Are no-analog climates in balsam poplar’s (Populus balsamifera) future (and past)?

Background/Question/Methods

Because current climates may only represent a subset of the climates a species is adapted to, understanding past climates can provide a fuller view of the climatic tolerances of a species. This can provide unique insights into how species may respond to future changes in climate.  If, for instance, future climates were to shift in the direction of climates a species has experienced in the past, it’s possible the species may be preadapted to future climates.  Conversely, if the future climate shifts in a direction the species has not experienced, the species may be adversely affected.  We used balsam poplar (Populus balsamifera) as a case study to determine if the climates its populations have experienced since the last glacial maximum differ from currently available climates as well as future climates.  Using ordination, we compared paleo-climatic conditions over the past 22 kya at sites containing balsam poplar fossil pollen to current climates experienced by balsam poplar.  

Results/Conclusions

The ordination analysis showed that fossil pollen sites largely fall within the current climatic space occupied by balsam poplar.  Pollen sites, however, tend to be underrepresented in the warmest climates where balsam poplar is currently present.  Furthermore, climate at some pollen sites had no modern analog in North America.  These no-modern-analog climates tended to have higher average water deficit and evapotraspiration.  Furthermore, we found that the climate conditions currently experienced by balsam poplar fall nearly entirely within all climates available within the last 22 kya, suggesting that the climate balsam poplar currently experiences has been continually available since the last glacial maximum.  Our analyses also show that future climates are predicted to shift away from those no-analog climates experienced at some pollen sites and that within 100 years, some climates currently experienced by balsam poplar may have no analog in North America.  Our results could have important implications for understanding the effects of future climate change on balsam poplar.