The researchers at the Momentum Seed Ecology Research Group of the ELKH Centre for Ecological Research (CER) have demonstrated the suitability of grassland reconstruction for the restoration of landscape scars caused by human activities. They tracked the dynamics of artificially created grassland patches for several years and found that greater effort invested in the early stages of grassland restoration pays off in the long run, leading to the development of species-rich grassland communities and effective weed control through simultaneous sowing of grasses and forb species in fallow lands. The researchers aimed to determine the best timing for sowing grasses and forbs to achieve the highest possible species richness, enhance forb establishment, and hamper weed encroachment. The paper, which was published in the Scientific Reports journal, provides insights into successful grassland restoration techniques.
The members of the Momentum Seed Ecology Research Group followed the vegetation dynamics of artificially created grassland patches for several years. The researchers found that in the course of grassland restoration, efforts at the beginning pay off: the simultaneous sowing of grasses and forbs in fallow lands leads to the development of species-rich grassland communities and efficient weed control.
The aim of ecological restoration is to recreate something that has been lost or has deteriorated. Grassland restoration aims to recreate grassland ecosystems and communities. In many cases, it is not possible to recreate the original ecosystem, but restoration can still help to cover landscape scars created by human activities. Restored grasslands not only improve landscape aesthetics but also offer many different ecosystem services (e.g., foraging for livestock, nectar for pollinators, effective carbon capture and storage, and soil erosion control).
When grassland restoration is carried out with seed sowing, the success of restoration depends on many factors, such as the identity of sown species, the timing of sowing, and the quantity, quality, and proportion of sown seeds. In the current study, the researchers aimed to find the best timing to sow grasses and forbs to achieve the highest possible species richness, enhance forb establishment, and hamper weed encroachment.
"The matrix of the grasslands is composed of grasses. Previous works found that sowing grass seeds certainly results in a closed grass sward within a few years and also hampers weed encroachment. This is why grass sowing is preferred in landscape-scale restoration works. But it also has its drawbacks: the new grassland will be species-poor, as the closed grass sward hampers the establishment of other grassland species," explained Réka Kiss, the first author of the paper published in Nature - Scientific Reports.
To create species-rich grasslands, the use of diverse forb seed mixtures is needed. However, the compilation or production of such seed mixtures requires more effort (seeds of more species are needed in good quality and high quantity). As a result, a diverse seed mixture is less likely to be used in the early stages of restoration. In later stages, however, it will require more effort from practitioners to secure the successful establishment of species.
"We were curious about the most suitable timing: If we want to sow both grasses and forbs in a fallow for a species-rich grassland, what is the time-lag where we can achieve the most with the least effort?" explained Réka Kiss. "At the beginning of the experiment, we created 36 patches in a recently abandoned land. We sowed exclusively grass seeds, exclusively diverse forb seed mixture (20 species), or both of them into the patches. When we combined grass with the forb seed mixture, we sowed them simultaneously, while the diverse seed mixture was sown with a delay of one, two, or three years."
By following the development of the patches for several years, the researchers found that the best results were achieved when seeds were sown simultaneously, without any time-lag. In such patches, species richness was the highest, the weeds were less successful, and the establishment success of sown forb species was the most successful. This is the most cost-effective and most successful method among the studied sowing regimes. If simultaneous sowing is not possible, sowing forbs one year later than grasses is still effective. However, after one year, the advantage received by grasses cannot be overcome by the forbs, and their successful establishment in later stages can only be promoted by active interventions.
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. Doi: 10.1038/s41598-022-25837-4