Growth basal area handbook

Abstract

Growth basal area (GBA) is that basal area at which dominant trees grow at 1.0 inch in diameter per decade at age 100. Diameter growth rate of 1.0 inch per decade is a constant used to compare sites; basal area is a variable used to express stockability. GBA is a field method for estimating site potential for stockability using current stand growth. Parameters measured are basal area per acre and rate of diameter growth. Current basal area is adjusted by use of a GBA curve to that basal area which will result in 1.0 inch diameter growth per decade of dominant trees, the GBA of the site. Two GBA curves are provided. The GBA concepts employed, development of GBA, determination of GBA, use of GBA, and GBA in relation to stand growth are discussed. GBA is combined with site index to index different productivity levels within a site index class and to help identify those productivity levels in the field. Appendixes provide description of a GBA slide rule, additional data, and forms for determining GBA.