Theory

1. Incorporating ecological concepts into channel design: structural and functional approaches to restoration Nira Salant Intermountain Center for River Rehabilitation and Restoration Principles of Stream Restoration and Design: Part II August 2011

2. Ecological restoration defined Evolutionary strategies Population dynamics Community structure Theory Structure and components Function and process Science Passive Active Practice

3. Ecological considerations for restoration Assuming goal is ecologically successful restoration… Natural drivers Function and process Dynamic systems Part of a watershed Habitat Structure and components Typical restoration Biological success Survival, growth, reproduction …we need to ensure that the habitat characteristics preferred and required by biota are present and persistent at the relevant scale

4. Ecological approaches to restoration: Structural versus functional Functional • Food web interactions • Production (1o or 2o) • Nut. cycling, OM processing • Population dynamics • Disturbance regime • Restoration actions • Connectivity • Flow and sediment regimes • Channel complexity • Riparian processes Structural • Focal species • Species diversity • Functional groups Restoration actions • Channel configuration • Instream habitat restoration • Stocking

5. Structural approaches to restoration • Channel configuration • Instream habitat restoration • Stocking Follstad Shah et al. 2007 One of the most common river restoration practices Habitat degradation considered most serious threat to biodiversity Only 2% of U.S. rivers of high natural quality (Benke 1990)

6. Instream habitat restoration Basic assumption: Species richness and abundance are limited by degree of physical habitat heterogeneity “If you build it, they will come” Kerr et al. 2001 Basic approach: Restoration of resources or environmental conditions necessary to sustain an individual population or group of populations

7. Instream habitat restoration: Focus on creating habitat heterogeneity Niche theory: diversification/specialization Environmental conditions favorable for a larger number of species Range of conditions available for different life history requirements Reduces competitive dominance Provides refugia from predators and disturbance Relevant at a range of spatial scales Food resources, hydraulics & competition Food resources, temperature, & stream size Substrate, hydraulics & food resources Particle Habitat unit or reach Channel

8. Instream habitat restoration: Common approaches Actions Boulder additions LWD additions Add pool-riffle sequences Channel reconfiguration Goals Increase habitat quality/quantity Increase hydraulic heterogeneity Increase substrate heterogeneity Increase food resource quality/quantity Ultimate objective: Increase fish density and biomass Native or sport fish? Fish diversity?

9. Instream habitat restoration: Does it work? Sometimes. Narrow focus on physical structure Fitness Reproduction Survival Growth Other factors may be limiting to growth, survival, etc. Habitat Physical Chemical Biotic • Primary production • CPOM & FPOM • Predators/competitors • Disease • Connectivity • Substrate • Flow depth, velocity, etc. • Temperature • Connectivity • DO • Nutrients • pH • Salinity • Conductivity

10. Limiting factors Variation among life stages Schlosser 1991

11. Instream habitat restoration: Limiting factors Select habitat suitability indices for brown trout Any one habitat factor could be limiting; depends upon conditions and life stage Restoration often only address physical factors, which may or may not be limiting Altered physical conditions may not persist over time <10 C >10 C % pools during late growing season, low-water Rubble Gravel Fines Dissolved oxygen (mg/l) Dominant substrate Fry Adults and juveniles Riffle-run areas Spawning areas % cover during late growing season, low water Max water temperature during summer (degrees C) Fines Site-scale physical Reach-scale physical Water quality

12. Instream habitat restoration Using suitability indices to guide design Example 1: Does the percentage of pools remain suitable as flow changes? > 20% pools, ideally between 50-70% But recognize that too many pools can create problems for other life stages if substrate changes % pools during late growing season, low-water Riffle-run areas Spawning areas Construct or provide structures to create pools, but beware unintended negative effects (e.g., Donner und Blitzen River) Fines

13. Instream habitat restoration Unintended negative effects: Donner und Blitzen River, Oregon 2001 (before weirs installed) 2009 (5 years after weirs installed) Pools 71% Riffles 13% Loss of riffles and pools, increase in fines Pools 63% Riffles 10%

14. Instream habitat restoration Using suitability indices to guide design Example 2: Do pools remain deep enough to provide thermal refugia and/or cover at low flow? Is there enough overhead cover at low flow? Relate discharge to pool depth and pool depth to maximum water temperatures Fry Adults and juveniles % cover during late growing season, low water Quantify sources of cover throughout the year Example 3: Is bed composition suitable and heterogeneous to accommodate different life stages?

15. Suitability Indices: Ecohydraulic Models Suitability indices for depth and velocity (based on spawning habitat preference) Spatial distribution of depth and velocity Spatial distribution of suitability

16. Instream habitat restoration: Does it work? Sometimes. Discordance between spatial scale of restoration relative to the perturbation Larson et al. 2001

17. Instream habitat restoration: Bottom line Structural restoration can be ecologically successful, but only if: • Habitat quality, quantity, or heterogeneity are limiting factors • Larger-scale processes do not override reach-scale responses • Targeted biota should be there, can get there, and will stay there • Constructed habitat persists under imposed flow and sediment regimes Structures can increase physical heterogeneity… …and still have non-significant effects on fish populations Structures Structures None None From Pretty et al. 2003

18. Functional approaches to restoration Restoration of processes that sustain lotic ecosystems Food webs Nutrient cycling Resource transfer Dynamic properties of natural systems contribute to proper function Processes often operate at large spatiotemporal scales

19. Functional approaches to restoration: Strategies ProcessesStrategies Population dynamics Restore connectivity Resource transfer Longitudinal, vertical, and lateral OM matter processing Increase channel complexity/retentiveness Nutrient transformation Resource production Restore energy inputs: sunlight & OM Food web dynamics Habitat maintenance Restore natural flow and sediment regime Biotic interactions Disturbance regime

20. Functional approaches to restoration: Examples Restore energy inputs: autotrophic and heterotrophic production Two basic energy sources: Allochthonous and autochthonous Productivity potential of a system is generally driven by the amount of basal resources (bottom-up control) Type of basal resource can determine trophic structure and function Terrestrial organic matter Sunlight Allan 1995

21. Functional approaches to restoration: Examples Restore energy inputs: allochthonous energy sources Supported by breakdown of organic matter by microorganisms (heterotrophic) Coarse particulate organic matter (CPOM) Leaves, needles, woody debris, dead algae Fine particulate organic matter (FPOM) Soil, feces, reduced CPOM; 1 mm – 0.5 µm Dissolved organic matter (DOM) Carbs, fatty acids, humic acids; <0.5 µm > 1 mm • Controls on breakdown: • Microorganisms (bacteria, fungi) • Macroinvertebrates (shredders, collectors) • Mechanical abrasion • Leaf chemistry • Temperature

22. Functional approaches to restoration: Examples Restore energy inputs: autochthonous energy sources Photosynthesis (primary production) Vascular plants Mosses Algae Bacteria Diatoms Phytoplankton • Controls on production: • Light • Nutrients • Substrate • Temperature

23. Functional approaches to restoration: Examples Restore energy inputs: autotrophic and heterotrophic production Dominant type of energy source varies with stream size, substrate, riparian vegetation, and location in the watershed Allochthonous: narrow, coarse substrate, forested, low-order Autochthonous: wide, fine substrate, high-order River Continuum Concept Longitudinal variation in energy production and trophic structure

24. Functional approaches to restoration: Examples Restore energy inputs: tools for heterotrophic systems 1. Replace non-native riparian vegetation with native species Speed of breakdown (refractory vs. labile) Nutritional value Contribution to secondary production From Dudley and Neargarder, unpublished data

25. Functional approaches to restoration: Examples Restore energy inputs: tools for heterotrophic systems 2. Increase channel complexity and OM retention with natural structures Consider type of structure and disturbance effects Loss of mosses during restoration shifted resource base from detritus to algal production, resulting in altered benthic community Mosses and woody debris contribute to habitat, hydraulic refugia, and retention (esp. at high discharges) From Muotka and Laasonen, 2002

26. Functional approaches to restoration: Examples Restore natural disturbance regime Townsend et al. 1997 Intermediate disturbance hypothesis Greatest biodiversity at intermediate levels of disturbance frequency and intensity Evolutionary adaptations to a disturbance regime • Life history • Behavioral • Morphological E.g., disturbance-vulnerable caddisflies downstream of dam

27. Functional approaches to restoration: Examples Restore natural disturbance regime: evolutionary adaptations • Life-history • Synchronization of life-cycle event (e.g., reproduction, growth, emergence) with occurrence of disturbance (long-term average) • Type of disturbance: high predictability and frequency • Examples: • Cottonwood seed release • Salmonid egg hatching

28. Functional approaches to restoration: Examples Restore natural disturbance regime: evolutionary adaptations • Behavioral • Direct responses to an individual event; based on environmental cues • Type of disturbance: low predictability, high frequency, high magnitude • Morphological • Growth forms and biomass allocation; tradeoff with reproduction • Type of disturbance: large magnitude and high frequency

29. Natural flow regime Timing, frequency, magnitude, duration, predictability • Chemical • Dissolved Solids • Nutrient Cycling • Physical • Sediment Transport • Channel Morphology • Thermal Regime • Biological • Community Composition • Life History Strategies • Biotic Interactions Functional approaches to restoration: Examples Restore natural disturbance regime: tools for restoration Ideally, return or replicate natural flow regime and sediment supply Job becomes much more difficult when this is not possible Goal should be to recreate processes that sustain natural chemical, physical and biological functions and patterns Use channel design to best replicate natural disturbance regime, given the current governing conditions

30. Functional approaches to restoration: Examples Potential ways channel design can recreate natural disturbance regime Design channel for frequent (~2 year) overbank flooding Seed germination, riparian growth (OM, sediments, water) Design channel with lateral and vertical high-flow refugia Lateral pools Large woody debris, aquatic vegetation Side channels Off-channel ponds connected at high flow In general, create conditions for regular bed mobilization (flood flows), moderate levels of bank erosion, and some instream deposition  Dynamic, self-maintaining channel But remember, each system is unique

31. Functional approaches to restoration: Challenges • Difficult to identify relevant processes, spatiotemporal scales and limiting factors • Assessments can require high level of expertise and be costly and time-consuming • Lack of standardized methods Benefits • Ecological goals are more likely to be achieved • System will require less long-term maintenance • Whole-system recovery rather than single feature response

32. Implications for practice • Prioritize restoration efforts by assessing the source and scale of degradation processes, the condition of the regional species pool and identifying limiting factors • Assess whether a structural approach will be adequate or whether a functional approach to restoration is needed, but also recognize that structural changes may help restore process and function • Realize that temporal variability can be as important as spatial variability (some natural systems are dynamic); realize that each system is unique • Biotic variables may be as important to restore as physical variables; physical improvements may not illicit positive biological responses • Monitor both abiotic and biotic variables at concordant and relevant spatiotemporal scales to quantify links between restoration actions and desired ecological responses

33. Extra slides

34. Instream habitat restoration: Limitations of structural approach (1) Additional abiotic and biotic drivers Interactions: Slope and primary production Heterotrophic or allocthonous energy sources Kiffney & Roni 2007 Wallace 1999

35. Spatial scales of variability: Macroinvertebrates Top and bottom of individual particles (~10-3 m) Why: food resources, hydraulics & competition

36. Spatial scales of variability: Macroinvertebrates Habitat unit: pool versus riffle (~102 m) Why: Substrate, hydraulics, food resources • Collector gatherers • Shredders • Depositional • Fine sediment • Scrapers • Filterers • Current loving • Erosional • Coarse sediment

37. Spatial scales of variability: Macroinvertebrates Longitudinal (RCC) (~104 m) Why: Food resources, temperature, stream size

38. Chemical • Dissolved Solids • Nutrient Cycling • Physical • Sediment Transport • Channel Morphology • Thermal Regime • Biological • Community Composition • Life History Strategies • Biotic Interactions Natural flow regime Timing, frequency, magnitude, duration, predictability

39. From Ebersole et al. 1997

40. From Ebersole et al. 1997

41. Limiting factors Connectivity (lateral and longitudinal) Competition, predation, non-native species Disease Species adaptations (disturbance regimes, habitat requirements, spatial/temporal scales of habitat use) mayfly fluvial trout Adapted from Lake 2007

42. Historical events Instream habitat restoration: Does it work? Sometimes. Evolutionary processes Disturbance regime Regional Species Pool Anthropogenic activities Physiological constraints Biotic filters: Competition / Predation Restoration Abiotic filters: Habitat / Dispersal Hierarchy of interacting variables that influences reach scale conditions Local community composition