vigour {Iso}

vigour

Description

Growth vigour of stands of spruce trees in New Brunswick, Canada.

Usage

data("vigour")

Format

A data frame with 23 observations (rows). The first column is the year of observation (1965 to 1987 inclusive). The other five columns are observations on the vigour of growth of the given stand in each of the years.

Details

The stands each had different initial tree densities. It was expected that vigour would initially increase (as the trees increased in size) and then level off and start to decrease as the growing trees encroached upon each others' space and competed more strongly for resources such as moisture, nutrients, and light. It was further expected that the position of the mode of the vigour observations would depend upon the initial densities.

Source

These data were collected and generously made available by Kirk Schmidt who was at the time of collecting the data a graduate student in the Department of Forest Engineering at the University of New Brunswick, Fredericton, New Brunswick, Canada. The data were collected as part of his research for his Master's degree (supervised by Professor Ted Needham) at the University of New Brunswick. See Schmidt (1993).

References

K. D. Schmidt (1993). Development of a precommercial thinning guide for black spruce. Thesis (M.Sc.F.), University of New Brunswick, Faculty of Forestry.

Examples

 matplot(vigour[,1],vigour[,2:6],
         main="Growth vigour of stands of New Brunswick spruce",
         xlab="year",ylab="vigour",type="b")