This directory contains the timber measurements from the Oregon Transect 
in Excel format.  This is the final version.

The objective of the sampling was to select 20 trees at each stand for 
measurement of height, crown width, DBH, and height-to-crown distance.  
The data were collected using variable-radius plot sampling.  The general 
procedure was to lay out a transect through the stand using steel tape 
and hand-held compass and locate "points" along the transect.  Each point 
is the center of a variable-radius plot.  The points are separated by 
100-150 feet, depending on the size of the stand and the prism factor.  
This distance is chosen before data are collected.  

A prism factor is selected in advance that will require about 4 points 
to attain a sample of 20 trees.  If the last point takes the tree total 
beyond 20, only DBH measurements were made of such trees.

Point No.: This is the number of the point along the transect.

Factor: This is the prism factor, in square feet per acre.  That is, 
each tree that is counted using the prism represents a fixed contribution 
to the the DBH per acre.  So if 8 trees are in at a point with a 20 prism, 
the stand basal area is 8*20=160 sq ft DBH per acre.

Tree No.:  Each tree is numbered sequentially as it is selected by the 
prism measurement.  The starting tree is the first tree clockwise from 
due north.

Spp.: These are species codes as indicated on the spreadsheets.

DBH, in.: Diameter at breast height, in inches.  Measured with a 
diameter tape.  In some stands (e. g.., the Juniper site), trees with 
multiple stems were common.  In that case, the DBH's of the multiple 
stems were measured and then their basal areas were combined and reduced 
to a single DBH value that gives the combined area.

Hgt., ft.: Height of the tree, in feet.  Obtained by clinometer for angle 
and steel tape for distance.

Crown Width: Width of crown, in feet.  Measured using steel tape from 
below by looking up and judging when the tape indicates the edge of the 
crown.  Somewhat subjective.

R^2: Squared crown radius.  (For modeling purposes.)

Hgt to Crown: Distance in feet from the base of the tree to bottom of the 
crown.  Measured using clinometer and steel tape.  Point on tree that is 
"base of crown" is somewhat subjective.

Trees/ Acre: Since each diameter has a different probability of being 
sampled, each tree that is counted represents a different number of 
trees per acre.  So if you want to find the number of trees per acre 
at the point, you have to add up the contribution of each tree.  The 
Trees/Acre value is the contribution of each tree, in trees per acre.

The following are variables that we use in our geometric-optical modeling, 
in which we take the crown to be a spheroid-on-a-stick.

Crown Height: Difference between tree height and height-to-crown; feet.

h: Height to center of crown, feet.

b: Half of crown height, feet.

r: Horizontal radius of crown at widest part; half of crown width, feet.

b/r: Ratio of b to r.

b/h: Ratio of b to h.

At the bottom of the table are some summary statistics that we use in 
our modeling.  For all but the Trees/Acre column, the mean is simply 
the mean value for all of the trees measured.  However, the selection 
of trees is with a probability proportional to their DBH, so the simple 
mean of these values not a true mean, but rather a basal-area weighted 
mean.  The same is true for standard deviation and coefficient of 
variation, since these are simply the s. d. and c. v. for the trees 
measured.  (We use the basal-area weighted statistics in our models, 
since they are  better descriptors of the upper canopy layer.)

If you want to obtain unweighted means, you have to "un-weight" them 
by weighting them by the Trees/Acre value and then normalize by the sum 
of the weights.

NOTE: For the Cascade Head Site, the data are collected from the site 
that we are referring to as the "old growth site."  This is actually a 
heterogeneous site, with one portion containing younger (but still 
pretty big) trees and another portion with a number of old-growth trees.  
Our data were collected from the younger portion.