Vortrag, 42. Jahrestagung der Gesellschaft für Ökologie (GfÖ), Lüneburg: 10.09.2012 - 14.09.2012
The role of diversity within versus among plant species in the response of plants to climate change has not yet been explored adequately. Here, frost following midwinter thaw events, which are expected to increase in frequency and duration due to climate change, was used as a climatic stressor to explore variation within and among species responses. Twelve ecotypes of Arrhenatherum elatius from 4 European countries and 7 grassland species (grasses, herbs, leguminous herbs) from one German location were grown from seed and acclimated to winter temperature (‐3°C) and light period in a growth chamber. In February, plants were thawed for 2 days or 6 days at 10°C, or subjected to control conditions, before being frozen to ‐10°C at 2°C/h, lasting 23 h in total. Direct root damage was assessed via plant ability to take up 15 N tracer. A second set of replicates for all treatments was transferred to a greenhouse and grown at 10‐15°C for three weeks. Development of cover and greenness over time were quantified by digital pictures. Aboveground (live and dead) and belowground biomass was measured. The variation in greenness and live above ground biomass were more than two‐fold greater within species compared to among species. There was an interaction between within‐species (ecotypic) and among‐species biomass and greenness responses, which was explained by higher frost sensitivity within A. elatius ecotypes than among species. Overall, compared with the control, the 2 day and 6 day thaw periods reduced live aboveground biomass by 17% and 59%, and increased dead biomass by 20% and 180% respectively. The results indicate that variation within a single plant species can be greater than variation among different plant species growing in one environment. This intraspecific variation should be considered in attempts to model the responses of species to climate change. The data further imply that increased variability in winter temperature conditions can result in considerably higher frost damage as plants lose frost hardiness during short warming phases.