Modelling vegetation management treatments with the Tree and Stand Simulator

Abstract

The Tree and Stand Simulator (TASS) has been used for over 20 years in British Columbia to generate yield tables for managed stands. In order to explore the impacts of weed control on site productivity we chose two vegetation management research trials where 10-to 15-year post-treatment data were available (Boston Bar and Mica research sites). Tree survival and height growth results were used to adjust the TASS input parameters to simulate the various brushing treatments. At the Boston Bar site, all vegetation reduction treatments shortened the Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) physical rotation age by up to 10 years and culmination mean annual increment (cMAI) was increased 8% to 11% relative to the untreated control. At the Mica site, the glyphosate and all repeated manual cutting treatments resulted in a shortening of the Engelmann spruce (Picea engelmannii Parry) rotation age by seven years and increased cMAI by approximately 11% to12%.

Long-term effects of site preparation and postplanting vegetation control onPicea glaucasurvival, growth and predicted yield in boreal British Columbia

“…Mason and Milne (1999) identified the use of data from old studies and the identification of treatment response mechanisms as complementary strategies to facilitate the ability to model silviculture treatment effects on conifer growth. Early conifer responses to silvicultural treatments have been simulated using TASS (Harper et al, 2008). However, TASS is a single canopy model, and does not directly consider growth suppression from long-term vegetation community competitors or model mixed coniferÁbroadleaf stands.…”

Effects of vegetation control treatments for release of Engelmann spruce from a mixed-shrub community in southern British Columbia – Year 15 results

“…The substantial variability between plots and the small number of replications used in this study provided poor statistical power and a lack of statistical evidence to support apparent treatment differences. TASS simulations of the treatments indicated that the glyphosate and repeated cutting treatments may shorten physical rotation age by 7 years (a 14% reduction in rotation length), increase culmination MAI by between 11% and 12%, and increase merchantable volume at age 42 by 18% compared to the untreated control (Harper et al 2008). Since these estimates do not include consideration of the small component of broadleaves present on this site (models for mixed-species stands are not yet available for this region), they are likely to slightly overstate differences in total (conifer plus broadleaf) yield.…”

“…Fifth-year results from this study were presented by Comeau et al (2000) and 10-year results were presented by Biring et al (2003). Yield forecasts for the treatments used in this study are presented by Harper et al (2008).…”