In recent years, it has been increasingly recognized that old-growth grasslands, which have persisted for hundreds to thousands of years under climates suitable for forest development due to natural and anthropogenic disturbances, are globally widespread. These grasslands may maintain levels of biodiversity and ecosystem services comparable to those of old-growth forests. In Japan, there are likely hundreds of thousands of ancient grasslands nationwide. However, despite being located close to human settlements, most of these grasslands are at risk of disappearing without their environmental value being properly recognized. To evaluate the environmental value of old-growth grasslands, we have conducted a research project over the past three years. In this presentation, we introduce an overview of how the long-term persistence of grasslands hovers species diversity, functional diversity, and ecosystem services, including pharmaceutical potential, soil surface erosion prevention, carbon storage, and aesthetic value.
This project was conducted mainly in grasslands at Sugadaira and Mine-no-hara Highlands in Nagano, as well as in adjacent plantations or secondary forests. Grasslands that have been continuously maintained for 300–1000 years or longer were defined as old-growth grasslands (10 sites), whereas grasslands established 50–70 years after forest clear-cutting were defined as secondary grasslands (9 sites). Understory vegetation of adjacent forests with stand ages ranging from 40 to 90 years were used as comparison sites. Plant species richness was higher in grasslands than in forest understory and was higher in old-growth grasslands than in secondary grasslands. Corresponding to plant species richness, species richness of butterflies and grasshoppers also increased. Furthermore, functional diversity calculated based on 23 above- and belowground plant traits was higher in old-growth grasslands than in secondary grasslands. In addition, fine root biomass in surface soils was greater in both secondary and old-growth grasslands than in forests. Soil shear strength related to surface erosion resistance was higher in old-growth grasslands than in secondary grasslands, corresponding to higher species richness and fine root biomass. The proportion of plant microbial symbiont-derived isolates showing antimicrobial activity was approximately twice as high in old-growth grasslands as in secondary grasslands and forests. Moreover, species dependent on old grasslands provide important aesthetic ecosystem services, and their value may be more strongly recognized through accumulated knowledge and experience. Overall, our results revealed the hidden environmental value of old-growth grasslands, providing strong motivation for their conservation.