Earlier flowering onset induced by air heating occurs only in certain grassland species in the Giessen T-FACE experiment

This study investigates the flowering onset of species in an extensively managed, temperate grassland under future atmospheric conditions. Free air CO2 enrichment experiments combined with a warming treatment via IR heaters (T-FACE) are state of the art for investigating future developments in terrestrial ecosystems. This study presents the first results of a new approach to T-FACE technology. In this experiment, the air temperature is increased directly via heating elements, thus creating more realistic environmental conditions for future climate studies. Plant phenology, a widely used indicator of changing environmental conditions, was therefore one of the first subjects to be investigated with the new system. Four grasses and five herbaceous plants were monitored several times a week for the onset of flowering over a period of five years. These were Arrhenatherum elatius, Holcus lanatus, Poa pratensis, Trisetum flavescens as well as Draba verna, Galium album, Geranium pratense, Glechoma hederacea and Sanguisorba officinalis. While significantly earlier flowering was observed in some species, other species showed no change in the onset of flowering. Results suggest that changes in the onset of flowering were mainly seasonal and independent of the functional plant group.