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Linking hydroperiod with water use and nutrient accumulation in Everglades tree island habitats

Xin Wang, Leonel Sternberg, Vic Engel, Mike Ross University of Miami

Tree islands in the Everglades

• Tree island habitats are important feature in

the Everglades ecosystem.

Tree island structure and formation

Upland hammock Lowland swamp Freshwater marsh

Tree island nutrients

• Phosphorus concentration of tree islands can

be up to 100 times higher than that of the surrounding marshes.

• Where are these nutrients coming from?

– Bird guano theory – Transpiration driven theory

Bird guano theory – birds and other wildlife are the primary nutrient source of tree islands

Transpiration theory – plants pull up nutrients into tree islands from surrounding marsh water.

Study area – Shark River Slough and adjacent prairie landscapes

My hypothesis

Tree islands located in the prairies would have limited water availability and lower P concentration than tree islands in the Shark Slough. Tree islands actively transpiring during the dry season can accumulate more nutrients than tree islands with lower dry season transpiration.

Two things we test

• Prairie tree islands transpire less than slough tree

islands

– Carbon isotope ratio as a proxy for water deficits – Satellite image remote sensing – Sap flux probes for direct measurement of plant water uptake

• Prairie tree islands accumulate less phosphorus than

slough tree islands

– Soil nutrient concentration – Nitrogen stable isotope ratio as a proxy for P availability – Leaf tissue nutrient concentration

Water use tests

Carbon isotope ratio as a proxy for water deficits

Shift in Carbon isotope ratio from wet season to dry season means dry season water deficits in plants.

v u ltu re s a tin le a f c h e k ik a g ro s s m a n A 4 9 0 0 E 4 2 0 0 N P 2 0 5

δ

13C (per mil)

• 3 2
• 3 1
• 3 0
• 2 9
• 2 8
• 2 7

W e t s e a s o n D ry s e a s o n

* * * *

Slough tree islands Prairie tree islands

Satellite remote sensing

High NDWI means plenty of water in plant canopy.

Water uptake measured by sap flux probes

Rechargeable Battery Solar Panel Data Logger

Nutrient accumulation tests

Soil total P concentration

ss81 irongrape vulture satin leaf ss37 panther gum bo lim bo m anatee black ham m

• ck

grossm an E4200 m

• squito

ficus pond NP205 A4900

S

• il total P

(μg/gdw )

20000 40000 60000 80000

Slough Tree Islands Prairie Tree Islands

Slough tree islands have much higher soil total P concentration than prairie tree islands.

Foliar N isotope ratio as a proxy for P availability

Distinct foliar N isotope ratio: Slough islands +6.06±1.89 Prairie islands ‐1.58±1.53 Slough tree island plants have more P available than prairie tree island plants. High foliar N isotope ratio means high P availability

Nutrient concentration in the leaf tissue

All species MF BS CD EA SF

Foliar N/P ratio

10 20 30 40 50 Slough tree islands Prairie tree islands

* * * * *

‐ P + P

Application and significance of the study

• Links hydroperiod to tree island water use and

nutrient accumulation status – important for tree island conservation and restoration

• Introduces useful tools for both observational

study and long term monitoring

– Stable isotope proxy – Satellite remote sensing – Sap flux system

Acknowledgements

Everglades Foundation South Florida Water Management District Everglades National Park