Structural and chemical differences between shoot- and root-derived roots of three perennial grasses in a typical steppe in Inner Mongolia China

Determining the variation in roots traits within a grass root system is important for understanding the role of fine roots in carbon and nutrient cycling in grassland ecosystems, where the majority of biomass and litter accumulation occur belowground. However, few studies have been conducted in this regard. In this study, the structural and chemical traits of shoot-derived and root-derived roots were examined in three perennial grasses-Cleistogenes squarrosa, Achnatherum sibiricum and Stipa grandis-aiming to explore structural differences, responses to nitrogen and water addition in different types of roots and their correlations with aboveground plant nitrogen. Our results showed significant differences between these two root types, with root-derived roots having higher N concentration, tissue density, and specific root length, but lower C: N and diameter than shoot-derived roots. Trait relationships between root N concentration and tissue density for the two root types differed from that reported among species. These traits in different types of roots were insensitive to resource addition. Furthermore, N concentration in shoot-derived roots was more strongly linked to aboveground plant N concentration than root-derived roots. The results of this study demonstrate structural differences within the root system that may reflect functional heterogeneity in grass roots.