Stocking

Stocking Charts for Oak History Forests

Stocking equations, and charts derived from them, are commonly used as standards for defining and controlling the density of oak stands. Currently available standards express stand density as "stocking percent," a measure of relative stand density (Stout and Larson 1988). Related stocking charts specify the upper and lower limits of absolute measures of stand density (i.e., basal area and numbers of trees per acre) that define the normal range of residual stocking for thinning and other silvicultural operations. The upper and lower levels of this range are called A and B levels, respectively. A level, also called 100 percent stocking, represents stands at average maximum density. B level represents the minimum stand density at which trees use all the growing space, assuming trees are well distributed. There are stocking charts for the oak-hickory forests of the Central States (Gingrich 1967), and northern red oak forests of New England (Sampson and others 1983) and Wisconsin (see figure) (McGill and others 1991, Isebrands and Dickson 1994).

Stocking percent provides a better measure of the degree of tree crowding than basal area alone because large trees require less space, proportionate to their basal area, than small trees. Thus, for a given basal area per acre, stands comprised of large trees are less crowded than stands comprised of small trees. The application, derivation, advantages, and limitations of stocking concepts are discussed in more detail by Ernst and Knapp 1985, Gingrich 1967, Leak 1981, Leary and Stansfield 1986, Stout and Larson 1988, Isebrands and Dickson 1994.