Research Topics > Ecology > Methods

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Effect of Reach-Level Changes in Ditch Morphology and Riparian Vegetation on Macroinvertebrate Communities in an Agricultural Landscape

Methods

General Design

• Study reaches (150m long) selected a-priori
  
  
• Control (n=6): No mature trees; bw/cw < 0.3
  
  
• Bench (n=6): No mature trees; bw/cw > 0.5
  
  
• Tree (n=7): Mature trees on both banks

Field Work

Benthic Community (sampled June 15 to July 15)

• 6-10 Hess samples per reach
  
  
• Each reach sampled one time in either 2001 or 2002

Morphology and Substrate (surveyed spring, summer or fall)

• 2-4 cross-sections and longitudinal profile
  
  
• Modified Wolman Pebble Count
  
  
• Performed in either 2001 or 2002

Habitat Evaluation

Qualitative Habitat Evaluation Index (QHEI, Ohio EPA) completed for each site

Six category separations used:

1. Substrate
2. In-stream cover
3. Channel morphology
4. Riparian conditions
5. Riffle/run development
6. Pool/glide development

Laboratory Work

• Separated macroinvertebrates from sample debris by visual inspection
  
  
• Identified to lowest possible taxon (genus or species) and enumerated macroinvertebrates
  Exceptions:
  • Chironomidae (midges)
  • Oligochaeta (aquatic worms)
  • Hydracarina (water mites).

Computations and Data Analysis

• Morphology Metrics
  • Bench development, water depths, channel gradient, wetted perimeter
    
    
• Substrate Metrics
  • Texture class composition (relative %) of bed substrate
  • “Percent finer than” parameters (D16, D35, D50, D84, D95)
    
    
• Macroinvertebrate Community Metrics
  • Taxa richness
  • Shannon diversity
  • Density
  • %EPT
  • Modified ICI
  • Rarefaction
    
    
• ANOVA and nonparametrics (Kruskal-Wallis and Mann-Whitney) analyses used for group comparisons
  
  
• Forward and backward stepwise linear regressions

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