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

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

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

DFC Model

• Only growth and yield model used as a regulatory tool

• Derived from ORGANON, SMC version

• A whole stand model

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

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!

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

DFC: Desired Future Condition

• Characteristics and functions of mature, unmanaged riparian forests – Habitat conditions

desirable for salmon recovery

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

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

RMZ’s: a Graphical Depiction

• Zones – core, inner and outer

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)

RMZ Widths, by Stream Size

Inner and Outer Zone Widths for Current "DFC" Rules

020406080

100120

iz small iz large oz small oz large

Zone and stream size combination

Wid

th (

ft)

I

II

III

IV

V

Forest Practices Rules Stand Age-140 Basal Area Targets

Basal Area Target

285 275 258224

190

0

100

200

300

I II III IV V

Site Class

Bas

al A

rea

(sq

ft/a

cre)

Stand Basal Area for DFC Rules is Calculated fromthe Area-Adjusted Core+Inner zones

DFC: Desired Future Condition

• Management today that puts stands on a trajectory towards “DFC”

• Stand growth and Rx details derived from the DFC Model

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

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

Desktop Analysis Results

Inner Zone Area vs. the Number of Trees per Acre Represented by a Single Tree in DFC Model

Calculations for the Thin-from-Below Prescription

0

2

4

6

8

10

Individual Stands

Tree

s pe

r Acr

e;

Inne

r Zon

e A

rea

(Acr

es)

Number ofTrees per AcreRepresented by One Tree

Area of Inner ZoneStands (Acres)

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

DFC Model Related Reports

• Desktop analysis

• Riparian stand characteristics

• Sensitivity analysis (Roorbach et al.)

• FPA field check review

• Model and manual problems

• Synthesis

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

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.

Desktop Analysis: Follow-up Exploratory Study

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

• Developed specific objectives

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

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

Desktop Analysis Results

Core+Inner Zone BA-140 by Rx's, across all Site Classes

0

100

200

300

400

500

Riparian Prescription

Bas

al A

rea

(ft2

/are

a)

no-cut

Opt-1

Opt-2

366.3 335.9 299.2

150 150 108

Desktop Analysis Results

Stand Age 140 Basal Area per Acre, by Site Class and Riparian Prescription

0

100

200

300

400

500

1 2 3 4 5

Site Class

Bas

al A

rea

per

Acr

e

(ft2 /a

cre) no-cut

Opt-1

opt2

Desktop Analysis Results

DFC Model After Thin Leave Trees per Acre, by Rule Constaint, for the 140 Stands Requiring 60 or fewer

Residual Trees per Acre

56

57

58

59

60

61

Individual Stands

Tree

s pe

r Acr

e

One Stand Constrained by basal area

One Stand Constrained by Basal AreaAND Trees per Acre

All other, 138 out of 140 Stands, Constrained by Trees per Acre

Desktop Analysis Results

DFC Model After Thin Leave Trees per Acre, by Rule Constraint, for the Ten Stands Requiring More Than 60

Residual Trees per Acre

60.8 61.5 62.2 63.7 64.9

70.9 71.5 72.8 73.1

97.0

60

70

80

90

100

Individual Stands

Tree

s pe

r A

cre

Stands Constrained by Basal Area

=>Stands Constrained

by TPA<=

Desktop Analysis Results

Timber Harvest Constraints for the Thin From Below Prescription: Trees Per Acre and Basal Area per Acre

-100

0

100

200

300

400

500

Riparian Stands, Sorted by Ascending Stand Age 140 Basal Area, Minus One Tree

Bas

al A

rea

(ft2

/acr

e)

and

Tre

es p

er A

cre

7 stands constained by basal area only

1 stand constrained by basal areaAND trees per acre

142 stands constrained by trees per acre only

basal area

Trees per Acre

Desktop Analysis ResultsSite

ClassSteam Size

Floor Width

Average floor width plus and

minus one standard deviation

Number of Stands

Constrained by Floor Width

Number of Stands

Constrained by Basal Area

Target

Total

1 Small 80’ 103.0 12.6 0 5 5

1 Large 100’ 102.0 4.0 3 1 4

2 Small 80’ 87.4 7.1 7 25 32

2 Large 100’ 102.6 5.7 20 7 27

3 Small 80’ 80.4 1.8 38 2 40

Desktop Analysis Results

Floor Width and Basal Area Credit for Site Class 2, Large Stream Stands

0

100

200

300

400

Individual Stands

Flo

or

wid

th (

ft);

Bas

al

Are

a C

red

it (

sqft

/acr

e)

credit

f loor

120'

100'

0

360.5

Desktop Analysis: Conclusions

• DFC model projected core+inner 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

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

Site and Stand Analyses:Site Class

Number of Riparian Stands by Site Classand DNR Region

0 0

9

01 4

45

92

39

25

81 3 2 10 0 0 1

0

10

20

30

40

50

NW OLY PC SPS

DNR Region

Nu

mb

er

of

Rip

ari

an

Sta

nd

s

1

2

3

4

5

Site and Stand Analyses:Major Species

Number of Riparian Stands by Major Species and DNR Region

18

55

103

38

26

9

0

10

20

30

40

50

60

NW OLY PC SPS

DNR Region

Nu

mb

er

of

Rip

ari

an

Sta

nd

s

DF

WH

Site and Stand Analyses:HA BA by Major Species

Core vs. Inner Zone Harvest Age Basal Area by Major Species

050

100150200250300350400

Core Inner

Riparian Management Zone

Ba

sa

l Are

a

(sq

ft/a

cre

)

DF

WH

For DF, n = 74

For WH, n = 76

Site and Stand Analyses:Conclusions (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

Site and Stand Analyses:Conclusions (Cont.)

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

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

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

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

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

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.