This project analyses height growth performance among approximately 700 individual aspen trees from various clones over 22 years. The focus was on understanding how height measurements compared among clones, and how their height growth is further impacted by climate variables like temperature and precipitation. Knowledge about varying growth responses and patterns is especially crucial in times of fast changing climate conditions.

The trial was planted in June 2002, ca. 60 km southwest of Edmonton, Alberta, choosing an Alpha design with randomized replications and blocks as the experimental design. Height measurements were taken in year 1, 3, 4, 5, 7, 12, 19 and 22 after establishment. Clone-level height performance was analyzed by ranking clones based on their mean heights at trial age 22 and comparing the top 5, 10, and 15 clones to the baseline mean using one-sample t-tests. Height performance during three climate periods Cold & Dry (2003–2005), Warm & Dry (2005–2007), and Cold & Wet (2010–2014) was assessed using measurement years 3, 5, and 12, with the top 5 clones in each climate class compared to baseline means. Sex-based height differences at year 22 were evaluated using linear regression models, with confidence intervals quantifying differences across provenances. 

The top-performing clones showed clear trade-offs between maximizing height gains and maintaining genetic diversity. The top 5 clones achieved the greatest height gains (+2 m above baseline) but with limited provenance diversity, while expanding to the top 10 or 15 clones slightly reduced gains but increased diversity. Clone C3014 excelled across all conditions, demonstrating adaptability, but other clones such as C8012 (Cold & Dry), C4029 (Warm & Dry), and C6028 (Cold & Wet) also showed strong climate-specific performance. Sex-based analysis revealed significant height differences in certain provenances, with female trees generally outperforming males and non-blooming individuals. Companies should adopt a balanced strategy, prioritizing top-performing clones for yield while diversifying selections to enhance resilience and adaptability to climate and ecological variability.