Interactive effects of photoperiod, soil moisture and carbon dioxide of ecophysiological traits of yellow birch (betula alleghaniensis)

Abstract

Climate change is expected to drive tree migration, a phenomenon of significant ecological importance. The projected northward migration of boreal and temperate trees by 10°N in the next century, due to increasing atmospheric carbon dioxide [(CO2)] concentration, will likely expose them to new set of environmental conditions. These conditions, such as photoperiod regime and soil moisture availability, will likely influence eco-physiological traits in trees. The ability of these migrating trees to acclimate to these new conditions will be essential in determining the limit and success of their migration. In this study, I investigated the interactive effects of (1) elevated carbon

dioxide and photoperiod and (2) elevated carbon dioxide and soil moisture regime on the eco- physiological response of yellow birch (Betula alleghaniensis) seedlings, research that holds

significant implications for our understanding of tree species migration and climate change.

Seedlings were exposed to factorial combination of two levels of [CO2] (400 vs. 1000 μmol mol- 1

) and two soil moisture regimes (well-watered (WW) vs. drought stress (DS)), and factorial combinations of two levels of CO2 and three photoperiods (45° (seed origin) 50° and 55°N latitudes)). In the first set of experiments, we observed that elevated carbon dioxide and longer photoperiod significantly decreased electron transport rate (Jmax) and ratio of electron transport rate to carboxylation rate (Jmax/Vcmax). Total leaf area (TLA), specific leaf area (SLA), leaf dry mass (LEAFDM) and total seedling dry mass (TSDM) were significantly increased under elevated carbon dioxide and longer photoperiod. Furthermore, the phenological study of yellow birch revealed that the timing of bud set and leaf senescence was delayed at (P50) and advanced at the longest photoperiod of 10°N (P55). Yellow birch might not tolerate freezing temperatures when exposed to (-45°C). This could reduce the cold hardiness performance of yellow birch in response to a changing climate. These findings open new avenues for future research in understanding the complex interplay between climate change, tree physiology, and species migration. In the second experiment, a significant interaction effect was observed between soil moisture and carbon dioxide on height growth and specific leaf area (SLA). Drought stress significantly decreased tree height and SLA under elevated carbon dioxide. Also, drought stress and elevated carbon dioxide significantly increased root dry mass (ROOTDM), root mass ratio (RMR), maximum electron transport rate (Jmax) and ratio of electron transport rate to carboxylation rate (Jmax/Vcmax). These findings underscore the potential implications of climate change on tree species survival, advocating immediate action to mitigate its effects.