Assessing operational silviculture and modeling juvenile growth in Saskatchewan white spruce (Picea glauca (Moench) Voss) plantations

• Author / Creator

  Johnson, Kirk M

• White spruce (Picea glauca (Moench) Voss) plantations are often established with mechanical site preparation and tending. These silvicultural treatments encourage plantation survival and can influence growth, composition, and yield. To assess operational silviculture and model managed stand growth, 16 white spruce plantations (13-18 years old) and 18 white spruce Permanent Sample Plots (20-29 years old) (PSP’s) were sampled across the Prince Albert Forest Management Agreement in Saskatchewan between 2011 and 2012.
  Analysis of Covariance (ANCOVA) with soil moisture regime indicated that white spruce height was not significantly different between Bracke mounding, v-plow scarification, disc trenching, and disc trenching/tended treatments. However, v-plow scarification appeared to increase the DBH of young white spruce relative to Bracke mounding. This DBH difference was linked with a significant change in grass competition but could not be linked with changes in overstory vegetation. Site differences complicated analysis and may have obscured silvicultural effects. In addition, the effectiveness of each silvicultural treatment could not be explored, since a ‘raw planted’ control could not be located.
  To estimate subsampled heights, generalized mixed-effects height-diameter models were developed for the PSP dataset. Generalized models containing top height and density often explained the most variation. Small sample sizes prevented validation of the PSP height-diameter models, limiting their use to the fitted PSP data.
  Using repeated measurements in the PSP dataset, short-term Mixedwood Growth Model (MGM) projections (1996-2011) were compared to observed growth between 1996 and 2011. Site index assumptions (i.e. height-age site indices or ecosite-based site indices) largely dictated MGM performance. However, given accurate site indices, modeled white spruce height and DBH tracked observed growth in most spruce-aspen mixedwoods. Modeled white spruce height and DBH were overestimated in juvenile stands (50% basal area) by age 60 and white spruce dominant (>75% basal area) by age 120. Increasing deciduous competition slowed succession but did not prevent hardwood-leading stands from becoming mixedwoods by age 120. Site index assumptions (i.e. ecosite-based site indices) strongly influenced modeled succession and long-term outcomes.

• Subjects / Keywords

  • Boreal forests
  • Plantation
  • White spruce
  • Silviculture
  • Mixedwood growth model
  • Saskatchewan

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R37M04B87

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.