Post-restoration vegetation and seed bank dynamics: New paper in Restoration Ecology

Our new paper about the effects of post-restoration management on vegetation and seed bank dynamics has recently been accepted in Restoration Ecology.

The citation of the paper is:

Valkó, O., Deák, B., Török, P., Tóth, K., Kiss, R., Kelemen, A., Miglécz, T., Sonkoly, J., Tóthmérész, B. (2020): Dynamics in vegetation and seed bank composition highlight the importance of post-restoration management in sown grasslands. Restoration Ecology doi: 10.1002/rec.13192

The paper is freely available in the journal homepage (please click here to access the paper).

Sowing low-diversity grass seed mixtures is a widely available, and feasible tool for restoring large grassland areas within a relatively short timeframe. After seed sowing, a weed-dominated vegetation is typical in the first years, which is replaced by a dense and species-poor vegetation characterised by the sown grasses from the second or third year after restoration. Even though the aboveground vegetation is usually species poor, the seed bank is quite diverse, as it still holds the legacy of the former degradation in terms of the dense seed bank of weeds (see our former study, Török et al. 2012). This is very important from the conservation point of view as these weed seeds can be easily 'activated' and germinate in case of degradation, improper management or abandonment. In a former study we found that even is succesfully restored grasslands, the cessation of management can lead to severe degradation within a few years (Kelemen et al. 2014).

 

After grassland restoration by seed sowing, a weed-dominated vegetation is typical in the first year.

The sown grasses can successfully replace the weeds aboveground: two or three year after restoration, a perennial-dominated dense sward is typical.

 

Unfortunately the weeds do not disappear completely: they are the dominant species in the soil seed bank.

In the current study we tested the effects of post-restoration management (mowing vs. abandonment) on the vegetation and seed bank of alkaline and loess grasslands, which were restored during one of the largest grassland restoration projects in Europe, where seeds of native grasses were sown (LIFE 04 NAT HU 119, ‘Grassland restoration and marsh protection in Egyek-Pusztakócs’ LIFE project). This study system offered a unique opportunity for testing the effects of post-restoration management on the vegetation and seed bank of two different types of restored grasslands. We found that the seed bank of the restored grasslands were still dominated by weeds, even eight years after restoration. Abandonment had a larger effect on the seed bank, than on the vegetation: the seed density of sown grasses and target species decreased, while that of weeds increased due to abandonment.

Our results suggest that seed sowing of grass mixtures is a feasible tool for restoring grasslands at large scales. However, the resulting vegetation usually has low biodiversity, and a high density of weed seeds is accumulating in the soil seed bank even several years after the restoration. Therefore, post-restoration management is necessary for suppressing weeds both above- and belowground.  We recommend designing the long-term management of grassland restoration sites already when planning the restoration projects to ensure the management plan is ecologically and economically feasible.  We also suggest that complementing the monitoring of vegetation development with the analysis of soil seed banks is important for evaluating long-term restoration success.

Abstract

Sowing grasses supports the rapid development of a closed perennial vegetation, which makes the method universally suitable for fast and effective landscape-scale restoration of grasslands. However, to increase their diversity and to create a natural-like species-rich grassland is a challenging task. Understanding the role of seed bank compositional changes and vegetation dynamics can help to design management regimes that support the establishment of target species and suppress unwanted weeds. Our aim was to reveal the effect of post-restoration management on the vegetation and seed bank dynamics in grasslands restored in one of the largest European landscape-scale restoration project. Eight years after restoration, we sampled the vegetation and the seed bank in 96 quadrats located in 12 restored grasslands in the Great Hungarian Plain. In each grassland stand, we studied and compared a mown (mown from Year 1 to Year 8) and an abandoned plot (mown from Year 1 to Year 3 then abandoned from Year 4 to Year 8). Mown and abandoned plots showed divergent vegetation and seed bank development. Abandonment led to the decline of sown grasses and higher cover of weeds, especially in the alkaline grasslands. Our study underlined that the developing seed bank had a limited contribution to the maintenance of biodiversity in both grassland types. We found that five years of abandonment had a larger effect on the seed bank than on the vegetation. We stress that long-term management is crucial for controlling the emergence of the weeds from their dense seed bank in restored grasslands.