Introduction
White spruce (Picea glauca) is known as one of the most widely distributed and most commercially valuable native boreal forest species in North America, which across Canada and Alaska to the northern United States. In Canada, white spruce comprises roughly a quarter of Canadian forest inventory. In Alberta Province, Canada, white spruce is one of the most valuable commercial tree species, which accounts for around 30% of the local total forest inventory and 48% of the volume of coniferous growing stock (Power & Gills, 2006). Besides high commercial value, white spruce also plays a significant role in the local ecological system. A wide variety of wildlife species including moose, caribou, woodpeckers, and northern hawk owls use white spruce communities as habitat.
White spruce (Picea glauca) is known as one of the most widely distributed and most commercially valuable native boreal forest species in North America, which across Canada and Alaska to the northern United States. In Canada, white spruce comprises roughly a quarter of Canadian forest inventory. In Alberta Province, Canada, white spruce is one of the most valuable commercial tree species, which accounts for around 30% of the local total forest inventory and 48% of the volume of coniferous growing stock (Power & Gills, 2006). Besides high commercial value, white spruce also plays a significant role in the local ecological system. A wide variety of wildlife species including moose, caribou, woodpeckers, and northern hawk owls use white spruce communities as habitat.
Meanwhile, the distribution, growth, and establishment of white spruce is estimated to be affected by climate change. With warmer climatic condition, some studies recommended that white spruce populations may expand their current region into areas formerly covered by permafrost or move northward and higher elevation (Davis & Shaw, 2001; Payette & Filion, 1985). Other studies suggested that some white spruce populations can be negatively influenced by a warming and drying climate, combining with more extreme events like drought (Barber et al., 2000; Wilmking et al., 2004). Since climate change associated with long-term temperature increases and precipitation pattern changes will add challenges for forest management, a scientific-based guidance of choosing white spruce seed source is desperately needed to reduce the uncertainty and risks of the future. To make a better choice of seed source, we should increase our understanding of the relationship between white spruce growth and climate between provenances.
One well-recognized method to study intraspecific genetics variation patterns and related genetic-environment interaction is known as provenances trials, which populations of different geographical origin are planted under same environment condition. By provenance trials, previous studies on white spruce have indicated origin-related resistance index to white pine weevil (Alfaro et al., 1996), wood quality (Lenz et al., 2010; Beaulieu et al., 2002), and bud morphogenesis (Pollard & Logan, 1979). With same method, some other studies focused on survival and growth patterns (Lu et al., 2014; Li et al., 1997; Rweyongeza et al., 2007), budbreak time (Pike et al., 2017), photosynthetic-related traits (Benomar et al., 2016), and maladaptation risks (Gray et al., 2016) of white spruce for climate change adaptation.
Although provenance trail is one very common method, the provenance scale of the majority of current experiment is not large enough to represent the wide range of white spruce populations. Also, using tree ring widths to analysis white spruce growth-climate response between provenance is relatively rare. Analyzing tree ring widths is an effective approach to assess the tree growth. Since tree growth per year is a direct proxy for diameter increment; adverse climatic conditions are interpreted as a decline in tree growth and tree ring width, and suitable climatic conditions are associated with rising of tree ring width. Comparing with tree volume and diameter, wood cores are easier to collect and no need to measure every year. Each wood core can record the tree growth situation for decades with tree rings. Therefore, this study will explore the different growth-climate provenance responses by tree ring analysis. To assess climate and response of different white spruce provenance, this project will answer the following questions:
Although provenance trail is one very common method, the provenance scale of the majority of current experiment is not large enough to represent the wide range of white spruce populations. Also, using tree ring widths to analysis white spruce growth-climate response between provenance is relatively rare. Analyzing tree ring widths is an effective approach to assess the tree growth. Since tree growth per year is a direct proxy for diameter increment; adverse climatic conditions are interpreted as a decline in tree growth and tree ring width, and suitable climatic conditions are associated with rising of tree ring width. Comparing with tree volume and diameter, wood cores are easier to collect and no need to measure every year. Each wood core can record the tree growth situation for decades with tree rings. Therefore, this study will explore the different growth-climate provenance responses by tree ring analysis. To assess climate and response of different white spruce provenance, this project will answer the following questions:
- Are there differences in the tree ring width among provenances?
- If so, individuals from which provenance(s) have better performance?
- Are there differences in the tree ring width and climate relationships between provenances and regions?
Two possible results(see Flowchart 1):
- All white spruce population planting under identical climatic conditions will have the generally identical tree ring widths, which further indicate weak and insignificant growth-climate responses among provenances;
- White spruce has origin-specified tree ring widths and growth-climate relationships.