Abstract: Global climate change and human activities have profound influences on structure and function of terrestrial ecosystems, and alter the quantity and quality of litter. The changes in litter accumulation might directly and indirectly affect population maintenance and regeneration in grasslands. However, how belowground bud bank, shoot population, and their relationships respond to the changes in litter accumulation in temperate grassland has not been fully explored. Based on a long-term litter manipulation experimental platform in the typical steppe of Inner Mongolia, we measured belowground bud density, aboveground shoot density, annual net primary productivity (ANPP), and key soil physicochemical properties under three litter treatments (removal and addition of 50% litter, and the ambient condition as the control), aiming to clarify the effects of litter accumulation on population regeneration via belowground bud bank. Results showed that compared with the control and litter addition, litter removal significantly increased both belowground bud density and aboveground shoot density, but had little influences on bud number per shoot (i.e., meristem limitation index). Structural equation model (SEM) further confirmed that litter manipulation affected belowground bud bank and aboveground shoot population mainly by direct pathway, rather than indirectly though influencing ANPP and soil factors. Our study indicated that appropriate litter removal could facilitate population maintenance and regeneration via belowground bud bank in typical steppe, and that litter accumulation directly, rather than by altering soil environment, affect population regeneration in grasslands. Our study reveals the influencing mechanism of litter accumulation on population regeneration via belowground bud bank in temperate grasslands, and provides important theoretical basis for grassland restoration and management under climatic changes and human disturbances.

Key words: bud bank, clonal trait, litter accumulation, global change, population regeneration