Forest MeasurementForest Measurement

Kenneth WilliamsFisheries Extension Specialist Langston University Aquaculture Extension Program

Elements of Forestry

BiometricsBiometrics

Measure growth and response to management practices

Try to get the most accurate information at the least cost.

Primary Forest ProductsPrimary Forest Products

Sawlogs – min. 8 feet long and 6-8 in. dia. At small end.

Bolts – less than 8 feet lg. used for pulp and paper.

Chips – small pieces of wood obtained by cutting up logs and sawmill waste. Used in manufacture of a variety of products and as fuel.

SawlogsSawlogs

BoltsBolts

ChipsChips

ScalingScalingMeasuring the amount of timber in the

forest or at the sawmill.Board foot - = a plank 1 ft. long x 1ft.

Wide x 1 in. thick

Measurement ToolsMeasurement ToolsLog RulesLog Rules

Doyle (1825)– grossly underestimates volume of logs under 20 in. in dia. Still used because it is simple and it encourages delivery of large logs to the mill.

V= (D – 4)2 L/16 – V = volume in board ft., D = small end dia. in

in. L = length - 3-4 in. for trim.

Measurement ToolsMeasurement ToolsLog RulesLog Rules

Srcibner log rule (1846) under estimates volume

International log rule – most accurate. Volume of entire log estimated in 4 ft. increments. Assumes a ½ in. increase in dia. for each segment.

Actual volume measurement most accurate but not used.

Measurement ToolsMeasurement ToolsLog RulesLog Rules

Volume from log scale is gross scale. Net scale is gross scale minus volume of

defects (rot, crookedness etc.)in log.

Log Measurement for Pulpwood Log Measurement for Pulpwood and Firewoodand Firewood

Standard cord – 4 ft. high x 4 ft. wide x 8 ft. long

Short cord, face cord – 4 x less than 4 x 8Rick – 4 x 18-24 inches x 8 ft. used for

firewood measurement

Product GradingProduct GradingDefects lower quality – knots, spiral grain,

stain, rot.

Product Grading of Hardwood Product Grading of Hardwood LogsLogs

Veneer class – high value and some low value logs that veneers can be cut from.

Factory class – boards that can be remanufactured to remove most defects and obtain clear facing and soundness.

Construction class - suitable for sawing into ties and timber and other items to be used in 1 piece for structural purposes.

Local – use class – low quality woods, for mine timbers, pallets and crating.

Product Grading of Softwood Product Grading of Softwood LogsLogs

Veneer class – high value veneersSawmill class – structural timber

Land Survey and MappingLand Survey and Mapping

English units used in U.S.1 chain = 66 ft.80 chains = 1 mile1 acre = 10 sq. chains1 sq. mile = 640 acres1 section = 160 acresMetric- 1 hectare (ha) = about 2.5 acres

DistanceDistance

Can be measured by pacingChaining with a 100ft steel tapeMost commonly now with electronic optical

instruments.GPS for exact locations and direction.

Land SurveysLand Surveys

Metes and bounds system – property lines based on physical features. Ex. Streams ridges, large rocks, fences and roads.

Rectangular survey system – conceived by Thomas Jefferson. Uses carefully established baselines and meridians to reference land location.

Land SurveysLand Surveys

Rectangular survey system – baselines run east and west. Meridians run north and south. The intersection of the two is called an initial point.

Standard parallels are established every 24 miles (parallel to baselines). Guide meridians are placed every 24 miles connecting the parallels. Because earth curves, they are closer together in the northern U.S.

Township Township GridGrid

Land SurveysLand Surveys

Resulting 24 sq. mile tracts are subdivided into 16 townships,. Each about 6 sq. miles.

They are consecutively numbered north and south of the baseline.

Townships east and west of the meridian are called ranges and are numbered.

Township Township sectionssections

Land SurveysLand Surveys

Townships are sub-divided into 36 sections.Sections are about 1 sq. mile or 640 acresSections are divided into quarter-sections of

160 acres.These are divided into 40 acre parcels

known as forties.

Section and Section and QuartersQuarters

Forest MappingForest Mapping

Aerial photographsIncreasingly – satellite imaging

Timber Survey TypesTimber Survey Types

National surveys – used for setting forest policies.

State inventories – to develop management plans for state and county forests.

Local inventories – provides details on quantity and location of timber.

Timber appraisals – determines value of timber for land sales.

Standing Tree MeasurementStanding Tree Measurement

Diameter at breast height (dbh) – diameter of tree stem at 4.5 feet from ground on the uphill side of tree.

Measured with a tree caliper, diameter tape or electronic instrument.

Standing Tree MeasurementStanding Tree Measurement

Biltmore stick – hold measuring stick against tree and eyeball the width on a ruler marked to give diameter.

Basal AreaBasal AreaBasal Area – Area in square feet

of the cross section of a tree at breast height.

Basal area of a forest stand - sum of tree basal areas divided by area. It is expressed as sq. feet per acre. Used to measure the degree of crowding in a stand of trees.

HeightHeight

Hypsometers, mostly electronic now.

Total height often not as important as mechantable height or length. A measure of the usable portion of a tree above stump level (1 ft.)

Volume and MassVolume and Mass

No instrument available. Must be estimated from other tree dimensions. Use tree height plus dbh. Can use tables made for this purpose.

Most accurate to use an optical dendrometer to measure upper stem diameters.

How wood is How wood is used from a treeused from a tree

Age and Radial IncrementAge and Radial Increment

Increment borer to extract a core of wood.

Forest SamplingForest SamplingSample trees selected in groups at different

locations, each group called a sampling unit.

Sample plots can be square, rectangular or circular. Usually 0.01 to 0.2 acres.

All trees or all merchantable trees with a mid-point at dbh lying within the plot boundary are tallied.

Used to estimate avg. number of trees, basal area and volume per acre.

Bitterlich MethodBitterlich MethodAlso known as horizontal point sampling –

tally all trees with dbh larger than angle gauge viewed from each sample point.

Plot SizePlot Size

Larger size more accurate but more time consuming and expensive to do.

Rule of thumb: Use a plot size that gives an avg. of 15-20 trees per plot.

Sampling MethodSampling Method

Random sampling – sample units located completely at random within each stand.

Assures unbiased sampling.

Sampling MethodSampling Method

Systematic sampling – also called line plot cruising is easier to do.

Sample units located at specific intervals along a straight line running across forest property.

Cruise lines must go up and down slopes because conditions tend to change with changes in elevation.

Random vs Systematic SamplingRandom vs Systematic Sampling

Systematic SamplingSystematic Sampling

Number of sample units is determined by maximum allowable error.

The more sample units, the smaller the error.

Ex. Saw timber sale – 3-5 % error. Long range management plans 10-20% error OK.

Uniform vs Clumped DistributionUniform vs Clumped Distribution

Sampling MethodsSampling Methods

Foresters use statistical formulas to determine the minimum number of plots required to achieve a specified sampling error.

Sampling carried out by 2 person crews. Crew chief is responsible for locating sample units and recording data. Second crew member responsible for tree measurements.

Forest Growth and Yield Forest Growth and Yield

Forest yield – volume of timber at a specified point in time.

Forest growth – changes in volume that occur over an interval of time.

Sample plots measured at 5 -10 year intervals to determine growth. Must mark plots well to find them again after long time intervals.

Components of Forest GrowthComponents of Forest Growth

Ingrowth – the volume of new trees that were too small to measure during previous sampling period.

Survivor trees – Trees that are alive and tallied at both measurement periods.

Survivor growth – difference in volume of these trees at the two measurements.

Components of Forest GrowthComponents of Forest Growth

Mortality – the volume of trees that were alive at the 1st measurement but died before the 2nd measurement.

Cut – volume of trees that were harvested during the measurement period.

Components of Forest GrowthComponents of Forest Growth

Net change in tree volume = ingrowth + survivor growth – mortality – cut.

Factors that affect rate of forest growth:– Site quality– Stocking– density

Site QualitySite Quality

Forest stands are classified according to site quality.

The site productivity measure most often used is site index- the average height of dominant and codominant trees at a specified site index age, usually 50 years.

Height and age are used to produce curves and tables for easy reference.

Site QualitySite Quality

Site index is correlated with topography and soil conditions.

It does not work well in uneven-aged stands and areas of mixed species.

Site Index CurveSite Index Curve

Stocking and DensityStocking and Density

Stand density – the degree of stem crowding in a stand.

Stand basal are used as a measure of stand density. Compare sampling data to density tables to determine acceptable ranges.

Stocking – ability of a stand density to meet management objectives. (overstocked, understocked etc.)

Overstocked StandsOverstocked Stands

Stocking ChartStocking Chart

Stocking and DensityStocking and Density

Height growth is not affected by stand density.

Not a strong relationship between basal area and site quality.

Main difference in wood volume between good sites and bad sites is on good sites the height is greater.

Growth and Yield ProjectionGrowth and Yield Projection

A variety of models are used that include site quality, tree species and past performance to predict growth and yield of a particular forest stand.

These models help determine optimal management techniques, plantings, thinnings etc.

Water quality and quantity

Wildlife populationsRecreational use

Multiple Use MeasurementsMultiple Use Measurements

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