Assessing Variability Among Hydrogeomorphic Riverine Wetland Subclasses

Transcription

1 Assessing Variability Among Hydrogeomorphic Riverine Wetland Subclasses Daniel Dvorett1,3, Joseph Bidwell2, Craig Davis1, and Chris DuBois3 1 Department of Natural Resource Ecology and Management, Oklahoma State University, 008C Agricultural Hall, Stillwater, OK University of Newcastle, School of Environmental and Life Sciences, Callaghan, NSW 2308, Australia 3Oklahoma Conservation Commission, 2800 N. Lincoln Suite 60, Oklahoma City, OK 73105

2 Wetland Program: EPA Core Elements Monitoring and Assessment Baseline extent Condition and function Trends and changes over time Regulation Voluntary restoration and protection Water quality standards for wetlands

3 Identifying Impairment How do we identify anthropogenic impairment of wetlands?

4 Assessment Methods Biota- IBI Condition- RAM Function- HGM

5 Assessing Functions using HGM Identify reference standard sites Pristine or least altered Develop assessment models for functions Algorithm of assessment variables presumed to impact function Flood energy dissipation ={VFREQ [(VMACRO + VMICRO + VDTREE + VCWD)/4]}1/2 Compare study sites function to reference standard function Functional Capacity Index FCI= Site FC / Reference Standard FC

6 Calibrating Assessment Models Need to ensure that assessment model output is related to level of disturbance and not natural variability Data collected from a variety of reference sites that range from highly altered to pristine/least altered Assessment Model Calibrated Variables

7 Natural Variability Natural variability can render assessment model output useless in identifying impairment High Signal to Noise Low Signal to Noise Assessment Variable Value Assessment Variable Reference Standard Disturbance effects Natural variability

8 Where Does Classification Fit In? How do we separate natural variation from variation introduced by disturbance?

9 HGM Classification HGM includes functional classification based on three components: Geomorphic setting, Water source and its transport, and Hydrodynamics. From Brinson, M.M A Hydrogeomorphic classification for wetlands. U.S. Army Corps of Engineers, Washington, DC. Wetlands Research Program Technical Report WRP-DE-4.

10 HGM National Classes 1. Depressional 2. Lacustrine Fringe 3. Riverine 4. Slope 5. Tidal Fringe 6. Mineral Salt Flats 7. Organic Salt Flats Depressional Riverine Lacustrine Fringe Slope

11 Regional Subclassification To further reduce natural variability in HGM National Classes due to hydrology, geomorphology, climate and geography

12 Objectives Assess if subclasses indeed reduce natural variability for assessment variables? Identify relationships between disturbance and assessment variables? Assess the amount of natural variability remaining within subclasses that may be confounding relationship between disturbance and assessment variables?

13 Subclasses Collected assessment variables from two HGM riverine subclasses in May and June of Oxbows -Riparian

14 Study Sites

15 Assessment Variables-Vegetation Point Intercept % Cover Herbaceous % Cover Shrub/Sapling % Canopy Cover % Vine Cover % Litter cover Line intercept CWD volume CWD stem count 10 meter belt transect Tree Density Tree Basal Area Snag Density

16 Assessment Variables-Soil Structure Surface (0-5 cm) and Subsurface (15-20 cm) Composite of 4 soil samples Metrics: % Clay at surface and subsurface % Silt at surface and subsurface % Sand at surface and subsurface % Organic matter at surface and subsurface

17 Assessment Variables-Water Chemistry Sample taken from the middle of the water column: Hardness Conductivity Alkalinity

18 Do Subclasses Reduce Variation? Methods: Redundancy Analysis Subclass- environmental variable 21 assessment variables- response variables?

19 Do Subclasses Reduce Variability? 14.2 % Variation among assessment variables explained by subclass (p = 0.002)

20 Disturbance and Assessment Variables Methods: Land use score o Total Land Use Score = Σ LU * PC/100 % Human altered land 100 m and 1000 m buffers RDA and forward stepwise regressions 2001 NLCD Class Land Use Coefficient Water 1.0 Developed, Open Space 0.7 Developed, Low Intensity 0.2 Developed, Medium Intensity 0.0 Developed, High Intensity 0.0 Bare Rock/Sand/Clay 0.4 Deciduous forest 1.0 Evergreen Forest 1.0 Mixed Forest 1.0 Scrub/Shrub 1.0 Grasslands 1.0 Pasture/Hay 0.7 Cultivated Crops 0.2 Woody Wetlands 1.0 Herbaceous Wetlands 1.0

21 Disturbance and Assessment Variables Results No significant results from RDA for all assessment variables or suites of variables used in assessment models Forward stepwise regressions: Subclass Assessment Variable Disturbance Factor R 2 Dir. p Oxbow % subsurface organic hum. alt. 100m Riparian % subsurface sand hum. alt. 100m Riparian % surface silt hum. alt. 100m Riparian % subsurface silt hum. alt. 100m

22 Disturbance and Assessment Variables What could be causing the limited relationships between disturbance and assessment variables? Remaining natural variability within the subclasses o Precipitation o Stream Order o Groundwater Other disturbance factors/ magnitude of disturbance may be an issue

23 Conclusions The natural variability of assessment variables within subclasses may be masking landscape disturbance effects Assessment models may only be reliably able to identify severe landscape degradation or on-site disturbance. The inability to relate assessment variables with disturbance means that assessment model output may not be related to wetland impairment

24 Current Work Evaluating the effectiveness of IBI, CRAM and HGM functional models to evaluate the condition of 25 oxbows in the Cross Timbers. Collecting additional data on on-site anthropogenic stressors, and landscape alteration at various scales. Goals: Develop an assessment of oxbows using metrics/models that are responsive to anthropogenic disturbance. Expand oxbow assessment protocols to other wetland subclasses.

25 Funding provided by USEPA through a Wetland Program Development Grant 104(b)(3) Dr. Loren Smith Dr. Brian Carter Dr. Michael Palmer Haley Eyer Jeff Tibbits Cameron Goforth Bill Hiatt Acknowledgments

26 Questions?