Compatible growth and yield equations for eastern redcedar forest types

The Tennessee Valley Authority (TVA) recognized the need for better resource management on nonindustrial private timberlands. To aid these landowners, the Woodlands Resource Analysis Program (WRAP) was developed. WRAP'S purpose is to identify the desires and objectives of a landowner and provide a series of management strategies which can be implemented by the owner.

A limitation, however, exists in WRAP'S usefulness for eastern redcedar forest types. Because there is a lack of information on growth and yield in these forest types, WRAP'S simulators, presently, cannot carry out projections. The purpose of this study was to develop and provide compatible growth and yield equations for eastern redcedar forest types for use in WRAP.

The data used in this study were gathered from TVA's continuous forest inventory project. Plot summaries were developed with information divided into the three forest components of: eastern redcedar, pine species, and hardwood species. From this information, equations were fitted to predict the annual per-acre growth rates of total merchantable basal-area, total merchantable cubic-foot volume, and sawtimber basal area for each component.

By integration of the growth rate functions, equations to predict the future values of total merchantable basal-area, total merchantable cubic-foot volume, and sawtimber basal-area were developed. Functions were also developed to estimate future cubic-foot volumes of sawtimber from estimates of sawtimber basal-area. Equations were then developed to convert sawtimber cubic-foot volume to board-foot volume yields.

Overall accuracy of these equations were as good as projections based on mean growth rates, however no better.

The limiting factor was the poor fit of the basal-area growth rate equations. Their fit was poor because the base data were not designed to be used in this type of study. Variables necessary to predict basal area growth rates were not available. Even with their various predictive abilities, these equations can be utilized because there exists no other system of this type to estimate the growth and yield of eastern redcedar forest types.