Gridling Efficiency: Influential Factors In Managing Ailanthus Altissima Spread In Slovenia

The tree of heaven (Ailanthus altissima) is due to its rapid spread and negative impact on biodiversity on the list of invasive species that need to be eradicated or its spread controlled. This mechanical control, such as girdling, can lead to permanent solutions in the field of invasion biology. Previous studies have reported that girdling was more effective than felling a tree. The presented study aimed to analyze the productive times considering different factors at girdling Ailanthus altissima. Time studies were conducted to monitor worker time needed for bark girdling of Ailanthus altissima. This involved identifying 9 sites in the Slovenian Kras Region with a total area of 4 ha. Girdling was performed at 20 to 30 cm above the ground while avoiding herbicides and chainsaws. Such a method would contribute to the weakening of the trees. The effect of griddled tree characteristics, stand conditions, terrain conditions, and physical activity of examined workers were therefore investigated. Linear regression models were built to explain and predict productive time. Different field-collected and remotely sourced variables were used as independent predictor variables. Eight factors were identified as influencing as the model showed their statistical significance. It includes eight independent variables relating to tree characteristics (Diameter), terrain and stand characteristics (Relief, Basal area), preparation and work organization (walk distance, Tree marking), and worker characteristics (Age, Body weight, Metabolic equivalent). The productive time required to girdle a single tree is affected mainly by terrain conditions (e.g. is increased by 78.27 seconds if the relief of the work site changes from angular or convoluted compared to smooth to undulating). The study shows that under average conditions (taking the average values of the independent variables into account) the productive time required to ring a single tree and move to the next tree would be 2 minutes and 16 seconds in the case of favorable terrain and previously marked trees to be ringed; and up to 3 minutes and 53 seconds in the case of unfavourable terrain and unmarked trees to be ringed. Considering the area as a output, workers would spend 26 hours of productive time to ring trees over an area of one hectare. In summary, the chosen method of gridling to control the spread of invasive tree species is physically difficult and rather time-consuming. There is also the question of the effectiveness of the action taken with the chosen removal method using hand tools, as the effect has yet to be seen after the first growing season. In particular, the chainsaw girdling method should be investigated because of possibly higher efficiency as well as the effectiveness of the measure.