Examining adaptation to climate change in the water use patterns of boreal bog trees

Abstract:

The SPRUCE experiment has been running for 5 years now. The canopy-high open top enclosures facilitate an unprecedented evaluation of a native ecosystem’s response to climate change through whole ecosystem warming and elevated CO₂ manipulation. Initial plant physiology work from the experiment has documented divergent water use strategies between the two dominate tree species. Water potential and sapflow data indicated larch (L. laricina) has increasing transpiration rates with warming treatment, in turn increasing plant water stress. In contrast, spruce trees (P. mariana) have tight stomatal control, leading to declining rates of transpiration with warming in the first year and no response in the second year of treatment. We also know elevated CO₂ conditions increased water use efficiency in both species.

We want to know how the water strain from warming and the easier carbon payload of eCO₂ treatments will interact. Will larch’s propensity to lose water persist as it puts on new needles and xylem tissues each year? Will the more conservative spruce risk carbon starvation, or adjust its stomatal response? And will a competitive edge emerge upsetting the balance of power between this long-time niche companion? In this study, we investigate environmental controls on diurnal and annual patterns of transpiration and stomatal regulation. We test the interactive effects of warming and eCO₂ on phenology and productivity potential. And we use interannual sapflow data to assess the level of physiological adaptation of bog trees to climate change conditions.