Download Poster presented at the 2007 Fall meeting of the American

Water source utilization and nutrient status in upland plant communities in Everglades National Park (ENP)
Amartya K Saha1 ([email protected]), Leonel O da S L Sternberg1 ([email protected]),Fernando Miralles-Wilhelm2
1Department
1. What are the water sources for upland plant communities (hammocks
and pinelands) in the ENP and how they vary with season.
2. Are foliar nutrient concentrations indicative of higher nutrient levels in
hammock soils ?
Hypotheses
Results (continued)
A: Water sources
Fig 7A: monthly rainfall over 2005-2006
In the wet season, hammock plants use mostly soilwater
while pinelands use mainly groundwater
In dry season, litter layer dries, so both hammocks and pinelands
use groundwater
Fig 7B: hammock and pineland plant average % groundwater
utilized through a year. Vertical dotted lines in plot 3 indicate the
wet season.
In the wet season (June – September end),
hammocks (filled circles) use less groundwater
than pinelands (empty circles) (25% in comparison to 40%).
As the dry season progresses, the difference between hammocks
and pinelands reduces until in mid May (late dry season)
both communities have approximately 90% of their water
coming from groundwater.
B: Foliar nutrient status
Hammock plants attain higher foliar concentrations of N and P
by virtue of access to nutrient-rich soil litter water.
Tree
island
sites
The Study
(March 2005 – March 2006)
1. Three hammock/pineland pair sites
2. Rain and GW sampled every 2 weeks in each site
3. Plant stems (water) and leaves (nutrients)
sampled every 2 months (species in adjacent table)
4. 5 individuals of 5 species per hammock or
pineland  25 for hammock + 25 pineland
50 plants per site. 3 sites.
200
100
0
M
A
M
J
J
A
S
O
N
D
J
F
M
2005 - 2006
1.0
B
0.8
0.6
0.4
0.2
0.0
Mar
Fig 7C: Daily groundwater level at station NP72 (ENP)
Dashed horizontal line indicates level of 50% groundwater usage,
with increasing usage at lower levels.
Jul
Nov
Mar
4
C
Results
Fig 1: Hammocks and Pinelands occur on the Miami Rock Ridge on eastern edge of
the park. Study sites shown. Photo shows hammock on the left and pineland on the right.
300
3
Daily groundwater level
above NAVD, feet
Hammock/Pineland
sites
A
Monthly Precipitation (mm)
Our main questions
400
Groundwater Fraction of Stemwater, x
2
of Biology, University of Miami, Coral Gables, FL 33124, USA
Department of Civil and Environmental Engineering, Florida International University, Miami, FL, USA
2
1
0
-1
1.Isotopic composition (δ18O, δ2H) of rain, groundwater and soilwater
are different, thus enabling determination of plant water sources
M A M
J
J
A
S
O N
D
J
F
M
Hammocks and Pinelands  highest elevations in the Everglades
only areas above water in the wet season); only 4 % of park area; habitat for terrestrial life,;
high floral species diversity, several endemics, northernmost range of evergreen
tropical species from the Neotropics
Long Pine Key
Sisal Pond
Fig 4: δ18O values of rain (○),
groundwater (●) and soilwater
(hammock (▲) and pineland
(∆)).
Upper panel shows rainwater
being isotopically diluted in the
wet season, a trend also
reflected in groundwater, which
however displays lower
amplitude owing to its larger
volume.
The lower panel depicts soil
water showing the same trend.
However soilwaters are also
enriched evaporatively in the
heavier isotopies of water,
especially evident in the dry
season.
8
6
2
0

 O %0
4
Hammock
-2
Pineland
-4
-6
Closed canopy, higher
photosynthetic biomass
per unit area
-8
Mar
Open canopy
Jul
Nov
Mar
Mar
Jul
Nov
Mar
Mar
Jul
Nov
Mar
8
6
Natural fires burn off organic
matter

Humid microclimate
stops fires
 O %0
4
2
0
-2
-4
-6
Organic soil layer
present
Soil only in cracks and
sinkholes
-8
Mar
Jul
Nov
20
30
40
50
60
transect points
Fig 2: average soil depth in hammock (left)
and pineland (right) in cm. Long Pine Key, ENP.
Nov
Mar
Mar
Jul
2005 --- 2006
Nov
Mar
2005 --- 2006
20
20
10
10
0
0
-10
-10
-20
-20
-30
-30
-40
-40
-50
-50
Fig 5: Plot of δ 18O vs δ2H for rain (○),
groundwater (●) and soilwater
(hammock (▲) and pineland (∆)).
The global meteoric water line is
also included. Both rain and groundwater
cluster around the meteoric water line
year round.
In the dry season, soilwater veers to the
right of the meteoric water line,
a trajectory typical of evaporatively
enriched water.
-60
-10
-8
-6
-4
-2
0
2
-10
-8
-6
-4
-2
0
2
4
6
 18O‰
 18O‰
•
This organic soil layer in hammocks caused by litter accumulation . So
how may this litter layer influence this difference between hammocks and
adjacent pinelands ?
2. Pineland plant stemwater δ18O better correlated with groundwater.
Hammock plants not correlated with groundwater in wet season.
0
0
-1
-1
Hammock Stemwater 
• Litter layer traps rain in wet season. This water solubilizes nutrients
present in decomposing litter/leachates from leaves.
-2
-3
-4
-5
-6
-5
-4
-3
-2
Groundwater 
Fig 3: hammocks (left) have a soil layer (that traps rain) while pinelands
(right) so not. Blue shows water table (groundwater). Wet season.
-2
Nutrient
Hammock soil
(ppm)
Groundwater
(ppm)
Available P
2.1 - 44.5
0.03 - 0.05
nitrate
5.5 – 126
0.01 –0.15
ammonium
6.52 – 150
0.09 - 0.15
1.5
1.0
0.5
Table 2: Hammock soil and groundwater nutrients. Data from Long Pine Key,
ENP
0.0
0.00
0.01
0.02
0.03
0.04
0.05
0.06
%P (mg P/mg dry leaf)
Hammock plants (●) have significantly higher foliar N and P than pineland plants (●).
However there is a strong species effect.
-1
0
Conclusion
Water trapped in the organic litter layer is a significant source for hammock plants,
especially in the wet season. The litter layer provides a vadose zone for the roots
of flood intolerant hammock trees.
In the dry season hammock trees utilize more groundwater while the litter layer
dries out. However, if water levels fall very low, then hammock plants may
encounter difficulty in sending roots through the limestone bedrock to access the
lowered groundwater table.
This has implications for hydrological management upstream of the Everglades, for
maintaining water levels within the above bounds for preserving upland
ecosystems.
Pineland plants also depend upon both sources, however depending upon the
species, they are more tolerant of some flooding. They can share a similar
susceptibility to low water levels in the dry season.
-3
-4
Acknowledgements
-5
-6
-6
2.0
dry season
-60
Pineland 
soil depth to bedrock (cm)
Jul
wet season
 2H ‰
10
Mar
2005 --- 2006
average soil depth hammock and pineland, Long Pine Key
90
80
70
60
50
40
30
20
10
0
-10 0
Mar
Nutrients
%N (mg N/ mg dry leaf)
Royal Palm
-6
-5
-4
-3
-2
-1
0
Groundwater 
Fig 6: Left plot: correlation of average hammock plant δ18O with
groundwater δ18O. The right hand plot = correlation of pineland plant
δ18O with groundwater δ18O. Pineland plants have a higher correlation
with groundwater on average (R2 = 0.75) as compared to
hammock plants (R2 = 0.57), signifying a greater usage of groundwater.
Funding: NSF Biocomplexity Grant
Fieldwork and labwork: Help from Maria Camila Pinzon, Yiming Lin, Patrick
Ellsworth, Frans Juola, Diego Melgarejo, Pab Pandit, Saha family, Angela Garcia, Bruno
Rosado, Cassandra, Shu Ju.