The Effect of Cutting Technique On The Mortality and Resprouting Vigour of Hybrid Poplar Stumps

Short rotation coppice is a modern industrial crop and its profitability depends on the mechanization of all management operations. Once the crop is mature, trees can be felled with a variety of machines, but shears represent the most effective solution. However, shears can inflict a certain degree of stump damage, which has raised concerns about stump mortality and re-sprouting vigour - both crucial to coppice regeneration. This study compared the mortality and resprouting vigour of stumps cut with shears and with chainsaws – the latter representing the control treatment. Measurements were taken on 6 compartments on 5 sites. On each compartment, 10 sample plots were established, each consisting of two parallel row segments containing 10 live stumps each (e.g. 20 stumps per sample plot). One row segment was cut with a shear-type felling head, the other with a chainsaw-type felling head. One year after cutting, researchers determined for each stump the following parameters: diameter of the stump, number of live shoots, diameter and height of the 5 tallest shoots. Data were pooled into a structured database and statistically analyzed using R open software. Clone selection and site fertility had a very strong effect on stump mortality and resprouting vigor – the former possibly more dependent on clone, the latter on site fertility. Cutting technique had no effect on stump survival and a very small effect on resprouting vigor, which was represented by a consistently larger number of shoots on stumps cut with shears. The data also suggested that the five dominant shoots sprouted after shear cutting might not grow as fast as those sprouted after chainsaw cutting, but the statistics were inconclusive in that regard. If so, a likely explanation could be found in the harder competition resulting from the larger number of shoots; that would reduce the growth potential of dominant individuals on less fertile sites.