Co-seeding of grasses and forbs supports restoration: our new paper in Scientific Reports

Our new paper by Réka Kiss about our experiment testing priority effects in grassland restoration has recently been published in Scientific Reports.

The paper is open access and can be downloaded from the journal homepage (please click here).

Kiss, R., Deák, B., Tóth, K., Lukács, K., Rádai, Z., Kelemen, A., Miglécz, T., Tóth, Á., Godó, L. & Valkó, O. (2022): Co-seeding grasses and forbs supports restoration of species-rich grasslands and improves weed control in ex-arable land. Scientific Reports 12: 21239. https://doi-org/10.1038/s41598-022-25837-4 

Our aim was to test whether the timing of seed sowing has an effect on grassland recovery and to test how can we support the successful implementation of grassland restoration projects. Choosing the proper timing of seed sowing and the optimal amount and species composition of the sown seed mixtures are very important for maximising restoration success and saving costs.  The matrix of seed mixtures are generally the grass seeds, which have an important role in weed suppression. In large-scale restoration projects, it is not always possible to compose and use a diverse seed mixture in the entire area; thus, they often use low diversity grass seed mixtures. On the one hand, seed sowing of grasses leads to a rapid and predictable vegetation development, and we can expect a species-poor grass-dominated vegetation two or three years after seed sowing. On the other hand, increasing the diversity of these species-poor sown grasslands requires novel methods and a lot of extra work in the future.

In our project we sowed grass (Festuca pseudovina) seeds in 2014 and a diverse seed mixture (containing 20 forb species) in different combinations (together with the grass seeds, and 1, 2 and 3 years later). We studied the species composition of the developed communities and evaluated which solution is the best in terms of weed suppression.

Our results clearly showed that the best solution is sowing the diverse seed mixture together with the grass seeds. This treatment resulted in the most diverse vegetation, the lowest level of weed encroachment and the highest number of established target species. In large restoration sites, which are embedded in an agricultural landscape, the spontaneous establishment of target species is very unlikely, given their impoverished seed banks and the lack of propagule sources. In such areas, active introduction of target species is inevitable for restoring species-rich grasslands. Our results suggest that it is a much more practical and cost-effective solution to sow the diverse seed mixture together with the grass seeds, at the very first stage of grassland restoration.

Abstract

Sowing is widely used for the restoration of species-rich grasslands but still there are knowledge gaps regarding the most suitable application of different seed mixtures. We tested the effect of seed mixtures application timing on the establishment of sown forbs and weed control. 36 experimental plots with nine sowing treatments were established in an abandoned cropland in Hungary. Grass seeds, diverse forb seed mixture and the combination of the two were applied: diverse forb mixture was sown simultaneously or 1, 2 or 3 years after grass sowing, in plots sown previously with grass or in empty plots (fallows). All sowing treatments supported the rapid establishment of the sown species in large cover and hampered weed encroachment. Forbs performed better when sown into fallows than in grass-matrix and forbs establishment was worse in older fallows than in younger ones. Grasses expressed a strong priority effect, especially when forbs were sown at least two years later than grasses. We also investigated the relation between seed germinability, weather parameters and establishment success. Germination rate in the greenhouse could not predict the establishment success of forbs in the field and showed great differences between years, hence we recommend sowing target forbs in multiple years.