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Background and Rationale
Forests are essential for providing ecosystem services that support both environmental stability and human welfare. In Canada, Aspen stands are widespread and contribute significantly to the landscape's ecological and economic value (Laganière et al., 2017). Understanding the growth patterns of different Aspen genotypes and their response to climate variables is essential for developing productive and resilient forests in an uncertain future. However, there are unresolved gaps in understanding sex and genotype-specific reactions to environmental stressors (Dias de Andrade Silva, 2024). The availability of localized studies is insufficient, but necessary to cover regional differences in climate sensitivity (Anyomi et al., 2012).
Figure 1: This figure by Dias de Andrade Silva (2024) shows mean SE of basal area increments (BAI, mm2 ) of Populus tremuloides from 1992 to 2020 with predrought (1997-2001, blue), drought (2002-2003, red), and post-drought (2004-2007, green) periods highlighted. Cathedral, Dominion, EtaLake and Tower are separate Aspen populations in Alberta, therefore representing different genotypes and their variation in growth as a response to changing climate conditions.
Aspen trees exhibit notable genetic diversity, with many clones displaying unique growth characteristics and resilience levels (Dayanandan, 1998). This genetic variation provides a potential for improvement in forest management, where certain genotypes might be selected due to better growth characteristics or resilience to certain climate conditions (Figure 1). Furthermore, examining growth differences based on sex could provide additional value, especially if certain sexes demonstrate better growth performance (Figure 2), or imporved resistenance traits (Figure 3). Prior studies have suggested that male and female trees may vary in their growth patterns and stress responses due to different reproductive and physiological demands (Sakai et al., 1985).
Despite growing interest in the general climate responses of Aspen, few studies have examined these responses at the level of individual clones over extended periods of time.
Figure 2: This figure by Dias de Andrade Silva (2024) shows mean SE of a) diameter at breast height (DBH, cm), and; b) wood specific gravity (g/mL; c) of mature aspen trees within the AW2 (Pembina) CPP region, in Alberta, Canada. The P-values correspond to results of ANOVAs with pooled variances where DBH or wood specific gravity were the response variables, and sex was the explanatory variable. Different letters indicate significant differences at alpha = 0.05.
Figure 3: This figure by Dias de Andrade Silva (2024) shows mean SE of resistance, recovery, resilience, and relative resilience indexes obtained from sampled trees in study areas within the AW2 (Pembina) CPP region, in Alberta, Canada. The P-values correspond to results of linear mixed effect models where resistance, recovery, resilience, and relative resilience indexes were the response variables, and sex was the explanatory variable (stand age was included as a covariate and area as a random effect). Significant differences at alpha = 0.05.
Research Objectives
The primary objective of this research is to investigate the impact of seasonal climate variables, particularly temperature (Figure 4) and precipitation (Figure 5), on the growth patterns of various aspen clones over a 22-year period, from 2002 (trial establishment) to 2023 (year of latest measurement). This study seeks to identify clones that are better or worse adapted to those conditions. Furthermore, a growth performance comparison on clonal level will help to provide valuable information on high performing Aspen clones. Such information could be valuable for forest management, where fast growing or resilient clones might be prioritized for replanting.
Another key objective of this study is to explore the influence of sex on aspen growth across different provenances. Understanding these sex-based growth patterns could enable forest managers to make more informed decisions about the composition of future forest stands.
By identifying adapted, high-performing clones and exploring sex-based growth differences, this project aims to improve Aspen management practices in Alberta, Canada. These insights will help Albertan forest managers to make informed decisions on whether or not a certain clone or provenance is suitable for their regional climate conditions and their goals in producing timber. Furthermore, this project will contribute to other studies in this field by adding another region and another set of provenances to the list of already researched genotypes. This contribution might be of use for future large-scale data compiling and its use for decision-making in Canadian forest management.
Figure 4: Change of mean temperature in spring and summer from 2002 to 2023.
Figure 5: Change of accumulated winter, spring and summer precipitation from 2002 to 2023.
References
Anyomi, K. A., Raulier, F., Mailly, D., Girardin, M. P., & Bergeron, Y. (2012). Using height growth to model local and regional response of trembling aspen (Populus tremuloides Michx.) to climate within the boreal forest of western Québec. Ecological Modelling, 243, 123–132. https://doi.org/10.1016/j.ecolmodel.2012.06.020
Dayanandan, S., Rajora, O. P., & Bawa, K. S. (1998). Isolation and characterization of microsatellites in trembling aspen (Populus tremuloides). Theoretical and Applied Genetics, 96(6/7), 950–956. https://doi.org/10.1007/s001220050825
Dias de Andrade Silva, R. (2024). Genetic variability and drought responses of young and mature aspen in Alberta.
Laganière, J., Boča, A., Van Miegroet, H., & Paré, D. (2017). A Tree Species Effect on Soil That Is Consistent Across the Species’ Range: The Case of Aspen and Soil Carbon in North America. Forests, 8(4), 113-. https://doi.org/10.3390/f8040113
Sakai, A. K., & Burris, T. A. (1985). Growth in male and female aspen clones: a twenty-five-year longitudinal study. Ecology (Durham), 66(6), 1921–1927. https://doi.org/10.2307/2937388
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