dsd-int 2016 modeling invasive species in river systems_ interaction with native ecosystem engineers...
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Modelling invasive species in river systems: interaction with native ecosystem engineers
and effects on morphodynamic processes
Mijke van Oorschot
Maarten Kleinhans, Gertjan Geerling, Hans Middelkoop, Rob Leuven, Gregory Egger
Patterns in vegetation
Patterns Allier river, France
Patterns in fluvial morphology
Eco-engineering effect of vegetation
Vegetation
Hydrology River morphology Sediment balance
Vegetation
Hydrology River morphology Sediment balance
Eco-engineering effect of vegetation
Interaction creates dynamic
patterns
0
250
500
750
1000
1250
1500
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Dis
ch
arg
e (
cu
bic
m /
s)
mean minimum maximum
Period 1968 - 2000
River morphology Sediment balance
Modeling vegetation – morphology interactions
What is the long-term effect of dynamic vegetation on the
morphodynamics and vegetation pattern of a meandering river?
Static vegetation uniformly sown
Crosato & Saleh, 2011
Nicholas, 2013
Vegetation model
Riparian vegetation
Morphodynamics
Colonization
Sedimentation & Erosion
Development Mortality
Flow (regime) Bed level
Interactively coupled
Matlab
Delft3D- flow
Colonization
Sedimentation & Erosion
Development Mortality
Flow (regime) Bed level
Morphodynamics
Vegetation
Hydraulic resistance
New substrate
Burial Scour
Uprooting Flooding Desiccation Colonisation
location
Vegetation model
Vegetation processes
Colonisation
1. Colonisation window 2. Water levels during dispersal period
Lowest water level
Highest water level
Bare substrate
Interaction & Mortality
Ecological time steps
Year + 1
Vegetation processes
Changing characteristics over time
Age Age Age
Shoot (m) Root (m) Frontal area (m)
Interaction
Year + 1
Colonisation
Vegetation processes
Changing characteristics over time
Chezy roughness by Baptist
Frontal area Vegetation size
Interaction
Year + 1
Colonisation
Vegetation processes
Slope
Threshold
Flooding (days) Desiccation (days) Flow velocity (m/s)
Mortality (%)
Interaction & Mortality
Year + 1
Colonisation
Vegetation processes
Flooding (days) Desiccation (days) Flow velocity (m/s)
Mortality (%)
Sensitive
Resistant
Burial : sedimentation > shoot height Scour: erosion > rooting depth
Different at each age and life-stage!!
Interaction & Mortality
Year + 1
Colonisation
Van Oorschot, M., Kleinhans, M., Geerling, G., Middelkoop, H., 2016. Distinct patterns of interaction between vegetation and morphodynamics. Earth Surface Processes and Landforms 41, 791–808.
1. Without vegetation
2. Static vegetation (uniform, no growth, no mortality)
3. Dynamic vegetation (riparian trees)
4. Invasive species (riparian trees + invasive herb)
5. Human pressures (climate change, dams)
Model runs
Model result
Dynamic vegetation patterns, aging, sustained dynamic meandering, distinct patterns in river morphology
Chute cut-offs
Oxbows
Flow
Comparison to aerial photos
500 m
Comparison to aerial photos
Young Old
Young
Old
% C
ove
r
Empirical Data
Dynamic
Stripes
Areas
Dots
Synthesis dynamic vegetation
Dynamic vegetation; settling, growth and mortality, creates natural biogeomorphological
patterns
Invasive species
What is the long-term effect of an invasive riparian plant on native vegetation community and river morphology?
Fallopia japonica (Japanese Knotweed)
Invasive species
• No invaders
• Dense invaders (‘aggressive’)
– High fraction in cell
• Sparse invaders (‘mild’)
– Low fraction in cell
Invasive species results Movies bed level plus vegetation
Aggressive invaders
Mild invaders
Results invasive species
No invaders Mild invader Aggressive invader
• Mild invader facilitates native vegetation • Aggressive invader constrains native vegetation
Effect on native vegetation cover
Results invasive species
Center cell
Edge cell
Neighbour cell
Morphodynamic effects
Invader inclusion = larger vegetation patches
Aggressive invader
Mild invader
No invader
Aggressive invader
Mild invader
No invader
Results invasive species Morphodynamic effects
• Shielding by vegetation patches • Invader inclusion = more native colonization in center
and edge of cell
Where do native seedlings colonize?
Aggressive invader Mild invader
No invader
Synthesis invasive species
Invasive and native species interact through morphodynamic processes
Dams: work in progress
• Modified upstream discharge boundary to simulate 2 dam operating scenarios
Dams: results vegetation
Construction dam
• Stabilization dam: aging vegetation, reduction colonization peaks • Reversed dam: initial aging, reduction colonization peaks and
total reduction of vegetation
Dams: results habitat suitability Post-processing
How are other riverine species affected by dams?
Salmon
Pike
Helophytes & Macrophytes
Bivalves
Dams: results habitat suitability
Delft3D Model results
Statistics
Post-processing
run HABITAT model
Salmon
Pike
Helophytes & Macrophytes
Matlab Python scripting
HSI results
Year +1
Bivalves
Dams: results habitat suitability Post-processing
• Dams decrease good habitat of fish • Reversed dam increases good habitat water plants • Stabile dam decreases good habitat water plants
Conclusions
• We can model the dynamic interaction between vegetation and river morphodynamics
• Settling, growth and mortality of vegetation creates natural biogeomorphological patterns and continuous dynamic meandering
• Invasive and native species interact through morphodynamic processes
• Working on dam effects, dam removal, climate change, estuarine species and interaction with mud
Thank You! Van Oorschot, et al., 2016. Distinct patterns of interaction between vegetation and morphodynamics. ESPL 41, 791–808.
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