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Wetland Functional Assessment

Wetland Functional Assessment. Wetland Function. The biological, chemical, and physical processes that occur in wetlands

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Wetland Functional Assessment

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  1. Wetland Functional Assessment

  2. Wetland Function • The biological, chemical, and physical processes that occur in wetlands • Different types of wetlands provide different functions well (ex. Most depressional wetlands are good for long term water retention while most slope wetlands do not provide this function)

  3. Functional Assessment Uses • Minimal Effects Determinations • Assessing the change of wetland function and its significance • Wetland mitigation • Assessing the functions of the disturbed wetland to design mitigation to replace loss of function

  4. Hydrologic Functions • Water retention (short term and long term) • Energy dissipation

  5. Biogeochemical • Cycling of redox-sensitive compounds • Sediment retention • Carbon sequestration

  6. Functions pertaining to the Food Web • Biodiversity/Habitat Support • Plant Community Structure and Composition • Vertebrate Community Structure • Invertebrate Community Structure

  7. Role of Hydric Soils • Hydric soils play a direct role in the wetland functions of • Water retention • Sedimentation • Biogeochemical cycling of nutrient • Carbon, nitrogen, phosphorous, etc.

  8. Soil Characteristics that May Affect Wetland Functions • Permeability • Drainage class/hydroperiod • Cation exchange capacity • Organic carbon content • Slope • Microtopography • Soil ecology (microbial community)

  9. Soil Features Used as Indicators in Functional Assessment • Permeability • Texture, structure, evidence of soil compaction • Drainage class/hydroperiod • Surface color, presence of organic soil material on surface, soil color, redox features • Cation exchange capacity • Surface color, presence of organic soil material on surface, percent clay

  10. Soil Features Used as Indicators in Functional Assessment • Organic matter • Surface color, presence of organic soil material • Slope • Direct measurements or visual estimate • Microtopography • Visual estimate of surface roughness • Soil ecology • Organic matter content, redox features

  11. Soil Characteristics Used to Evaluate Hydrologic Functions • Water retention • Long-term storage • Slope • Drainage class/hydroperiod • Permeability • Short term storage • Slope • Microtopography • Permeability • Surface organic carbon content

  12. Soil Characteristics Used to Evaluate Hydrologic Functions • Energy dissipation • Slope • Microtopography • Surface texture

  13. Soil Characteristics Used to Evaluate Biogeochemical Functions • Cycling of Redox-Sensitive Compounds (nitrogen cycling) • Permeability • Drainage class/hydroperiod • Organic carbon content • Soil ecology (microbial community) • Sediment retention (phosphorous retention) • Permeability • Slope • Microtopography • Cation exchange capacity

  14. Soil Characteristics Used to Evaluate Biogeochemical Functions • Carbon sequestration • Organic carbon content • Drainage class/hydroperiod • Topography • Microtopography

  15. Nitrogen Removal • Wetlands remove 70 to 90% of N from water. • Seasonally saturated wetlands are the most efficient at utilizing nitrogen.

  16. Phosphorous Removal • Wetlands retain about 45% of phosphorous from waters. • Uplands are better at removing P. • An upland buffer between wetlands and open water will optimize removal of phosphorous.

  17. Carbon Processes • Sequestering 22,000 kg of C in humus requires kg 1833 lbs. of N, 440 lbs. of P, and 315 lbs. of S. • 22,000 lbs/acre of C is equivalent to an increase of about 0.7%.

  18. N and P Storage in Wetlands (lbs/acre)

  19. Soil Characteristics Used to Assess Functions Pertaining to the Food Web • Plant community characteristics and evidence of disturbance are commonly used to assess these functions. • Most soil characteristics directly or indirectly affect the food web.

  20. Use of Wetland Functional Assessment • Minimal Effects Determinations • If alteration of wetland will have minimal effects on characteristics involved in wetland function, then mitigation is not required.

  21. Mitigation • Functional assessment can be used on the wetland being disturbed to assess the changes in functional capacity due to the disturbance.

  22. Mitigation • Replacement of characteristics required for functions being lost through disturbance can be required in mitigation for the disturbance (ex. Organic carbon is required for cycling of redox-sensitive compounds thus organic carbon requirements may be required for mitigation)

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