A subset of tree growth observations from a Ponderosa pine growth database.
The ppine data frame has 166 rows and 8 columns.
Usage
data(ppine)
Format
This data frame contains the following columns:
elev
Altitude of the plot, in feet above mean sea level.
smi
Summer moisture index is the ratio of growing season heating
degree days to growing season precipitation.
dbh
Diameter of the tree at breast height (4.5 feet).
tht
Total stem height for the tree.
cr
Crown ratio code. The scale is from 1 to 9 where a crown class of
one represents a crown ratio between 0 and 15 percent. A crown
ratio code of 2 represents a crown ratio value between 16 and
25%,...,8=76-85%, 9 >=85%.
ba
Plot basal area at the beginning of the growth period.
dg
Five-year diameter increment.
hg
Five-year height increment.
Details
The exogenous variables are elev, smi, dbh,
tht, cr, and ba; the endogenous variables
dg and hg. There are no lagged variables in the dataset
and the observations are for a single remeasurement.
The data was provided by the USDA Forest Service Intermountain
Research Station.
Source
William R. Wykoff wwykoff@fs.fed.usRocky Mountain Research Station, 1221 South Main Street, Moscow, ID 83843