9:00 am - 10:00 am
Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Dawei Luo. This seminar is open to the general public to attend via Zoom: https://us02web.zoom.us/j/84349861035?pwd=QXBLRld1cGVKZ081WXN2WFpZaXFYQT09
Incorporating genetic gain into growth and yield projections for Alberta’s white spruce and lodgepole pine tree improvement programs
Alberta’s forestry has been facing challenges from a shrinking forest land-base and a decrease in forest stand productivity in past few decades. Tree improvement, due to its great potential for forest-based ecological and economic benefits, is recognized as one of the most efficient approaches in addressing the issues raised. However, there are still some knowledge gaps limiting the application and benefit assessment of tree improvement programs. Given that white spruce (Picea glauca (Moench) Voss) and lodgepole pine (Pinus contorta Dougl.) are the two most important commercial tree species in Alberta, these species are the focus of this thesis.
In this thesis, five chapters are included, with three data chapters (Chapters 2-4) focusing on: 1) estimating genetic gain at rotation age and corresponding growth and yield from improved white spruce and lodgepole pine seedlots; 2) climate change effects on improved white spruce and lodgepole pine performance; and 3) early growth of improved white spruce in mixedwood stands in northeastern Alberta.
In Chapter 2, taking advantage of the latest height measurements from all progeny trials in the province of Alberta for white spruce and lodgepole pine, I adjusted and compared two available age-age correlation equations developed previously in Lambeth’s (1980) and Rweyongeza’s (2016). The results presented in Chapter 2 indicate that the adjusted Lambeth equations, with re-estimated parameters, are the most robust for both species and should be further incorporated into Alberta’s growth and yield models. The phenotypic age-age correlation shows no significant deviation from the genetic age-age correlation for either species. The stand volume generated from the growth and yield projection system (GYPSY) model using the new adjusted Lambeth equations shows that white spruce has a higher age-age correlation, and therefore, a higher percentage improvement in volume per hectare compared to lodgepole pine regardless of rotation age.
In Chapter 3, the most recent height measurements from progeny and provenance trials of white spruce and lodgepole pine, and three Representative Concentration Pathways (RCPs) were selected to to incorporate climate change into growth and yield prediction for both species. An adjusted Pooled Transfer Function (PTF) was developed, which relates standardized population height with population climate transfer distance and population climate, and was merged with GYPSY using the new adjusted Lambeth equations.to predict the effect of climate change on the growth and yield of unimproved and improved stands in Alberta, Canada. The simulation results indicate that height growth is strongly influenced by the mean coldest month temperature (MCMT) for white spruce and mean annual precipitation (MAP) for lodgepole pine. Regardless of the RCPs, by 2090, climate change-related growth expansions for white spruce stands are expected to be greater in areas with low provenance MCMT than in areas with high provenance MCMT for both improved and unimproved seedlots. Unimproved and improved lodgepole pine stands, however, are expected to show decreased height growth in most regions in Alberta. For both species under all RCPs, improved seedlots will be outgrown by unimproved seedlots in locations where climate change favours height growth, while improved seedlots will retain their growth advantage over unimproved seedlots in locations where climate change shows an overall negative effect on height growth.
In Chapter 4, data collected from four Forest Management Units (FMUs) in northeastern Alberta was used, the results indicate that the improved white spruce seedlot, which originated from a tree improvement program with an approved height gain of 1.9% at a 100-year rotation, did not show any advantage in height or diameter at the sapling stage. A distance-independent competition index based on Lorimer’s index, that included size ratio between competitor aspen and subject spruce, accounted for most of the variation in diameter and height growth from 2016-2018 (age of trees 8-10 years) when a power function was used. The competition effects on height and diameter growth differed significantly, however, between unimproved and improved seedlots across ecosites, height growth was less sensitive to the competition effects than diameter growth.
These results of this thesis reduce the current knowledge gaps, through providing robust adjusted age-age correlation equations and an adjusted PTF as a quantitative method to estimate growth and yield of improved forest stands under different climate change scenarios, for the purpose of improving forest management strategies.