A study of small-plots of old-growth Douglas Fir in Oregon.

Usage

data("johnson.douglasfir")

Format

A data frame with 1600 observations on the following 3 variables.

row: row
col: column
volume: volume per plot

Details

A study in 40 acres of old-growth Douglas-Fir near Eugene, Oregon. The area was divided into a 40-by-40 grid of plots, each 1/40 acre. The volume represents the total timber volume (Scribner Decimal C) of each 1/40 acre plot.

The authors conclude a 1-chain by 3-chain 3/10 acre rectangle was most efficient for intensive cruise work.

To convert plot volume to total volume per acre, multiply by 40 (each plot is 1/40 acre) and multiply by 10 (correction for the Scribner scale).

Source

Floyd A. Johnson, Homer J. Hixon. (1952). The most efficient size and shape of plot to use for cruising in old-growth Douglas-fir timber. Jour. Forestry, 50, 17-20. https://doi.org/10.1093/jof/50.1.17

References

None

Examples


library(agridat)
data(johnson.douglasfir)
dat <- johnson.douglasfir

# Average volume per acre. Johnson & Hixon give 91000.
# Transcription may have some errors...the pdf was blurry.
mean(dat$volume) * 400
#> [1] 91124.25
# 91124 

libs(lattice)
levelplot(volume ~ col*row, dat, main="johnson.douglasfir", aspect=1)

histogram( ~ volume, data=dat, main="johnson.douglasfir")