1 We investigated the fine-scale below-ground distribution of plant parts in a mountain grassland. Roots and rhizomes were identified to the species level by tracking their connections to above-ground parts.
2 Fine-scale horizontal heterogeneity of total root and rhizome biomass at different depths was recorded at the same time in the same grassland.
3 Both pairwise and multivariate statistical analysis showed that in the 0–3 cm layer the frequencies of roots and rhizomes of individual plants were closely coupled to the occurrence of the same species immediately above-ground. In contrast, in the 3–6 cm layer, these correlations peaked when root and rhizome frequencies were compared with plants above-ground displaced by a horizontal distance of 2 cm. This confirms the predominantly inclined growth of both roots and rhizomes; while the inclined growth has been shown regularly by studying single plants, the current study shows its prevalence at the community level as well.
4 The similarity to the above-ground patterns in the upper soil layer was due to the spatial constraints of plant presence above-ground; in contrast, the spatial patterns in the 3–6 cm layer were independent of plant presence above-ground. The role of root growth plasticity is discussed in this context.
5 Autocorrelation analysis of the root data revealed that there was a pronounced difference in the grain of horizontal spatial pattern between total root biomass and species-specific root frequencies. All the species had rather loose root systems and clumps of one species rarely extended more than 0.5 cm. In contrast, there was significant long-range clumping of root biomass up to 10 cm. The below-ground heterogeneities in overall biomass and in species-specific distributions were therefore probably determined by different environmental processes.
6 No such difference in clumping range between total biomass and species-specific frequencies was observed in above-ground parts. This was attributed to homogeneity of the above-ground resource (light) compared with the inherently heterogeneous nature of the below-ground resources, and the different nature of competition for these resources may account for differences in vegetation patterns above- and below-ground.