5. Conclusions
In this study, we conducted experimental manipulations combining five density gradients and six common species of different plant functional types from grasslands in temperate China. Our results showed that the amount of photosynthetic products allocated belowground for each species was lower than that allocated aboveground, particularly for the annuals. Among the different plant functional groups, the R/S of annuals is much lower than that of perennials, suggesting that estimating the belowground biomass of annual-dominant communities with the empirical R/S of perennial plant communities in the field can induce large uncertainties. The R/S of C4 plants is lower than that of C3 plants, suggesting that the expansion of C4 herbaceous plants may have large impacts on future belowground C pool dynamics of grassland ecosystems in the future. The allometric relationships between shoot and root biomass obtained in this study were species-specific and could be modulated by density, which is not in line with allometric partitioning theory. These findings highlight the need to consider the effects of plant functional type and density on above- and belowground biomass allocation patterns when estimating and predicting the future belowground C dynamics of grasslands in the context of climate change.