The responses of temperate and sub-arctic bryophytes to changing environmental conditions

Abstract

Climate change presents a serious threat to many global ecosystems. Warming is predicted to be greatest at high latitudes, where increased temperatures are expected to lead to a longer growing season and an increased incidence of potentially damaging winter freeze-thaw events. The impact of these environmental changes on the native flora is not yet fully understood. The bryophytes are an ancient group of non-vascular plants which often form a large proportion of the plant community in the arctic and boreal regions. The response of these organisms to climate change has often been overlooked, despite the significant role they play in carbon uptake and storage in many ecosystems.
The study used infra-red gas analysis to measure the change in net photosynthesis and respiration rates in several bryophyte species in response to changing microclimate. Experiments were conducted under controlled laboratory conditions using samples of the common moss species Polytrichum juniperinum, Hylocomium splendens and Aulacomnium palustre, collected from the North Pennines, UK. Additional measurements of gas exchange rates in the species Hylocomium splendens, Aulacomnium turgidum and Tomentypnum nitens were taken at a site near Inuvik, NWT in the Canadian arctic.
The results of the study support the existing evidence that many bryophyte species are adapted to photosynthesis at low temperatures (<10°C), and are therefore unlikely to benefit from an increase in summer temperatures in terms of carbon uptake and growth. The study also found evidence that cycles of freezing and thawing during the winter and early spring cause a significant reduction in carbon uptake in both P. juniperinum and H. splendens compared to a single period of sub-zero temperatures. This damage was reduced in P. juniperinum when the plants were air-dry at the time of freezing. The data arising from this study are important to improve existing models of carbon exchange in bryophyte-dominated ecosystems.