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Research Topics
> Ecology > Introduction
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Introduction | Methods | Results
Effect
of Reach-Level Changes in Ditch Morphology and Riparian
Vegetation on Macroinvertebrate Communities in an Agricultural
Landscape
Introduction This
research is a part of a large effort to improve stream ecosystem
integrity and water quality within agricultural landscapes,
while maintaining drainage function. Two-stage ditches that
include a low depositional floodplain are being proposed
as a viable alternative to the current one-stage ditch design.
This feature is expected to increase channel stability and
create habitat. Our objective was to determine the relative
effects of riparian tree development and two-stage channel
morphology on the benthic macroinvertebrate community.
Our
work addresses important aspects of channel restoration within
heavily farmed areas, which is highly relevant to
Ohio and the Midwestern United States.
- Crop agriculture accounts
for 24% land use in the lower 48 states
- Agriculture is listed
by US EPA as the #1 cause for water quality impairment
in rivers and streams
- Channel modification due to drainage improvement
efforts is a significant factor for this impairment
- Agriculture
is indispensable and soil drainage is important for
productivity
Addressing Stream Impairment
- Riparian buffers
are used to mitigate nonpoint source pollution
- Both grassed
and forested buffers are shown to be effective
- Proposed strategies
for improving drainage ditch design has strong implication
for riparian zone
- Two stage ditch design
Stream Ecology
- Strong link between riparian
zone and benthic community in small streams
- Disturbance may
be a primary factor shaping stream communities
- Aquatic community
responds to land use conditions at local (reach level)
scales
One-Stage Ditches
One-stage ditch |
One-stage ditch at high water |
Newly constructed one-stage ditch |
Charachteristics of one-stage ditches:
- Unstable morphology
leading to extreme erosion/deposition processes
- Intensified
storm flow velocity and shear stress
- Over-widened lower
energy base flow channel
- Little flow heterogeneity
- Typically fine
bed substrate (poor quality)
- Sparse development of habitat
and flow refugia
Two-stage ditches
Two-stage ditch |
Two-stage ditch at high water |
Newly constructed two-stage ditch |
Charachteristics of two-stage ditches:
- Successional
to the one-stage ditch, and formed by erosion and deposition
processes
- May not develop in presence of riparian
trees
- Appears to be more stable form
- May provide
reduction in storm flow velocity and shear stress
- Narrower
higher energy base flow channel
- Better riparian connection
- Potentially improves
habitat and flow refugia
Tree-Lined Ditches
Tree-lined ditch |
Tree-lined ditch at high water |
Outside view of a tree-lined ditch |
Charachteristics of tree-lined ditches:
- Often has one-stage morphology
- Favor over-widened,
lower energy base flow channel
- Intensified storm flow velocity
and shear stress
- Provides debris, detritus, and structure
that can be used as habitat, refugia and food resources
- Reduces
incident sunlight, and maintains lower temperatures
Objective and Hypotheses
Determine the relative
effects of ditch morphology and riparian vegetation on
benthic community assemblage at
the reach level.
H1: Trees provide better habitat and
food diversity than open canopied sites which enhances
the benthic
community.
H2: Small floodplain benches within ditches
reduce the severity of disturbance events and improves
habitat, which enhances
the benthic community.
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