Forest Measurement Elements of Forestry Kenneth Williams Fisheries Extension Specialist Langston University Aquaculture Extension Program

Biometrics Measure growth and response to management practices Try to get the most accurate information at the least cost.

Primary 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.

Sawlogs

Bolts

Chips

Scaling Measuring 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 Tools Log 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 Tools Log 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 Tools Log 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 and Firewood Standard cord – 4 ft. high x 4 ft. wide x 8 ft. long Short cord, face cord – 4 x less than 4 x 8 Rick – 4 x 18-24 inches x 8 ft. used for firewood measurement

Product Grading Defects lower quality – knots, spiral grain, stain, rot.

Product Grading of Hardwood Logs 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 Logs Veneer class – high value veneers Sawmill class – structural timber

Land Survey and Mapping English units used in U.S. 1 chain = 66 ft. 80 chains = 1 mile 1 acre = 10 sq. chains 1 sq. mile = 640 acres 1 section = 160 acres Metric- 1 hectare (ha) = about 2.5 acres

Distance Can be measured by pacing Chaining with a 100ft steel tape Most commonly now with electronic optical instruments. GPS for exact locations and direction.

Land 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 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 Grid

Land 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 sections

Land Surveys Townships are sub-divided into 36 sections. Sections are about 1 sq. mile or 640 acres Sections are divided into quarter-sections of 160 acres. These are divided into 40 acre parcels known as forties.

Section and Quarters

Forest Mapping Aerial photographs Increasingly – satellite imaging

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

Basal Area Basal 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.

Height 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 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 used from a tree

Age and Radial Increment Increment borer to extract a core of wood.

Forest Sampling Sample 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 Method Also known as horizontal point sampling – tally all trees with dbh larger than angle gauge viewed from each sample point.

Plot 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 Method Random sampling – sample units located completely at random within each stand. Assures unbiased sampling.

Sampling 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 Sampling

Systematic 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 Distribution

Sampling 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 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 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 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 Growth Net change in tree volume = ingrowth + survivor growth – mortality – cut. Factors that affect rate of forest growth: Site quality Stocking density

Site 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 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 Curve

Stocking 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 Stands

Stocking Chart

Stocking 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 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.

Multiple Use Measurements Water quality and quantity Wildlife populations Recreational use

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