Semi-natural grasslands as a nature-based solution for climate change mitigation: An assessment of carbon and plant communities across age gradients

Semi-natural grasslands have the potential to sequester carbon and enhance biodiversity and therefore offer opportunities as nature-based solutions for climate change. However, our understanding of how their potential for carbon storage might work alongside their diversity benefits is based on a small quantity of variable evidence. Here, we use a chronosequence approach to investigate soil carbon and plant diversity in semi-natural grasslands across 5 regions in England, ranging from fields that have been newly established to fields over 150 years old. Our results show that soil organic carbon (SOC) stock was up to 104 % higher in older (25 + years), compared to younger (0–24 years) fields in the top 30 cm. Environmental metrics specific to each site, in particular soil clay content and mean annual rainfall, were among the strongest predictors of SOC stock. Plant diversity was not found to increase consistently with age, but plant species community composition shifted from a high proportion of ruderal species to stress tolerant species. These results highlight the potential opportunity that established, undisturbed semi-natural grasslands present in tackling the twin crises of climate change and biodiversity loss. Further investigation on the legacy effects of past management and land use is needed. • Soil organic carbon increased with grassland age, for a 0–15 cm soil depth. • Plant species community composition shifted from ruderal to stress tolerant species. • Soil organic carbon was best predicted by rainfall, clay content and grassland age.