Urban timber volume estimation How to measure forests in urban areas with limited resources Technische Universität München

Urban timber volume estimation

How to measure forests in urban areas with limited resources

Technische Universität München

Content

1. Need of forest measurements2. Single tree volume measurement3. Measuring forest stands4. Methodological background5. Urban forest cover6. Application in Dar es Salaam7. Draft results8. Considerations9. References


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Need of forest measurements

Three principle reasons (WEST, 2004):1. To help with decisions about how to manage forest at different scales

(timber import/export; source of employment/water supply; contribution to income)

2. To assist their management (level of change over time; timber supply in the long term)

3. Research (factors determining forest growth; climate impacts; etc.)


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Single tree volume measurement Technische Universität München

Function Species and location

Vu=0,298*D²*H Eucalyptus regnans, New Zealand

Vu=0,005+0,330*D²*H Pinus taeda, southern USA

Vo=0,450*D1.92*H0.90 Juniperus procera, Ethiopia

Pictures from AVERY & BURKHARD, 2002; table below adapted from WEST, 2004

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Measuring forest stands

1. Using stand volume tables: limited to monocultures, no dynamics


Stand volume table for Scots Pine in north eastern Germany (LEMBCKE, KNAPP & DITTMAR, 2000)5

Measuring forest stands

2. Conduct a complete survey, i.e. measuring all trees of a single forest stand: limited to small stands (time and cost intense)

3. Conduct an inventory, i.e. measuring samples of the forest stand: different inventory designs• Random sampling• Block sampling• Stratified sampling• Systematic sampling• …• …


Problem: they all need ground measurements…

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Methodological background

How to measure forest where resources (time, money, persons, access rights etc.) are limited?Idea: To adapt the statement: “…FAO estimated total growing stock by taking subregional averages of growing stock per hectare and multiplying these by the forest area for the respective years.“ (FAO 2010)for our UMT and LC Analysis


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Urban forest cover

Part of the LC-analysis Tree cover classes according to FAO landcover classes have to be defined Def. of forest (FAO 2010): land spanning more than 0.5 ha with a minimum tree

height of 5m and at least 10% tree cover Def. of OWL: …5-10% tree cover or accumulated cover of trees, shrubs and

bushes above 10%

UMTs with tree cover

Land cover analysis

UMTs


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Application in Dar es Salaam

Case study: Dar es Salaam (area of whole city according to UMT map approximately 1500 km²?)

Inputs: aerial image of 2008 (pixel size approximately 0,45m*0,45m), Urban Morphology Type Map (extent covering approximately 390 km²)

first land cover analyses for UMTs „1.3 Mixed farming“ and „2.5 Bushland“

Differentiated tree cover by tree/crown size for Dar 2 classes distinguished by crown diameter (threshold 6m

diameter):– Large trees– Small trees/shrubs


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UMT Code UMT Class

Polygon count

Area_Sum [sq_km] Area [ha]

# Sample points

1.3 Mixed farming 12 49,072683 4907,27 400

2.5 Bushland 16 8,28113 828,11 100

Draft results Technische Universität München

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bare ground/soil

grasses large trees sand small trees/shrubs

05

101520253035404550

surface share in UMT 2.5 Bushland (100 sample points)

%

bare gr

ound/soil

cultiva

ted cr

ops

grasse

s

large

tree

s

palm tr

ees

sand

small

tree

s/shru

bs

urban

stru

ctures

IIwate

r05

10152025303540

surface share in UMT 1.3 Mixed farming (400 sample points)

%

LC-type

Land cover within UMT

1.3

Growing Stock per ha (FAO

2010, Tab 10) [m³/ha]

Growing stock in

UMT [m³]Large trees 2,75%

10(OWL) 490727

Small trees/ shrubs

12,75%

LC-type

Land cover within UMT

2.5

Growing Stock per ha (FAO

2010, Tab 10) [m³/ha]

Growing stock in

UMT [m³]Large trees 2,00%

10(OWL) 82811

Small trees/ shrubs

39,00%

Considerations

Calculated volumes are intended to act as general overview/orientation Range of tree species might differ from rural areas Ground truthing to validate Method is applicable to each case study city with an UMT mapping and

LC-analysis Single trees grow different compared to trees in forest stands Forest growth calculation is dependant from standing volumes Can be the basis for estimation of the biomass and carbon sequestration


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References

Avery, T.E., Burkhart, H.E., 2002: Forest Measurements, Fifth Edition; McGraw-Hill Series in Forest Resources

FAO 2010: Global Forest Resources Assessment 2010 – Main Report; FAO Forestry Paper 163; Food and Agricultural Organisation of the United Nations, Rome

Lembcke, Knapp, Dittmar, 2000: Ertragstafel für die Kiefer (Pinus sylvestris L.) im nordostdeutschen Tiefland; Landesforstanstalt Eberswald

West, P.W., 2004: Tree and Forest Measurement; Springer-Verlag, Berlin Zöhrer, F., 1980: Forstinventur, ein Leitfaden für Studium und Praxis; Pareys

Studientexte 26; Verlag Paul Parey, Hamburg und Berlin


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Urban timber volume estimation How to measure forests in urban areas with limited resources Technische Universität München