Long-Term Warming and Nitrogen Addition Regulate Responses of Dark Respiration and Net Photosynthesis in Boreal Bog Plants to Short-Term Increases in CO2 and Temperature

Abstract

Boreal bog plants adapted to cold and low available nutrient conditions might be strongly affected by global changes, including elevated CO2 (eCO2), warming (W), and increasing nitrogen (N) availability. Here, we examined responses of dark respiration (Rd) and net photosynthesis (Anet) in four dominant bog plants to five levels of short-term increases in both CO2 and temperature (CTI); and the effects of long-term (6 years) W and N addition on these responses. Results indicated that CTI increased Rd; meanwhile, the increase of these environmental variables decreased Anet in all these boreal bog plants. Long-term nitrogen addition simulated the increases of Rd and decreases of Anet in Trichophorum cespitosum. Long-term warming mitigated the increases of Rd in Andromeda glaucophylla and Gaylussacia bigeloviana, and the decrease of Anet in Gaylussacia bigeloviana. These findings highlight the importance of long-term warming and nitrogen addition in regulating responses of boreal bog plants to short-term CTI, suggesting the necessity to investigate the long-term effects of these environmental changes when projecting responses of boreal bog vegetation to global changes.