The task of developing an inventory of a forest can be daunting. For instance, how does one go about getting information about a plot of forestland that is 200 to 300 acres in size? It would be impossible to measure and record every tree.
Foresters collect data from sample plots from the forest. The plot may be a quarter-acre in size, and they might take data from 25 to 30 plots. Within each plot the species; tree sizes, usually diameter and log length; conditions, especially of the trunks; and locations are recorded. The location includes the plot location within the forest, and many times the locations of individual trees within the plot.
The data from all the plots are then summarized, and a process called developing an assessment of the woods is completed. This leads to the development of a plan for the forest.
When inventorying urban and landscape trees, the system may employ a plot sampling or a complete inventory. For public trees, a complete inventory typically is undertaken. The argument for this is that since it is not a natural forest, sampling would not give statistically valid data, and the information gathered may be applied directly to management needs for an individual tree. Again, data from all the trees are summarized in an assessment then used to develop a management plan. If other aspects of the urban forest, such as private property or wooded areas, need to be inventoried, a sampling technique may be employed.
What technique should be used in a greenway where there is a mix of landscape trees and forestland? It may require both techniques and two inventories. The landscape tree inventory may be used for landscape trees in mowed areas, while a sampling may be used in wooded areas.
Because greenways may be long narrow strips of land, a special plot system may be employed that takes a cross section of the greenway at periodic intervals.
An aerial imagery inventory has its own unique set of uses and has a completely different approach with its unique data set of information collected.