INTRODUCTION

Background

White spruce is an important commercial forestry species favorable for its timber about 43 million white spruce trees are planted each year to regenerate harvest and degraded areas. The species is a dominant component of the boreal and foothills natural regions in Alberta (ATISC,2007). However, as a result of climate change, the geographic ranges of White spruce species are moving toward the poles or to higher altitudes, in response to shifts in the habitats to which these species have adapted (Rweyongeza et al.,2008). This movement is projected to eliminate the suitable habitat of many endemic or range-restricted species (Parmesan, 2006) with this elimination becoming more pronounced in the future. This suggests that assisted movement of species outside their historic range may be necessary for the purpose of conservation (Gray et al., 2011).

Changes in this environment will reduce the ability of populations to be productive and have an increased frequency of diseases and pest attacks. Therefore, assisted migration is a desperate solution that will help trees move along with the fast-changing climate to avoid maladaptation (Wang et al.,2019). This study assessed growth performance for White spruce seed sources that have been transferred to different locations and different climates. The results of this experiment can be used to infer growth response to future climate change. This study also evaluated which provenances perform best over multiple climatic conditions. Populations that have great environmental tolerances are desirable for reforestation and assisted migration because they can withstand the high uncertainties in future climate projections.

The concept of assisted migration of seed sources

Assisted migration involves transferring seeds or material from a known location to an area with a similar climate to what the tree may be exposed to under climate change. Trees may often be planted further than their native locations to increase forest productivity when basic requirements of survival and reproduction are met, (Mangold and Libby 1978). The native plant vegetation guide of Alberta states that native plant material is encouraged for reforestation with the assumption that local sources are best adapted to the environment in which they occur. This deployment strategy may no longer be viable as we see trends toward warmer and drier climate conditions over the last several decades (McKenney and Pedler, 2009).

Therefore, establishing plantations with populations of forest trees adapted to future climates has been posed as a key climate change adaptation strategy because it addresses the fundamental issue of the uncoupling of plant adaptation to its environment (Miller et al.,2007). Assisting populations to move populations northward via assisted migration or local seed transfer is one proposed strategy to predict and mitigate the effects of climate change (Figure 4).

Present and Future Climate Characteristics of Alberta

The average projected changes of precipitation and temperature of Alberta with reference to the baseline period, between 2011 and 2100, will be about +20 % and 4.4 °C (Jiang et al.,2017) and a mean annual temperature increase by 1.3% (Wang et al.,2016). Figure 5 shows the full range of potential climate outcomes. The cool and hot models are representative of the minimum and maximum amount of change expected showing shifts of major subregion climates northward. The maximum shifts expected suggest that the immigration of exotic species to Alberta will become vital ( Schneider,2013). Tree species and their populations are usually genetically adapted to the local climate conditions where they occur based on the assumption that the local environment is best for local seed sources ((Zihaohan et al.,2021). Tree populations are expected to exhibit poor adaptation if planted outside their local environment. (O'Neill and Aitken, 2004).)

There has been a continuous increase in global temperatures. This results in a discrepancy between the current climate, tolerance of the species, and genetic adaptation to local conditions (Gray and Hamman,2013). This discrepancy has brought about serious disruptions to forest health and productivity in western Canada. ( Hauvenet et al., 2013 ) Assisted migration of plants northward and upward, may be necessary, especially for species that are less mobile or adaptive (Hoegh-Guldberg and others 2008). This will elevate the chances that climate conditions to which local populations are adapted match current and future growing environments, and ultimately support forest health and productivity for the coming decades (Zihaohan et al.,2021).

References

ATISC 2007. Controlled Parentage Program Plan for region G2 White spruce tree improvement project in the northwest boreal region in Alberta. Region D1. In: Technical Report 07-09. Alberta Tree Improvement & Seed Center 34 pp.

Gray LK, Gylander T, Mbogga M, Chen P, Hamann A (2011) Assisted migration to address climate change: recommendations for aspen reforestation in western Canada. Ecol Appl 21:1591–1603

Hoegh-Guldberg, O., Hughes, L., McIntyre, S., Lindenmayer, D. B., Parmesan, C., Possingham, H. P., & Thomas, C. D. (2008). Assisted colonization and rapid climate change. Science, 321(5887), 345-346.

John Pedlar, Dan McKenney Canadian Forest Service, Natural Resources Canada CIF Lecture Series, November 15th, 2017

Millar, C. I., Stephenson, N. L., & Stephens, S. L. (2007). Climate change and forests of the future: managing in the face of uncertainty. Ecological applications, 17(8), 2145-2151.

Parmesan, C. (2006). Ecological and evolutionary responses to recent climate change. Annu. Rev. Ecol. Evol. Syst., 37, 637-669.

Rweyongeza, D. M., Barnhardt, L. K., & Hansen, C. R. (2011). Patterns of optimal growth for white spruce provenances in Alberta. Alberta Tree Improvement and Seed Centre, Alberta Sustainable Resource Development.

Schneider, R. R. (2013). Alberta's natural subregions under a changing climate: past, present, and future.

Wang, Y., Pedersen, J. L., Macdonald, S. E., Nielsen, S. E., & Zhang, J. (2019). Experimental test of assisted migration for conservation of locally range-restricted plants in Alberta, Canada. Global Ecology and Conservation, 17, e00572.