BB) - marsh (buttonbush) Flag Pond (GP) - slough (arrowhead) North Marsh Cypress (NMC) - "pond" cypress Burned Cypress (BC) - burned "pond" cypress Camp Pines (CP) - myrtle prairie (pine-palm)

Duevers' (DUE) - myrtle prairi"e (pine-pRIm)

Central Marsh Transect:

Central Ha.rsh Pine (CMP) - pine-palm,etto Myrtle (HY) - myrt1f~ prairie l-let Prairie (HP) - marsh (mixed vegetation) Hammock (HA) - hammock (maple-bay) Pond Cypress (PC) - "pond" cypress Near Cypress (Ne) - "bald" cypress Gator Hole (GH) - slough Central Marsh Willow (CMW) - willow Central Marsh (CM) - marsh (sawgrass--arrowhead) Far Cypress (FC) - "bald" cypress

South Dike Transect:

Burned Above (BA) - burned "pond" cypress Near Above (NA) - logged and burned "bald" cypress Near Below (NB) - logged and burned "bald" cypress Mid Above (MA) - marsh (sawgrass-arrowhead) Mid Below (HB) - marsh (sawgrass-arrowhead) Far Above (FA) - logged "bald" cypress Far Below (FB) - logged ''bald'' cypress Dike End (DE) - "pond" cypress

Gordon Swamp (GS) - "pond" cypress

Dwarf Cypress (DC) - "dwarf" cypress

629

J-----, Ir-

J--­ ---.---­

MOORE HAVEN

- - Cl~Wisro:N ,

I I I I I 1__ --- ­ --- ­ - ­

CORKSCREW SWAMP

SANCTUARY

GULF OF

ME)(ICO

Z <t w o o o ~ z <t ...J.-,­<i

F -19. 2 • Weather stations.

630

Table 2

Measurements made or in progress in Corkscrew Swamp study

Category Parameter

Weather ALe tem;Jeratures

Coruparison of air temperatures in cypress and pine habitats

Soil temperatures

Relative humidity

Daily soil temperatures at main weather station since

Narcll, 1975 (on a maximum-minirr,um soil thermometer

supplied by Dr. Carlos Blasquez of the University of

Florida Agricultural Experiment Station in Immokalee)

Hydrology Evaporation

Precipitation

Watl~r level in major habitats

Seasonal fluctuations

Maximum and minimum levels

Water flows

Evapotrauspiration from water level recorder charts

Hydroperiods

Long term sanctuary surface water levels

631

Chemical Wa;ter chemistry

cycles Alkalinity" hardness, pH, conductivity

Organic, amnonia, and nitrate nitrogen

Ortho - and total phosphate

Inorganic and organic carbon

14 trace elements

Soils Soil profiles along transects and at other selected sites on

the sanctuary

Rod penetration measurements of organic soils Ol Central Harsh

Transect

Car'bon dating of base of Central Marsh peat

Central Marsh and cypress peat profiles

Chemical and physical analyses of soil samples from each 'veIl

site

VegetatiQ~ Relative elevation and elevation variability of habitats

~d Pro- Undl:!rstory productivity

ductivity Annual tree and shrub productivity

The diurnal cycle of dissolved oxygen and temperature in wet

prairie, "pond II cypress~ "bald" cypress, slough and

sawgrass marsh habitats (quarterly)

Structural descriptions

DBH/height relationships of major tree species

Tree species/size distri.bution in cypress habitats

DBH of cypress along Central Marsh Transect

Canopy cover

Root biomass distribution

632

Litter

Animals

Shrub and tree biomass on Grapefruit Island, Central i'~rsh

Transects, South Dike and North Marsh Transects

Ele,ment analyses of:

Vegetation (roots, understory, shrub) from Grapefruit

Island, South Dike, Horta Marsh, and Central Harsh Transects

Calculation of submerged aqu,atic productivity in wet prairie,

"pond" cypress, "bald" cypress, slough and sawgrass marsh

habitats (from quarterly diurnal curve data)

Cypress annual ring studies

Cattle grazing studies

Litter standing crop

Litterfall

Decomposition rates

Seasonal large wood litterfall

Element analyses of litterfall and decomposition materials

Element analyses of samples c.ollected to date of:

Litterfall

Litter decomposition materials

Fish, crayfish, and benthic populations in "bald" cypress, "pond"

cypress and marsh

633

RESULTS

\oleE\ t her

Data in this report cover the period from June. 1974 through

August. 1975 for the 'Corkscrew Swamp stations. and from June. 1974

through July. 19'75 at the surrounding, U. S. Department of Connnerce National

Oceanic and Atmospheric Administration (NOAA) stations shown in Figure 2.

Immokalee. the furthest inland station (44 miles) has the highest ele­

vation (35 feet). The Naples station is (m coastal dunes (elevation 4

feet) within t,.o miles of t,he Gulf. while Ft. Myers lies in the Caloosa­

hatchee ValleY approximately 17 miles inland from the Gulf at an elevation

of 15 feet. The more distant NOAA stations. Moore Haven. Clewiston. and

Tamiami Trail. 40 Mile Bend. are the only ones in southwest Florida with

evaporation pans. Corkscrew Swamp lies in a lowland area (elevation

20 feet) between the coastal dunes and the "Immokalee Rise" to the

east, approximately 25 miles from the Gulf.

Air Temperature~

Average monthly air temperatures are shown in Figure 3 and monthly

extremes in Figure 4. Temperature differences between Corkscrew Swamp

oand the surrounding stations are generally small «5 F for averages

and <80

F for extremes), but consistent over long periods. Corkscrew

temperatures are similar to those of the coastal stations durin g t.he

summer and fall, but are routinely more extreme during the dry winter

and spring months. This is probably because the extensive surface water

in the Corkscre~7 area during the wet season moderates temperatures as

does the Gulf at Naples and Ft. :Hyers. Divergent July temperatures at

Corkscrew in 19]'4 and 19'75 reflect the slm-ler developJ'!1ent of 1975 wet

season. It is thus no surprise that Immokalee, the highest and driest

station (in terms of surface water), has the most extreme minimum tempera­

tures, but Immokalee's relatively low maximums are unexplained.

A maximum-ininimum thermometer placed in the ''bald'' cypress along the

Central Marsh TI'ansect in late January is read at approximately weekly in­

tervals. Figure 5 shows a comparison of these temperatures with those

from the main we~ather station which is in pine-palmetto habitat. Maximum

70 cypress temperatures were consi stent1y lower by about 30 to F during

the dry season and 1° ·to 3° F during the wet season. Minimum air tempera­

tures in the cypress were moderated during the dry season by 2 ° to 40 F,

but were compara,ble to the pine habitat lows during the wet season. The

more moderate temperatures in the cypress during the dry season are undoubtedly

635

C CORKSCREW SWAMP SANCTUARY I IMMOKALEE N NAPLES F FT. MYERS

100

90

80

LL 70 0

W ~

0::: ::>..- 60 <0::: W 0.. ~ I

F? I e_ N/ AVERAGEI

MAXIMUM

w 50..­0:::-<

40

30

20

Fig. 3. Average air temperatures.

636

90

C - CORKSCREW SWAMP SANCTUARY

I - IMMOKALEE N - NAPLES

100 F - FT. MYERS

MAXIMUM

80

70

w 60 a:: ::J

~ a:: ~ ~ 50 w ..... a:: ~

40

MAXIMUM

30

20 •

J 1974

J A I S

I o

J N

I o

I J 1975

I F

I M

I A

I M ,

I J

I J

I A

Fig. 4. Air temperatures.

637

AIR TEMPERATURES -- MAIN WEATHER STATION I FINE PALMETTO) PINE CYPRESS _·······'BALO" CYPRESS

35 95

3085

0 2575 MAXIMUM

'L .... ~

MINIMUM

0 25 '-0-,..........-...--..,,----.-..,,--...-...--.--....--..--,.-....--.--...-...............-- ­15 15 29 12 26 10 24 1 21 5 19 l! 16 30 13 21

FEEiRUARY MARCH APRIL MAY JUNE JULY AUGUST SEPTEMBER

1915

Fig. 5. Air temperatures; pine/cypress.

638

associated with the higher water table .and the dense forest providing

better shelter from sun and wind. During the wet season, temperature­

moderating surface water extends into the pinelands~ and the slight

reduction in cypress maximum temperatures is due primarily to shading

by the dense canopy.

Soil Temperatu~

Monthly a"l7erage and extreme soil tE'.mperature data are summarized in

Figure 6 for the period from thermometer installation in February through

August 1975. The maximum':'minimum thermometer has a temperature probe buried

4 inches below the ground surface at the main Corkscrew weather station

and is monitor(~d daily. There are no other known soil thermometer stations

in South Florida at present.

Relative Hunlidj:E,l

Average and extreme relative humidity values are shown in Figure 7.

The constant 100% maximum values are higher than actual because of the

properties of the hygrothermograph. The minimum values are much more repre­

sentative of ac:tual conditions. The 0700 hours average monthly values for

the Ft. Myers NOAA station are probably ,comparable to the actual maximum

values for the Corkscrew Swamp area and the 1300 hours average monthly

values for Ft. Myers are more or less equivalent to the minimum values for

Corkscrew (Figure 7).

As expected~ ave.rage minimum relative humidity vTaS lower at both sta­

tions during the dry season. However, Ft. Myers reported higher 0700 hours

relative humidity during the dry months, perhaps due to morning fog~ whIch

rarely occurs during the wet season.

639

110

100

i: 0

... "" :> 70 ~

"" ... t>..

"... .... :=! 0

'" 60

50

40

A M J J A s o N o 1975

Fig. 6. Monthly soil temperatures.

640

100

90

80

60

~ ~

>- 50 I­o :::E :)

:r: 40 w > I­~ --l W 0:: 30

20

10

MAXIMUM a AVERAGE MAXIMUM RELATIVE HUMIDITY ARE ALWAYS 100%

AVERAGE

FT. MYERS 0700 HOURS AVERAGE

o L..-...----r--,.--• ..---• ..---r.---",_--,.._ ....--•.---r.--..,-,--,.r----,• .---...,.'--,•J J AS 0 N D J F M AM J J A

1974 1975

Fig. 7. Relative humidity; Corkscrew S\I1amp Sanctuary.

641

Evaporation

Evaporation rates in southwest Florida were at a distinct minimum

during early winter (Figure 8) when temperatures (Figure 9) and average wind

velocity (Figure 10) were low. Understandably maximUIll evaporation took

place during late dry season when temperatures and average wind velocity

were high and relative humidity low.' Evaporation rates declined slightly

but remained fairly high during the wet season due primarily to high summer

temperatures.

Moore Haven had by far the greatest evaporation rate of the stations

in southwest Florida (Figure 8), undoubtedly due to much higher average

wind velocities (Figure 10), since temperatures show little station to

station variation (Figure 9). Evaporation rates at the other southwest

Florida stations were comparable to those at Corkscrew.

Precipitation

In south :F'lorida, the rainy season typically begins in late May and

extends into early October. Local summer thunderstorms produce wide varia­

tion in precip1.tation, whereas dry season rainfall comes primarily from

frontal systems affecting large geograph.ic areas (Figure 11). Although dry

season precipitation at the four Corkscrew stations generally varies less

than 0.5 inch/month,' wet season rainfa.ll may vary up to 5 inches/month.

Figure 11 also indicates that Ft. Myers rainfall data would be most

useful in reconstruction of long-term weather patterns at Corkscrew. Al­

though Ft. Myers is the farthest of the three stations, the similarity in

rainfall is not surprising since it most closely resembles Corkscrew in

distance inland and elevation.

642

2

~x[f) W :I: CU z 5

z 0 i= <t 0:: 0 4 a.. ~ w

3

o '---r--,.....--r.--r---.--...,..----,.~ ---.---.,_._....._--..__..,.-_....._.....,.__....-:'. J J A S 0 N OJ F M AM J J A

1974 1975

Fig. 8. Evaporation.

9

8

M 7

6

C - CORKSCREW SWAMP SANCTUARY

T - TAMIAMI TRAil 40 MILE BEND

CL- ClEMSTON

M - MOORE HJWEN LOCK

643

110

10

MC

T90 CL

~ MAX IMUM

80­

lJ.. o

T lJ) \.U

~ 70 Tt CL0:

W ~ a.. ~

~ 60

z ~

CL

I , i f J J A S o N D J F M A M J J A

1974 1975

Fig. 9. Evaporation pan temperatures.

CL ~ i= 50 <t 0: o a.. ~ w 40

30

20

C - CORKSCREW SWAMP SANCTUARY

T - TAMIAMI TRAIL 40 MILE BEND

CL - CLEWISTON

M - MOOREHAVEN LOCK CL

..

644

3500

3000

2500

$2000 w .J

:= 0 z 3: 1500 .J

~ 0 ~

1000

500'

C - CORKSCREW SWAMP SANCTUARY

T - TAMIAMI TRAIL 40 MILE BEND CL - CLEWiSTON

M - MOORE HAVEN LOCK

M

.. o I i i i

J J A S o N M A M J J 1974

Fig. 10. Total wind/month at evaporation stations.

645

646

Table 3 compares total annual rainfall and evaporation at the south­

west Florida weather stations. Excluding Moore Haven evaporation va1ues~

which appeared unusually high~ evaporation. pan water losses exceeded

rainfall by appr()xima~ely 20 to 30 inches during the study period. At

Corkscrew~ rainfall representE!d only 55% - 66% of evaporation pan losses.

Hydrology

The 1975 dry season, an unusually severe drought period~ was similar

to that of 1974~ but the 1975 wet season developed very differently. In

1974~ the water t:able rose rapidly after heavy rains in late June and

remained more or less stable into September~ then began to drop, whereas

in 1975~ it rose gradually through Septemher before beginning a slow de­

cline in Octobli:!r.. lImolever~ total dry season rainfall and total wet season

rainfall were comparable for the two years as were maximum and minimum

water levels. In total annual rainfall~ 1974 ~las the second lowest year

of the 14 on record at Corkscrew and 1975 will most likely rank below .

average. These years also had the lowest dry season water levels since

1962.

WateT: Levels

Seventeen months of water level records at 28 well sites are shown

in Figures 12 through 15. The rapid rise in 1974 wet season water levels

following heavy rain from a tropical depression, and the subsequent sta...;

bi1ization of water levels through the surr~er were discussed last year.

Water levels began to decline in September, 1974, when the rainy season

ended, but stabilized duri.ng November and December due to minimum

647

TABLE 3. Annual Precipitation and Evaporation for Corkscrew Swamp and Surrounding NOAA Weather Stations.

August 1, 1974 - July 31, 1975

Precipitation (Inches) .

Evaporation. (Inches)

Corkscrew (Avg. ) 41.16 Corkscrew 67.54

Station 1 44.31

Station 2 37.30

Stati0n 3

Station 4 I

42.21

40.81

Ft. Myers 41.49 Tamiami Trail 40 Mile Bend

62.77

Naples 43.81 Clewiston 63.41

Immokalee 49.75 Moore Haven 80.11

648

100

3~

,s

u 50

I~

n

o

~ -I!'

",-so '" ~ ~-1;

"' r'£ \J_-lS 4:0'1 I- .­.j:­

~ \.0 '"cJ

.to

~ -~

~

'f'IS -12 ,

'­ •.• __ -...1. L r i

o ,G'R(\UAolO' SU~'ACf

.. ~ - .

Fig. 12. Ground water levels - upland habitats.

'2

0 IGJH~Uh'b .fv'lt'Ae1

'3,

'00

Yo

1$

Z~

10

IS

o

-lS ·1

'tJ~

£ ~s ~""'J0\ i=·,S :l V1 l ­

o OJ

V -100

....., -125

-110 4

'ns .'2

11"21 2l'!S /2. I~

AP~I'- 1 ""A'i

Fig. 13. Ground water levels - marsh habitats.

..-0

'2

..,

~'2J .J.

OiP(;!..:·R:.:O:::U::..:....::.O::..:s:.:'J;,:1t:.::~;;:,.:::e~..'­ _

-12

0'\ :....., f-'

:~I ~

u

o

..zs

Vl~ rJ

~ !.''ll ~ZI­:z ­~

-as

.e

-ni

Fig. 14. Ground water levels - cypress habitats.

I

! .

I'

o o o

o o o

o o o

o .. 4 o ...

! 4o ... 0 ...o ...

4 c' ... ... 0

o o ... ... 0o

.. 0o o

o o

o o

o .. ..o .. ...

o o .. .. o

..... 0 .. 0

o o ..o o "0".. o ..

o o

o o

o o

o o o o o o o

o o

o o

o o

o o

o o

~: o

""0 .e 0

~:~o

.­"0... ... ... q,.

0... .. ... ... 0

.. .. ... .. 0

.. 0 o!! .. .. ...

0 ii 0 0

z 0> .... 00

0 ~ C>

h ~ 0 4)- ., .... ..,~ 53lDNI

.g ~ .... Woo"

!:~ "'~- ... ..... 0

-0<:

~~ ~g I""'L'-'

;;; ~ .... ... 1/>-::> 0'"-::>

0<

J:i0,..N ~

~g

g;'" N ... .... .. ... ~~

:0 !!?C ::. ~vj ,. r-­... <T'­~J ~ til :;lei? ~

CIl~~ ~ 'oJ -r-! 0­1'-) ,.0

CIl ::Oi'j .c ~Ci!

-e ... :a;: ~

0 N rl

rl ~-:> -.-I ~~ .,.;;) ;3:

"' ...... ·,1":' '"d ~

.,.~-.., CIl ~€? '"d'1 ;,

~ rT;;- 0

Po ~~ ~::c: .. (1 _}l til-."-Cl .-.lN .~ <llt: C':J

0 5 ~ -.~ <ll<) "'1 :0: rl,c:- ­<. f:l 1-1~aJ <ll ~~ ~

~O CIl ~i<ot

~~ '"d V\;( ~ _w

;j ... Ii: .... 0 _Of) 1-1 N ... '" 0

~"" ::~ Lf)·':-10.,.< rl ~

"''?:i bO -:t~"t" -rl ... ... r...

~ ~ :;]llJ ",2 -:;>

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~~ ..., l;1

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0 ~

~ ~ ~

'1 ~ r; 0¥ i1 ~ ~

S:-;::U.'JW1J.l'ol3::>

652

evaporation rates (Figure 8) and light rains accompanying several cold

fronts. The decline resumed in January and intensified in March as

evaporation rates increased. When rainfall became more frequent during

late May, the dry down stopped at a point: about 6 inches below the 1974

minimum. Water levels finally began to rise in mid-June with the advent

of regular rains, despite high evaporaticm rates. By early August, they

had stabi1ize~, but were approximately 6 to 10 inches lower than in 1974.

Additional rains in September brought thE~ water table to within several

inches of the 1974 level.

Seasonal water level patterns in the major habitats were similar

to those observed last year. Water levels in marsh and cypress were

consistently higher than in upland habitats (Figure 12) with two under­

standable exceptions during the dry seaSCln in an area of strong ground­

water flow. Agnin, the range of wat;er 1Elve1s for undisturbed marsh and

cypress generally overlapped through the dry season and diverged during

the wet season (Figures 13 and 14). However, .the Central Marsh deep

peat sawgrass site had water levels consistently within the range of

the cypress habitats, as did all the willow sites (Figure 15).

The water level range for a particular habitat type was small during

the wet season but broadened considerably in the dry season. Variation

can be attributed to differing organic c~mtent of the soils and the prox­

imity of some sites to major groundwater flow routes. The narrow upper

band on the marsh graph (Figure 13) and the highest dry season water

tables in the cypress (Figure.14) are associated with deep organic sedi­

ments ( 3 feet). TIle lowest dry season levels for each habitat type

were found along the eastern edge of the cypress on the Central Marsh

653

Transec t (WP, H/\., PC) where we measured t:he highes t groundwater flow

rates (probably due to the porous shell beds underlying the area).

These sites account for the narrow lower band on the marsh and cypress

graphs (Figures 13 and 14) and the lowest upland dry season levels

(Figure 12).

Data from the sanctuary staff gauge at Lettuce Lake, a slough through

the "bald" cypress near headquarters, has been added to Figure 15. During

the wet season water levels at Lettuce Lake are normally about a foot

higher than those at any other monitoring site. The unusual dry season

pattern of water levels, several feet above those of the other sites, is

due to water pwnped into the area.

Hydroperiods

One of the main objectives of this study is to determine annual

periods of inundation for the major habitat types. Figures 16 through

18 illestrate that the habitat types segreeate solely on the basis of

hydroperiod, but even more clearly when hydroperiod is plotted against

maximum or minimum water levels. It is extremely important to remember

that relationships between the points are approximately consistent but

their position on the axes may vary in accordance with the rainfall regime

of a particular year. The range of values for each habitat in Figures

16 and 18 is broadened by the previously mentioned influence of ground­

water flow routes and variation in organic content of the soils.

Six major habitat types can be clearly differentiated on the basis

of hydroperiod and maximum and minimum \\Tater levels: pine-palmetto,

hammock, myrtle prairie, cypress, marsh, and slough. Additional hydro­

period influences on suceessional patterns are revealed when fire

654

300 +-PINE PALMETTO ~ -HAMMOCK PEAT..::.-:5 -3'

~4' - MYRTLE PRAIRE

~ - MARSH

250, T - CYPRESS - - POND

"0 w r­<l: Cl

5 200 ~

w r-Ul

Ul

~ Cl 150

0\ Vl Cl

0Vl Ci: ~'lPrs'W Q. $rw 4l0 tm

~~~'h~ ._­ ~ w 't :t: IUU

111 ~:t~ty)~~t~~f' ­~ "-1\ *'1'll>1 'I\-'I~~I

it ~

50

~t~P1: -80 • - 60 - 50 .. 40 - 30 -20 -10 GROUND

SURFACE/974 MINIMUM WATER LEVEL (INCHES) -70

Fig. 16. Hydroperiods and minimum water levels - 1974.

30

250

o w ~ o z ~ 200

w .... en0\

\.l1 (/)0\

~ o

g 150 cr \,IJ Q. 0a: 0 >­:I: 100 LO r-­~

I

rt ~

50J.

o

'to - PINE PALMETTO f- HAMMOCK

'0/1- MYRTLE PRAIRE .:>l:. - MARSH

f- CYPRESS - POND

r.::1

~ ~~8- n IMi! I!O " "Me ~.::-~ ..:>k~ ~~,1..e FCINMw~E9~ ~..r.:.~ ~ -5*­~ ""'- ~B·J!: ,. ~ ..lI::..~~ • ~ ~.ll:. ~ ~ .IlL .L ~ ~

-,,--~..lt..1$'" ~ L~..:!L EJ .:i!.. J1L~-..l C ~ ~ ~

~RI 0 ~., ~~fflt ~

~ JO 5 GROUND

SURFACE 5

1974 MAXIMUM

10

WATER

1$

LEVEL (INCHES)

20 25 30

Fig. 17. Hydroperiods and maximum water levels -1974.

300 4 - PINE PALMETTO

.. - HAMMOCK •PEAT-.3+

<9> - MYRTLE PR,'RE 5-" ".§J <:. -PEAT~. - .... ~ .. ?=. <-r

x. • MARSH ;;::: ~ ~ -;L~ ~~M~~ V a - ~~ .£cl-~~M'H Ti!~ ~ ,FCYPRESS ,. ';"1' NAi "If:9 '1~ - POND 'i': "9 "-""':... ,>\- "'- "'­

~f.tTifil *-"'..I"~ r,';l~-"-~ "f~ """",""§j ... i"J = ""'­.:It.. ..:i:.. .lit- ~ ~ ~ -*' ..'!II. -*- JII:,

~B:JL ~'*-.*- '»':l.:..p.ok. .:L

~~~p:;) ~ ":~ Lill.i i¥' ~ ~~~~~~

*~'rf'ft#,q>q>~~~'f~~~Vt~W

4>+ •.,'CMP,

-80 -70 - 60 -50

1975 MINIMUM

- 40

WATER

-30

LEVELS (INCHES)

-20 -10 GROUND SURFACE

Fig. 18. Hydroperiods and minimum water levels - 1975.

frequency is considered in relation to eaeh of these habitats (Figure 19).

The pine-palmetto habitat occurs on the highest areas of the sanctuary.

The vegetation endures only sporadic t brief and shallow inundation t but

frequent fire.

The sanctuary hammocks are also on relatively high ground t but last

year had hydroperiods of approximately 80 dayst while the pine-palmetto

had less than 10 days inundation. The hammocks under study are both small

islands on limestone outcrops in deeper water habitats which had hydro­

periods of 180 to 210 days last year. These deeper water "moats" protect

the islands from fires t which are elsewhere frequent at sites with a simi­

lar hydroperiod.

The myrtle prairies t inundated for approximately 100 days last. year,

are vulnerable to spreading fires during dry periods because they are asso­

ciated with larger upland areas. Without fire they may develop

into hammocks, but frequent fires maintain them in a short grass-forb

seral stage with varying densities of sabal palm and slash pine. Intermediate

fire frequency (apparently the present condition) leads to dense stands of

wax myrtle with some remnants of the short grass-forb seral stage and some

ymmg hammock trees.

Marshes have hydroperiods only slightly shorter than those of cypress

habitats. Although the marshes are wet for much of the year t and are most

likely to burn when the water table is below ground, low intensity fires

are frequently able to sl~tain themselves on an accumulation of standing

dead shoots and burn over standing water. lUthout periodic fire, it is pos- \

sible that the marshes ~~u1d eventually succeed to cypress (myrtle and

ultimately hammock in the higher areas). Invasion of many of the marsh sites

by willow, buttonbush, and myrtle strongly argues for the importance of fire

in maintenance of the marshes.

658

50 100 . 150 200

3

10

APPL E POP ASli SLOU6H

~?

HAMMOCK

250

o

FIRE FREQUENCY (YEA~S BETWEEN FIP.£:S)

30

0\ VI \.0

HAMMOCK I HAMMOCK I HAMMOCK HAMMOCK

HYOl'OPEJUOO (DAYS)

Fig. 19. Hydroperiods and fire frequencies of major south Florida Habitats.

As noted above, hydroperiods are only slightly longer in the cypress

than in the marshes, but the difference appears to extend the period of

fire protection sufficiently to allow cypress to become established. Once

the cypress forest is in existence, its moist microclimate and relatively

sparse understory further reduce the likelihood of fire. Both willow sites

have hydroperiods in the cypress range, which suggests they are an early

seral stage leading to cypress forest.

An important point in this interpretation is that the distribution

of cypress and marshes are not necessarily fixed boundaries, and are

constantly shifting as low rainfall cycles, with their attendant in­

creased fire frequency, alternate with high rainfall cycles.

The Flag Pond (FP) study site is a rather shallow representative of

the slough habitat formed by an irregular series of lettuce lakes, pop ash

and pond apple sloughs, and "gator holes" extending through the ''bald'' cy­

press.

The natural hydrology along the South Dike Transect was altered by

dike construction in 1967-69, and, as a result, several of the sites do not

have expected hydroperiods and maximum water levels (Figure 17). This suggests

that these sites may be shifting to a new habitat type. The increased wet

season water levels and hydroperiods at the sites above the dike are in

the normal range for cypress habitats, but the sites below the dike have

unusually low wet season water levels for the hydroperiod. Since fire

frequency is probably determined by hydroperiod rather than wet season water

levels, sites belm.] the dike should return to their original condition ­

marsh in the center and cypress in the logged areas on either side. Thus

the Hid Above (HA) site appears to be the only habitat changed by dike

660

construction and, under the present hydrological regime, should become

cypress forest. Although the Mid Below (MB) site still appears to have

normal hydroperiods, purposeful exclusion of fire has allowed it to

become overgrown by shrubs and it may eventually succeed to cypress forest.

Long-~ Water ~ Records

The above analyses of hydroperiod and water level fluctuations pro­

vide insight into the annual hydrological cycle at Corkscrew Swamp, but

many years data are required to determine the range within which this

cycle varies. We are trying to correlate water levels at our wells with

those at the sanctuary's Lettuce Lake staff gauge, for which approximately

15 years of records are available.

Corkscrew Swamp Sanctuary personnel have kept daily records of water

levels at several stations along the boardwalk since 1959. The first sta­

tion was establi.sh~d just tnside the cypress fringe near headquarters, a,tic

the second at Lettuce Lake, a slough in the "bald" cypress. Water level

data are complete for the period, except for times of severe drought when

the water level dropped below the ground surface, and for parts of 1970

and 1971, when monitoring was temporarily suspended. Daily rainfall records

have also been kept by the sanctuary staff.

Several major environmental changes occurred in or near the sanctuary

during the period of record. The first change was the construction of the

Golden Gate Canal system, which extended to within 3 miles of the southern

boundary of the sanctua~, and was completed in 1966. In 1967, a dike was

constructed along the south edge of the sanctuary. Eowever, portions of

the dike washed out during 1968 and were not fully repaired until 1969.

The South Dike was built by connecting portions of the old logging tramway

661

system. using dragline fill across the Central Marsh. The dike permitted

control of surface water flow to the south during the wet season. In

late 1970, four new pumps went into operation along the northeastern edge

of the big cypress "horseshoe." (Another pump had been used in this area

periodically since 1963). The pumps were operated to maintain water in

the vicinity of the boardwalk later into the dry season.

We analyzed the water level records from the boardwalk staff gages

in an attempt to correlate any changes III the hydrology of the area with

known environmental modifications. Examined were: rainfall (for speci­

fic seasons) in relation to 1) minimmn annual water levels; 2) water level

decline during the dry season; 3) average wet season water levels, and

4) length of hydroperiod at a variety of water levels.

Minimum dry season water levels were analyzed initially in relation

to total annual rainfall, but when little correlation was found, periods

of shorter duration and closer proximity were investigated (March 1 ­

April 30, March I-May 31, January I-April 30, January l-¥ay 31). Although

rainfall for all of these latter periods influenced water levels similarly,

the correlat.ion was strongest for the January I-May 31 period (Figure 20).

In general, water levels dropped further during seasons with lower rainfall,

and neither the Golden Gate Canal nor the South Dike appeared to affect

the relationship. The few years that do deviate from the average all had

higher than expected water levels and all occurred after the pumps were

in operation. The years prior to pump ::I.nstallation and after the Golden

Gate Canal system was completed showed no deviation from the pre-canal

construction pattern of minimum water levels.

Dry season water level decline versus rainfall was also examined for

the March I-April 30, March I-May 31, January I-April 30, and January 1­

662

30

25

20

(J)

w :c u z

15 ..J w > W ..J

0:: w

10 ~ ~

~ ::l ~

Z

~ 5

o

.1972

.1973

• .1965 1975

o 5 10 15 20 25

RAINFALL (JANUAFIY 1- MAY 31) (INCHES)

Fig. 20. Minimum annual water levels.

663

May 31 rainfall periods. Again, all periods seemed similarly influen­

tial, and the January 1 - May 31 period was selected to illustrate the

relationship (Figure 21). With 14 inches or more rainfall during this

period, water levels dropped 7 inches or less during the dry season.

Runoff and evapotranspiration were probably both factors in this decline.

However, with less than 12 inches of rain, water levels dropped much

more rapidly from January through May. As surface water flows become

insignificant~ evapotranspiration probably becomes the dominant factor

affecting water levels in the now dry forest and remaining ponds. As

the ponds disappear, the water table becomes more remote from the ground

surface and both evapotranspiration and groundwater flow gradually de­

crease. Thus, an amount of rainfall too small to significantly affect

wet season water levels could be critical to offset these processes

and slow the rate of dry season water level decline. Again, no effects

of the canals were evident, but records for several of the post-pump

installation years indicated an arrested decline in water level.

Wet season water levels were analyzed by averaging the Lettuce Lake

staff gauge readings taken on the first days of July, August, September

and October, and relating these values to total rainfall for the period

June I-September 30. Essentially, the swamp compares to a river: in­

creasing rainfall results in even more rc:tpidly increasing water levels

(Figure 22). All pre-South Dike wet seasons had a consistent relationship

with rainfall, while data for virtually all post-South Dike wet seasons

indicated increases in wet season water levels of 5-10 inches. The dike

d1.d not affect 1968 water levels, possibly because of controlled releases

and washouts that year. As discussed later for the hydroperiod data,

664

'\ri w :r U Z

'-J

~

('()

?( ~ I

7­U <

• ::::> Z

35

25

15

10

5

Fig. 21. Dry sc~gon water level decline.

o s /0 :5

665

'V1 l!J ::r: oIL<J z

'-J ~ cl. w co JlO o t; o I

~ .11'J'7'l­::> h

'-J

J: ~ '2 o ~ 35

!.!... C

J­• VI

.-..z u. UJ

~ 'Z o l'7 30 J W /" ·1')75ill J

FlU_ 22. Averag~ ~ct

35

season water levels.

666

the dike did not appear to affect water levels much below the 30 inch

mark on the Lettuce Lake gage~ which is where levels were during most of

the 1975 wet season.

One of the major characteristics determining distribution of habitats

in south Florida is hydroperiod. We evaluated this factor by plotting

the number of months (June I-May 31) that water levels were above specific

heights at the Lettuce Lake staff gauge against rainfall for the same period.

Initially~ we plotted 10, 20 t 30 t and 40 inch levels~ but the data for 10.

20~ and 40 inches provided little useful information. There were few years

with any months at the 40 inch level~ and most years had levels of 20 inches

for 9 or more m.onths. and 10 inches for 11 or more m.onths. Since the range

between 20 and 40 inches indicated the only significant year-to-year varia­

tion in hydroperiod, we plotted the number of months that water stood at

25~ 30 and 35 inches for each year (June I-Nay 31) against rainfall for

that period.

There appeared a very nearly direct relationship between length of

hydroperiod and rainfall. Hydroperiods for post-canal construction years

were no shorter than those of pre-construction years. However t hydroperiods

at the 25 and 30 inch levels were 1-3 months longer most years after the

South Dike was built (Figures 23 and 24). Both pre- and post-South Dike years

exhibited similar variation in hydroperiod at the 35 inch water level (Figure 25).

When water levels reach a certain height (between 30 and 40 inches) signi­

ficant quantities of water probably leave the sanctuary to the west through

Gordon Swamp and are not affected by the South Dike. This t and the increasing

influence of groundwater flow as compared to surface flow t at low water

levels t leads us to expect a distinct effect of the South Dike only at an

intermediate water level (around the 30 inch mark at the Lettuce Lake).

667

, . ~ .

12 r_--=3.>L -..::5~O~ __~--S~5.L. (;~:.~O~ _..!7~O~J(:.,~5~o ''''--_ IQ10

.qG.q

IJ

. 10

q 01%1

3

2.

0 1.....----­4-5

Fig. 23. nydrop"dod at the 2S-inch lev"l.

50 --55 _0 /00 65

F:AI~JFALL (JIJN~ 1- illl- 'f ~1) (Il..f ~~ W~S)

'70

668

..J <.

'2 r--_--:~~15!._ __.::<.5..:::!) ~!5~5~· ..:":::.O:::_ __!.I:"'t::5L_ '1.!.J:!.D~_.

II

10

3

2 I

FiC' 24. Ilydrop<>rio<\ ,\t the 30-inch level.

cL----~-­~,1S 10

N73 • ·1"115

669

45 50 55 60 65 7012 , __J-. .,J' .....::.:'.....:.' ........' .L'-------',-- ­

" 10

9

8

.,9707

0 w ~ 60 z ~ z

5(J)

I r .1961 0 z ~ 4 .1967

.,975

3

.,974 .1966

2 e1963.1968

965

~1970 o L.&:1..;::9.;:::6...:4......,:IL-_...JL1..:;,9..:;,6.;;:2.,.. -,.. -"r-­ ..., ----­.., _

45 50 55 60 65 • 70

RAINFALL {JUNE I - MAY 31 } (INCHES)

Fig, 25. Hydroperiod at the 35-inch level.

670

· ,

Flow to the west would also place an upper limit on the increase in wet

season water levels with increasing rainfall, due to impoundment by the

dike.

Throughout the above analyses, no effects of the Golden Gate Canal

system on minimum dry season water levels, dry season water level decline,

wet season water levels, or hydroperiod in the vicinity of the Corkscrew

Swamp Sanctuary Lettuce Lake staff gauge were detected. The only noticeable

changes in any of these parameters occurn!d during the years following:

1) construction of the South Dike, when increases of 5-10 inches in wet

season water levels and lengthened hydroperiods (at the 25 and 30 inch

water leveDof several months were recorded; and 2) during periods when

the pumps were in operati.on, raising minimum water levels 6-12 inches and

slowing the rate of water level decline. The strong correlations with

rainfall (except for the appar~nt responses to the South Dike and pumps)

found with theBe rough analytIcal methods argue for the conclusions

reached above, and indicate that even stronger correlations would probably

be found with more sophisticated analysis.

An even better understanding of the j~pacts of canals, dikes, and

other developments in the Corkscrew area ~rill be possible if we can cal­

culate historical water levels at our study sites.

Water level patterns at the wells and staff gauge were virtually

identical during the heart of the wet season (when surface water was wide­

spread and rainfall was regular) in 1974 a.nd 1975. But when rains became

infrequent, and surface water began disappearing from the higher sites,

the rate of water level decline at the well sites nO longer corresponded

consistently uith that at the staff gauge. Only three nearby loTell site

671

fe eMP21

20

19 q/r.,/7+

1//2/7'1 I12/1/7<1

13 l/3th5

~ G~u~"O~ cL -<:: :r ::I:

§l 17 311/75 il)

Q

f? e ';/5/15 ~ I" ~ ::> tj)

g 13 /74- b::;::::::::::::::::=f=::::==~b-J

lOIS/1+ l-----t--~___!_._

__---r-­....---

I J:; /75 ------:'

----+---------­

~1?/7~ .------..1

~\ \ I

'VIFig. 30. 1974-1975 water level decline - cer.tral marsh tr"n"..cl.

I I I II I

678

//

Fe Ct...", I'C PC Hba P ,.1 CMP21

2.0

_ ..+----k ~ cJ ..:: 18 ~ T G~UNP:'Cl(fM:.!.

~ 7/N/7S U cl o /1. t­o u >­w

~ It.. ,:) \I)

t "r

6z 15

'}: l.:J !..I

QH ;z: c

~ ~ d 13 p loJ ~ :;l.... <n ~ /2.

Fig. 31. 1915 ~ater level

679

I I I I rise - ceutral maroh transect.

I I I I I !

Transect area from the high ground to the east, but once surface water

levels are constant, water begins to cross the transect moving south from

Corkscrew Marsh.

Evapotranspiration

Evapotranspiration is the final factor we need to evaluate to

develop a water budget for Corkscrew Swamp. We will use and compare sev­.

era1 techniques to measure this parameter: 1) estimation as a fraction of

evaporation pan losses; 2) estimation from local climatic data; and 3) use

of water level recorders to measure the diurnal fluctuation of ground or

surface water levels. Methods I) and 2) will provide data for the area

as a whole, whereas water level recorder data will give us information

on specific habitats. We have adapted two water level recorders so that

they can be mounted on our 1 1/4 inch well pipes and are more or less

portable. With these we will get data from each well site and

detailed information on neasonal variation in evapotranspiration in each

major habitat.

An example of the water level recorder data is shown in Figure 32.

Diurnal water level fluctuations are relatively small when surface water

is present, but, when it recedes below ground, the daily amplitude increases

until the water table goes below the main plant root mass. Thereafter

the amplitude decreases lIDtil virtually all of the water losses are due

solely to steady groundwater flow.

l.;rater Chemistry

Ground and surface YTater samples hav,~ been collected on nine

680

i

(CHW~ CM, and FC) dry down patterns paralleled that at Lettuce Lake. The

sanctuary began pumping water into Lettuce Lake in January so water levels

at the staff gauge are not comparable to those at the wells thereafter.

This preliminary analysis indicates we will be able to use the

Lettuce Lake staff gage records to calculate approximate maximum water

levels at our well sites for the 15 year period of record~ and if the

differences in dry do"Wll patterns prove consistent in 1974, 1975, and

1976, we should be able to develop a reasonable estimate of hydroperiods

since 1959. Estimation of minimum water levels has proven difficult due

to the complicating factor ofipumping in the staff gage vicinity, but may

be feasible with more elaborate analytical methods. When the details of the rela­

tionship between Corkscrew rainfall data and the Lettuce Lake water levels

have been worked out~ correlati.on between Corkscrew and Ft. ~1yers rainfall

data would permit reconstruction of the annual hydrological cycles at the

Lettuce Lake~ and subsequently our well sites, back to the early 1900's.

Water Flows

Flows at all points where surface water enters and leaves the sanctuary

have been measured at five different wat:er levels over the past two wet

seasons. Also, at the highest water level, we measured the rate and direc­

tion of water flows at each of the well sites on the Central Marsh and North

Marsh transects. After we compile this data and survey two small areas

over which there is some overland flow, we can calculate the relative amounts

of water passing through the various habitats and, using thee water level

recorder data, total surface water inflow and outflow for the sanctuary_

Although we know that groundwater also flows generally south and west,

672

major groundwater flows are much more difficult to locate, much less

measure. Figures 26 through 31 indicate the seasonal location, direc­

tion, and relative intensity of major flows in the transect areas during

1974 and 1975.

When the water is shallow, surface water comes into the Grapefruit

Island Transect marsh area from adjacent uplands, but as the waters rise

the dominant flow is southeast from Corkscrew Marsh through Mud Lake

and Ruess Marshes toward North Marsh (Figures 26 through 27). Ground­

water moves to the south towards Little Corkscrew Island, suggesting

the presence of relatively porous soil strata under the island.

Flows under the North Marsh Transect were erratic as the rains began,

but after wet season levels stabilized, surface water generally moved

southward at similar rates at all study sites (Figures 28 and 29).

There were small flows from the western end of the transect to adjacent

uplands in fall and winter, probably replacing evapotranspiration losses.

The major stream crossing the Central Marsh Transect passes under the

"pond" cypress (PC) and mixed marsh (WP) lvhen surface water is present,

but shifts to the "pond" cypress as the "rater table goes below ground (Figures

.30 - 31)., The strong groundwater flows in this area travel through

a thick bed of porous shell, the upper edge of which is 4-6 feet below

the ground surface. Early dry season water levels at wells in this vici­

nity were distinctly lower inside the pipe. We attribute this to water

moving faster through the shell bed than it can be replaced from the

surface. Minor outflows to the east during the fall and winter may be

associated with evapotranspiration in the adjacent uplands. Early in the

wet season, when lvater levels are rising" water flows into the Central Marsh

673

LeI MLM GI RM RI21

8/6/74

20 9/3/74 10/1/74

GROUND SURFACE ~-

-- -- -­19

12/3/74

18

11/5/74

11/7/75

17

~ w W lL. /6

z 0 i= « > w 15 -I w

14

13

12

Fig. 26. 1974-1975 water level decline; Grapefruit Island transect.

674

21

" " ,,

Fig. 27. 1975 water level rise; Grapefruit Island transect.

Lei

20

8/20/75 GROUND, SURFAC

19

18 6/6/75 7/15/75

/7 7/8/75i="

w w lL

16 z 7/1/750 I- 6/24/75« > w 6/17/75 ...J 15 w

5/28/75 14

13

MLM GI R RI

.

675

12

CP 13 e. NMC. FP SP21

20

2/~/1'f 'l/'3/7'/­/0/J/74

G.~ceND SVR~

ICJ

~ UJ W ~ .5/~ /15 I ' -----<f-i"

-.J 1'+ I ~

3 5/21/75,:----. ~ .. 1- ­~

~ 13 I e I~

'/1:J IIn < :?

1'1g. 28. 197 /,-1975 waler level decline - north r,.ush transect.

I I"

676

----

c 8B sBF NMe21

,/, ," ,, "

5/27}75

Fig. 29. 1915 vater level rise - north m.,rsh transect.

---

c,/iO/7Sl------i--f---r-­

677

w Ifn~R. If BOile G- Rf) ()iV D+ ,ABLE

I'"( -+

SEPTEMBER 11,1974 (4")

--------­ +­, OCTOBER 6,1974 ( 2")

SEPTEMBER 16,1974 ( 3")

-OCTOBER 21,1974 ( 10") -OCTOBER 13,1974 ( 4")

JANUARY 15, 1975 ( 22") OCTOBER 26,1974 ( 13")

MARCH 26, 1975 ( _ 43 i) JANUARY 20,1975 ( 26")

MAY, 1975 (_ "0'')

--1..­__---1_--+-.­MIDNIGHT MIDNIGHT MIDNIGHT MIDNIGrlT MIDNIGHT

bAY I DAY 2 DAY 3 DAY 4 DAY 5

't' ALL CAMP PINES WELL. (MYRTLE PRAIIRIE) NORTH MARSH TRANSECT

Fig. 32. Daily variation in water levels.

occasions since December, 1974, and six of them have been analyzed for

water chemistry data. The data have been compiled, but not yet sum­

marized. Analyses included alkalinity, hardness, pH, conductivity, or­

ganic, ammonia Clnd nitrate nitrogen, ortho- and total phosphate, inor­

ganic and organic carbon, and the following trace elements: Na, K, Ca,

Mg, Mn, P (colorimetric), Zn, Pb, Cu, Cd, Fe, Ni, F , and CI. Alkalinity,

hardness, and pH were analyzed at Corkscrew; conductivity, nitrogen,

phosphate and carbon by Lloyd Chesney at Dr. Patrick Brezonik's labora­

tory at the Unniversity of Florida; and the 14 trace elements at the

University of Florida Institute of Food and Agricultural Sciences Analy·~

tical Research Laboratory (IFAS Lab.).

Diurnal cycles of dissolved oxygen and temperature are shown in

Figures 33 and 34 for September, 1975. These parameters are measured

quarterly, but equivalent measurements were not possible in March or

June, 1975, because all habitats were dry. Except for the mixed marsh

(and even that, during the early morning hours) dissolved oxygen levels

are extremely low in all habitats. Distinct diurnal variation in both

dissolved oxygen and temperature was evident only in the marshes.

Soils

We examined soil profiles at over 100 sites during the 1975 dry

season. The work was concentrated along the transects, but additional

selected sites (a dome, a marl prairie, a stunted cypress forest, etc.)

were also examined. These data have been compiled but not analyzed. After

we examined soil profiles, we collected samples at two to nine selected

depths (depending on variability of the profile) for structural and chemical

632

85 84

2

82 81

80

79 78

2 80 79

78

77

76 IL.. z 75 0w CI

........ ...4 83

"POND" CYPRESS

DISSOLVED OXYGEN

,,~ ..,--------................ ~' ........... _---,

........ _---... " ........._------------/'

.........-----174

........----.....1

............................

TEMPERATURE ..,,/.........:::.. .. ... _--............. --- ....---------_._------,... ....._--

DISSOLVED OXYGE'" o ----/

Ol- .

O~---__---------.---------_l SLOUGji

~

"BALD" CYPRESS

2 CENTRAL MARSH

...... TEMPERATURE ..... ' --------..... ",,'... ......

.......... --.._-_ ..... ' DISSOLVED OXYGEN

0000 0400 0800 1200 1600 2000 24ro

Fig. 33. Diurnal dissolved oxygen and temperature cycles, Sept. 10-11, 1975.

683

w>­X o n ~

~ <Xc 0::w

2> 81 ~ -' o 80 ::E en

79 ~en c 78

77 76 75

74

82 81

80

79 78

77

76 75

10

MIXED MARSH9

8

86

7 -~-

"­01 5 81 E TEMPERATURE ~

lL.

z w C> >­X 0

e w >....J

4

... ... ..., ... ... .. _---,

..."',...,_._---­ -

80

79

78

0

w 0:: :J I­« 0:: w a. ::E

0 (f)

e 3

DISSOLVED OXYGEN 77

w l­

76

" 85

" ... " ... 84...,,

... 6 ... 83,

...

" ... ..., 82,

2

O. L.­ - ----I

0000 4000 3000 1200 1600 2000 2400

Fig. 34. Diurnal dissolved oxygen and Sept. 10-11, 1975.

temperature cycles,

684

analyses. The soils will be analyzed for the same elements as the

water chemistry samples, so that interactions may be evaluated. These

analyses are in progress at the IFAS Lab.

Patrick Gleason, Pete Stone, and Bruce Cutright from the Central

and Southern Florida Flood Control District (FCD) collected peat cores

in the Central Marsh and "bald" cypress habitats along the Central }farsh

Transect in July, 1975. They are examining incompletely decomposed

plant tissues to determine the species composition of the peat strata

and the succession of communities in each habitat. If time permits,

they will also conduct pollen analyses on these samples to detect vege­

tation changes during the past several thousand years in the general

vicinity of Corkscrew Swamp. One sample from the bottom peat of the

Central Marsh core was forwarded to the University of Miami Radiocarbon

Dating Laboratory. It was assigned an age of 4720 + 90 years B.P.,

which approximates the accepted age of the earliest peat development

at a variety of sites in south Florida.

Organic soil depth was measured along the Central }~rsh Transect by

pushing (by hand) a metal rod into the soils at 100 foot intervals. The

measurements were begun at the myrtle well because little organic matter

is present in the soils of the drier habitats due to frequency of fire

and relatively rapid oxidation when the ground is dry. Correlation with

soil profile data is not complete, but preliminary comparisons indicate

that this method does yield a rough approximation of organic soil depth.

The results generally confirm the expected profile presented in last year's

annual report, but provi.de greater detail and more accurate depth measure­

ments (Figure 35). It also indicates the lack of correspondence between

depressions in the mineral soil beneath the peats and at its surface.

685

20

19

18

17

16

,\ I I \'I

I, I,,,

I I15

,'\\ , \ I

\'14 I _

,I, 1/P ,l.IJ ,W .• 1\ ,0\ "::: 13co IJ~ ,I ~ la,0' z I, • , I

o I " I , ' " , BASE OF PEAT I~. " I \ .~ 12 t I' ~ \ ~ f t:> I I

" I' \1

Y .. \ ,\ /\ ,"'1 II

I: I I .' 'J

l.IJ ,I II _I

I '..,' v' t" ~ G.1 I I I , ,II , ~ I ,(:)

l.IJ II ; :\ I I , ' I \ !~ 10 I

I,::l V) I ~ " V

,,,­ "'IV) I•<f 9 I

,­I

~

, I I

8 I I

7

'" "PONd' 6 1"BALo"cYPRES CENTRAL MARSH !WIll BALD cYPRESS CYPRE..JMARS

5 I I I I I I I I 7,000 6,000 5,000 4,000 3,000 2,000 1,000 °

Fig. 35. Estimated depth of organic soils - Central marsh transect.

The rod penetration method detected the presence of lime rock where it

was situated directly beneath the peat. The only are.;iS where rock was

frequently encountered by this method was in the Central Marsh and the

adjacent willow habitat.

Structural Characteristics of Plant Communities

We plotted DBH and height of the major tree species at the Central

Marsh Transect intensive study sites (and some pine on Ruess Island)

and found excellent correspondence between the two parameters regardless

of site. Figures 36 .- 39 illustrate the relati.onship of these measures

in the most frequently encountered species. DBII alone apparently pro­

vides an adequate measure of tree size for calculating biomass or de­

termining the vertical distribut:lon of trees (unless, of course, a tree

has been topped or developed an unusual growth form), and is particularly

useful when time is limited or the forest so dense that the treetops

are hard to see.

Where cypress, maple, and red bay occur together, cypress clearly

dominates the canopy and the hardwoods remain in the subcanopy (Figures

36 - 38). Since cypress seedlings are shade-tolerant, this relationship

would probably last for long periods with the exclusion of fire.

A comparison of DBH frequency by species on the "pond" and "bald"

cypress tree productivity plots is shown in Table 4. The equal number

of species, but smaller number of individuals in the "bald" cypress is

noteworthy, as is the absence of willow and appearance of pop ash in

the "bald" cypress.

The DBH of cypress along the Central Marsh Transect gradually in­

creases from the "pond" cypress towards the center of the strand until

687

120

o o o

100 o o

o

0­00 CT.J

80~ I )C

b t=: y.J: ~; ~ w lJJ III *"'''l,(,.j(, ,c ~ 1­ )l~~1 .

60 "~)("l' : X ~ :I: ')(~ 'J.i:/. I:I: "I­~ ~z(~ z(w I j( )(~ ~:I:

)01. l( ~

40~ I l;;.ff! •

" . ~X ""j.

20~ it

0 0

0 0

0

• HAMMOCK

o "BALD" CYPRESS X "POND" CYPRESS

o 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 74 80 DB H (INCHES)

Fig. 36. DBH/height - cypress.

•

•

•

• • •

60 •

••

o

o o • 50

I I •• 'X'.. ••0

• .. oeo 0 0

401 I · •

l­0' w CP w

I.L.'" ~

I- 30 J: ~

w VI CD ;:)

,.'. .)(.

0•••0' .'. •• • ••• }C. •• 0

o 09-:" ~ :

"06 '." • . o' , " • .

'"\ 00.0: ........J: I J: • 0 VI . b··

'0' , 0

:d&- •201 f. • • • HAMMOCK qo • o "SALO' CYPRESS0 x "PONO' CYPRESS

0 I I

10

o 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 DBH (INCHES)

Fig. 37. DBH/height - maple.

• •

60~ I I •

0

50~ I • •

Q; •4°l ., ••. •

•

••

.'

-'" 1Il • . ... .

• • • CO .,f- I :)

:I: ....0:: :I:a- t!) '-' .... e .. •- 1Ilw

0 :I: Qe '" .. . '-.0

3°l .tr.·-.

I •• •;0 ., . • ,~~.,; ..

20-1 ,- • • • HAMMOCK•"• :. o "BALD" CYPRESS

X "POND" CYPRESS• •

10..1 I,

o 2 3 4 5 6 7 8 9 10 \I 12 13 14 15 16 17 18 19 20 DB H, inches

Fig. 38. DBH/height - red bay.

90

eo

70

60

Q) --Q)

50 ......

0\ :I:: '-0 t.:> f-' ­

l.LJ 40J:

.,,,, '"""

20

10

•

o •

• ••

• •

•

•

If) CD ~ a:: :I:: If)

•

• • ••• ••

•

• •• • •.. . ... • • • • ... I··

~ .....- :: ..Wt­......., ~, .

o

o ~o

o

o

o

o

00

•

• CENTRAL MARSH

o RUESS ISLAND

o<?

TRANSECT

o r 2

T 3 4 5 6 7 8 9

DaH,

10 11

inches

12 13 14 15 16 17 18 19 20

Fig. 39. DBH/height - pine.

2TABLE 4. DBH of Trees in "Pond" Cypress Plots (225m Plots).

DBH Inch Class Cypress Fig. Willow Pond Apple

Holly Maple Red Bay

Pop Ash

1. 5-1. 9 2-2.9 3-3.9 4-4.9 5-5.9 6-6.9 7-7.9 8-8.9 9--9.9 10-10.9 11-11. 9 12-12.9 13-13.9 llf-l!+.9 15-15.9 16-16.9 17-17.9

Total

19 37 25 28 10 10 14 12 10

5 9

12 3 4 1 1 1

201

2 1

3

9 7 8

2

26

,4

1

c­

-'

I 3

1

5

1 1 3

1

6

2 2

4 0

DBH of Trees in "Bald" Cypress Plots (2 25 2 m Plots).

1.5-1. 9 1 4­ 1 4 1 11 2-2.9 1 l'

~. 11 1 11 3-3.9 1 3 6 4-4.9 1 6 5 5-5.9 3 6 6-6.9 1 3 7-7.9 1 2 3 8-8.9 1 9-9.9 1 1 10-10.9 1 1 1 11-49 12

Total 12 4 0 10 1 32 3 - 46

692

it abruptly decreases in the willow (Figure 40). At present we assume

that the largest trees are the oldest and younger trees are becoming

established in the Central Marsh willow and along the outer border of

the rtpond" cypress. We have taken cores from all but the largest cypress

and are studying them to ascertain age and growth rate.

Vegetation

Habitat Elevat1.ons

We have used ground elevation at eacll well site to characterize

the elevation of the habitat in which it is located. To assess the

accuracy of this assumption we surveyed elevations at 25-foot intervals

along the transects (except South Dike) and calculated the average ele­

vation and its variability in each habitat (Table 5). Ground elevations

at 11 of 22 well sites were within 0.01 to 0.11 foot «2 S.E.) of the

habitat mean and only four were 0.30 to 0.42 foot off. One of these

four. Grapefruit Island. was probably at ~m elevation more representative

of the hammock habitat than the other surveyed points which were along

the path leading in from the edge of the hammock. Elevations of the

other three well sites were more than two standard errors, but less than

0.18 foot, above the mean. One other site, in the "bald" cypress on the

west side of the Central Marsh (FC). measured 0.53 foot higher than the

mean. but when elevations of slough areas were omitted from the ca1cu1a­

tions. was only 0.04 foot above average.

Sites along a transect can be segregated by elevation into the

same habitat groups distinguished by hydroperiod and maximum or minimum

693

10

• ~

~t¥) <:J Z

'-J

:r ~o

o

10 \ ~·lg. 40. DBH of cypr",,~ on era,.,. ,;""cclon chrollgh RCrand.

o I 2. :1 4 :5 " 73 '1 I..:) :1 12 lJ I'}- lei l~ 17'[;'1 2.")

ms.-,!l,NC.E r-:COf"\ 2:DG£ OF .'5T~ND (1.:)0 FEET)

694

. ,

TABLE~. Habitat and Well Elevations Along Transects.

Description Well

Elevation Mean S.E. Minimum Maximum Number of Points

Surveyed

Grapefruit Island Transect:

LCI MLM GI RH RI

19.49 18.94 20.02 18.99 20.14

19.38 18.95 19.67 19.04

°20.24

0.07 0.03 0.07 0.03 0.04

19.07 18.28 19.36 18.50 19.85

19.69 19.40 20.02 19.44 20.70

9 70 9

44 30

North Marsh Transect:

CP Be LC FP BB SP MC ~'11W

19.20 17.82 1'7.98 17.63 18.30 18.53 18.18 17.92

19.18 18.2l} 17 .96 17.56 18.14 18.42 18.22 17.99

0.02 0.08 0.08 0.03 0.04 0.02 0.02 0.07

19.08 17.82 17 .65 17.35 17.85 18.32 18.03 17.92

19.26 13.93 18.16 17.79 18.47 18.52 18.37 18.06

12 16

6 17 32 15 24

2

Central Harsh Transect:

Of? NY WP HA PC NC (See Below) CMH CM FC (See Below)

18.99 18.48 17.87 18.57 17.26 17.14 17.20 17.74 17.69

19. Qt. 18.31 17.79 18.52 17.59 17.12 17.50 17.75 17 .16

0.08 0.03 0.03 0.09 0.04 0.07 0.06 0.01 0.15

18.22 18.13 17.57 18.24 17.12 15.76 16.89 17.47 15.11

20.00 18.68 18.02 18.72 17.95 17.85 17.85 18.01 18.15

22 21 19

5 23 36 19 61 31

NC: Slough Forest

17.14 16.69 17.28

0.14 0.06

15.76 16.60

17.15 17.85

10 26

FC: Slough Forest

17.69 16.38 17.65

0.23 0.05

15.11 17.35

17.51 18.15

12 19

695

water levels (Figures 16 - 18). However, the North Marsh Transect

burned cypress site has a mean elevation more comparable to that of

marsh than cypress, which suggests that fire may have reclaimed a

"marsh habitat" into which the adjacent cypress forest had expanded.

Marsh Transect at bimonthly intervals from September, 1974 through July,

1975. Net annual understory production was calculated by subtracting the

lowest biomass values from' the highest (Table 6). Only in the Central

2Marsh did understory productivity exceed 1 g/m ·day (and this value may

well be low since th:ls area burned completely in March, 1975 and produc­

2tivity was 4 g/m ·day from March to September).

The timing of peak standing crops of understory vegetation varied

considerably from habitat to habitat (Table 6), 2nd was quite erratic

through the year at some sites. The values for the "bald" cypress are

particularly suspect because of the extreme heterogeneity and clumping

of types of understory vegetation (dense clusters of fern, lakes covered

with floating duckweed or water lettuce i.n the wet season with bare mud

or dense grass in the dry season). One explanation for some of the

irregular productivity patterns might be the presence of two distinct

communities - one a flora adapted for growth during wet season inundation,

and another adapted for growth during thE! relatively arid conditions of

dry season. Unfortunately, sampling was too infrequent to evaluate

this possibility.

696

2TABLE 6. Understory Bioreass (g dry weight/m ).

Description 8/28-9/7 11/6-8 1/8-20 3/3-14 5/1-2 7/11-14 Annual Production Dry Weight

g/m2/yr-

Pine X S.E.

134 27

139 31

224 90

91 22

98 19

86 11

138

Mixed Harsh X S.E.

150 19

220 128

64 20

312 44

84 4

124 24

248

Halmnock -X

S.E. 23 9

20 12

32 10

54 7

36 6

28 5

34

0' \0 -.J "Pond" Cypress X

co 'I:' ~ • .1:.1.

71 30

119 45

57 .." ,Lt­

154 32

106 31

153 16

97

"Bald" Cypress -X

S.E. 182 124

230 123

1 1

40 19

282 95

39 9

281

Central Marsh X S.E.

763 156

348 64

288 44

* 212*

36 312 52

716 76

551

* 2Biomass was 0.2 + 0.2 g dry weight/m two days after burn: 3/11/75.

·,

Productivity of Submerged Aquatic Vegetation

Using the diurnal curve technique, we estimated the productivity

of submerged aquatic vegetation from the data on the daily cycle of dis­

solved oxygen and temperature. Sampling was begun in September, 1975, and

will be continued quarterly. If we.had begun sampling six months earlier,

aquatic production in March and June would have been zero since the water

table was below ground at all sites. Both gross production and respiration

were surprisingly low in all habitats, and actually close to zero in the

" pondII cypress (Table 7).

Overstory Productivity

In December, 1974, we measured DBH and height and tagged all shrubs

(woody plants > 3 feet h:i:gh and < 1.5 inches DBH) in two 10 X 10 m plots

at each of the intensive study sites alon.g the Central Harsh Transect.

At the same time we similarly measured and tagged all trees (woody plants

> 1.5 inches DBH) in two 25 x 25 m plots at the same sites. In December,

1975, we will remeasure the shrubs and trees to estimate net production

during 1975. In addition to productivity' data, this study has yielded

valuable information on the stratification, density, basal area, and diver­

sity of the plant communIties.

Vegetation Biomass

We have accumulated some information on biomass from the productivity

studies, and during the past dry season we also harvested understory vege­

tation and shrubs on the Grapefruit Island and Central Marsh Transect.

698

TABLE 7. Productivity of Submerged Aquatic Vegetation Based on Diurnal Curve (September 10-11, 1975).

Description Gross Production Respiration (g!m2'day) (g!m2 'day)

"Pond" Cypress 0.1 0.2

Slough 0.6 1.1

"Bald" Cypress 0.5 0.7

Central Harsh 0.6 0.8

Mixed Marsh 1.5 1.2

699

2Near each well, the understory was clipped on ten l-m plots and the shrubs

on two 10 x 10 m plots. and tree DBR and height were measured on two

25 x 25 m plots. We are now compiling this data, and will sample the

South Dike and North Marsh Transects this 'winter.

2Root samples were taken from 1 m pits at our intensive study sites

along the Central Harsh Transect in May and June, 1975. Strata sampled

were 0 to 15 em, 15 to 31 em, then 31 em intervals to the water table or

the bottom of the root zone.

The hammock root pit was located in an open area, at least 3 m from

the nearest tree. t-korby plants were prililarily small shrubs, forbs,

ferns, and grasses. Scattered large rocks(> 15 em diameter) were first

encountered at approximately 61 em and shell dominated at 122 em, other­

wise sand was the dominant substrate. Significant qua.ntities of organic

matter were found only in the upper 5 em of the profile. Roots in the

hammock were strongly concentrated in the upper 15 em of the soil profile,

primarily as a dense mat of small « 1 em)! roots (Table 8). There were

also a few larger roots (1-4 em) in this zone, but only small roots in

deeper strata.

The vegetation on the "pond" cypress site included forbs, grasses, and

sedges although a cypress (approximately 31 ern DBR) bordered one edge of the

plot. The soils were primarily sandy with about 10 em of organic matter

at the surface and shell below 122 em. A mat of small « 1 em) roots

dominated the surface 15 em and also to a lesser extent the 15 to 31 em strata

(Table 8). , Large (> 4 em) roots began to appear in the 15 to 31 em strata

and dominated between 31 and 61 em. Root size thereafter gradually de­

creased with depth. At 150 em the larger roots had almost disappeared with

only a few small «.1 em) roots continuing to greater depths.

700

2TABLE 8. Dry Weights (g/m ) of Roots in Undisturbed Habitats.

Depth 0-15 em 0-6"

15-31 em 6-12"

31-61 0-6"

em 61-91 em 6-12"

91-122 em 36-48"

122-152 em 48-60"

Pine 2261 1219 809 310 * * Mixed Marsh 297 20 7 ')f\ * * Hammock 562 32 34 -8 1 *

-...J 0 I-'

"Pond" Cypress

"Bald" Cypress

1076

940

420

693

1479

943

438

20Lf

313

*

251

* Central Marsh 778 18 6 * * *

*No sample taken.

--~._._---- .­

The "bald" cypress site was located at the edge of a deep slough

on bare ground, adjacent to a large pond apple tree and several dead

cypress knees, and approximately 5 m from a 75 cm DBH cypress. The soil

was predominantly peat down to 91 cm where sampling ceased when water

was encountered. Many dead roots varying from small « 1 cm) to large

(> 4 cm) were found at all depths sampled" Various sized pond apple

roots made up most of the sample, with larger sizes dominating in the

surface 31 cm 'and small sizes increasing with depth (Table 8). The

dense surface mat found at other sites was not seen in the "bald" cypress.

Central Harsh vegetation was primarily arrowhead and sawgrass, and

the substrate was peat down to a depth of more than 150 cm. Roots, pri­

marily arrowhead roots and tubers with some sawgrass rhizomes and pigweed

roots, were strongly concentrated in the surface 15 cm (Table 8). The

smaller biomass at lower depths was primarily arrowhead roots with some

salo/grass rhizomes at 15 to 31 cm. There lvere virtually not roots below

50 cm.

The mixed marsh sitE~ was vegetated with grasses and forbs, although

a small « 10 cm DBH) cypress was within :2 m of the plot. The substrate

sampled for roots was almost exclusively sand. The roots were primarily

small « 1 cm) and decreased rapidly with depth (Table 8). The only

larger roots (1 to 4 cm) were from the cypress tree and occurred in the

top 31 cm. A cursory check showed virtually no roots below 61 cm.

Small pine « 10 cm), palmetto, and scattered grasses and forbs

vegetated the pine-palmetto site. The soils were sandy at all depths

sampled down to the water table at 91 cm, where the root biomass was

still large, but rapidly decreasing. Palmetto roots « 1 cm) dominated

at all depths, while pine roots (1 to 4 cm) decreased in importance with

depth. 702

Vegetation Chemistry

Samples of practically all species encountered in the shrub biomass

plots, of understory vegetation in these plots, and of roots from all

depths in the root pits are now being analyzed. Pete Straub at the

University of Florida Center for Wetlands is measuring nitrogen and phos­

phorus, and the Soils Analytical Lab9ratory is analyzing for the remaining

elements, the same ones monitored in the water and soils.

i1iscellaneous Vegetation Studies

We feel reasonably certain that we can detect annual rings and

will be able to age a tree to within about 5% of its actual age. The

frequency of incomplete and false rings Dlakes meaningful year-by-year

comparisons between trees highly unlikely, although longer term cycles

may be detectable in trees of sufficient age (> 100 years). Because

we have not yet aged enough trees to evaluate the many environmental

variables affecting development of annual rings, discussion of their

implications is not justified at this time.

We have been using a densiometer to measure seasonal variation in

percent canopy cover of the intensive study sites at biweekly

intervals since March, 1975. The primary purpose of these data is to

time leaf fall and leaf out, but, since the measurements began in March,

after most of the deciduous trees had already leafed out, percent

canopy coverage has so far been fairly constant (Figure 41).

The largest variations to date can be attributed chiefly to different

observers learning to use the densiometer.

We have obtained a number of color photographs taken on the

703

H" HAMJ't\Ot.K Be.:SALDh

.e'lPRESS PC. -"POND" C:iPR!SS

H

10 BC. PC.

P- PINE-,.. 4<..

20

p 10

~~g. 41. Percent canopy coverage.

704

sanctuary from 1955 to 1968 and are now photographing the same locations.

We believe that comparisons of these pictures will yield valuable graphic

information on vegetation changes from the mid-1950's to the mid-1970's.

Reasonably accurate records of factors that might have influenced the

character of the plant communities are available and should help explain

any detectable changes. However, superficial examination of the photo­

graphs indicates surprisingly little change in the pine, marsh, and

cypress habitats during the 20-year period.

Incidence of Fire

In conducting this project we have become thoroughly familiar with

almost all areas of the sanctuary, and the widespread influence of fire

has become strikingly apparent. We believe that there is no place on the

sanctuary that has not been touched by fire at least once during the

past 50-100 years. The only remaining indications of the old fires are··

scorched logs and stumps, but ~e have found these throughout the "bald"

cypress, even in the bottoms of the deeper sloughs. In fact, we suspect

the sloughs were originally formed by peat fires.

Litter

There are three important aspects of litter in relation to the

rest of the system: standing crops, rate of litter fall (inputs), and

rate of decomposition (outputs). We are me:asuring each of these at the

705

Central Marsh Transect intensive study sites. At the forested sites

1itterfa11 is measured as two components, one non-woody and small wood,

and another large wood. At each site the smaller litter is collected

2biweekly from six 1-m fiberglass screen-bottomed boxes and the large

2wood bimonthly from the ground at four permanent 2-m plots. Decomposi­

tion bags were placed beneath the litter boxes and sampled quarterly.

2 2Standing crop is measured bimonthly at the same 1-m plots (O.5-m

plots in the marshes) where understory productivity is sampled. Litter­\

fall in the marshes is calculated from changes in bimonthly standing

crop corrected for decomposition.

Non-Woody and Small Wood Litter

We began sampling the small litter component of litterfa11 in

September, 1974 and have now completed one annual cycle of biMeekly

collections (Table 9) . All sites exhibited a seasonal cycle with one

or two periods of maximum 1itterfal1 and a single minimum (Figures

42 - 45). There were also one or more isolated periods of exceptionally

high 1itterfal1 in each habitat except the "bald" cypress. The extreme

in the "pond" cypress in December corresponded to the first major cold

front that winter and the high values in the hammock coincided with

maple 1eaffa11. In the pine-palmetto habitat, the two periods of peak

1itterfal1 ,,,ere due to falling needles, but we are uncertain why this

occurred when it did.

The pine-palmetto 1itterfa11 was always dominated by pine needles,

except at one locat.ion where wax myrtle 1ea.ves normally equalled or

exceeded them. Additional litter included occasional palmetto fronds

and pieces of pine bark.

706

2TABLE 9. Total Annual Litterfall (gm/m Dry Weight).

9/22/74

Description x ----_._-­ .---~_.~._--~.-

Pine 130.1

- 9/22/75

S.E.

32.9

Hanunock 751.5 38.8

"Pond" Cypress 590.9 14.5

"Bald" Cypre 88 500.7 56.8

707

1.4 .

1.3

1.2

,., 1.1 0 "0

"­E 1.0 0

0' 0.9 -en ~

~ 0.8 ~

'-oJ Z 0 ~ 8 0.7-1 T

~~ Q6l! (15"1 1

02"1

0.1 ~

.1.67

II J

II

It .J. T

T Ij T

I 1 ~

Fig. 42 Pineland litterfall.

7.37 7

6 I I

7,44

>. 0 '0 ....... '"E 0 5l ~I 0,

(f) I ­Z ~ 4 .... z 0 u

-..J

1.0 x 0 3w

a

10: ~ .... I ­..J 2 1In

illll!l!!!il! IfI

I i I I

o

Fig. 43. Hammock litterfall.

7-f

1··04 I

6

0"""0

E :!i~ 5

4I I -...l I-'

I II I 0 ~ 3 I

CD a: f-f ­

..J 2

w

I I I I 1I II I

I I I E

J: I i I I I: J:

0 ~ .

Fig. 44. "Pond" cypress litterfall.

5

,.. Cl "Cl "'­E 4 Cl.. Cll

t/)

I ­;z W I-;z 3 8

-...J ~ ~ x

o c:l

c: w 2 l-I ­...J

III· T II I

1 I IiT

IhH1III P fht 1

Fig. 45. "Bald" cypress litterfall.

Hardwood leaves always dominated the hammock litter with varying

quantities of ferns, palm fronds, insect frass, and especially pine

needles and twigs.

In the "pond"· cypress, cypress leaves dominated the litterfall

from early August into February, while hardwood leaves, ferns, and

twigs were a more or less constant low input throughout the year. Litter­

fall increased slightly in March when the cypress shed their pollen­

producing cones (Figure 44).

The greater percentage of hard\-lOods in the ''bald'' cypress is re­

flected in the co-dominance of hardwood and cypress leaves in the litter

from July through December. From April through June neither type of

leaf was consistently predominant:, hut both were present 'vitb the t\.;igs

and ferns which dropped year round. The relatively low litterfall in

the autumn of 1974 (in comparison to 1975) may be attributable to heavy

insect defoliation of the large cypress trees during early summer 1974

Large Wood Litterfa1l

Large wood litterfall plots were set up in June, 1975 to supplement

the litter box data, and to date they have yielded virtually nothing.

Standing Crop ~ Litter

No clear seasonal patterns were evident for the standing crop of

litter (Table 10). Even though large logs and stumps were weighed

separately, the sporadic occurrence of large wood litter appeared to

mask the smaller amounts of litter being deposited seasonally. Although

lacking the wood litter. the Central Harsh did not shm. a seasonal cycle

712

TABLE 10. Standing Crop of Litter (~/rn2).

The sporadic apperance of large wood litter (grn dry weight/m ) is indicated in parentheses.

8/28 - 11/ 1/ 3/ 5/ 7/ 9/07 6-08 8-20 13-14 1-02 11-14

Pine X 455 379 773 (2184) 466 879 ( 507) 1004 (4922)

S.E. 87 88 168 176 221 420

Mixed Marsh X 431 (795) 616 (1654) 336 ( 116) 312 748 644 ( 820)

S.E. 86 248 96 44 196 252

'-l I-' w

Hammock X

S.E.

937

125

1103

173

( 806) 1026

105

1318

173

1102

107

(1803) 1365

154

"Pond" Cypress-X

S.E t

1160

242

(310) 1107

91

(2196) 1259

174

(312) 1236

336

1343

339

(2012) 1612

326

"Bald" Cypress -X

S.E.

866

191

(682) 1462

244

( 120) 727

159

(1547) 1471

320

(759) 1213

209

(3615) 964

292

TABLE 10. (continued)

8/28 ­ 11/ 1/ 3/ 5/ 7/ 9/07 6-08 8-20 3-14 1-02 11-14

Central Marsh X 865 964 1492 600 468* 312 432

S.E. 160 104 124 132 108* 40 48

* Tv,O days after burn 3/11/75. -....J f-' .p.

because of the fire in March, 1975. The data for each habitat will be

combined to estimate the average annual standing crop of this component.

Litter Decomposition

To measure decomposition rates we filled fiberglass screen bags with

litter from the understory productivity plots and replaced. them in the

appropriate habitats in October, 1974. Samples were collected quarterly

and percent losses determined.

Even at the sites with the highest decomposition rates, more than

60 percent of the litter remains from one year to the next (Table 10).

When we calculated the amount of litterfall lost at these decomposition

2rates, we found an annual litter build-up of approximately 90 g/m in

2the pine-palmetto, 610 g/m2 in the hammock, 500 g/m in the "pond" cypress,

2and 375 g/m in the "bald" cypress. This suggests a 20 to 50 percent

annual increase in the standing crop of litter in these habitats. Incor­

poration into the peat in the regularly inundated areas and consumption

by fires (frequent in the upland areas) are probably the other major

losses from the litter.

The extremely low variability in bag to bag litter losses within a

given habitat and season is striking, even when it is taken into considera­

tion that the litter came from the same source (Tables 11 and 12).

Explanations for both the seasonal variation and site to site varia­

tion in decomposition rates are unclear but more than the two expected

major factors are apparently involved. Low temperatures undoubtedly have

a retarding influence, as indicated by thE~ low rates from January to April

(Figure 46). However. the period from October to January was not all

that much warmer, yet litter decomposition was much faster. We thought

715

TABLE 11. Seasonal Litter Decomposition by Habitat (Percent Loss).

Habitat January 10 April 23 July 14 October 3

Pine-Palmetto

*Hean + S.E. 7.8 + 0.3 9.8 + 0,,9 13.7+1.4 31.1 + 4.1 %Days Inundated 0.0 0.0 0.0 0.0 Incremental Loss 7.8 _2.0 3.9 17 .4

Mixed Marsh

Mean + S.E. 11.3 + 1. 7 14.1 + 2.3 22.2 + 2.4 28.6 + 1.3 %Days Inundated 85.0 0.0 0.0 95.0 Incremental Loss 11.3 2.8 8.1 6.4

Hammock

Mean + S.E. 8.7 + 1.0 13.1 + 0.9 12.8 + 0.9 18.5 + 0.9 % Days Inundated 0.0 0.0 0--:-0 0.0 Incremental Loss S.7 <f.4 -0.3 5.7

"Pond" Cypress

Mean + S.E. 13.3 + 0.7 12.4 + 1.6 13.9 + 2.6 16.1 + 0.8 %. Days Inundated 100.0 19.0 0.0 99-:-0 Incremental Loss 13.3 -0.9 1.5 2.2

"Ba1d lf Cypress

Hean + S.E. 12.3 + 0.7 14.5 + 1.1 22.7 + l.8 25.3 + l.8 % Days Inundated 100.0 34.0 0.0 100.0 Incremental Loss 12.3 2.2 8.2 3.4

Central Marsh

Mean + S.E. 6.4 + 0.7 8.6 + 5.6 19.1 + 0.5 30.5 + 3.1 % Days Inundated 100.0 17.0 l.0 100.0 Incremental Loss 6.4 2.2 10.5 1l.4

Total Days 88.0 103.0 82.0 8l.0

* Mean Total Loss, since October 14 + one Standard Error.

716

• I

TABLE 12. Seasonal Litter Decomposition by Water Depth (Percent Loss).

Habitat January 10 April 23 **July 14 October 3

Slough Shore

*Mean + S.E. 10.6 + 0.1 10.7 + 1.4 37.7 + 1.0 % Days Inundated 0.0 0.0 0.0 Incremental Loss 10.6 0.1 27.0

Mid Depth

Nean + S.E. 10.2 + 0.5 10.7+l~.1 20.9 + 3.1 % Days Inundated 100.0 34.0 50.0 Incremental Loss 10.2 0.5 10.2

Slough Bottom

Hean + S.E. 14.1 + 1.0 1.6.5 + 0.7 26.0 + 0.4 % Days Inundated 100.0 51.0 61.0 Incremental Loss 14.1 2.4 9.5

Average - All Depths

l1ea~ -I­ S.E. 11.6 + 0.6 12.0 + 1.6 19.9 + 2.0 28.2 + 2.3 % Days Inundated Incremental Loss 11.6 0.l1 7.9 8.3

Total Days 88.0 103.0 82.0 81.0

* Mean Total Loss, since October 14 + Standard Error.

** Location of bag in pond unknown. Except Average - All Depths values, October 3 increments and PDI for six month period.

717

35r----------------------------...,

eMP CM

WP GH

NC

VI VI 0 ..J

HA .... z w PCu a::: w c..

5

J F M A M J J A s o

Fig. 46. Litter decomposition rates.

718

MONTHS

inundation might be important, but, when the percentage of time the

bags were inundated was compared to the incremental loss during that

period, there was no consistent correlation applicable at different

sites (Table 11) or slough depths (Table l2). An initial loss of litter

due to handling may have been included as part of the October to January

losses, so a second set of decomposition bags was placed at the same

sites in May, 1975 using currently available litter.

Benthos

2All benthic samples Here taken with a IS-em Ekman dredge mounted

on a pole in the vicinity of the productivity plots on the Central Marsh

Transect (except during low water when the ''bald'' cypress samples came

from a nearby "gator hole"). Sampling began in January, 1975.

Amazingly few benthic organisms were found in the bottom sediments

of the "bald" cypress habitat (Ta.ble 13), perhaps because of decimation

during the previous severe dry season. Ho·wever, although organisms were

scarce throughout the year, more were present in recently flooded sedi­

ments than in sediments which had been inundated for a number of months.

Initial sampling in the marsh and "pond" cypress habitats revealed ben­

thic populations very similar to those in the "bald" cypress, except for

relatively large nematode populations in the marsh.

The substrates are somewhat different in the three habitats sampled.

The "bald" cypress sediments are peaty, those of the "pond" cypress covered

with litter (cypress needles), and the marsh sandy. In fact, the marsh

surface was so sandy that we found it necessary to wash the samples on

18 mesh/inch fiberglass screen (and some organisms, most likely small

nematodes, were probably lost).

719

· I},

TABLE 13. Seasonal Benthos Populations Along Central 2 Marsh Transect. Benthos (Numbers/IS cm ).

Chironomid Honths Water Number Larvae Crayfish Nematodes Inundated Depth (in.) of Samples

"Bald" Cypress

1/31/75 0.6 0 7.00 8-15 5* 7/07/75 2.5 1.8 2.0 0.50 17 4

7/31/75 0.3 0 1.0 1.25 30 3

"Pond" Cypress

7/31/75 0 0.8 0.8 0.75 11 3

Hixed Marsh

7/31/75 0.3 2.0 18.7 0.50 2 3

*Kot sampled

720

Fish

Fish sampling was also done in the "bald" cypress, "pond" cypress,

and marsh habitats along the Central Marsh Transect. Fish were trapped

2in a l-m Wegener Ring, and removed with a dip net.

"Bald" cypress sampling began December 13, 1974, when the habitat

had been inundated for six months, and was suspended in March after the

last "gator hole" dried up. 'Although the water was receding during the

December-March sample period, fish did not become concentrated and

crayfish disappeared altogether (Figures 47 and 48). Why the fish pop­

ulations declined with water level in the "bald" cypress, while they

increased tremendously in the other two habitats is unknown. No fish

kills were observed to account for the lowered populations. It seems

some environmenta], factor triggers crayfish to burrm., before all surface

water is gone. In May, 1975, we encountered crayfish near the water

table in the "pond" cypress root pit at depths of 4 - 5 feet.

Initial sampling for the 1975 wet season began June 30. The area

had been inundated, in pockets, for about 10 days, and average water

depth in the "gator hole" was 10 inches. No fish were taken in the samples,

but there were a few small crayfish (5 - 10 mm). The July 7 sample at

water depth 17 inches still yielded no fish. After two days of rain, fish

were first observed in the "gator hole" on July 14 at average water depth

30 inches. The first fish were collected in the July 16 samples. Samples

taken July 31 indicated increasing fish and crayfish populations, although

Gambusia were the only fish species present. In the September 17 samples

crayfish numbers decreased, although size of inidividuals increased.

Fish were more numerous, but Heterandria lNas the only additional species

encountered.

721

------

45

35

25

15

5

45

0:: w a.

0:: w (D

~ z

25

15

5

45

35

25

15

5

MARSH

TOTAL FISH/ ----- CRAYFISH

----- ----<-...... ­/- ...

~--,..--,/~'-----N 0 J A S

!974

~POND"

/; I

L­

N

,," 0

1974

"BALD"

CYPRESS

..",....-===:::::... J A S

1975

CYPRESS

,-­, -­------------ ,,~ N D J F M'J AS

1974 1975

Fig. 47. Fish samples - Corkscrew Swamp Sanctuary.

722

45

35

25

15

5

N ::E

a: w a.

a: w m ::E ::> z

45

35

25

15

5

45

35

25

15

5

MARSH

FLAGFISH

------ GAMBUSIA

i,, GAMBUSIA AND FLAGFISH

N D "S

1974 1975

II POND II CYPRESS

, " , ""

/ GAMBUSIA... N D S

1974 1975

"BALD" CYPRESS

"-' ..--- ......_­- .......... - ,- -----­

" ,,~

v N D J F M J A S

1974 19·75

Fig. 48. Fish samples - Corkscrew Swamp Sanctuary.

723

~ .

Species found in the "bald" cypress since December, 1974 include:

Gambusia affinis mosquito fish

Jordane11a f10ridae flagfish

Heterandria formosa

Poeci1ia 1atipinna sailfin molly

Lucania goodei b1uefin killifish'

Fundulus chrysotus golden top minnow

Chaenobrytus gulosus war mouth

Icta1urus nebu10sus brmm bullhead

At the "pond" cypress site, the first fish samples were taken in

November, 1974, when the area had been inundated for five months. The

last set of sampl~s before dry dOltlfl in January, 1975 included hir;her

numbers of both species and inidividua1s. The site was again inundated

about the second week of July, 1975. Sampling on July 28 revealed cray­

fish but no fish. In the September 17 samples, we found a lesser number

of larger crayfish, a few Gambusia and one Heterandria. Species composi­

tion was virtually identical to that in the "bald" cypress, with the

brown bullhead deleted and an unidentified small centrarchid added.

Fish sampling in the marsh also began in November, 1974 when the

habitat had been inundated for 5 months. By December 9, fish populations

had doubled, while crayfish numbers were decreasing. As the water re­

ceded, available habitat was shrinking, apparently concentrating fish

2and triggering crayfish to burrow. Although the number of fish/m were

essentially the same in the marsh as in the "pond" cypress, the major

species composition was reversed. F1agfish were about twice as numerous

as Gambusia in the marsh, and Gambusia three times as numerous as f1agfish

724

•

in the "pond" cypress. Marsh fish sampling resumed July 31 when the

area had been inundated for 2 weeks. There were crayfish in all samples,

but only one fish, a Heterandria. There were fewer, larger crayfish

and more fish in the September 17 samples. Species composition was

similar to that of the "pond" cypress samples minus the centrarchids.

725