Flowering phenology of a herbaceous species (Poa annua) is regulated by soil Collembola

• Collembola can regulate flowering phenology of a plant species (Poa annua).
• The flower emergence of P. annua was advanced by 2 weeks in presence of Collembola.
• Collembola modified some biotic (fungal biomass) and abiotic soil properties.
• Collembola also contributed to impact P. annua morphology and physiology.

The role of soil organisms as possible driver of flowering has never been investigated. We hypothesized that Collembola (microarthropods) will change plant allocation to reproductive modes by changing soil nutrient availability. Individual seedlings of Poa annua   were planted in microcosms, in the presence or absence of Collembola. Collembola affected biotic (fungal biomass) and abiotic (N−NO3−N−NO3−, P2O5) soil properties and some morphological (number of leaves, root biomass) and chemical (C:N, K, Mg, N) traits of P. annua. As a result, flowering of P. annua was promoted by the presence of Collembola. This provides experimental evidence that soil microarthropods can affect the reproduction strategy and phenology of a plant.