Abstract: Climate change and human disturbance have resulted in the continuous increase of degraded grassland area in China. Nutrient addition is considered as one of the effective measures for grassland restoration. We conducted a nitrogen (N) and phosphorus (P) addition experiment in a degraded grassland in the semi-arid meadow steppe of Inner Mongolia. We investigated the responses of belowground bud banks and their relationships with vegetation to nutrient additions at different times (early-spring or middle-summer). Results showed that summer nutrient addition significantly increased bud density and aboveground shoot density, while early-spring nutrient addition had no significant influences. Nutrient additions at different times significantly decreased meristem limitation index. Plant functional groups showed specific responses to nutrient addition. Nutrient addition significantly reduced shoot density of forbs. Summer nutrient addition significantly increased bud density and shoot density of bunchgrasses, meristem limitation index, of which was significantly decreased under nutrient addition at different times. Nutrient addition significantly increased both bud density and shoot density of rhizomatous grasses. Our results indicate that summer nutrient addition greatly increases vegetation regeneration potential, and different responses of plant functional groups to nutrient addition determine vegetation restoration and succession dynamics in degraded meadow steppe.

Key words: bud bank, degraded grassland, nutrient addition, plant functional group, vegetation restoration