Ungulate impact on rowan (Sorbus aucuparia L.) and Norway spruce (Picea abies (L.) Karst.) height structure in mountain forests in the eastern Italian Alps

摘要: Abstract A new approach for studying browsing impact on the regeneration of rowan (Sorbus aucuparia L.) and Norway spruce (Picea abies (L.) Karst.) is presented. This can be a useful, complementary tool to damage surveys because it helps identify possible underestimation in cases where most palatable species are likely have completely disappeared due browsing. The wild ungulates height structures populations these two was studied at four sites Trentino area (Italy). recorded (affected by ungulate browsing) were compared with predicted then residuals calculated from power function models. (rowan) showed that all study there decrease individuals classes affected Indeed, greater density ungulates, decrease, site highest (Paneveggio), total absence between 100 160 cm. On contrary, among we did not observe high number In order better define temporal dimensions browsing, dendroecological conducted. Abrupt growth releases tree rings indicate exactly when leader single escapes intense An abrupt release chronology each thus constructed differences, terms length intensity evidenced. show particular differences distribution spruce, whereas significant difference first three Paneveggio site. After 1985, no further suppression observed therefore hypothesize following date, so prevented any growing beyond height. fact Paneveggio, splitting population two: one part established grew above before recent increase, while second made up those trees after explosion which time measurement had either yet reached or been kept suppressed lower vegetation layers