Invasive plant species and their suppression in the Maribor forest management region.
As far back as in the sixties of the previous century we began systematic planting of alien tree species in the Maribor forest management region. Among them the most popular were Douglas Fir, White Pine, Sudetian and Japanese Larch, Austrian Pine, Red Oak, Eastern Black Walnut and Black Locust. In some cases, some of them became dominant and even invasive (predominantly the Black Locust and the Red Oak). When managing the alien tree species, it is necessary to highlight the benefits and problems that these species are bringing. After the ice storm in 2014, the invasive alien species (IAS) have expanded primarily in forests. In recent years, IAS have become more and more conspicuous in the forest clearings, which were caused as a result of natural disasters, bark beetle hot spots and regular cuts. Additionally, the forest edges and the forests along the watercourses are also exposed to great intrusion of IAS. The methods of suppressing IAS and their effectiveness depend on the type of plant, extent of distribution and costs of suppression measures. They should be based on examples of good practice. By reducing and removing measures we can greatly reduce their number. It is important to act quickly while they are still rare or while they are still young. In the case of invasive alien tree species, we try with silvicultural measures to reduce their lot in the forest and therefore prevent them spreading to new areas. We do this by thinning in the early stages of forest stands and by removing invasive tree species and regulating light. At present, the main silvicultural problem in our area presents difficulties with the regeneration of forests due to large coverage of American Pokeweed, partly due to Princess Tree and Himalayan balsam. Because they are wide spread, suppression of these species by pulling them out is too expensive. In the past few years, we have tried to suppress them in the early stages of forests by harvesting twice a year. With this treatment, we want to help the native species to reach higher density as soon as possible, because it is known that invasive species are less competitive in conditions of shading. In the years to come it will become evident how successful we have been.