assessing the impact of land cover spatial resolution on forest fragmentation modeling

Assessing the Impact of Land Assessing the Impact of Land Cover Spatial Resolution on Cover Spatial Resolution on

Forest Fragmentation Forest Fragmentation ModelingModeling

James D. Hurd and Daniel L. CivcoJames D. Hurd and Daniel L. CivcoCCenter for enter for LLand use and use EEducation ducation AAnd nd RResearch esearch (CLEAR)(CLEAR)

Department of Natural Resources Management & Department of Natural Resources Management & EngineeringEngineering

The University of ConnecticutThe University of ConnecticutU-4087, Room 308, 1376 Storrs RoadU-4087, Room 308, 1376 Storrs Road

Storrs, CT 06269-4087Storrs, CT 06269-4087

OutlineOutline

• The Forest Fragmentation Model

• Application to land cover of different spatial resolutions

• Concluding remarks

Forest FragmentationForest FragmentationModelingModeling

Developed by Riitters Developed by Riitters et al.et al. (2000) to assess (2000) to assess global forest fragmentation from 1 km land cover global forest fragmentation from 1 km land cover data.data.

Adapted for use on Landsat derived Adapted for use on Landsat derived land coverland cover information information (30-meter spatial resolution).(30-meter spatial resolution).

Categorizes Categorizes forestforest pixels into 6 types: pixels into 6 types:• Core forest• Perforated forest• Edge forest• Transition forest• Patch forest• Undetermined forest

Background

Forest Fragmentation Forest Fragmentation ModelModel

9x9 Analysis Window

Forest PixelNon-Forest Pixel

Based on Image Convolution.Based on Image Convolution.

Uses a roving analysis window of fixed size to Uses a roving analysis window of fixed size to determine vales of Pf (amount) and Pff determine vales of Pf (amount) and Pff (adjacency).(adjacency).

Forest Fragmentation Forest Fragmentation ModelModelHow It Works

Pf =57 forest pixels81 total pixels = 0.70

9x9 Analysis Window


Pf = proportion of forest pixels in analysis window.



Pf =57 forest pixels81 total pixels = 0.70

Pff =86 pixel pairs, both forest119 pixel pairs, at least one forest

= 0.72

144 pixel pairs in a 9x9 window(72 vertical, 72 horizontal)

9x9 Analysis Window

Pff = how connected are those forest pixels.


• Core forest, Pf = 1.0• Perforated forest, Pf > 0.6 and Pf – Pff > 0• Edge forest, Pf > 0.6 and Pf – Pff < 0• Transition forest, Pf < 0.6 and >0.4• Patch forest, Pf < 0.4• Undetermined forest, Pf > 0.6

and Pf = Pff


(Riitters et al., 2000)

Core ForestCore Forest - all surrounding grid cells are - all surrounding grid cells are forest.forest.Perforated ForestPerforated Forest - the interior edge of a - the interior edge of a forest tract such as would occur around a small forest tract such as would occur around a small clearing or house lot.clearing or house lot.Edge ForestEdge Forest - the exterior edge of a forest tract - the exterior edge of a forest tract such as would occur along a large agricultural such as would occur along a large agricultural field or urban area.field or urban area. Transitional ForestTransitional Forest - about half of the - about half of the surrounding grid cells are forest.surrounding grid cells are forest.Patch ForestPatch Forest - less than 40% of surrounding - less than 40% of surrounding grid cells are forest.grid cells are forest.

Definitions


Pf = 0.70



Pf = 0.70

Pf - Pff = 0.70-0.72 = -0.02How It Works


EDGE FOREST


9x9 analysis window27x27 analysis window81x81 analysis window

Analysis windows ofdifferent sizes can beapplied.

As analysis window size increases, the amount of core forest decreases.

Analysis Window Sizes

9x927x2781x81


Three Related Items to Consider

1. Spatial resolution of input land cover.

2. Width of desired edge (i.e. how far from a non-forested feature do you need to be before you are in core forest?).3. What analysis window size will you use?


Core Forest to Non-forestCore Forest to Non-forest

n x n pixel analysis window, where n is oddminimum pixel distance = 1 + [(n – 1) / 2]

Minimum distance = minimum pixel distance * pixel resolution

A core forest pixel will be at least the minimum distance from a non-forest pixel (pixel center to pixel center).

Core Forest to Non-forestCore Forest to Non-forest9x9 analysis window = 1 + [(9 - 1) / 2] = 5 pixelsFor 30 m pixels = 5 x 30 = 150 m (pixel centers)

(5 x 30) – 30 = 120m (pixel edges)

5 pixels(150 m)(120 m)

No longer core forest

Three Related Items to Consider

1. Spatial resolution of input land cover.

2. Width of desired edge (i.e. how far from a non-forested feature do you need to be before you are in core forest?).3. What analysis window size will you use?


Application to Land Cover Application to Land Cover of Different Spatial of Different Spatial

ResolutionsResolutions

Using Analysis Windows of Same Pixel Dimensions

1 - meter 5 - meter 10 - meter 30 - meter

Larger spatial resolution created by degrading the 1-meter spatial resolution land cover

Land CoverLand Cover

Forest Fragmentation ResultForest Fragmentation Result


5 x 5 Analysis Window

Application to Land Cover Application to Land Cover of Different Spatial of Different Spatial

ResolutionsResolutions

Using Analysis Windows of Same Areal Extent

Land CoverLand Cover

Larger spatial resolution created by degrading the 1-meter spatial resolution land cover


271x271 55x55 27x27 9x9

Analysis Window Area = approx. 7.3 hectares



Developed, 21.46

Non-fores t, 2.54

Perforated, 36.89

Patch, 0.76Trans ition,

9.46

Edge, 12.38

Core, 14.03

Water, 2.48

30 – meter, 9x9

water, 0.94

interior, 10.91

perforated, 9.51

edge, 46.43

patch, 0.39 developed, 20.50

non-forest, 2.64

transition, 8.67

water, 0.91

interior, 11.80

perforated, 1.82

edge, 53.50


non-fores t, 2.60

trans ition, 8.57

water, 0.93

interior, 11.67

perforated, 0.34edge, 55.09


non-forest, 2.57

transition, 8.60

1 – meter, 271x271 5 – meter, 55x55

10 – meter, 27x27

Pf = 0.765Pff = 0.744

Pf - Pff = 0.021

9x9 Analysis Window

30 – meter Land Cover30 – meter Land Cover9x9 Analysis Window9x9 Analysis Window

PERFORATED FOREST

Pf = 0.844Pff = 0.916

Pf - Pff = -0.072

27x27 Analysis Window


EDGE FOREST

Pf = 0.848Pff = 0.966

Pf - Pff = -0.118



EDGE FOREST

Pf = 0.847Pff = 0.983

Pf - Pff = -0.136



EDGE FOREST

• Core forest, Pf = 1.0• Perforated forest, Pf > 0.6 and Pf – Pff > 0• Edge forest, Pf > 0.6 and Pf – Pff < 0• Transition forest, Pf < 0.6 and >0.4• Patch forest, Pf < 0.4• Undetermined forest, Pf > 0.6

and Pf = Pff

Edge/Perforated DefinitionEdge/Perforated Definition

Land Cover 9x9 Analysis Window

9x9 Analysis Window applied to 30-meterspatial resolution land cover

Altering Definition of Altering Definition of Edge/PerforatedEdge/Perforated

Results of Forest Frag. Model using a 27x27 Analysis Window on 10m Land Cover

Riitters Original DefinitionsPerforated Pf – Pff > 0

Edge Pf – Pff < 0

Altered DefinitionsPerforated Pf – Pff > -0.05

Edge Pf – Pff < -0.05



NOT SO GOOD BETTER MORE LIKE 30m9x9 FF RESULTS



Edge Pf – Pff < 0








Water, 4.19

Core, 32.19

Edge, 6.79

Transition, 1.71 Patch, 1.90

Perforated, 35.56

Non-forest, 0.00

Developed, 17.65

Water, 4.18

Core, 25.39

Edge, 6.20


Perforated, 42.89

Non-forest, 0.00

Developed, 17.78

Water, 4.38

Core, 26.53

Edge, 6.29


Perforated, 41.87

Non-forest, 0.00

Developed, 17.50

Water, 4.33

Core, 26.16

Edge, 5.43


Perforated, 42.99

Non-forest, 0.00

Developed, 17.68

30- meter 9x9 (original definitions)10- meter 31x31 (Pf-Pff > OR < -0.1) 30 – meter, Pf – Pff threshold = 0.0

5 – meter, Pf – Pff threshold = -0.11



Class Edge Bias = 0.0488 * ln(r) - 0.1601

Class Edge Bias CurveClass Edge Bias Curve

where r = land cover spatial resolution

CLEAR WebsiteCLEAR Website

clear.uconn.edu

http://clear.uconn.edu/projects/landscape/forestfrag/ff_tool.htm

CLEAR WebsiteCLEAR Website

Downloadable ToolDownloadable Toolfor ESRI ArcGIS 9.2for ESRI ArcGIS 9.2

Concluding RemarksConcluding Remarks

Concluding RemarksConcluding RemarksWhen applying Forest Fragmentation model, three

items to consider:- land cover spatial resolution- desired width of edge/perforation- analysis window size

The spatial resolution (and landscape pattern) of the land cover impacts the result of the model:- it may be desirable to alter the definition of edge and perforated.

Ultimately the results are only an approximation, but:- provide a powerful visual impact- allow for the quantification of forest fragmentation.

Assessing the Impact of Land Assessing the Impact of Land Cover Spatial Resolution on Cover Spatial Resolution on

Forest Fragmentation Forest Fragmentation ModelingModeling

CCenter for enter for LLand use and use EEducation ducation AAnd nd RResearch esearch (CLEAR)(CLEAR)Department of Natural Resources Management & Department of Natural Resources Management &

EngineeringEngineeringThe University of ConnecticutThe University of Connecticut

U-4087, Room 308, 1376 Storrs RoadU-4087, Room 308, 1376 Storrs RoadStorrs, CT 06269-4087Storrs, CT 06269-4087

[email protected]

assessing the impact of land cover spatial resolution on forest fragmentation modeling

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