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Physical Stream Habitat. What is “Habitat”?. Broad Definition (EPA): “The spatial structure of the environment which allows species to live, reproduce, feed and move” In Relation to Streams (USGS): - PowerPoint PPT Presentation
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Physical Stream Habitat
What is Habitat?Broad Definition (EPA):The spatial structure of the environment which allows species to live, reproduce, feed and move
In Relation to Streams (USGS):The physical and chemical characteristics of a stream that determine suitability for habitation and reproduction of stream organisms
What is Physical Habitat?The template of water depth, water velocity, substrate, cover and temperature that supports the stream ecosystem USGS
Stream MorphologyAquatic CommunityPhysical HabitatChemical HabitatInterspecies InteractionsLand UseVegetationHydrologicConditionsGeologyTopography
Measurable Characteristics of Physical HabitatChannel morphology / typeFlow regimeSediment texture / mobilityBank structural features / stabilityRiparian condition and connectivityPhysiochemical temperature, DO, metals, nutrients, turbidity, etc.
Mill Creek
Salmon and trout habitat requirements include: adequate but not excessive stream flows cool well-oxygenated unpolluted water streambed gravels that are relatively free of fine-sediments adequate food supply instream structural diversity (interposed pools, riffles, hiding and resting cover)
Washington State Dept of Fish Wildlife
Physical stream characteristics affect stream organisms by defining: Habitat volume Habitat quality Disturbance magnitude Disturbance frequency
Habitat varies over spatial & temporal scalesStream CorridorRestoration, 199x
LargeScaleFineScaleHeirarchical Classification System
Scalar UnitDefinitionRole in Habitat CharacterizationWatershed BasinArea defined by topography that contributes water and sediment to the stream networkDetermines boundary conditions within which river operatesSegment Physiographically defined unit, based on relief, morphology and landscape positionDetermines boundary conditions within which river operatesReach TypeLength of channel with uniform constraints resulting in a specific assemblage of geomorphic unitsDescribes channel planform and geometryGeomorphic UnitFluvial channel forms representing distinct form-process associationsDetermines channel character and behaviorHabitat TypePatches of relatively uniform flow and substrate characteristics Describes ecologically relevant hydraulic and substrate conditions
103 m102 m101 m100 m10-1 mWatershedSegmentReach TypeGeomorphicUnitMicrohabitatTypeHow is each scale important to the species of interest?
Temporal Variability incorporates predictable and unpredictable cyclesMacroinvertsSalmon
Physical habitat a function of processes operating at multiple spatial and temporal scalesHow do we objectively assess it?
Define Stream Habitat Types (Classification)Bisson et al, 1982McCain et al, 1990 (USFS) Hawkins et al, 1993 (USFS)Thomson et al, 2001 (UK, AUS)Fish -Centric
McCain et al, 1990
McCain et al, 1990Bisson et al, 1982
Hawkins et al, 1993
Hawkins et al, 1993
McCain et al, 1990
Hydraulic HabitatFlow types can be distinguished by velocity and depth using Froude Number F =vgd
Panfil & Jacobson, 2000
Thomson et al, 2001
Stream Habitat types are created and maintained by erosion and deposition of sediments.Hjulstroms Diagram
Mechanics of Habitat FormationShear Stress/Velocity Reversal HypothesisHelical FlowContraction/Expansion of Flow
t = rghsv ~ f(Rs)Knighton, 1998
Helical flow in meander bendsKnighton, 1998
Flow contraction and expansionWohl, 1998
Increased roughness reduces shear, promoting deposition of finer materialMcBain & Trush, 2004
Diversity is a function of fluctuations in erosion and deposition processes over varying scalesWhat promotes Habitat Diversity?Disturbance
Natural flow regime Varying sediment inputs
Structural diversity - LWDNatural stream systems are subject to the full spectrum of spatial & temporal disturbancesEpisodic Sediment Transport
Natural Flow Regime5 characteristics:FrequencyMagnitudeDurationTimingRate of ChangeKey factor = extremes included
Disturbance acts to reset processesMount, 1995
Large Woody DebrisIncreases local scour and depositionProvides structural habitatTransient nature (moves, breaks, clumps, decays)All add to habitat diversity and complexity
Buffington & Montgomery 1999Plane BedWood-poorPool-riffle
Buffington & Montgomery 1999Wood-richPool-riffle
Stream habitat diversity maintained over time
Species adaptSalmon spawning and run timingFoothill Yellow-legged Frog oviposition timing Cottonwood regeneration accidental forest
Redrawn by Bledsoe from Schlosser (1995)Diversity in Trout Habitat
Alterations to flow regime & sediment supply alter habitat diversity & biodiversityStream Corridor Restoration, 1998
Alterations to Stream SystemsFlow extraction diversions groundwater withdrawalFlow augmentationag runoffhydropowerSedimentation development loggingminingSediment Lossdamsmining
Channel Bed Coarsening Loss of Fines/Gravels Vegetation Encroachment Low bed mobilityDegradation Channel Bed Fining Excess Fines/Gravels Lack of vegetation High bed mobilityAggradation
Effect of DamsBlock Sediment
Flatline Hydrograph
Disrupt ConnectivityChannel Degradation bed coarsening, loss of fines/gravelsLoss of extreme flows (loss of disturbance) low bed mobility, vegetation encroachment, low habitat diversityBlock habitat access, alter water chemistry, shift from lentic to lotic system
What can we do to improve spawning habitat conditions downstream of dams?
Broad Definition incorporates all physical and chemical constituents along with biotic interactions
Specific Def incorporates the quality of instream and riparian characteristics that influence aquatic community structureHave to think big picture, but in terms of or specific to the species of interestAlthough physical habitat varies over space and time, for practicality, we focus on an accessible habitat of importance to the species of interest.
For fish, the most limiting habitats are generally spawning and summer low flow. In spring habitat quality is low (lack of adequate substrate) and disturbance could be high. In summer, both habitat volume and habitat quality are low, even though disturbance is low.Fluctuations in Sediment Transport (the real disturbance) is a result of fluctuations in flow regimeIf Physical habitat forms the template for aquatic communities, biological potential is limited by the quality of physical habitat
Thus Habitat Diversity and Biodiversity are linked