Exploitable results Phytophagous insects in ecotones and their impact upon forest ecosystems stability and regeneration The project aimed to verify if: - the ecological structure of dendrophagous insect guilds on ecologically analogous host trees is similar under corresponding environmental conditions (in this case, such guild may be formed by close insect species); - the distribution and the feeding activity of insect species are affected by the complex of transitions among ecosystems at different scales (ecotones), through changes in quality and quantity of their food bases. These transitional zones are revealed by the distribution of epigeic arthropods. The following groups of vicariant tree species were considered in various forest ecosystems of the Alps, Middle Siberia and Kamchatka: - Pinus cembra (Swiss stone pine) - Pinus sibirica (Siberian pine); - Pinus mugo (dwarf mountain pine) - Pinus pumila (dwarf Siberian pine); - Abies alba (European fir) - Abies sibirica (Siberian fir); - Picea abies (Norway spruce) - Picea obovata (Siberian spruce) - Picea jezoensis (Yezo spruce); - Larix decidua (European larch) Larix sibirica (Siberian larch) - Larix gmelini (Dahurian larch). At each site epigeic arthropods were sampled by pitfall traps along transects crossing the forest border. Phytophagous insects were sampled along the same transects by various techniques (registration of damaged food units such as leaves, shoots, cones and seeds, and trapping with visual and pheromone traps). 1. Epigeic insect communities. Species richness and diversity of carabids, staphilinids and spiders are comparable throughout almost all the ecosystems considered. Several examples of vicariant species of indoctorinating arthropods between Europe, Siberia and Kamchatka were found. 2. Transitional zone between ecosystems. A transitional zone is revealed by interpenetration of indicatoring epigeic arthropods only in case of succession or colonisation of an open area by the forest. In a few cases the transitional zone was present even in absence of colonisation, probably because pioneer trees were removed by man or stock. The width of the transitional zone seems to vary both in space and time, from a minimum of a few metres to the whole transect length (60m). It may extend far beyond the meadow limit of the transect at timberline. 3. Edge effect of phytophagous insects. The great majority of phytophagous insects seem to be more abundant on border and pioneer trees, even when epigeic arthropods did not reveal the presence of a transitional zone. This feature is of extreme importance in pest management for several applied consequences it may have. 4. Forest border and communities of phytophagous insects. The high similarity among communities of phytophagous insects of five-needle pines throughout Europe and Asia, likely extendible to the other conifers considered in this project, suggests that they originated on common ancestors and successively they adapted to new conditions. Considering the similar way by which several vicariant species react to the forest border, it can be concluded that border and pioneer trees may play an important role in the formation and maintenance of forest insect communities. È in corso la ricerca di dati su OpenAIRE... Si è verificato un errore durante la ricerca dei dati su OpenAIRE Nessun risultato disponibile
