Winter warming pulses differently affect plant performance in temperate heathland and grassland communities
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Winter air temperature variability is projected to increase in the temperate zone whereas snow cover is projected to decrease, leading to more variable soil temperatures. In a field experiment winter warming pulses were applied and aboveground biomass and root length of four plant species were quantified over two subsequent growing seasons in monocultures and mixtures of two species. The experiment was replicated at two sites, a colder upland site with more snow and a warmer, dryer lowland site. Aboveground biomass of Holcus lanatus declined (−29 %) in the growing season after the warming pulse treatment. Its competitor in the grassland mixture, Plantago lanceolata, profited from this decline by increased biomass production (+18 %). These effects disappeared in the second year. There was a strong decline in biomass for P. lanceolata at the lowland site in the second year. These two species also showed a decline in leaf carbohydrate content during the manipulation. Aboveground productivity and carbohydrate content of the heathland species was not affected by the treatment. The aboveground effects of the treatment did not differ significantly between the two sites, thereby implying some generality for different temperate ecosystems with little and significant amount of snowfall. Root length increased directly after the treatment for H. lanatus and for Calluna vulgaris with a peak at the end of the first growing season. The observed species-specific effects emphasize the ecological importance of winter temperature variability in the temperate zone and appear important for potential shifts in community composition and ecosystem productivity.
KeywordsWinter warming Climate change Freeze–thaw Plant productivity Nutrient cycling
This study was funded by the German Science Foundation (DFG JE 282/5-1). We thank Anna Bischoff for analysing the root scans, and Elke and Stefan König for installing the field experiment.
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