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Halting the loss of grassland biodiversity and restoring degraded ecosystems are high priority tasks in the EU Biodiversity Strategy. Sowing low-diversity seed mixtures is widely used in grassland restoration because of its high predictability and fast, promising results. Generally, the sown perennial grasses establish within a few years and form a dense sward, which effectively suppresses weeds. Unfortunately, these grasslands are often species-poor because the sown grasses hamper the colonisation of target grassland forbs. Our aim was to test a novel approach to increase the diversity of species-poor grasslands. We selected eight 8-year-old grasslands restored by low-diversity seed sowing where we created 32 establishment gaps by breaking up the grass sward and sowing a high-diversity seed mixture (35 native species). Altogether, we established three grazed gaps (1m × 1m, 2m × 2m and 4m × 4m) and one fenced gap (4m × 4m) per site and monitored the presence and abundance of sown and non-sown species within a time frame of two years. We asked the following questions: (1) Which target species establish most successfully? (2) What is the effect of establishment gap size on the establishment success of target species and weeds? (3) What is the effect of management (grazed versus not managed) on the species composition of the establishment gaps? Our results showed that by creating establishment gaps and sowing diverse seed mixtures, we were able to overcome microsite and propagule limitation, successfully introducing target species into the species-poor grasslands. We found that all sown species established in the gaps, and the majority of the species maintained or even increased their first-year cover in the second year. Smaller gaps were characterised by lower cover of sown species and a quite stochastic development compared to the larger ones. Weed cover was moderate in the first year and decreased significantly in the second year, regardless of gap size. Therefore, in restoration practice, the use of larger establishment gaps is recommended. We found that the cover of sown species and weeds were similar in the grazed and unmanaged gaps during our study. However, management by extensive grazing might be crucial in the long-term because livestock can disperse target species propagules and create microsites. Our study shows that establishment gaps can serve as biodiversity hotspots. Further studies need to clarify to what extent they can improve the restoration success across the entire grassland.
Extensively managed pastures harbour rare and endangered species and have a decisive role in maintaining grassland biodiversity. Traditional herding of local robust cattle breeds is considered as a feasible tool for preserving these habitats. We studied the scale-dependent effects of grazing on the species richness and composition of three dry grassland types in the Great Hungarian Plain: Achilleo setaceae-Festucetum pseudovinae and Artemisio santonici-Festucetum pseudovinae alkaline grasslands, and Potentillo arenariae-Festucetum pseudovinae sand grassland. We asked the following questions: (1) Does extensive grazing have a scale-dependent effect on plant species richness of alkaline and sand grasslands? (2) How does grazing affect the proportion of specialists, generalists and weeds in the three grassland types? We sampled ten sites of each grassland type, including five extensively grazed and five non-grazed sites (altogether we had 30 sites). We used a series of nested plots each consisting of 10 plots from the size of 0.01 m² to 16 m². We revealed that grazing has contrasting effects in the three grassland types, and had a considerable effect on their species richness even at small scales. In both alkaline grassland types, total species richness was overall higher in grazed plots but it increased in a similar manner for both ungrazed and grazed habitats across plot sizes. Small-scale heterogeneity likely due to the uneven distribution of grazing, trampling and defecation together with mitigated rate of competition allowed more species to co-exist even at small scales in grazed alkaline grasslands. Grazing increased the richness of specialists, but likely due to the salt stress, establishment of weeds was hampered. Open gaps formed by trampling likely supported the establishment of several specialist species such as Plantago tenuiflora and Puccinellia limosa which are typical to open alkali grasslands. Contrary, in sand grasslands, we did not detect any effect of grazing on total species richness, likely due to the adverse effect of grazing on the species richness of specialists and weeds. In contrast with the former findings we detected significantly higher species richness in 0.01 m² and 0.0625 m² plots in the grazed sand grasslands, but found no differences at larger scales. Whilst species richness of specialists was significantly decreased, richness of weeds was increased by grazing. Decrease in the specialist species richness was likely due to the lack of their evolutionary adaptation to grazing. Degradation caused by grazing and trampling together with the propagule pressure from the neighbouring anthropogenic habitats resulted in an increased richness of weeds in the grazed sites.
Understanding plant-plant interactions is essential in planning and implementing effective grassland management strategies. Positive and negative interactions generally co-occur in plant communities and the net effect of these interactions may depend on the disturbance regime, including grazing. Shrubs can act as biotic refuges by physically protecting neighbouring plants from herbivores. As a result, we would expect that in pastures the diversity and flowering success of plants is higher in the close vicinity of shrubs compared to the open vegetation. Nevertheless, we can also assume a competitive trade-off cost for plants that grow together with shrubs. In this study, we assessed the small-scale effects of dwarf shrubs (30–40 cm in diameter) on species density and flowering success. Specifically, we considered three types of microsites: (i) shrub interior, (ii) edge of shrub, and (iii) open pasture (more than 2 meters away from the shrub). We surveyed these three types of microsites using 10 × 10 cm sized plots both in grazed and ungrazed meadow steppe, in central Hungary. The highest species density was found at the edge of shrubs, both in grazed and ungrazed vegetation. Meanwhile, species density did not differ significantly between shrub interiors and the open pasture. However, in grazed vegetation, species flowering success was significantly higher in shrub interiors and edges than in the open pasture; no significant trend was observed for this measure in ungrazed vegetation. In contrast to previous studies, we did not detect a competitive effect of small-sized shrubs on plants in ungrazed vegetation. Our results indicate that small-sized shrubs protect other plants from herbivores and that the edge effect plays an important role for the maintenance of small-scale species diversity in pastures. Overall, our results underline the beneficial effect of biotic refuges in pastures and we suggest that retaining a sparse population of small-sized native shrubs is advantageous from a conservation point of view.
Knowledge about the drivers of vegetation dynamics in grasslands is fundamental to select appropriate management for conservation purposes. In this study, we provide a detailed analysis of vegetation dynamics in alkali grasslands, a priority habitat of the Natura 2000 network. We studied vegetation dynamics in five stands of four alkali grassland types in the Hortobágy National Park (eastern Hungary), between 2009 and 2011. We analysed the effect of fluctuations in precipitation on both the overall vegetation composition and on the cover of each species using Self Organizing Map neural networks (SOM). We found that SOM is a promising tool to reveal plant community dynamics. As we analysed species cover and overall vegetation composition separately, we were able to identify the species re-sponsible for particular vegetation changes. Fluctuations in precipitation (a dry season, followed by a wet and an average season) caused quick shifts in plant species composition because of an increasing cover of halophyte forbs, probably because of salinisation. We observed a similar effect of stress from waterlogging in all studied grassland types. The species composition of Puccinellia grasslands was the most stable over the three years with varying precipitation. This was important as this grassland type contained many threatened halophyte species. Self-organising maps revealed small-scale vegetation changes and provided a detailed visualisation of short-term vegetation dynamics, thus we suggest that the application of this method is also promising to reveal community dynamics in more species-rich habitat types or landscapes.