Possible Mechanisms Regulating Everglades Ridge and Slough Soil Topography

1. Possible Mechanisms Regulating Everglades Ridge and Slough Soil Topography Eric Jorczak

2. Pre-drainage Everglades hydrology • Sheet flow of water • Long hydroperiod:minimized soil oxidation • Water depths often less than 1 meter: extensive plant growth Source: S.F.W.M.D

3. ridge slough Cross section of ideal ridge and slough topography Up to 60cm organic soil accretion

4. Ridge and slough in WCA-3A ridge slough • Distinct edges • Linearity • Soil topography

5. ridge slough Figure 2. Ridge and slough community in Water Conservation Area 3A (photo taken May 2002).

6. Recent changes to hydrology have altered: • sheetflow • hydroperiod • water depths Source: S.F.W.M.D

7. Impacts due to altered hydrology: Loss of linearity of ridges and sloughs in WCA-3B

8. Impacts due to altered hydrology: larger ridge smaller slough larger ridge Ridges often encroaching into sloughs

9. Impacts due to altered hydrology: Oxidation of ridge soil, results in a narrowing of the soil topographic difference between ridge and slough

10. Everglades restoration • Restore the ridge and slough since it is the most extensive landscape feature in the Everglades and is necessary to preserve the biological diversity • The persistence of the ridge and slough requires maintaining the soil topographic difference • Hydrology management influences soil topography

11. Possible mechanisms that regulate soil topography • Soil topography mirrors the underlying bedrock topography • Suspended solids transport is greater in sloughs • Water level and hydroperiod influence soil oxidation • Greater slough soil decomposition rate based upon liter quality, lower rates of litter production • Fire, wind

12. Objectives – Investigate possible mechanisms that may regulate ridge and slough soil topography by comparing ridge versus slough: • Soil topography compared with bedrock topography • Water velocity and total suspended solids • Soil oxidation by measuring rates of carbon dioxide and methane emission Goal –Propose which mechanisms seem more likely to influence the ridge and slough soil topography

13. ridge ridge slough slough Hypothesis #1: Bedrock topography mirrors ridge and slough soil topography water water soil soil bedrock bedrock

14. Site selection 3A1 less impacted 3A2 • Based upon differences in hydrology and ridge slough habitat condition • Covered Water Conservation Area-3A and Everglades National Park impacted Figure 3. Location of ten sites used in study, red markers indicate sites used for characterization survey only. Yellow markers indicate sites used for both characterization and long-term monitoring.

15. Methods – Soil and bedrock topographic survey • Soil and bedrock depth measured every 5 meters along a transect • Inserted a metal rod down to the bedrock and measured soil depth and bedrock depth relative to the water surface ridge slough ridge

16. ridge slough Ridge and slough cross section of site 3A1 plants water soil bedrock

17. Ridge and slough cross section of site 3A2 ridge slough plants water soil bedrock

18. Ridge - slough soil elevation and bedrock elevation

19. 13.8 21.5 14.1 6.6 5.0 11.9 16.2 6.4 10.9 7.2 Figure 14. Difference in soil surface elevation between ridge and slough vegetative communities Soil topographicdifferences 3A1 3A2 • High variability • Vanishing sloughs

20. Conclusions 1 – soil and bedrock topography • No relationship was apparent between ridge and slough topography and the underlying bedrock topography • The differences in soil topography between a ridge and slough are probably not caused by bedrock topography

21. Hypothesis #2: Compared to ridges, sloughs have greater: • Water velocity • Total suspended solids • Total suspended solids transport

22. Study sites 3A1 3A2 • Chosen based upon differences in hydrology and ridge and slough habitat condition ENP1 ENP2 Figure 1. The four study sites with average flow direction and magnitude.

23. Methods - water velocity measurements • Sites visited approximately once every 3 months over two years • Triplicate measurements of water velocity using a dye tracer at three locations in each ridge and its adjacent slough • Measured water depth in each ridge and slough to calculate water flow

24. Methods - total suspended solids • Triplicate samples at three locations in the ridge and its adjacent slough • Four liters of surface water were filtered through a glass fiber filter using a portable pump • Filter was oven dried at 104oC and weighed for mass of solids per liter of water filtered • Total suspended solids transport was calculated by: velocity * water depth * TSS

25. Average water velocity Often significant differences between ridges and sloughs

26. Water velocity seasonality Some sites had greater slough velocity, others had greater ridge velocity

27. Average total suspended solids Sloughs generally had higher total suspended solids

28. Average total suspended solids transport Often significant differences between ridge and slough total suspended solids transport

29. Conclusions 2 – hydrologic survey • Water velocities are seasonally variable and not always greater in sloughs • Total suspended solids transport is often greater in sloughs due to greater total suspended solids concentration and/or higher flow of total suspended solids • Total suspended solids transport may influence soil topography especially if solids settle on the ridges

30. Hypothesis #3: A) Compared to ridges, sloughs have greater: • Methane emission when soils are flooded • Carbon dioxide emission when soils are saturated or drained B) Carbon dioxide emission will be greatest when soils are drained

31. Methods +5cm 0cm (soil surface) water table -15cm

32. Methods - continued • Cores were submerged in a water bath to stabilize their temperature and prevent air leaks • Ambient air was passed through the headspace of each core and volume was measured as it bubbled out the top

33. Methods - continued • Headspace gas was sampled 2 or 3 successive days each week over 7 weeks • Analyzed for carbon dioxide and methane using gas chromatographs

34. Methane emission No significant difference between ridge and slough methane emission

35. Methane trends

36. Carbon dioxide emission No significant difference between ridge and slough carbon dioxideemission in either treatment

37. Carbon dioxide emission Significant difference between water table treatment and carbon dioxideemission

38. Carbon dioxide trends

39. Conclusions 3 – methane and carbon dioxide • No significant difference in methane or carbon dioxide emission between ridge and slough soil • Drained soil emitted approximately 3 times more carbon dioxide than flooded or saturated soil • A water level change can influence soil topography, especially if soils are drained.

40. Summary • Total suspended solids transport is often significantly greater in sloughs and may influence soil topography, especially during peak weather events • A change in water level affects soil oxidation rates and can therefore influence soil topography • All aspects of hydrology such as water depth, hydroperiod, and flow should be considered when restoring the ridge and slough soil topography

41. Acknowledgements • Committee: Dr. Mark Clark (chair), Dr. Wiley Kitchens, Dr. Jim Jawitz • Wetland Biogeochemistry Laboratory for facilities and expertise provided • Equipment fabrication and field assistance from Charles Campbell • Funding Agency: Everglades National Park, Department of the Interior • Family and Friends

42. Thank You