Simulation de la structure optimale des hêtraies de protection contre les chutes de pierres | Simulation of the optimal structure of beech forests protecting against rockfall

Adequate management practices to attain the profiles specified in the Swiss guidelines for the management of mountain protection forests are not always unequivocally clear. This applies among others for beech forests that have a protective function against rockfall. We defined two management scenarios, one of which aims at harvesting trees starting with a minimum diameter at breast height of 40 cm, whereas the other one is focused on the creation of small gaps (area of 500 m2) over a maximum of 10% of the total stand area. These scenarios along with a control scenario characterized by no management were studied using the forest growth model BWINPro. In the control scenario, number of trees, basal area and standing volume were highest. The developments simulated under the two management scenarios were similar, when in scenario thinning harvesting levels corresponded to the growth over a 10-year period. In the other cases, number of trees, basal area and standing volume are lower under scenario gap because harvesting interventions occur more regularly. If the rocks have a volume exceeding 0.2 m3, the requirements of the profiles are attained more quickly under scenario gap, because in scenario thinning the larger trees are preferentially harvested. Because tree regeneration was not simulated, it is difficult to realistically predict the development of the number of trees. However, management interventions are needed in such forests, particularly if the profile for rocks with a volume below 0.2 m3 is to be attained and maintained.