Lesson 3 spacer Overview of Methods for Estimating Site Index
Lessons
Lesson 1
Lesson 2
Lesson 3
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Lesson Objectives

Methods for Estimating SI

BEC Method

Growth Intercept Method

Site Index Curve Method

Site Class Conversion Table

Two Useful Tools


Lesson 4
Lesson 5
Lesson 6
Lesson 7
Lesson 8
Lesson 9
Lesson 10
Lesson 11
Lesson 12
Appendices
Appendix 1
Appendix 2
Appendix 3
Appendix 4
Appendix 5
Appendix 6
Appendix 7
Appendix 8
Appendix 9
Course Homepage
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Lesson Objectives

Review the methods for estimating site index.

Methods for Estimating SI

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:

  • entering inventory label height and age into a SI curve
  • using the SI value from a nearby area
  • converting site class to SI.

There are three methods that use ground collected data. They are accurate and best suited for silviculture work. These methods are:

  • biogeoclimatic ecosystem classification method (BEC)
  • growth intercept method
  • site index curve method

These methods are each suited to specific stages of stand development (Figure 3.1).

SI methods commonly used at various stand ages

Figure 3.1. SI methods commonly used at various stand ages.

BEC Method

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.

Growth Intercept Method

The growth intercept method (Lessons 5 and 6) uses the height and age of sample trees measured on site to predict SI.

This method is best used on stands that have between 3- and 30-years growth above breast height.

Site Index Curve Method

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.

Site Class Conversion Table

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.

Two Useful Tools

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.

 

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