Maintaining FIA’s Credibility as

The Nation’s Forest Census

Dave StrubleMaine Forest Service

Critical Attributes

• Accurate

• Timely

• Unbiased

• Relevant

NRS EstimatesInventory Data for 2006

Release Date

GS Inventory

(MCF)

GS Net Growth(MCF)

GS Removals

(MCF)Growth/

Removals %

September 23, 2008 22,539,185 567,409 488,826 116%

December 13, 2008 22,539,000 468,600 528,300 89%

September 28, 2009 22,558,600 468,604 528,301 89%

November 30, 2009 23,163,397 518,760 559,434 93%

SOURCE Release Date

GS Inventory

(MCF)

GS Net Growth(MCF)

GS Removals(MCF)

Growth/Removal

%

NRS September 23, 2008 22,539,185 567,409 488,826 116%

MFS March 29, 2009 22,969,600 536,600 469,500 114%

RPA March, 2009 22,403,000 580,062 490,003 118%

Release Date

GS Inventory

(MCF)

GS Net Growth(MCF)

GS Removals

(MCF)

Growth/Removal

%

2003 22,413,400 512,526 525,772 97%

2006 23,163,397 518,760 559,434 93%

2007 23,110,605 555,368 570,735 97%

2008 23,148,203 573,196 562,230 102%

2003 - 2008Inventory

Change/Year

2008 Net Change

per Year

146,961 10,966

Tree-Level Volume Estimation• Previously (for the most part), individual tree volumes

were estimated and based on field-measured diameters, merchantable lengths, and cull discounts.

• It has found that “NOISE” in the measurements of tree lengths and assessment of cull outweighed the true “SIGNAL”; despite the fact that QA/QC checks were consistently meeting the Measurement Quality Objective (MQO) tolerances.

• A taper model is now used to estimate needed tree lengths (merchantable, sawlog) as a function of DBH and total height (mostly field estimated)

• Another model estimates the percent of total tree volume represented by cull, as a function of species group, D-Class, dead/alive, and tree class

2003 2005 2006 2007 2008Field Calls - Spruce/Balsam Fir 6,470 6,352 6,416 6,365 Modeled - Spruce/Balsam Fir 6,178 6,051 6,105 6,055 6,031

% Difference -4.5% -4.7% -4.8% -4.9%

Field Calls - Maples/Beech/Birch/Basswood 6,287 6,266 6,287 6,289

Modeled - Maples/Beech/Birch/Basswood 7,184 6,989 6,981 6,866 6,860

% Difference 14.3% 11.5% 11.0% 9.2%

Growing Stock Volumes (MMCF)

Comparing volume estimates using field collected data versus

modeled substitutes

FIA basis, annualized growing stock growth components, by inventory year (Million cubic feet per year)

-600

-450

-300

-150

0

150

300

450

600

750

1958 -272 574 -212 271%

1970 -136 637 -409 156%

1981 -198 472 -350 135%

1995 -226 405 -503 81%

2003 -246 513 -526 97%

2006 -289 519 -559 93%

2007 -275 555 -571 97%

2008 -269 573 -562 102%

Mortality Net Growth (G) Removals (R) GR Ratio

MFS basis, all softwood, all hardwood, and statewide (all species), displaying all components of change (cords/acre/year),

for the growth period of 1999-2001 to 2004-2006

-0.40

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

0.60

All Softwoods 0.07 0.25 0.32 -0.11 0.00 0.22 -0.18 0.04

All Hardwoods 0.04 0.19 0.23 -0.07 -0.02 0.15 -0.14 0.01

Statewide 0.11 0.44 0.56 -0.18 -0.01 0.37 -0.32 0.05

Ingrowth AccretionGross

GrowthMortality

Net GSIncrement

Net Growth

TotalRemovals

Net Change

Comparing FIA and MFS annualized harvest estimates of all species (million cubic feet)

-600

-500

-400

-300

-200

-100

0

1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010

FIA All Spp GS Removals

MFS All SppPulpwood +Removals

Harvest green ton volume distribution, by product, from 1904 - 2008 (5-Year Trailing Average)

0

2,000,000

4,000,000

6,000,000

8,000,000

10,000,000

12,000,000

14,000,000

16,000,000

18,000,000

20,000,000

1904 1924 1944 1964 1984 2004

Biomass Chips Harvest (Green Ton)

Firewood Harvest (Green Ton)

Hardwood Pulpwood Harvest (Green Ton)

Softwood Pulpwood Harvest (Green Ton)

Hardwood Sawlog Harvest (Green Ton)

Softwood Sawlog Harvest (Green Ton)

Component Ratio Method (CRM) for Biomass

• In the past, merchantable volume and biomass were estimated using separate sets of equations.

• Now CRM harmonizes volume, biomass, and carbon estimates and is comprised of a series of steps.

• We are still trying to fully understand and match up transitions from 1982 to 2008. Suffice to say, the deck chairs keep getting reshuffled, and several 2008 estimates do not make sense.

Biomass Estimation Quandaries• 2008 growing stock bole biomass estimate (385 MDT) is

1.4% higher than its equivalent 1982 estimate (380 MDT).– Counter – The 2008 growing stock merchantable

bole cubic foot estimate is 8% less than its 1982 equivalent.

• Old version 2003 growing stock bole biomass estimate is 21% more than the new 2003 equivalent.– Counter – The new 2003 growing stock

merchantable cubic foot estimate is 4% more than 2003 equivalent.

• 2008 sapling biomass estimate is only 5.2% more than its 1982 equivalent.– Counter – The 2008 sapling stocking estimate (# of

stems) is 97% more than its 1982 equivalent.

Comparing Sapling Tree Estimates to their repsective biomass estimate (2 methods), Maine

-

50,000

100,000

150,000

200,000

250,000

300,000

1982 100,111 145,615 112,073

1995 134,782 208,586 149,572

2003 180,831 262,154 182,038

2008 193,056 299,799 117,876

Total AllSaplings

(Hundred Thousands)

Jenkins Process Biomass Estimate

(M Dry Tons)

FIA Published Biomass Estimate

(M Dry Tons)