Creo que esto es lo que estás buscando. Lo que está entre corchetes es optativo. Referencias útiles:

En http://www.calforests.org/glossary.html?letter=S

Site Quality:
The capacity of an area of land to produce forests or other vegetation. Factors influencing site quality include climate, soil type, slope, and biological factors. Site quality is usually expressed by an index based upon the height of a tree if it were allowed to grow free of competition for 50 years (site index of 80 means a tree on that site could grow to 80 feet in 50 years if it has no competition). Site quality is extremely variable within a small area.

IngentaConnect Earthworms as bio-indicators of forest site quality
The effectiveness of earthworm species as bio-indicators of forest site quality was tested by a dataset of 180 plots in temperate lowland forest (Flanders, ...
www.ingentaconnect.com/content/els/00380717/1997/00000029/0...

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DEVELOPMENT OF A FOREST SITE QUALITY CLASSIFICATION MODEL FOR MINE ...
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land into one of five forest site quality classes (FSQC). .... a soil-based model for estimating forest site quality on reclaimed surface mined land; ...
www.cses.vt.edu/PRP/Research_Results/ASMR_2005/0523-Jones-V...

Forest Ecology and Management : Comparing estimates of forest site ...
Site index is a useful tool for evaluating forest site quality, but the application of site index is currently problematic within the central Appalachian ...
linkinghub.elsevier.com/retrieve/pii/S0378112704000027 - Similar pages - Note this

Indicatory properties of soil solutions in the characteristics of ...
Indicatory properties of soil solutions in the characteristics of forest site quality. Pore&hook; bska, G., J Sienkiewicz, A Ostrowska ...
www.cababstractsplus.org/google/abstract.asp?AcNo=200431825...