INVESTIGATIONS CONCERNING ROOT PRUNING OF YOUNG FIR PLANTS (ABIES-ALBA MILL)

The success of stabilizing stands by introducing fir depends to a larg e extent on a sound knowledge of how the species-specific root system develops during the cultivation of plants. In order to clarify the inf luence of root pruning on the further formation of roots, 3 assortment s of plants 2 + 1 (3y.), 2 + 2+ 2 (6y.) and 2 + 6 (8y.) were treated w ith 4 pruning variants: 0: no root pruning, 1: shortening of the main root by 25 %, 2: by 50 %, 3: by 75 %. After planting out, plants were excavated annually after the conclusion of 1 to 6 vegetation periods a nd analyzed as well as photographed. The development of root collar di ameter, length of shoot, dry weight of root and shoot is rendered in a table. From these characteristics, a direct influence of the root pru niung variants cannot be ascertained. The formation of roots is demons trated primarily with the aid of photographs. Essentially one can dist inguish three types of roots: main roots in the shape of a tap root wi th formation of sinkers; tufted rootage, as well as well-developed and widely ramified lateral roots. After the last 6th vegetation period, development of a tap root from a tuft of vertical roots could be obser ved for the first time. It was also noticeable, however, that roots, w hich were crooked and stunted due to faulty planting or transplanting, have not grown into normal shape during the trial period. Optimal dev elopment of a strong tap root all age classes is only possible when fi r is propagated by natural regeneration or by sowing. If planting or t ransplanting is deemed necessary, it is more advisable to shorten a ve ry long tap root by pruning rather than to compress it in the ground.