Improving DWM Data Quality3rd of 3 Part Training Series

Christopher Woodall

DWM National Indicator Advisor

Outline

• QA/QC Analysis

• What Customers Want

• Measurement Errors Hot and Cold Checks

• Top Six List of Errors

• Training

QA/QC Analysis

The analysis of 2001-2004 DWM QA plots is currently ongoing. Matching algorithms are being developed for numerous measurement variables. Expect results for the 2006 P3 Training Sessions.

For more information contact: Chris Woodall @ NCFIA and Jim Westfall @ NEFIA

What Customers Want

Key

N

430°

150°

270°

30°

150°

270°

30°

150°

270°

30°

150°

270°

3

2

1

Transect Information

FWD < 0.25”& 0.26”-0.99”

FWD 1.00”-2.99”

CWD => 3.00”

6 ft. s.d.

10 ft. s.d.

24 ft. h.d.

s.d.= slope dist., h.d.=horizontal dist.

Sub-plot

Micro-plot

CWD Transect

FWD Transect

Distances between sub-plot points: 120 ft., Distance from sub-plot center and microplot center: 12 ft., Distance betweenSub-plot 1 and sub-plots 2, 3, and 4: 207.8 ft. at angles (degrees) 150, 210, and 270 respectively.

A uniform DWM sample design applied across

the entire United States producing per acre estimates of fuels, carbon, and wildlife

habitat

Measurement Errors

• Establishing Transects

• FWD Counts

• Slope versus Horizontal Distances

• CWD Diameters

• Correct Units for Duff, Litter, and Fuelbed Depths

• Microplot coverage and heights

Hot checks

Measurement Errors

• Number 1 priority is matching data and determining adherence to MQO’s

• Number 2 priority is determining cause for errors…then correcting cause

Cold/Blind Checks

Measurement Error Propagation

CWDDuff/Litter

FWD

Slash

Shrub/Herb

Transect

Database Processing Algorithms

Core TableMeasurement errors have varying magnitudes of effect

Measurement Error Simulation

Effect of 5, 10, 15% variation in down woody material measurement variables on total per acre tonnage estimates

0

1

2

3

4

5

6

7

8

5 10 15

Simulated Variation (%)

Va

ria

tio

n in

To

tal T

on

na

ge

Es

tim

ate

s

(%)FWD - 1-hr Count

Litter - Depth

CWD - Tran. Length

FWD - Tran. Length

Slash - Height1

Slash - Density

CWD - Diameter

Duff - Depth

Simulation Conclusions

Measurement variables whose errors least affect core table outputs: CWD decay, classes/transect lengths, litter depth, and FWD counts

Measurement variables whose errors most affect core table outputs: duff depths, CWD diameters, and slash pile densities

FIA’s Top Six LeastWanted DWM Errors

1. CWD Diameters2. CWD Lengths3. Duff Depths4. Litter Depths5. Slash Pile Density6. Missing Data

CWD Diameters

Crews mistakenly record CWD diameters to tenth of inch…used to P2 plots

Only measure to nearest inch!!

≠

CWD Lengths

Some log dimensions recorded in field are impossible

3 inches

15 feet

120 inches

=

Duff Depth

Duff is the heaviest down woody material per unit volume

Make sure your measurements (and units) are correct

Litter Depth

Much lighter than duff…however is usually much deeper

Don’t mistakenly enter the litter depth for duff depth

Slash Pile Density

Only neatly stacked wood can exceed 40-60% density!

Missing/Mismatched Data

AKA: Excruciating Headaches for Analysts

Missing/Mismatched Data

Example: DWM plot sheet indicates CWD transects on a condition class 2…however, only one condition class recorded in P2 record

Example: CWD piece is decay class 2, but is missing small and large end diameters

Might be your fault, might be data management’s fault, might be computer’s fault…no matter…do what you can to minimize mismatch errors

Training

Problem Areas

Problem: Field crews disturb the CWD too much trying to determine decay class or if segmented

Correction: Although field crews must disturb CWD pieces in order to acquire measurements, try to keep disturbance to a minimum

Problem Areas Cont’d

Problem: Field crews mistakenly enter extra digit for CWD diameter (40 instead of 4 inches)

Correction: Unless PDR’s catch them, be sure of very large CWD diameters

Problem Areas Cont’d

If CWD piece ends in water, treat as if underground,

measure piece to water edge

For FWD, if transect under water try to enter “0” values and

indicate in plot notes

Problem Areas Cont’d

Problem: Crews dig through litter hunting down pieces of FWDCorrection: Crews should only tally obvious FWD pieces, namely those on litter surface

Problem: Crews aren’t tallying FWD pieces hung up in slash/saplings Correction: Crews should tally all FWD pieces from forest floor up to 6 feet above ground

Problem Areas Cont’d

Problem: Crews either include too much of the litter layer or upper soil mineral horizons in estimation of duff depth

Correction: Crews should be absolutely sure of what is duff, litter, and mineral horizons. Be absolutely sure of duff measurements!!

Problem Areas Cont’d

Duff Depths:

1) Identify duff from mineral soil2) Don’t include moss or litter

material3) What to do with deep duff4) Anything over 1 foot be

absolutely sure

Problem Areas Cont’d

Problem: Crews can’t decide on the fuelbed height measurement

Correction: Crews should only take 15-seconds to determine height of dead, down woody material, don’t over analyze, use local knowledge and reasonable definition of fuel ladders

Problem Areas Cont’d

1) Measure from top of duff to top of fuel complex

2) Fuel complex composed of dead FWD, CWD, shrubs, and litter

3) Gaps allowed in fuel complex where one would reasonably expect flame lengths to connect

4) Plum-bob not required, ocular estimate around sample point

5) 15-second rule…Don’t over analyze height of fuelbed…Use your experience and logic

Fuelbed Depths

Problem Areas Cont’d

Problem: Condition class boundary runs through microplot

Correction: Use entire forested condition of microplot to estimate coverage and heights

=100% cover of litter for forested conditions (don’t include asphalt or other non forested conditions in cover assessment)

Problem Areas Cont’d

1) Train with idea of imaginary 6.8 foot radius cylinder

2) Make sure crews know what herbs and shrubs include

3) Gaps allowed in fuel complex as long as reasonable

4) Branches from shrubs rooted outside microplot allowed

5) Train about vines and canopy herbaceous plants

Microplot Heights

Problem Areas Cont’d

Only include epiphytes or hanging moss up to

6 feet in height

Include vines that are within microplot

Problem Areas Cont’d

Only estimate density of CWD within pileDensity should rarely exceed 40%

70% 20% 01%

Slash Pile Densities

Organizing Training Sessions

1) Part 1: Introduction to DWM2) Part 2: Field Methods3) Analyst Example (optional)4) Part 3: Improving DWM Data Quality5) Certification Test

1) Stations (test optional)2) Go over one subplot together as group3) Trainees do at least one subplot on their

own – hot audit and/or compare results

Classroom

Field

Bringing it all Together

1) Pick training location where many conditions classes and sampling scenarios exist (see word file)

2) Use powerpoint files to sculpt training session so trainees have understanding of why we need quality DWM data, what we use it for, the theory behind the sampling design, field methods, and problem areas

3) Setting up a quality station course can reduce questions during actual field season – may conduct test

Sample Design Changes

The DWM Indicator must be responsive to customer needs and improving science/techniques…

Don’t assume your ideas are insignificant, you collect the data, assume you know best and pass ideas upwards…

Submit your suggestions cwoodall@fs.fed.us

End of Part 3 of 3

http://www.ncrs.fs.fed.us/4801/national-programs/indicators/dwm/