RELIABILITY, PRESENTATION, AND RELATIONSHIPS AMONG DATA FROM INVENTORIES OF FOREST CONDITION

Variation is greater between stands than within, but within-stand variation can be significant and should be taken into account when determining the number of trees to be sampled per stand. In even-aged, predominantly single-species stands, 24 trees may be insufficient to characterize the condition of the trees in the stand. The simplest and most commonly used method of presenting the results of annual assessments is cumulative bar charts of crown density. Tables documenting the change in crown densities from one year to the next of trees in a given crown density class provide more useful information and are recommended. Assessments of forest condition normally only record crown density and crown discoloration. Neither of these symptoms is specific to any particular cause. It is possible to record a wide variety of features when assessing the health of a tree. Generally, either crown density or crown discoloration (or both) is correlated with many other symptoms of poor condition within the crown, but there are considerable differences between species, eg crown density is more useful for assessment of Norway spruce Picea abies than for Sitka spruce Picea sitchensis. Collection of data related to other symptoms is required. -from Authors