Long‐term effect of mowing on the restoration of Pannonian sand grassland to replace invasive black locust plantation

Abstract

Invasive species are among the main threats to grassland biodiversity, and nature conservation management seeks the best methods to eliminate them and to restore natural habitats. We studied the long‐term effect of mowing on the restoration of Pannonian sand grassland after elimination of invasive black locust (Robinia pseudo‐acacia) plantation in Hungary, Europe. Stands of R. pseudo‐acacia at three sites were felled and stumps herbicide‐treated in the winter of 1994–1995. Mowing with hay removal treatment was applied twice a year in 1995–2001 to assist grassland recovery. A block of 12 adjacent plots of 10 m by 10 m was assigned for the experiment at each site, with six control (unmowed) and six treatment (mowed) plots randomly selected. Vegetation was sampled in June and August yearly in 1995–1999 in all sites, plus in seminatural reference grasslands then re‐sampled six times until 2017 in two sites. Herbicide application with repeated mowing successfully eliminated R. pseudo‐acacia. In the unmowed plots, dense woody cover developed at all sites. Vegetation of mowed plots approached the reference grasslands in sites with better propagule availability of target species according to trajectory analyses. In these sites, higher cover of target species was found in mowed compared to unmowed plots, though still significantly lower than in the reference. Mowed plots were more prone to secondary invasion than the unmowed. The long‐term monitoring revealed that initial mowing assisted the restoration of Pannonian sand grassland, but further management is needed to control secondary invasion and increase target species cover.

The present and future of grassland restoration

“…Key issues explored in the Special Issue include grazing (Blackburn et al 2021 b ), fire, mowing, land‐use legacies (nitrogen deposition, weed invasion), soil seed banks (Valkó et al 2021), and abandonment of disturbance (Hernandez et al 2021; Price et al 2021; Reis et al 2021; Valkó et al 2021; Blackburn et al 2021 b ). Although restored grasslands have a disturbance requirement, optimal management may differ in restored grasslands from reference sites due to differences in species composition, land‐use legacies, weed invasions, or other factors.…”

“…Generally, some disturbance is necessary in restored grassland assemblages to promote native target species and reduce exotic species. For example, Reis et al (2021) reported that mowing promoted native grassland species and eliminated a woody weed (in combination with herbicide), whereas dense woody cover developed in unmown plots. Assis et al (2021) also found disturbance was required to reduce exotic grasses in Cerrado grasslands.…”

“…Muted responses to the management of restored grasslands may be due to propagule availability; hence, grasslands are typically seed‐limited (Seabloom et al 2003). For example, Reis et al (2021) reported that the composition of mown restored grasslands was most similar to reference sites in sites that had greater propagule availability of target species. Hernandez et al (2021) suggested recovery of invaded serpentine grasslands with disturbance management was due to the presence of natives in the soil seed bank in sites with a shorter period of invasion than in other regions.…”

“…Many of the papers in this Special Issue highlight the importance of long‐term management and monitoring to determine optimal management strategies. In most cases, abandonment of management negatively affected restored grasslands compared to grazing, fire, and/or mowing (Hernandez et al 2021; Price et al 2021; Reis et al 2021; Valkó et al 2021). Hence, restoration projects should ensure that resources are available for ongoing management at the planning stages.…”

“…Additionally, monitoring needs to be long term, because short‐term monitoring may lead to different conclusions about management efficacy. For example, Reis et al (2021) found that mowing was an effective post‐restoration management technique in the long term, while short‐term monitoring (3–5 years) would have concluded a failure of mowing.…”