Simulating the germination response to diurnally alternating temperatures under climate change scenarios: comparative studies on Carex diandra seeds

Abstract

Background and Aims Environmental temperature regulates plant regeneration by seed in several superimposed ways, and this complex regulation will be disrupted by climate change. The role of diurnally alternating temperatures (ΔT) in terminating dormancy will be a major player in this disruption, as its effects on seed germination are immediate. Methods We modelled the effect of ΔT on seed germination comparing two populations of the wetland sedge Carex diandra. We fitted a cardinal-temperature model to germination results in a thermal gradient plate, and used the model to simulate changes in germination under two representative concentration pathways scenarios (RCP2.6 and RCP8.5). Key Results Increasing ΔT decreased the base temperature for germination and the thermal time required for germination. RCP2.6 projected moderate increases in average temperatures and ΔT, whereas RCP8.5 projected higher warming and ΔT. The higher ΔT effect together with the warmer temperatures increased seed germination in both scenarios. By considering the effects of ΔT, the model projects considerable increases in germination. Conclusions Carex diandra germination will be very responsive to potential changes in ΔT as a consequence of climate change. This research highlights the role of ΔT in seed responses to climate change. Comprehensive cardinal-temperature models, encompassing the different effects of temperature on seed germination, are needed to understand how climate change will affect plant regeneration.