Contrasting sensitivity to extreme winter warming events of dominant sub‐Arctic heathland bryophyte and lichen species

• DOI: 10.1111/j.1365-2745.2011.01859.x
• Publication Date: 2011-06-22T09:49:17Z
• Authors: Jarle W. Bjerke; Stef Bokhorst; Matthias Zielke; Terry V. Callaghan; Francis W. Bowles; Gareth K. Phoenix
• Keywords: Bryophyte; Growing season; Subarctic climate

Summary 1. Climate change in northern high latitudes is predicted to be greater winter rather than summer, yet little known about the effects of climate on ecosystems. Among unknowns are an increasing frequency acute, short‐lasting warming events. Such events can damage higher plants exposed warm, then returning cold, temperatures after snow melt, and it not how bryophytes lichens, which considerable ecological importance high‐latitude ecosystems, affected by such However, even physiological adaptations these cryptogams environments general poorly understood. 2. Here we describe findings from a novel field experiment that uses heating infrared lamps soil cables simulate acute mid‐winter sub‐Arctic heath. In particular, report growing season responses dominant lichen, Peltigera aphthosa , bryophyte, Hylocomium splendens three consecutive winters. 3. While summertime photosynthetic performance P. was unaffected treatments, H. showed significant reductions net rates growth (of up 48% 52%, respectively). Negative were evident already during summer following first event. 4. lichen develops without going through critical phenological stages vulnerable organs produced, moss has seasonal rhythm, includes initiation young, freeze‐susceptible shoot apices early season; might damaged breaking dormancy warm 5. Synthesis. Different sensitivities bryophyte species unexpected, illustrate very ecology lichens cold biomes general. sharp contrast experiments show increased vascular plant biomass reduced biomass, results demonstrate may readily tolerated previously observed sensitivity co‐occurring dwarf shrubs, suggesting compensate for (or reverse) declines resulting warming.