Levels-of-Growing-Stock Cooperative Study in Douglas-Fir: Report No. 9 - Some Comparisons of DFSIM (Douglas-Fir Stand Simulation Program) Estimates with Growth in the Levels, of-Growing-Stock Study

摘要

Initial stand statistics for the levels-of-growing-stock (LOGS) study installations were projected by the Douglas-fir stand simulation program (DFSIM) over the available periods of observation. Thinnings were simulated by use of observed top height trends, actual residual basal areas, and actual ratios of cut tree diameters to stand diameter before cutting (d/D). Estimates were compared with observed gross and net volumes and basal area growth, net change in quadratic mean diameter, and change in number of trees. Although the LOGS installations include regimes quite different from those in most of the data used to construct DFSIM, overall agreement was reasonably good. Results indicate some density-related bias in the thinned stands and a need for revision in the method used to control the maximum density in the DFSIM program and in the associated mortality estimates.