Green hay transfer for grassland restoration: species capture and establishment

Green hay transfer from species-rich donor sites is now commonly used in Europe to restore species-rich semi-natural grassland, both on ex-arable land and on former intensive grassland. However, species transfer rates are usually well below 100%, and due to lack of further colonization by additional target species after initial restoration, continued progress toward the target plant community is often very slow. We used data from a restoration experiment aiming to reestablish species-rich grazed meadows of the MG5 grassland type according to the British National Vegetation Classification to investigate relationships between species abundance at a donor site, species capture by green hay and its seed content, and success of species establishment on experimental plots in formerly intensively managed species-poor grassland undergoing restoration. Our results show that species with higher abundance at the donor site were more likely captured as seed in green hay, and were more likely to establish after hay application at the recipient site. Species with low abundance at the donor site that also possessed specific germination requirements that might prevent immediate establishment after green hay transfer were particularly unlikely to get established after transfer. These findings can provide guidance for additional measures aimed at ensuring establishment of a wider range of target species. Such measures could include targeted sowing of species in addition to green hay application, and management of restored grassland swards to extend or reopen an initial window of opportunity for the establishment of green hay species that might not be germinable immediately after hay transfer.

Automated summary

The study found that species with higher abundance at the donor site were more likely to be captured as seed in green hay and establish after transfer, while species with low abundance at the donor site and specific germination requirements were less likely to establish immediately after transfer. These findings can guide additional measures to ensure establishment of a wider range of target species in grassland restoration.