Hay transfer is a nature-based solution for grassland restoration: our new paper in Journal of Environmental Management

Our paper has recently been published in Journal of Environmental Management.

Valkó, O., Rádai, Z., Deák, B. (2022): Hay transfer is a nature-based and sustainable solution for restoring grassland biodiversity. Journal of Environmental Management 311: 114816. https://doi.org/10.1016/j.jenvman.2022.114816 [IF2020: 6.789]

The paper is open access, and can be freely downloaded from here.

As we enter the United Nations Decade on Ecosystem Restoration, it became more important than ever to find nature-based solutions for the restoration of grasslands across the globe. Hay transfer is a promising restoration method that builds on locally available propagule sources. The idea of hay transfer is the relocation of plant material from a donor site to the restoration site, which serves a double aim by introducing target species and suppressing weeds. 

We tested the applicability of hay transfer in restoring species-rich grassland in a former cropland in Hungary, over six years of post-restoration monitoring. The study site was a really interesting and spectacular place: an ancient earth fortress built by the Sarmatians in Tápióság, Central-Hungary. The steep slopes of the earthwork could escape from being ploughed and therefore the grasslands on the slopes still harbour an outstandingly species-rich vegetation with many rare and protected species. However the plateau of the earthwork has been used for intensive agriculture for centuries, which posed a considerable threat for the grasslands on the slopes. That is why the Danube-Ipoly National Park Directorate carried out a restoration project in the framework of the EU LIFE project ‘Conservation of dry grasslands in Central-Hungary’ (LIFE12 NAT/HU/001028) with the aim to restore grasslands on the plateau and to create a buffer zone that can protect the grasslands on the slopes.

Agropyron cristatum and Marrubium peregrinum in the grasslands on the slopes.

Species-rich grassland on the steep slope.

We monitored the vegetation development of the restored site for six years. We found that six years after restoration, a species-rich grassland developed with 42 successfully established specialist species that had a cover of 45%. It was spectacular to see the year-by-year development of the grasslands and the increasing populations of the protected species, such as Centaurea sadleriana, Inula germanica and Ajuga laxmannii.

In the first year after hay transfer, the vegetation was mainly characterised by weeds and a high cover of the spread hay.

We were also interested in the origin of the established target species. Therefore we sampled the plant species composition of the three donor sites (from where the hay originated) and the area surrounding the restoration site (from where target species might be dispersed to the restoration site). We found that most specialist species became established from the hay from the second to the sixth year, but the surrounding areas also provided additional propagule sources. We were also interested in the characteristics that make target species successful colonizers. Among the eight analysed functional traits, seed mass of the transferred species was the best predictor of the establishment of specialists, and we found that small-seeded species had an establishment advantage in the first years after restoration.

Our results suggest that hay transfer can be a suitable nature-based solution for local grassland restoration projects and its potential should be utilized especially in regions where suitable donor sites are present in sufficient quantity and quality. With this method, we can ensure the conservation management (cutting) of the donor site and can also support the development of the target vegetation at the restored site.

Successfully recovered grassland six years after the hay transfer. In the foreground, there are flowering specimens of the protected and endemic Centaurea sadleriana.