资源环境科技发展态势分析平台

Forest managers are increasingly focused on promoting or maintaining forest structural complexity, including the heterogeneity of forest structures within stands. However, many of the forest growth models commonly used by forest managers assume that stands are structurally homogeneous. Therefore, using these forest models to project the development of structurally complex stands may provide inaccurate results. We investigated the accuracy and precision of individual tree growth estimates from an individual tree growth model commonly used by forest managers (Central Rockies Variant of the Forest Vegetation Simulator, FVS-CR) in six structurally heterogeneous ponderosa pine (Pinus ponderosa Douglas ex C. Lawson) stands. Furthermore, we examined whether the addition of non-spatial, semi-distance independent, or spatially explicit indices of local competition to the model improved the accuracy and precision of stand development projections over the 16-year study. We found that while the stand-scale estimates of growth were within the bounds of normal measurement precision, the estimates of individual tree diameter growth had a root mean square error (RMSE) that equated to 44% of the mean individual tree diameter growth. The addition of crown ratio to the model improved estimates more than the other investigated indices by halving the estimated bias and reducing the RMSE of the projected individual tree diameter growth by 4.8%.