FORCAT: A Single Tree Model of Stand Development Following Clearcutting on the Cumberland Plateau

Abstract

Abstract A single tree model, FORCAT, was developed as a forest management tool for the Cumberland Plateau region of East Tennessee. FORET (Shugart and West 1977), a gap model of forest succession in East Tennessee, served as the basic program for the simulation of stand regeneration, competition, tree growth, and mortality. Gap models have been used to simulate successional changes in species composition over periods of up to 1,000 years for many different forest types. Even though the output of gap models has included specific information such as basal area and density, the accuracy of short-term predictions of these variables remains relatively untested for forest management purposes. A test of FORET indicated that the model was not readily adaptable to different sites and management schemes. Therefore, major modifications to the basic program were necessary. Some of the more significant changes included in FORCAT are: (1) beginning the simulation with a mature stand (which was immediately clearcut) rather than bare ground, (2) growth rates based on site quality and local climatic conditions, (3) basing seed availability on species-specific characteristics, and (4) simulation of periodic clearcutting and prescribed burning. Validation tests showed that FORCAT successfully predicted basal area, numbers of trees, and species composition of 50- to 100-year-old stands. In younger stands, however, the number of seedlings of pioneer species was underestimated. This variance emphasizes the difficulty of projecting regeneration abundance and indicates the need for further model refinement. Nevertheless, FORCAT serves as a bridge from a highly theoretical model of forest succession to a useful forest management tool. Additional inputs controlling seed availability are needed to make FORCAT more broadly applicable to all forest types found on the Cumberland Plateau. Forest Sci. 32: 297-317.