Belowground Bud Bank Is Insensitive to Short-Term Nutrient Addition in the Meadow Steppe of Inner Mongolia

Abstract

Human activities and industrialization have significantly increased soil nutrients, such as nitrogen (N) and phosphorus (P), profoundly impacting the composition and structure of plant community, as well as the ecosystem functions, especially in nutrient-limited ecosystems. However, as the key propagule pool of perennial grasslands, how belowground bud bank and its relationship with aboveground vegetation respond to short-term changes in soil nutrients was still unclear. In this study, we conducted a short-term (2021–2022) soil fertilization experiment with N addition (10 g N m yr) and P addition (5 g N m yr) in the meadow steppe of Inner Mongolia, China, to explore the responses of belowground bud bank, aboveground shoot population and their relationships (represented by the ratio of bud to shoot density-meristem limitation index (MLI)) for the whole community and three plant functional groups (perennial rhizomatous grasses-PR, perennial bunchgrasses-PB, and perennial forbs-PF) to nutrient addition. The short-term nutrient addition had no significant influences on belowground bud density, aboveground shoot density, and MLI of the whole plant community. Plant functional groups showed different responses to soil fertilization. Specifically, N addition significantly increased the bud density and shoot density of PR, especially in combination with P addition. N addition reduced the shoot density of PF but had no influence on its bud density and MLI. Nutrient addition had significant effects on the three indicators of PB. Our study indicates that the belowground bud bank and its relationship with aboveground vegetation in temperate meadow steppe are insensitive to short-term soil fertilization, but plant functional groups exhibit specific responses in terms of population regeneration, which implies that plant community composition and ecosystem functions will be changed under the ongoing global change.