FOREST STRUCTURE

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FOREST STRUCTURE
By JWAN M. ALDOSKI Geospatial Information
Science Research Center (GISRC), Faculty of
Engineering, Universiti Putra Malaysia, 43400
UPM Serdang, Selangor Darul Ehsan. Malaysia.
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Why Sample Forest Vegetation?

• Need information on forest vegetation for making
  sound decisions

• What is the recreation potential?
• What silvicultural treatment will result in best
  critical habitat enhancement?
• What silvicultural treatment will result in best
  growth regeneration of the trees?
• What species is / are most suitable for
  reforestation?
• What is the value of the timber and the land?
• Is there sufficient value in timber to offset
  cost of silvicultural treatments?
• What is the status of biodiversity on the area?
• What is the status of the forest as a carbon
  sink?

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Why Sample Forest Vegetation?

• Ultimate objective is to obtain quantifiable
  information about the resource that allows
  reasonable decisions on its destiny, management,
  and use

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Forest Systems

• Forests are dynamic, biological systems changing
  continuously
• Trees change in size (growth)
• Trees die when old, when harvested, and/or when
  damaged by pathogens (mortality)
• New trees enter the system (recruitment)

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Forest Systems

• Four major stages of stand development
• Stand initiation stage
• Grass-forb
• Seedling-shrub
• Stem exclusion stage
• Sapling-pole
• Intermediate
• Understory re-initiation (mature)
• Old-growth stage
• Provide different habitats and growth potential

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Major stages of stand develop-ment
Forest Systems
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Stand dynamics vector
Forest Systems
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Visualizing Stand Dynamics
Lowland site, St. Edward State Park in 2004
C.E. SVS under LMS v2.0 Developed in
Silviculture Lab here in SFR (then CFR)
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Visualizing Stand Dynamics
Lowland site, St. Edward State Park 50
years later, i.e. in 2054 C.E.
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Forest Structure / Constitution

• Determined by
• Size variability
• Diameter
• Height
• Crown
• Frequency of occurrence shape, location of size
  distribution
• Age shape, location of age distribution
• Spatial arrangement of trees in stand

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Forest Structure / Constitution

• Five Typical Stand Structures
• Even-aged stand
• Two-aged stand
• Balanced uneven-aged stand
• Irregular uneven-aged stand
• Even-aged stratified mixture
• Represent different management options /
  potentials

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Five Typical Stand Constitutions

• Even-aged stand

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Five Typical Stand Constitutions

• Balanced uneven-aged stand

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Five Typical Stand Constitutions

• Even-aged stratified mixture

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Can we see the trees for the forest?

• Individual tree measurement forms the basis for
  all forest assessment / inventory
• Many relationships can be derived from individual
  tree attributes
• Species
• Age
• Diameter
• Height
• Direct measurement, sampling, prediction are all
  involved

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Individual Tree Measurement

• Diameter
• Most frequently measured diameter is Diameter
  Breast Height, or, DBH for short
• DBH is average stem diameter (in inches!) outside
  bark of the tree measured at breast height above
  ground level
• In U.S., breast height is taken to be 4.5 ft.
• On steep slopes measure on the uphill side of
  tree
• Leaning trees require measurement along the bole
• Trees forking below breast height are treated as
  two
• Trees forking above breast height avoid swells
• Other stem deformities move above it
• Most commonly used measurement device is the
  D-tape

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DBH
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Diameter Measurement

• Diameter classes
• Very often expedient to summarize inventory data
  into size classes based on DBH
• No matter the size of class used still measure
  to nearest 0.1 !
• 1-inch classes
• 2 class (1.6 to 2.5), 3 class (2.6 to 3.5),
• 2-inch classes
• 4 class (3.1 to 5.0), 6 class (5.1 to 7.0),

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Diameter Measurement

• Diameter (size) distributions

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Diameter Measurement

• Basal Area
• Cross sectional area of the tree at breast height
  assuming stem circularity always in square
  feet! (in U.S.)
• Area of circle, A p r 2
• Basal area, g p (DBH/2)2 (1/12)2 0.005454
  DBH2
• Average stand DBH is a useful statistic for
  management
• Quadratic Mean DBH (QMD) is the diameter of the
  tree corresponding to the tree of mean basal area

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Individual Tree Measurement

• Age
• Trees in temperate zones grow one distinctive
  layer of wood per year so age is found by
  counting these annual rings
• Care is needed to avoid counting false rings
• Tree Age
• Total Age Elapsed time since germination of a
  seed or time since budding of a sprout or cutting
• Breast-height age Elapsed time since tree height
  exceeded breast height
• Stand Age
• Plantation age Elapsed time since planting
  regardless of seedling age
• Even-aged vs. Uneven-aged

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Individual Tree Measurement

• Tree Height
• Total height distance from tree base to tip
  (volume, biomass, site quality)
• Height-to-crown distance from tree base to base
  of live crown
• Merchantable height Height to a minimum top
  diameter
• Instruments are called hypsometers
• Direct measurement Height poles
• Indirect measurement
• Similar triangles
• Trigonometric principles (clinometer)

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Height Measurement Tree Height DT BD.
DT/OD tan(TOD), therefore, DT OD x
tan(TOD) DB/OD tan(DOB), therefore, DB OD
x tan(DOB), Tree Height OD x tan(TOD) OD
x tan(DOB), or, Tree Height OD x tan(TOD)
tan(DOB). Horizontal distance OD is measured
with a tape. Clino measures tangents of angles
TOD, DOB in percent (100 x tan), so Tree Height
OD x TOD / 100 DOB / 100, or Tree Height
OD / 100 x TOD DOB
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Slope correction for height measurement
OD/OD cos(DOD) OD OD x cos(DOD) Measure
angle DOD with clinometer in degrees plug into
height equation Tree Height OD x cos(DOD)
/ 100 x TOD DOB
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Individual Tree Measurement

• Height in relation to age - Site Quality
• Trees are resource integrators
• Site Index The average height of undamaged
  dominant trees at a reference age
• Dominant tree height insensitive to crowding
• Reference, or base, or index age chosen
  appropriately
• Species dependent
• Sometimes dominant trees are unavailable
  challenge esp. in mixed stands
• Requires trees on the site

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Site Index

• James King (1966) published site index curves
  for Douglas-fir in the Pacific Northwest

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Continuous Forest Inventory

• The ONLY way to get a complete historical record
  on forest change is to monitor permanently
  monumented plots
• Data from Permanent Sample Plots (PSPs) is for
• Forecasting growth, i.e., developing and testing
  forest simulation models
• Studying the effects of cultural practices,
  insect attacks, weather, climate, etc.
• Studying how biodiversity, wildlife habitat
  quality, etc. change over time
• Chief purpose is to assess change so forest
  stewards are alerted to potential need for
  changing practices or policies

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Continuous Forest Inventory

• CFI is generally very low intensity
• TSPs will typically be used to supplement PSPs
• CFI plots must be representative of the forest
  no special reserve status
• Systematic sampling is often used
• Stratified sampling is often messed up by natural
  disaster, natural changes in species composition
• Sample size determination is difficult
• Must be applicable now AND in the future
• Large enough to be precise for several forest
  attributes
• Sampling intensities often range from 0.1 to 1

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Continuous Forest Inventory

• Plot locations are usually determined using a
  transparent grid with pin pricks on an
  appropriately scaled grid, then overlain onto a
  photomosaic or other map of the ownership, then
  transferred to 9 x 9 photos to take into the
  field
• Distance bearing to plot center is determined
  from the photo or map from a known permanent
  location (primary control) to avoid bias
• Plot center is marked with aluminum stake,
  re-bar, or PVC pipe
• Trees on plot are stapled, nailed and / or
  painted near breast height

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EXAMPLE
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Continuous Forest Inventory

• Five percent of all plots (randomly selected) are
  normally check-cruised for accuracy
• Measurement interval is typically 3 to 10 years
• Repeat measurement cycle is either annual or
  periodic
• In a periodic survey, with periodic measurement
  interval p, EVERY plot is measured every p years
• In an annual survey, 1/p plots will be measured
  EVERY year

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Summary Remarks

• Measurement data collected from trees in a forest
  system yields information
• - Forest Structure / Function
• Four major stages of stand development
• Five major age constitutions
• Sound data enables sound stand, forest, and
  landscape management decisions

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Permanent Sample Plot Layout

• Large Tree measurement plot
• 0.1 acre plot ? 37.2 foot radius
• white PVC pipe at plot center plot number
  written on it w/ indelible ink
• all trees within the plot have aluminum tags
• first tree on plot marked with pink flagging

• Small Tree measurement plot
• 0.025 acre plot ? 18.6 foot radius
• same plot center as large plot
• trees are not tagged
• perimeter is not marked

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THANK YOU