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Winter warming pulses affect the development of planted temperate grassland and dwarf-shrub heath communities

Background: Winter conditions are changing considerably due to climate change. Resulting alterations in the frequency of soil freeze–thaw cycles (FTCs) are ecologically important. Aim: We quantified the impact of winter soil-warming pulses on the community structure of temperate plant communities. Methods: The cover of vascular plant species in two vegetation types, each at three diversity levels, was recorded 1 year before to 3 years after an FTC-manipulation that added five additional FTCs. Changes in species abundance patterns (Bray–Curtis similarity) were analysed by linear mixed effect models. Results: Communities exposed to additional FTCs showed less change in their species abundance patterns than the reference plots. Community development in the grassland differed between the FTC-manipulation and the reference plots in the first growing season after the FTC-manipulation, but such effects disappeared over time, whereas the divergence from the reference plots in the dwarf-shrub heath started in the second year after the FTC-manipulation and effects grew over time. Responses to FTCs were related to growth forms: some grasses increased after the FTC-manipulation, whereas the cover of dwarf shrubs was reduced. There was less change in species abundance distributions in the more diverse communities with legumes present. Conclusions: Winter climate change is a critical driver of temperate ecosystems. Short-term climatic events can have long-term implications on the structure of ecosystems. Community composition regulates alterations in the development and competitive balance of plant communities caused by soil warming pulses.