Application of “clump technique” for root system studies of Quercus robur and Fraxinus excelsior

Amount and spatial distribution root-inhabited soil was investigated by application of the “clump technique” in 90- to 95-year-old floodplain forest of the southern Moravia, Czech Republic. The root-inhabited soil volume was estimated in two different ways. First we estimated the size of the theoretical “pot” which enveloped the whole root system in a series of individual trees. Secondly, root-inhabited soil volumes around clusters of roots of second and higher orders (“root-inhabited clumps”) were depicted and their shapes were approximated by ellipsoids. Spatial distribution of such “clumps” and their volumes and surfaces was described. Data were highly correlated with breast height diameter (DBH) and also with parameters of foliage (dry weight and surface of leaves). No difference was found in volume of root-inhabited soil between oak and ash of similar DBH. We found that only 73% of soil volume was filled with theoretical “pots” enveloping root system and only 13% of soil volume was inhabited with roots of second and lower order in the conditions of floodplain forest. Dry root biomass (including stumps) represented 13% of total tree biomass and thus played an important role in the carbon budget. Maximal amount of roots (and also maximum volume of root-inhabited soil) was found in depth from 40 to 100 cm. The scatter of root-inhabited soil parameters was significantly higher in ash, than in oak. Clump technique allows to assess utilization of soil by tree roots that may be further used for comparison of different tree species and different sites with focus on ecological limitation of growth.