Traditional burning and mowing practices support high grassland plant diversity by providing intermediate levels of vegetation height and soil pH

Question Which types of management practice promote plant species richness in semi‐natural grasslands? Which environmental factors might be involved in this management effect? How do different plant life‐form groups respond to these variables? Location Kaida Plateau, Nagano Prefecture, Japan. Methods In the study area, hay meadows were traditionally maintained through both burning and mowing every second year. Recently, however, meadows that have either been abandoned or maintained only by annual burning or annual mowing have increased. We compared plant species richness, vegetation height and soil pH and water content between traditional meadows and those abandoned or maintained only by burning or mowing. We also examined relationships between these variables and the species richness of plant life‐form groups. Results The mean total and rare plant richness (36 and eight species·m −2 , respectively) in traditionally managed meadows were higher than in meadows of other management types (<26 and ≤5 species·m −2 , respectively). Vegetation height (20–290 cm) and soil pH (4.2–6.2) varied among study plots. Burning and mowing frequencies negatively influenced vegetation height and positively influenced soil pH and/or water content. Traditional management practice provided intermediate vegetation heights (90 cm) and soil pH (5.3). Total species richness showed a unimodal relationship with vegetation height (peaking at 125 cm), and rare species richness was highest at intermediate levels of vegetation height (86 cm) and soil pH (5.2). Conclusions This study demonstrates that intermediate levels of vegetation height and soil pH have been maintained through traditional practices combining both infrequent burning and mowing. These practices are essential for conserving common and rare plant diversity in the study area with oligotrophic soil conditions.