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Why is forest inventory important?
 managing habitat
 maximizing profits
 carbon trading
 buying and selling land


Levels of measurement in forest inventory
 individual tree
 plot
 stand
 forest

plot
small group of trees that are measured

stand
a group of individual trees that are more or less homogeneous

forest
group of stands that cover an area of interest

accuracy
difference between a measured value and a true value

bias
difference between the average of repeated measurements or estimates and the true value

precision
the variation in repeated measurements or estimates



unbiased, imprecise result


why measure stem diameter?
 useful for predicting things that are hard to measure directly such as biomass
 may reflect monetary value of tree
 some species require certain tree sizes for habitat
 often reflects the competitive position of a tree

DBH
Diameter at 4.5 ft above ground

often used for DBH of small trees
tree calipers, usually two measurements are made at right angles and the average is taken

take diameter under bark to determine
amount of mulch that can be produced

why is measuring tree height important?
 length of the stem is important for estimating the tree's weight and how much wood it contains
 combined with age it is used to determine site productivity
 height can tell you whether the tree is dominant or not
 variations in height help determine the stand's structure (important for wildlife)

Why dominant trees important
 dominant are healthier and more valuable
 often chop down notdominant ones to release dominant trees

two types of height measured
 total height
 merchantable height

merchantable height
height to a diameter limit or to where the stem becomes unusable due to defects or branching

sawtimber diameter limit
10 inches

pulpwood diameter limit
4 inches


direct measurement method
measuring poles

clinometer gives heights based on d =
66'

laser hypsometer
 combines a clinometer with a laser rangefinder
 allows for d to be found quickly and accurately
 all calculations performed for you

if the ground is sloped...
calculate a new value for d

advantages of geometric method
 don't need to measure the distance to the tree
 slope of the ground does not matter
 equipment cost is very low
 accuracy is about the same as trigonometric method

geometric method disadvantages
 takes practice
 carrying around a big stick is a pain

stem volume
 volume of wood in a tree's stem
 given in board feet

board feet
1 foot x 1 foot x 1 inch

___ board feet in a cubic foot
12

stem volume importance
controls the amount of product that can be made from a tree

methods of stem volume measurement
 immersing the step in water and measuring the volume that comes out
 taking photographs of the stem and calculating the volume photogrammetrically
 profiling the stem using laser beams

sectional volume estimates
 volume estimates of a tree stem by estimating the volume of section of the stem and adding up the measurements
 typically applied to trees that have been chopped down
 used to create equations for predicting volume based on diameter and height measurements
 sometimes used for finding volume of logs

Volume functions
 allow you to estimate volume based on easily obtained measurements
 developed using regression

regression
 creating an equation for predicting one set of data based on another
 use higher order equations that incorporate powers of the predictor variable to follow curved line

multiple regression
multiple predictor variables can be used (DBH, height, and volume)

Types of volume equations
 regular
 local
 taperbased
 merchantable volume equations

regular volume equations
 based on DBH and height
 assumes the stem is a cylander

local volume equations
 based on only DBH
 find the height and DBH of a number of tree in area
 use regression to develop an equation for predicting height based on DBH
 substitute this equation into the regular volume equation

taper based volume equations
 based on two diameter measurements and height
 attempts to adjust volume based on how quickly the stem tapers
 gives good results in highly varied stands

merchantable volume equations
 based on DBH, height, and the smallest diameter that is merchantable
 tell you the amount of volume in sections of a stem that is above a certain diameter limit

Estimating biomass important
 estimating how much carbon dioxide the trees are storing
 determining how much pulp can be made from a tree
 determining how much heat the tree could produce when burned
 assessing the value of a tree for pulp or firewood

tree parts contain about __ percent carbon
50

obtaining direct biomass is difficult because
leaves, branches, and roots are hard to measure

below ground biomass is __times the above ground biomass
0.25

Important stand properties
 age
 basal area
 stocking density
 mean diameter
 quadratic mean diameter
 dominant height
 site productivity capacity
 volume and biomass per acre
 growth

ways to determine stand age
 planting date
 date of disturbance
 tree cores

basal area
 cross sectional area per acre or hectare
 add up the cross sectional areas and divide by plot size

point sampling___large trees and ___small trees

point sampling
use a basal area factor lens

borderline trees point sampling
 calculate the limit associated with the tree
 then measure the distance from the plot center to the tree
 if the distance is less than the tree, include the tree

stocking density
number of trees per unit area

quadratic mean diameter
mean diameter weighted by basal area so more emphasis is placed on larger trees

dominant height
 height of the tallest trees in a stand
 closely reflects how productive the stand will be

predominant height
measure and average heights of the n tallest trees in a plot (2050 stems/acre) 13 trees in .5 acre plot

top height method
measure and average the heights of the n trees with the largest DBH in a plot

site index
 how productive a site is
 height at a particular base age

current annual increment
how much the volume or biomass is increasing each year

mean annual increment
at what rate has the volume or biomass increased since the tree came into being

fixed plot estimating average volume or biomass per tree in plot.
 Usually measure this of 1/3 of trees
 multiply this value by the number of tree/acre or hectare

random sampling
plots placed randomly throughout the forest

systematic sampling
often done in forestry, all plots in a grid

cluster sampling
 used by USFS for the Forest Inventory and Analysis program
 specialized math needed

stratified random sampling
forest divided into stands and the number of plots established is proportional to the area of the stand

probability proportional to size
 variable correlated to the one you are interested in predicting is measure for all possible plot locations
 plots place randomly, but the probability of a location being selection is proportional to the variable that was measure
 increases accuracy

most common statistics for a forest inventory
 estimated means of the variable of interest
 95 percent confidence intervals for the means

