Lesson 8

Lesson Objectives

Site Class Conversion

Lesson Objectives

Learn to not use the site class conversion table.

Site Class Conversion

To use this method, the surveyor estimates site class (G, M, P, or L) and refers to a table to convert site class to SI (Figure 8.1). The resulting SI is very inaccurate. This method should only be used when SI cannot be determined with more accurate methods. A copy of this table is provided in Appendix 6 “Procedures for obtaining site index for silviculture polygons.”

The site class conversion table is required because it will take several years to replace all of the existing site class values with improved SI estimates. During this transition period, it will be necessary to convert site class to SI for some polygons. Over time, these interim SI values should be replaced with more accurate SI estimates based on appropriate ground sample methods.

A SI value obtained from converting site class is not sufficiently accurate for most silviculture decisions.

The site class conversion table is based on inventory leading species, region of the province (coast, interior or both) and site class.

When forest cover map labels were converted from site class to SI, the site class conversion table was widely applied to young stands.

Other methods that are frequently inaccurate (like the site class conversion table) include assigning to a polygon, the SI determined on an adjacent stand and assigning to a species, the SI determined for another species on the same site.

Inventory label leading species	Region	Good	Medium	Poor	Low
Ac	Province	26	18	9	3
At	Province	27	20	12	4
B, Ba, Bg	Coastal	29	23	14	5
B, Ba, Bg	Interior	18	15	11	5
Bl	Province	18	15	11	5
Cw	Coastal	29	23	15	6
Cw	Interior	22	19	13	5
Dr	Province	33	23	13	6
E, Ea, Ep	Province	27	20	12	4
Fd	Coastal	32	27	18	7
Fd	Interior	20	17	12	5
H, Hm, Hw	Coastal	28	22	14	5
H, Hm, Hw	Interior	21	18	12	4
L, La, Lt, Lw	Province	20	16	10	3
Mb	Province	33	23	13	6
Pa, Pf, Pj, Pl	Province	20	16	11	4
Pw	Province	28	22	12	4
Py	Province	17	14	10	4
S	Coastal	28	21	11	4
S	Interior	19	15	10	5
Ss	Province	28	21	11	4
Sb, Se, Sw	Province	19	15	10	5
Yc	Coastal	29	23	15	6
Yc	Interior	22	19	13	5

Figure 8.1. Site class conversion table.

Exercise:

If the inventory leading species is Hw, the stand is on the coast, and the surveyor estimates it is site class M (medium), what interim SI value should be used?