Book Description

This paper reports the first phase of a recent effort to evaluate the performance and use of the FVS-SEAPROG vegetation growth model. In this paper, we present our evaluation of SEAPROG's performance in modeling the growth of even-aged stands regenerated by clearcutting, windthrow, or fire. We evaluated the model by comparing model predictions to observed values from two sets of long-term permanent plots. We examined six variables: trees per acre, quadratic mean diameter, basal area per acre, height of the largest 40 trees per acre, cubic-foot volume per acre, and board-foot volume per acre. The differences between observed and predicted values were large enough to have important implications for the interpretation and use of the model's predictions. Of even greater importance was the evidence for considerable bias in quadratic mean diameter, basal area, height, and volume, all of which were systematically underestimated. Our results appear to validate the concerns expressed by users.