COMBINING HISTORIC AND CONTEMPORARY FIA DATA TO ASSESS LONG-TERM TRENDS: THE LONGLEAF PINE FOOTPRINT IN THE SOUTH

William BurkmanChristopher M. Oswalt

Analysis completed with contributions from:Christopher W. WoodallHorace W. Brooks

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Outline

• Brief background

• Methods of Investigation

• Results• Latitudinal/Longitudinal shifts• Central range thinning

• Highlights from FIA assessment

•Comments on outlook

Photo – Stephen F. Austin

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Background

• Longleaf pine forests were once – one of the most extensive ecosystems in North America (Landers and others 1995), occupying about 92 million acres in the southeastern United States (Frost 2006).

• Only a fraction of this longleaf pine remains today.

• The remaining longleaf pines are scarce, compared to their historical extent, and are spread among eight southern states in largely fragmented stands (longleaf pine is known to historically and currently occur in southeastern Virginia, however does not currently occur in the Forest Inventory and Analysis sample).

• Numerous studies recording the decline of Longleaf pine

• FIA Assessment of Longleaf Pine in the South (Oswalt et al. 2012)• Use of historical data was needed for comprehensive assessment of changes

Increase to 8.0 million acres

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Change in longleaf dominated stands – 1970’s to 2010

1970’s 2010

15 percent 7 percent

Oswalt et al. In Press

Longleaf pine = 3,300,717

LLP – Oak = 984,637

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Methods

• 1970’s vs. 2010

• Periodic, asynchronous inventories vs. Annual, continuous inventories

• Total Plots

State Forested plots LLP plots Forested plots LLP plotsAlabama 3,710 614 4,120 316 Florida 4,419 1,261 2,998 468 Georgia 5,926 987 4,516 280 Louisiana 2,481 262 2,469 123 Mississippi 2,780 326 3,547 188 North Carolina 4,732 341 3,524 128 South Carolina 3,986 634 2,433 206 Texas 1,961 109 2,192 29 Virginia 4,028 - 2,976 -

All 34,023 4,534 28,775 1,738

1970 2010

State 1970's 2010Alabama 1972 2011Florida 1970 2010Georgia 1972 2011Louisiana 1974 2010Mississippi 1977 2010North Carolina 1974 2011South Carolina 1978 2011Texas 1975 2010Virginia 1977 2010

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Methods – Forest type definitions

• Longleaf pine - 141• Longleaf pine occurs as a pure type comprises a majority of trees in the

overstory • Associates – Slash, loblolly and shortleaf pine, southern red oak, blackjack

oak, water oak, persimmon, and sweetgum• Sites – those areas that can and do burn on a periodic basis – usually occurs

on middle and upper slopes with low severity brush or hardwood competition

• Longleaf pine – Oak - 403• Associates – Longleaf pine and scrub oaks – primarily turkey oak, bluejack

oak, blackjack oak, and dwarf post oak• Sites – Common on sandhills where soils are dry, infertile, and coarse-

textured

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Graphical descriptions of forest types

Longleaf pine forest type

Longleaf pine – Oak forest type

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•

• Combine Outer Range analysis techniques from Woodall et al. (2009) with longitudinal band analysis techniques from Kai et al. (2012).

• Woodall et al. (2008 and 2009) describes the inherent difficulty in comparing historical and contemporary FIA Inventories.

• Here we overcome those difficulties by:• Greater electronic availability of historical data• Not examining seedlings• Greater similarity in periodic inventories within a single region• No attempt made at linking causality to long-term phenomenon (changing climate) that

would require a large span of time between inventories

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Methods

Defining the “Outer Range” (sensu Woodall et al. 2009 - also see Zhu et al. 2012)

90th & 10th percentiles calculated based on 1970’s presence

Eastern, Western, Southern, & Northern Outer Ranges (EOR, WOR, NOR, & SOR, respectively).

Primary focus was on “Outer Ranges” – The “heart” of the LLP range was investigated further for changes in area et al.

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Methods

• Comparison between decades of:• Mean latitude by 1 degree longitude classes• Mean longitude by 1 degree latitude classes

• Welch’s two-sample t-test

• Comparison across decades of:• Mean area• Mean biomass

• Welch’s two-sample t-test• Transformations• Presentation of back-transformed metrics

•

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Mean Latitude – Longitude for 1970 & 2010

Mean longitude

-90 -88 -86 -84 -82 -80 -78 -76L

atitu

de

class

26

28

30

32

34

36

38

19702010

Longitude class

-100 -95 -90 -85 -80 -75

Me

an

latitu

de

30

31

32

33

34

35

36

19702010

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Changes in Latitude

Longitude class

-88 -86 -84 -82 -80 -78 -76 -74

Mean latitude

34.0

34.2

34.4

34.6

34.8

35.0

35.2

35.4

35.6 19702010

Longitude class

-96 -94 -92 -90 -88 -86 -84 -82 -80M

ean latitude

28.2

28.4

28.6

28.8

29.0

29.2

29.4

29.6

29.8

30.0

30.2

19702010

Northern Outer Range Southern Outer Range

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Changes in Longitude

Mean longitude

-80.0 -79.5 -79.0 -78.5 -78.0 -77.5 -77.0 -76.5L

atitu

de

class

32

33

34

35

36

37

38

19702010

Mean longitude

-93.5 -93.0 -92.5 -92.0 -91.5 -91.0 -90.5

La

titud

e cla

ss

29.5

30.0

30.5

31.0

31.5

32.0

32.5

33.0

33.5

19702010

Western Outer Range Eastern Outer Range

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Potential “Thinning”

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Potential “Bright side” of the story

WOR Central EOR

Relative frequency

0.00

0.01

0.02

0.03

0.04

0.05

19701980199020002010

SOR Central NORR

elative frequency

0.00

0.01

0.02

0.03

0.04

0.05

0.06

19701980199020002010

WOR Central EOR

Relative frequen

cy

0.00

0.01

0.02

0.03

0.04

0.05

19701980199020002010

SOR Central NOR

Relative frequen

cy

0.00

0.01

0.02

0.03

0.04

0.05

0.06

19701980199020002010

LLP forest type across the South (excluding VA)

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From the FIA Assessment – Change in Diameter Distribution

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Challenges to Using Historical Data

• Electronic Availability • Regional differences in temporal richness of available data

• SRS – 1970’s• NRS – 1980’s • RMRS – 1980’s• PNWRS – 1990’s

• Temporal Consistency of Variables• Great example – collection of seedling data• Many others

• Temporal Consistency of Inventory Design• Multiple designs• Changes, Changes, Changes

• None of these challenges are insurmountable.• However, all of these challenges impact the strength of inferences that can be

made and the confidence in those inferences.

State 1970’s 1980’s 1990’sAL 1972 1982 1990AR 1978 1988 1995FL 1970 1980, 1987 1995GA 1972 1982, 1989 LA 1974 1984 1991MS 1977 1987 1994NC 1974 1984 1990OK (East) 1976 1986 1993SC 1978 1986 1993TN 1980, 1989 TX (East) 1975 1986 1992VA 1977 1985 1992

SC 1968 also available electronicallyVA 1984 renamed 1985

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CONCLUSION

Combination of Woodall’s “Outer Range” and Zhu’s “Longitudinal Bands”

Longleaf pine “footprint” has contracted since 1970

Most significant contraction in Northeast of range

“Rebounding” from low may be occurring

FIA data and analyses good at helping identify large-scale conservation issues – not so good (in many cases) at identifying cause and effect

William Burkman Christopher M. Oswalt

bburkman@fs.fed.us coswalt@fs.fed.us865-862-2073 865-862-2068Knoxville, TN Knoxville, TN