Regrowth and dry matter allocation in Quercus robur (L.) seedlings root pruned prior to transplanting

Two-year seedlings of Quercus robur (pedunculate oak) were root-pruned befo re transplanting in order to evaluate the importance of coarse versus fine roots on regrowth. Root systems were pruned by leaving c. 19, 13 or 7 cm ro ot from the root collar. Alternatively, coarse roots (>2 mm in diameter) we re removed, leaving only the taproot and the fine roots (<2 mm) attached, o r fine roots were removed from coarse roots and taproot. Growth of shoots a nd roots after one growing season was compared to an unpruned control under standard nursery conditions. Seedlings root pruned to 19, 13 or 7 cm were further tested under competition achieved by transplanting into a mixture o f clover and grass. Pruning of the root system significantly reduced regrow th in terms of total plant DW in accordance with the severity of pruning, s hoot DW being more affected than root DW. Removal of coarse roots depressed final root DW whereas removal of fine roots reduced shoot DW and hence roo t:shoot ratio increased. The study suggests that fine and coarse roots have different roles in root:shoot allocation. The competition test increased r oot:shoot ratio indicating that competition induced seedlings to allocate m ore of their resources into growth of the root system.