Vertical Hydrologic Exchange And Ecological Stability Of Desert Stream Ecosystem

1
Vertical Hydrologic Exchange And Ecological
Stability Of Desert Stream Ecosystem

• Maurice Valett, Stuart Fisher, Nancy Grimm, and
  Philip Camill

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Introduction

• "Streams and rivers are open ecosystems that are
  heavily influenced by interaction with adjacent
  systems"
• Material and Energy exchange
• physical-chemical
• Hyporheic Zone
• Biota
• distribution, diversity, abundance, compexity
• Biogeochemical
• saturated sediments
• Nutrient transport
• concentrations often high

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Introduction

• Sonoran Desert Streams
• Flash Floods
• decimate biota
• affect physical-chemical conditions
• Spatial Intermittency
• causes mortality
• alters hyporheic conditions
• Hydrologic Linkage
• Resistance
• Resilience

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Methods

• Hypothesis
• Hyporheic Zone (hydrologic linkage) would
• promote ecosystems resilience
• Reach Morphometry and hydrology
• Upwelling and Down welling
• Nutrient Concentrations
• NO3 -N
• SRP
• Chlorophyll Phaeophytin and AFDM
• Standing Crop
• Post Flood Recovery

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Results Physical
Spatial Variation Exchange
Upwelling
Stationary
Downwelling
Figure 1
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Results Physical
Temporal Variation Exchange
Upwelling
Stationary
Downwelling
Figure 2
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Results Nutrients
Exchange effects on Surface Chemistry
Table 1
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Results Nutrients
Exchange effects on Surface Chemistry
Figure 3
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Results Nutrients
Exchange effects on Benthic Algal community
Figure 4
Table 2
Upwelling
Downwelling
Upwelling
Downwelling
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Results Post Flood Recovery
Exchange effects on Post Flood Recovery
Upwelling
Downwelling
Figure 5
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Results Post Flood Recovery
Exchange effects on Post Flood Recovery
Upwelling
Upwelling
Downwelling
Downwelling
Figure 5
Figure 6
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Results Post Flood Recovery
Exchange effects on Post Flood Recovery
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Discussion Physical

• Spatial characterized by Vertical Hydraulic
  Gradient (VHG)
• Summer Floods increased upwelling magnitudes
  within 2 days
• Winter Floods decreased intensity of downwelling
  following a long post flood period
• VHG increased after a lag (Post Flood)

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Discussion Nutrients

• NO3-N concentration strongly correlate with
  magnitude of upwelling
• SRP dynamics controlled by physical-chemical
  processes
• Upwelling supported larger algae communities but
  was related to time (days post flood)

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Conclusion

• Link between hyporheic and benthic process
• supply limiting nutrients
• might be a source of algal drift and transport
• Open nature of streams promotes
• rapid recovery following disturbance
• RESILIENCE RESISTANCE
• physical
• chemical
• biological

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Arid fluvial (or riparian) ecosystems are subject
to a pendulum of extreme conditions within a
small-scale time and space continuum. How does
the hyporheic zone mitigate system stability in
regards to resistance and resilience in response
to a flash flood disturbance?