Review the methods for estimating site index.
There are several methods for estimating SI. These different methods produce SI estimates that differ in accuracy.
Site index can be determined from field collected data (preferred procedure) or office procedures. However, SI can be very inaccurate if it is determined from office procedures such as:
There are three methods that use ground collected data. They are accurate and best suited for silviculture work. These methods are:
These methods are each suited to specific stages of stand development (Figure 3.1).
The BEC method (Lesson 4) uses the biogeoclimatic ecosystem classification of a stratum to predict SI. Generally, SI is predicted from subzone and site series.
The BEC method is best used in very young stands, very old stands, and stands not suitable for other methods.
This method is best used on stands that have between 3- and 30-years growth above breast height.
The SI curve method (Lesson 7) uses the height and age of sample trees measured on site to predict SI.
This method is best used on stands that have between 30- and 140-years growth above breast height.
To use the site class conversion table (Lesson 8), the surveyor estimates site class and converts it to SI.
This method of obtaining SI should only be used in those cases where a more accurate method is not available.
1. SI Method Decision Key
A decision key (Lesson 9) has been developed to assist surveyors in determining the appropriate method to use to estimate SI.
2. Species Conversion Table
A species conversion table (Lesson 10) is available to predict the SI for one species from the SI measured on a different species on the same site.