Grassland Management in a Changing Climate: Insights From a Dutch Road Verge Study

Questions Biodiversity of European semi‐natural grasslands has declined over the last century, largely due to land‐use changes. To maintain or restore grassland biodiversity, mowing regimes are commonly applied. However, nitrogen deposition and climate change have affected the productivity and phenology of grasslands, resulting in further biodiversity loss and necessitating a reassessment of current mowing regimes. In particular, increasing the mowing frequency, adjusting mowing timing, and adjusting the mowing height may mitigate the effects of elevated nitrogen availability and climate change. This study aims to evaluate the impacts of these adjustments on plant diversity, vegetation composition, and aboveground biomass production across a productivity gradient. Location The Netherlands. Methods We performed a three‐year (2021–2023) field experiment in ten roadside grasslands across a productivity gradient. The treatments included the standard late‐August mowing (control), early‐November mowing, and combinations of a high (15 cm) or low (6 cm) cut in June followed by either late‐August or early‐November mowing. All treatments included hay removal. Results A delayed second cut reduced standing biomass across all productivity levels. Adjusted mowing regimes significantly affected vegetation composition, particularly in productive roadside grasslands. In these sites, mowing twice per year resulted in the highest species richness and number of characteristic species, especially when a low‐height June cut was combined with a delayed (early‐November) second cut. In contrast, adjusted mowing regimes (i.e., treatments differing from the standard control) had no biodiversity benefit in low‐productivity grasslands. Conclusion Our results indicate that in productive road verges, adopting more intense and differently timed mowing regimes can help mitigate biodiversity loss by addressing the increased productivity and prolonged growing seasons caused by nitrogen deposition and climate change.