CSX Relocation Study A method for delineating areas of possible gopher tortoise habitat.

CSX Relocation Study

A method for delineating areas of possible gopher tortoise habitat.


What do we know about gopher tortoise?

1. They prefer areas of deep sandy soils for burrowing.

2. They forage primarily on prairie grasses with wiregrass being a preferred food source.

3. They require open canopy for food and basking.

4. Landcover, soil and topography are key variables in defining gopher tortoise habitat. Can we collect and integrate these data in order to generally model possible gopher tortoise habitat?


Study Area

Pearl River Stone

Hancock

HarrisonJackson

Pearl RiverStone

Hancock

HarrisonJackson


Model Inputs: Soils

USDA SSURGO Finitesoils series maps provideinformation on numeroussoil properties.

We know that gopher tortoiseprefer non-flooded, sandy soilsthat support longleaf pine andprairie grasses such as wiregrass.


Model Inputs: Satellite Imagery10 meter SPOT imagery gives a useful overview of landcover. Values in the image allow discrimination between forested andcleared areas.

A review of the data shows thatvalues below 12 counts indicatebottomland hardwood or dense mixed canopy. Values above 197indicate disturbed/cutover/developedareas. We believe areas valued between 12 and 197 are candidatesfor inclusion in gopher tortoise habitat model.

Model limits


Model Inputs: Aspect

Aspect supplies the “sun face” of the landscape.

We think that gopher tortoisesprefer S, SW, W facing slopes fortheir burrows.

Model Range


Model Inputs: Slope

Slope is a derivative of elevation. Localslope is given in degrees.

We believe that gopher tortoise prefers areas with slopes that are above .2 degrees and below 6 degrees- Not flat and not too extreme.

Model Range


GT Habitat Model Logic:

1. If the Soil Class is “Escambia”, “Eustis”, “Lakeland”,”Latonia”,”McLaurin”, “Poarch”,“Ruston”, “Saucier”, “Smithdale” or “Susquehanna”, there is habitat value because the soilmeets gopher tortoise preferences for non-hydric, sandy soil that supports pine and prairie grasses.

2. If Satellite Imagery values are between 12 and 197, the indication is that landcover is neitherdense bottomland hardwood or disturbed/cutover/developed land.

3. If topographic slope is between .2 degrees and 6 degrees (less than 10% slope), the assumption is that the ‘micro-terrain’ will offer good burrow sites and access to forage sites.

4. If topographic aspect is between 135 and 315 degrees, the “sun face” is opposite the NW/NE quadrants. Burrow porches will provide better opportunities for sunning.

Every location in the study area will either conform to the model criteria or not. The modelingmethod looks at every location and determines a degree of conformity with the criteria.


if(( Layer( SSURGO, compname:c ) == "POARCH" ||

Layer( SSURGO, compname:c ) == "SAUCIER" ||

Layer( SSURGO, compname:c ) == "BENNDALE" ||

Layer( SSURGO, compname:c ) == "NUGENT" ||

Layer( SSURGO, compname:c ) == "SUSQUEHANNA" ||

Layer( SSURGO, compname:c ) == "MCLAURIN" ) &&

( Layer( Satellite Imagery ) > 12 &&

Layer( Satellite Imagery ) <= 197 &&

Layer( Satellite Imagery ) != NO_DATA ) &&

( Layer( Aspect ) > 135 &&

Layer( Aspect ) <= 315 &&

Layer( Aspect ) != NO_DATA ) &&

( Layer( Slope ) > .2 &&

Layer( Slope ) <= 6 &&

Layer( Slope ) != NO_DATA )){

OD = 100.000000;

Here is an example of what the model instructions look like:

A location meeting all criteria will have an outputvalue of “100”. This indicates a good possibilityof gopher tortoise habitat.


Model Output

This is the result of the model run. It shows all areas in the study region that represent possible gopher tortoise habitat classified as either “prime” or “marginal”.

When corridors are planned, there will be a “map” to guide transportation planners in avoidance or impact minimization.

Map can be used to quantify potential impacts within selected corridor alternatives.

Map can be used to plan verification field work.

Map can be loaded on handheld, GPS field systems like Pocket Dlog for navigation and ground truth activities.


Prime GT Habitat

Marginal GT Habitat

Roads

Streams

USFS Field observationOf GT burrows

There is observable correlation (spatially) between model output and empiricaldata on GT communities.


Model Statistics:

Stone ~42,000 acres of prime possibility and ~94,000 acres of marginal possibility.

Pearl River ~10,000 acres of prime possibility and ~21,000 acres of marginal possibility.

Hancock ~27,000 acres of prime possibility and ~64,000 acres of marginal possibility.

Harrison ~63,000 acres of prime possibility and ~94,000 acres of marginal possibility.

Jackson ~28,000 acres of prime possibility and ~49,000 acres of marginal possibility.


Hypothetical Example of Corridor Analysis for Gopher Tortoise Habitat.

Planned corridor. How much habitat is within corridor?

There are ~13,000 acres of prime possibilityand ~19,000 acres of marginal possibility ina total corridor area of ~79,000 acres.


Conclusion:

1. The method is based on a knowledge of species natural history and field observations.

2. The method is generally repeatable across regions given the same sets of geo-spatial data.

3. The method is extensible. It can be applied to habitat delineation for other terrestrial plant and animal communities. We observe that humans and trains have habitats too.

4. The method can be improved. Higher resolution topography (Lidar, OTF RTK) and MSS imagery can yield better spatial definition. More information on species natural history and wider field studies can contribute to model refinement.

CSX Relocation Study A method for delineating areas of possible gopher tortoise habitat.

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