Species-specific spatial pattern of below-ground plant parts in a montane grassland community

1 We investigated the fine-scale below-ground distribution of plant parts i n a mountain grassland. Roots and rhizomes were identified to the species l evel 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-gro und. 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 gr owth of both roots and rhizomes; while the inclined growth has been shown r egularly 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 d ue 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 cont ext. 5 Autocorrelation analysis of the root data revealed that there was a prono unced difference in the grain of horizontal spatial pattern between total r oot biomass and species-specific root frequencies. AII the species had rath er loose root systems and clumps of one species rarely extended more than 0 .5cm. In contrast, there was significant long-range clumping of root biomas s up to 10cm, The below-ground heterogeneities in overall biomass and in sp ecies-specific distributions were therefore probably determined by differen t environmental processes. 6 No such difference in clumping range between total biomass and species-sp ecific frequencies was observed in above-ground parts. This was attributed to homogeneity of the above-ground resource (light) compared with the inher ently heterogeneous nature of the below-ground resources, and the different nature of competition for these resources may account for differences in v egetation patterns above- and below-ground.