Heat Exchange Functions Project Approach

Scientific Literature Review of Forest Management Effects on Riparian Functions for Anadromous Salmonids

for the California State Board of Forestry and Fire Protection

by Mike Liquori, Dr. Doug Martin, Dr. Robert Coats, Dr. Lee Benda, Dr. David Ganz

Heat Exchange Functions •

Project Approach • •

Too COOL: insufficient growth & lower ocean survival Too HOT: lower abundance & risk of mortality

This project was contracted through the State of California Board of Forestry and Fire Protection Reviewed 185+ assigned scientific papers published after 1997 focused around 5 Riparian Exchange Functions Biotic & Nutrient Heat Water Wood Sediment

Biotic & Nutrient Exchange Functions •

Riparian leaf litter is an important food source

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Litter quantity & quality is important Highest: alder Moderate: maple, willow and cottonwood Low: conifers and oaks

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Structured around Key Questions defined by a 12-member Technical Advisory Committee (TAC)

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Opening the canopy cover over some streams increases ecological productivity

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Document reviewed by TAC and 7 senior scientists during a daylong Technical Exchange Forum

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Tradeoffs between nutrient exchange and other functions

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Provides support for riparian rule revisions being considered by the Board of Forestry

Stream temperatures affect the growth and mortality of salmonids

Heat regulation Water – response to flooding Wood recruitment potential

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A 100 foot wide no-cut buffer on both sides of a stream provides conditions similar to a “no harvest” level

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No-cut buffers may forego opportunities to: increase fish growth rate and biomass address other beneficial functions

General Themes 2. Spatial context is important, as it influences functional response patterns.

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Riparian shade helps to control heat input to streams, but other factors are important too

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No single, fixed-width buffer or canopy closure prescription can regulate heat objectives for salmon in all cases.

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Effective shading can be provided by: Lateral: buffer widths ranging from 30 to 100 ft Longitudinal: generally within 500 to 650 ft upstream

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Water temperature protection could be provided by varying the riparian shade requirements in relation to stream temperature sensitivity.

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The relative importance and sensitivity of riparian vegetation to influence stream temperature varies by at least 11 site specific factors

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Stream temperature targets can be helpful in managing to desired shade conditions

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Timber harvest in or adjacent to riparian areas can influence microclimate, HOWEVER microclimate changes have not been demonstrated to translate to changes in water temperature.

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Shade conditions inversely influence biotic and nutrient exchange functions.

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Similarly, the canopy that provides shade also influences: Water exchange functions Wood exchange functions

3. Both longitudinal AND lateral controls are important in maintaining the watershed-scale ecosystem structure that maintains aquatic habitats. 4. Disturbances are an important mechanism for establishing conditions that support riparian functions by affecting factors like: • • • • •

Stand structure Vegetative succession Wood recruitment Nutrient exchange Thermal regulation

5. Riparian zones can buffer a stream from direct management impacts, but they also alter the disturbance regimes in ways that can affect both short-term and long-term evolution of riparian areas. 6. There are dynamic interactions among and between riparian exchange functions that alter the importance of exchange functions for any particular setting.

Water Exchange Functions •

effect is likely to be small highly variable strongly influenced by the watershed context impacts are mixed

7. Active and strategic riparian management can limit risks and benefit salmonids • • • •

temperature regimes ecological productivity woody debris recruitment fuel loads and other disturbance risks

8. There are variations in the buffer width necessary to meet each function, and these variations depend on several factors 9. The reviewed literature offers many opinions, but limited hard data to evaluate the scientific effectiveness of any approach 10. Risks and benefits are inherently value judgments best determined by policy • Science can only provide the context

11. The geographic and watershed-scale variables for buffers requires a policy framework • Information in the literature is available, but inconclusive in the absence of a framework

Forest management activities in riparian areas might affect stream functions

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Management affects the riparian canopy canopy interception evapotranspiration

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There is little direct evidence of riparian effects: studied for entire watersheds riparian zones alone have not been studied

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The most sensitive hydrologic areas may be steep, zero-order basins (hollows) This was not a focus of this review

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Soil compaction in riparian areas can negatively affect hydrologic processes. Suggests limits for heavy equipment near streams

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Hyporheic flows are important ecologically forest management effects are unclear

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There is very little in the reviewed literature that can used to directly address the issue of buffer strip delineation relevant to the water function

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Regional differences are likely to reflect: Geology topographic variation dominant runoff mechanisms

Relevant Report Section

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Wood functions vary by stream type and geomorphic context

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There are three dominant sources of instream wood in California second-growth forests

Erosion Mechanism Surface Erosion Skid Trails and Yarding Ruts Bank Erosion Windthrow Gullies Road-Related Sediment Fire Mass Wasting Soil Piping

bank erosion: ~40-60% streamside landslides: ~30% treefall: ~10-30%

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The zone that can contribute 90% of observed wood recruitment varies depending on the dominant processes Bank erosion: < 30 feet Streamside landsliding: 100-200?? feet Wind: 75-130?? feet Treefall: <100 feet

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Wood recruitment potential depends upon:

How often disturbances occur How large the disturbances are Which type of disturbances are likely

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Active forest management can influence wood functions by manipulating riparian stand structure in ways that: a) affect the growth and mortality dynamics for the stand and b) influence the types, qualities and risks of disturbances

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Sediment sources from forest management include:

Instream wood can move downstream through:

Forest management appears to influence natural disturbance regimes by affecting

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Effective Effective Effective Varies Somewhat Effective Somewhat Ineffective Insufficient Information Insufficient Information Insufficient Information

Source Controls Runoff Controls Treatment Controls

Existing stand conditions Successional pathway Disturbance Regime

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Sediment Best Management Practices (BMPs) typically address sediment primarily in three general ways:

Flood: in larger streams Debris-flow: in steep, low-order streams

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Effectiveness of Buffers

Sediment Exchange Functions

The major factors that are reported to influence wood recruitment conditions include: Existing Stand Density, Composition And Structure Stream Type, Order and Watershed Context Vegetation Type and Soil/ Site Index Regional Context Disturbance Context

2.1 2.1.1 2.1.2 2.1.3 2.1.4 2.2 2.2.1 2.2.3 2.2.4 2.2.5

Wood Exchange Functions

surface erosion processes (rills and sheetwash) skid trails yarding ruts gullies soil piping roads fire mass wasting processes bank erosion windthrow legacy forest management practices

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Riparian buffers are mostly effective at limiting sediment delivery to streams

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In the absence of buffers, ground disturbances that are near streams have the potential to deliver sediment

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Selective forest management within buffers does not appear to substantially increase sediment production or delivery

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The extent that riparian buffers along headwater streams are necessary to prevent sediment delivery is not clear from the reviewed literature.

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Despite the lack of evidence for direct sediment delivery, instream sediment yields tend to increase following logging Sources of such sediment are not clear

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Source distance relationships for sediment also appear to vary with the dominant processes and site conditions

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The reviewed literature did not provide a sufficient guidance for the various landscape situations in California, although a more detailed analysis of data may lead to more definitive specifications for buffer width.

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Riparian sediment management objectives include mitigating for:

Bank Treefall Landslides Erosion Windthrow

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Adaptive Management

Decision-support tools

it ns c li tio p Ex mp u s As

Models & mapping capabilities Resource targets Riparian management specifications

Monitoring & Assessment

Design tools

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A science-based management framework will provide the necessary policy direction Establish value positions regarding various management approaches Identify clear functional goals and performance measures that define the decision space for science-based management Outline a planning approach that provides a policy-oriented framework (i.e. based in regulations, planning processes, etc) Develop Adaptive Management structures and procedures

For a Free Copy of the report, go to: http://www.soundwatershed.com/BOF.htm

External Science

Suggests the need for management decision-support tools that help integrate science with management

Scientific Basis

t en em ns ag tio an s ue Q

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But limited information about the effectiveness of different buffer strategies

al tu ep s nc del Co Mo

g s n ki ese r o th W o p y H

Policy Inferences Lot’s of good detail available from literature that supports specific rulemaking elements

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The current scientific basis for defining buffer widths in fish-bearing streams is often based on source distance relationships, HOWEVER, there are several important challenges associated with this approach. Source distance relationships: • Ignore the trade-offs between functions • Downplay the importance of the quality of contributed inputs • Only capture the effects of some disturbances • Describe the relative contribution, but not the total contribution • Ignore changes over time • Ignore the longitudinal context • Have not established instream biological responses

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Management should consider both lateral (width) and longitudinal (network) variation, which requires an understanding of how different ecosystem processes act to form and maintain habitats throughout the channel network. Important factors include: • River Continuum v. Network Dynamics • Geomorphic Context is Important • Biological Hotspots • Disturbance Cascades

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There are dynamic interactions among and between riparian exchange functions that alter the importance of exchange functions for any particular setting

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While riparian zones can buffer a stream from some direct management impacts, buffers do not protect streams from disturbances, but in fact alter the disturbance regimes in ways that can affect the functional response expressed by both short-term and long-term evolution of riparian areas.

Harvest-Related Sediment Hydrologic Link to Sediment Delivery Road Sediment Mass Wasting Impacts

Management Policies, Priorities and Goals

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Synthesis of Exchange Functions & Management Implications