The DFC Model: a Regulatory Tool Used in Riparian Forest Management in Washington

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The DFC Model a Regulatory Tool Used in Riparian
Forest Management in Washington

• Steve McConnell
• Upper Columbia United Tribes
• Spokane, WA
• Growth Model Users Group Meeting
• January 11, 2007

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Acknowledgements

• NWIFC, CMER, UCUT
• John Heimburg
• Dave Schuett-Hames, Ash Roorbach
• Chris Mendoza, Pete Heide
• Doug Martin, Nancy Sturhan
• Darin Cramer, Dawn Hitchens and Bonnie Thompson

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Presentation Outline

• DFC Model Attributes and Role in Management
• Desired Future Condition (DFC) management concept
• Key attributes of DFC Rules
• DFC Model role in management
• Model origins and characteristics
• Overview of CMER DFC related studies

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DFC Model

• Only growth and yield model used as a regulatory
  tool
• Derived from ORGANON, SMC version
• A whole stand model

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DFC Model

• Utilizes landowner collected data
• Simple enough for lay-persons to use
• Limited number of outputs only those that
  pertain directly to what landowners need to know
  to implement rules

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DFC Model Role

• Project stand basal area growth from current age
  to stand age 140
• Determines if stands will meet DFC Target
• Provides prescriptive details based on site and
  stand characteristics
• Takes a very complicated set of rules and makes
  them comprehensible!

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Characteristics of DFC Rules for Riparian Forests

• Fish-bearing streams on private forest lands in
  western Washington
• Core, Inner and Outer Zones
• Zone widths vary by site class (I-V) and stream
  size (LE or GT 10)
• The DFC target is a stand-age-140 basal area
  target, for each site class

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DFC Desired Future Condition

• Characteristics and functions of mature,
  unmanaged riparian forests
• Habitat conditions desirable for salmon recovery

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DFC Desired Future Condition

• Goal-oriented management system
• The stand conditions of a mature riparian
  forest, agreed to be 140 years of age a
  reference point on a pathway and not an endpoint
  for stands.
• Gauged against a stand basal area target

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Management Along Westside, Type F Streams Varies
By

• Site productivity site class I-V
• Stream-size LE 10 vs. GT 10
• Harvest method
• no-cut
• thin from below
• leave trees closest to the stream

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RMZs a Graphical Depiction

• Zones core, inner and outer

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RMZs Location, Activities Allowed and Size

• Core Zone closest to stream, no cutting, always
  50 wide
• Inner Zone some cutting, variable width (10 to
  100 feet)
• Outer Zone furthest from stream, more cutting,
  variable width (22 to 67 feet)

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RMZ Widths, by Stream Size
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Forest Practices Rules Stand Age-140 Basal Area
Targets
Stand Basal Area for DFC Rules is Calculated
from the Area-Adjusted CoreInner zones
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DFC Desired Future Condition

• Management today that puts stands on a trajectory
  towards DFC
• Stand growth and Rx details derived from the DFC
  Model

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DFC Model Problems

• Three errors in DFC Model calculations were
  identified, none of them making significant
  differences to the desktop analysis but possibly
  affecting implementation

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DFC Model Problems

• 1) Stand age 140 BAPA is inflated for stands
  younger than 35 years,
• 2) An incorrect value is used in for small stream
  site class 1, 2, and 3 per acre calculations
• 3) For Option 1, the DFC Model gives different
  inner zone leave tree numbers on the graphical
  interface than are counted in the inner zone
  stand table

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Desktop Analysis Results
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Sensitivity Analysis (Roorbach)

• Scrunches variability for most input variables,
  minimizing the difference in stand age 140 Basal
  Area
• Major Species, DF or WH, makes an important
  difference in DFC Model outputs the largest DFC
  Model related difference found

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DFC Model Related Reports

• Desktop analysis
• Riparian stand characteristics
• Sensitivity analysis (Roorbach et al.)
• FPA field check review
• Model and manual problems
• Synthesis

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Desktop Analysis Exploratory Origins

• Initial analyses were
• unstructured outcomes were evaluated without
  specific objectives.
• from a small sample of FPAs from the Olympic
  Peninsula,
• from FPAs that were approved just after new rules
  were developed

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Desktop Analysis Exploratory Results

• Noticed that projected ba-140 almost always
  exceeded rule ba target
• Determined that the required 57 ltpa was a
  constraint to inner zone timber harvest
• Later, determined that the option 2 minimum floor
  width also constrained timber harvest more than
  the rule ba target.

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Desktop Analysis Follow-up Exploratory Study

• Developed a Study Design (was not reviewed by the
  SRC)
• Developed specific objectives

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Desktop Analysis Follow-up Study Design

• Selected 150 FPAs from 2003 and 2004, 75 from
  each year
• Used first DFC worksheet from each FPA
• Developed criteria for rejecting FPAs that lacked
  data or did not meet criteria

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Desktop Analysis Follow-up Objectives

• Quantify DFC model-projected BA-140 for each of
  three riparian prescriptions 1) no-cut, 2)
  thin-from-below, and 3) leave trees closest to
  the stream
• Determine the effect of rule components (required
  leave trees option 1, and required floor
  widths, option 2) on DFC Model BA-140 projections

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Desktop Analysis Results
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Desktop Analysis Results
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Desktop Analysis Results
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Desktop Analysis Results
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Desktop Analysis Results
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Desktop Analysis Results
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Desktop Analysis Results
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Desktop Analysis Conclusions

• DFC model projected coreinner zone BA-140 exceed
  rule targets, because
• The 57 iz ltpa (opt-1) almost always (95.3 of
  worksheets reviewed) required leaving more trees
  than the rule target alone
• The minimum floor widths (opt-2) usually (63 of
  worksheets reviewed) required leaving more trees
  than the rule target alone

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Riparian Stand Characteristics

• Applicable only to subset of riparian stands that
  meet DFC requirements and selected by landowner
  for harvest
• Provide an overview of characteristics of stands
  submitted by landowners for management under
  current rules
• A few highlights only

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Site and Stand AnalysesSite Class
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Site and Stand AnalysesMajor Species
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Site and Stand AnalysesHA BA by Major Species
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Site and Stand AnalysesConclusions (Cont.)

• Most stands (88.7) were on Site Class 2 and Site
  Class 3
• There was an almost even split in of FPAs
  evaluated,by Species (74 DF and 76 WH)
• In core zones, on average, basal area and trees
  per acre were higher, and percent conifer lower

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Site and Stand AnalysesConclusions (Cont.)

• Stands with WH as major species had higher tpa,
  ba, and RD, but lower qmd than stands with
  Douglas-fir as major species

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DFC Field Check Study

• Most stand inventory and site attribute data
  collected were similar between landowner and CMER
  Staff
• Stream size
• Major species
• Stand age
• Stand inventory

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DFC Field Check Study

• Biggest differences to buffer strip configuration
  are a result of stream size call, CMZ delineation
  and landowner decision on outer zone trees

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DFC Field Check Study

• There were methodological findings, for example
• 1) there is no method prescribed for determining
  RMZ length and this can lead to a lot of
  variability,
• 2) the Board Manual and other materials provided
  to landowners are confusing, difficult to follow
  and have errors within

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Synthesis

• The basal area target is a less important
  constraint to inner zone timber harvest than is
  the leave tree requirement or minimum floor width
• Landowners use Option 2 (leave trees closest to
  the stream) preferentially

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Synthesis

• There may be differences in harvest age
  Douglas-fir and western hemlock stands in terms
  of basal area, tpa, relative density, qmd and
  conifer percent. Possibly there should be
  different management prescriptions for these.