FOREST STRUCTURE: Key to function ESRM 304. Why Sample Forest Vegetation? What is the recreation potential? What silvicultural treatment will result in

FOREST STRUCTURE: Key to function

ESRM 304

Why Sample Forest Vegetation?

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?

Need information on forest vegetation for making sound decisions

Why Sample Forest Vegetation?

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

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)

Forest Systems

Four major stages of stand developmento Stand initiation stage

Grass-forb Seedling-shrub

o Stem exclusion stage Sapling-pole Intermediate

o Understory re-initiation (mature)o Old-growth stage

Provide different habitats and growth potential

Major stages of stand develop-ment

Forest Systems

Stand dynamics vector

Forest Systems

Visualizing Stand DynamicsLowland site,St. Edward State Parkin 2004 C.E.

SVS under LMS v2.0Developed in SilvicultureLab here in SFR (thenCFR)

Visualizing Stand Dynamics

Lowland site,St. Edward State Park50 yearslater, i.e.in 2054 C.E.

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

Forest Structure / Constitution

Five Typical Stand Structureso Even-aged stando Two-aged stando Balanced uneven-aged stando Irregular uneven-aged stando Even-aged stratified mixture

Represent different management options / potentials

Five Typical Stand Constitutions

o Even-aged stand


o Balanced uneven-aged stand


o Even-aged stratified mixture

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

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

DBH

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), …


Diameter (size) distributions

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are needed to see this picture.


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 = r 2 Basal area, g = (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

QMD =Dg = g

0.005454


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


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 polesIndirect measurement

Similar triangles Trigonometric principles (clinometer)

DT/OD = tan(TOD), therefore, DT = OD x tan(TOD)DT/OD = tan(TOD), therefore, DT = OD x tan(TOD)DB/OD = – tan(DOB), therefore, DB = – OD x tan(DOB),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) + [– OD x tan(DOB)], or,Tree Height = OD x [tan(TOD) – tan(DOB)]. Tree Height = OD x [tan(TOD) – tan(DOB)].

Horizontal distance OD is measured with a tape.Horizontal distance OD is measured with a tape.Clino measures tangents of angles TOD, DOB in percent (100 x tan), soClino measures tangents of angles TOD, DOB in percent (100 x tan), so

Tree Height = OD x [TOD% / 100 – DOB% / 100], orTree Height = OD x [TOD% / 100 – DOB% / 100], orTree Height = OD / 100 x [TOD% – DOB%]Tree Height = OD / 100 x [TOD% – DOB%]

Height Measurement

Tree Height = DT + BD.Tree Height = DT + BD.

OO

TT

BB

DD

Slope correction for height measurementSlope correction for height measurement

OD/OD’ = cos(DOD’)OD/OD’ = cos(DOD’)

OD = OD’ x cos(DOD’)OD = OD’ x cos(DOD’)

Measure angle DOD’ with clinometer in degrees & plug into height Measure angle DOD’ with clinometer in degrees & plug into height

equation:equation:

Tree Height = [OD’ x cos(DOD’)] / 100 x [TOD% –DOB%]Tree Height = [OD’ x cos(DOD’)] / 100 x [TOD% –DOB%]

OO DD

D’D’


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

Site Index

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

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 (PSP’s) is for:o Forecasting growth, i.e., developing and testing forest

simulation modelso Studying the effects of cultural practices, insect attacks,

weather, climate, etc.o 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

Continuous Forest Inventory

CFI is generally very low intensityo TSP’s will typically be used to supplement PSP’s

CFI plots must be representative of the forest; no special “reserve status”

Systematic sampling is often usedo Stratified sampling is often messed up by natural disaster,

natural changes in species composition

Sample size determination is difficulto Must be applicable now AND in the futureo Large enough to be precise for several forest attributeso Sampling intensities often range from 0.1% to 1%


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


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

periodico In a periodic survey, with periodic measurement

interval p, EVERY plot is measured every p yearso In an “annual” survey, 1/p plots will be measured

EVERY year

Summary Remarks

Measurement data collected from trees in a forest system yields information- Forest Structure / Function

o Four major stages of stand developmento Five major age constitutions

Sound data enables sound stand, forest, and landscape management decisions

Permanent Sample Plot LayoutLarge Tree measurement plotLarge Tree measurement plot

0.1 acre plot 0.1 acre plot 37.2 foot radius 37.2 foot radius white PVC pipe at plot center ; plot number white PVC pipe at plot center ; plot number

written on it w/ indelible inkwritten on it w/ indelible ink all trees within the plot have aluminum tagsall trees within the plot have aluminum tags first tree on plot marked with pink flaggingfirst tree on plot marked with pink flagging

Small Tree measurement plotSmall Tree measurement plot

0.025 acre plot 0.025 acre plot 18.6 foot 18.6 foot radiusradius

same plot center as large plotsame plot center as large plot trees are not taggedtrees are not tagged perimeter is not markedperimeter is not marked

Plot and Tree Enumeration Card Page of Date Team Forest Compartment Stand Plot Aspect Slope Elevation Tree Spp DBH Ht. Dist S (o) B. (%) T. (%) C. (%) Add-on Comment(s)

Upper Canopy Surveys

Field Trip to St. Edward State Park Tue and Wed (24th & 25th) Depart from behind Bloedel Hall (C-10

parking lot) promptly at 12:30 P.M. Bring warm clothes, sturdy footwear, rain

gear, etc.

Documents

FOREST STRUCTURE: Key to function ESRM 304. Why Sample Forest Vegetation? What is the recreation potential? What silvicultural treatment will result in