Interannual and spatial variability of maple syrup yield as related to climatic factors

Abstract

Sugar maple syrup production is an important economic activity for eastern Canada and the northeastern United States. Since annual variations in syrup yield have been related to climate, there are concerns about the impacts of climatic change on the industry in the upcoming decades. Although the temporal variability of syrup yield has been studied for specific sites on different time scales or for large regions, a model capable of accounting for both temporal and regional differences in yield is still lacking. In the present study, we studied the factors responsible for interregional and interannual variability in maple syrup yield over the 2001–2012 period, by combining the data from 8 Quebec regions (Canada) and 10 U.S. states. The resulting model explained 44.5% of the variability in yield. It includes the effect of climatic conditions that precede the sapflow season (variables from the previous growing season and winter), the effect of climatic conditions during the current sapflow season, and terms accounting for intercountry and temporal variability. Optimal conditions for maple syrup production appear to be spatially restricted by less favourable climate conditions occurring during the growing season in the north, and in the south, by the warmer winter and earlier spring conditions. This suggests that climate change may favor maple syrup production northwards, while southern regions are more likely to be negatively affected by adverse spring conditions.

Impacts of Climate Change on the Timing of the Production Season of Maple Syrup in Eastern Canada

“…The period of syrup production [ 4 ] as well as the annual yield [ 5 , 6 ] have been shown to depend on climatic conditions, and therefore vary between years and regions. Recently, sugar maple producers in the province of Québec (which is responsible for 75% of the world production) have expressed concerns about the high year to year variability in the timing of the season (Houle, unpublished data).…”

Managing for delicious ecosystem service under climate change: can United States sugar maple (Acer saccharum) syrup production be maintained in a warming climate?

“…In fact, our results of projected changes in habitat are strongly associated with the projected reduction of the number of days to reach 75 growing degree days (GDD75). This relationship indicates a consistent pattern of reduction of habitat related to a loss in days to GDD75, a strong predictor of variability in syrup production across the United States and Canada (Duchesne & Houle 2014). Further, changes in GDD75 show greater magnitude of change toward the southern extent of sugar maple where the production season is already constrained by temperature ( Figure 6).…”

“…Because the current cohort of sugar maple trees live a long time and a significant portion of them will still be present in 2100, and because over 680 million trees exist in the next smaller cohort not yet optimal for tapping (but many will be in this century (Table 2)), and because technologies to increase sap harvest are improving, it is not unrealistic to assume some increased level of tapping and production can be sustained over the next few decades. However, with the reality that sap flow seasons are likely to be diminished especially in the southern portion of its range (Duchesne & Houle 2014;Skinner et al 2010), and that sugar maple trees growing in these southern zones face higher climate change risk and pressure, even these new cohorts may provide limited opportunity to increase, or even in some cases, maintain syrup production in these areas. In contrast, in northerly areas where habitat appears to be stable or improving (much more so under the mild scenario of climate change as compared to the harsh scenario), there may be increased opportunities for maple syrup with the new cohort of trees coming up and the remaining large untapped potential of trees (Figure 2, Figure 3).…”

“…Houle et al (2015) suggest that this can be compensated for by matching this phenological shift by shifting the season up to 19 days earlier in the coming decades, a result consistent with our predicted change in GDD75 under GFDL-A1Fi of 22 days by the end of the century. However, it is also important to consider climatic conditions throughout the year, including not only the growing season conditions, where new growth and hence resources are generated in the tree for future sap production, but also winter conditions which need to be cold enough to support strong carbohydrate concentrations (Duchesne & Houle 2014). In the end, it is both seasonal and year-long processes that are required to produce profitable maple syrup, and uncertainty around how climate conditions may change on a daily and seasonal basis could greatly influence future realities for maple syrup production.…”

“…However, this shift is not expected to occur uniformly across the range of sugar maple. Southern latitudes have the potential of shifting to climates where optimal sap flow days are curtailed by too few cold day-warm night cycles (Duchesne & Houle 2014). The contrast between northern and southern potentials for sap production going forward with intensifying climate change suggests that a broad-scale analysis of both potential for maple syrup and climate change impacts on tree species habitats is needed.…”