Reconstructing 1824 Tallahassee Woodlands

The Results

Reconstructing the 1824 Woodlands

in the Tallahassee Red Hills Region

RMSE: 0.4570714

RMSSE: 0.9872133

Mean Error: 0.001572082

Mean Standardized Error: 0.003336705

Average Standard Error: 0.4630765

All transects with observations of pine, oak, hickory and/or dogwood and NOT beech or magnolia were considered to be a candidate for the SPOH woodland type.

Transects vs. Bearing trees

250 transects met this requirement, or ~40% of the dataset.

Philip Griffith

Transect data, by its nature, contains a coarser grain of observation than bearing tree data, which has a very fine grain of observation.

A fine grain of observation is an improper scale to study the phenomena in question, and therefore leads to inaccurate study results, in this case, the omission of a predominant forest type: SPOH woodland.

The Goal

Create a map of an endangered ecosystem as it may have looked 190 years ago.

Shortleaf Pine-Oak-Hickory (SPOH)

Upland Mixed Woodland (FNAI, 2010)

Characteristic species:

• Southern red oak
• Mockernut hickory
• Post oak
• Shortleaf pine
• Longleaf pine
• Flowering dogwood

Absent:

• American beech
• Southern magnolia

Range: Jackson to Marion county, parts of southeast Georgia

Follows old upland areas containing richer soils (e.g. Orangeburg, Lochloosa & Kendrick soil types), hence much of its former areas have been historically cultivated.

May have covered large areas of the Tallahassee Red Hills Region

The Method

Study Area: ~900 sq km (14 townships)

The Data

Tallahassee Red Hills Region:

• Sandy red clay
• Hilly topography
• Water oak-sweetgum-loblolly

woodland type

General Land Office Survey Notebooks

from the original 1824 survey of Florida

Data: 617 observations from 401 pages in volumes 1, 3, 14, 28, 43 & 63 of the GLO notebooks

Township: 6 sq mi

Section: 1 sq mi

Quarter-quarter section:

40 acres & a mule

Public Land

Survey System

Corners of sections were marked by a monument.

Created in 1812, the General Land Office surveyed, platted and managed the sale of all public lands in the US.

Prominent trees around the monument were marked and recorded to aid in relocation.

• Witness or bearing trees
• Usually four

Transects vs. Bearing trees

Indicator Kriging

The happenstance of history

Step 1

• Create points representing each transect

Similar procedures were used to record quarter posts halfway between section corners

• Line trees
• Usually two

Inverse Distance Weighting (IDW)

Bearing tree observations are used almost exclusively in studies involving GLO survey data.

Kriging uses known values and a semivariogram to predict unknown values.

Data was aggregated to the genus

Step 2

• Assign transect line observations to points
• Species... present = 1, absent = 0

Objection 1: selection bias

Semivariogram: a graph showing how distance and data are related;

a representation of spatial autocorrelation

A model is chosen to best describe the values represented in the semivariogram.

When predicting an unknown value at a point, the surrounding known values are weighted according to the chosen model.

Data is missing!

Objection 2: grain of observation

Indicator kriging uses binary values to estimate the probability of a value's presence at a location.

Pine

Hickory

Oak

Dogwood

Sweetgum

Bay

Beech

Magnolia

Sourwood

Chincopia

Haw

Persimmon

Cherry

Lin

Ash

Cypress

Blackgum

Sassafras

Maple

Elm

Poplar

Holly

Hazel

Ironwood

The GLO notebooks provide an invaluable record of detailed presettlement land cover in much of the U.S.

...were referenced to section boundaries, called transects.

Notes regarding...

• quality of land
• water bodies
• soil types
• tree species
• natural & artificial features

Public Land Boundary Information System (http://www.labins.org/)