Determination of some factors leading to the infestation of Ips sexdentatus in crimean pine stands

Abstract

Large infestations of bark beetles result in the death of many trees in large forest areas. Ecological-based modeling approaches that include the factors causing infestations are important for accurately predicting whether these infestations will occur, suggesting ways to avoid large infestations, and understanding sustainable forest management. In the present study, the effects of some stand characteristics and topographical and climatological factors on the of Ips sexdentatus infestation at pure and mixed Crimean pine stands were evaluated. Ten factors were considered as important for predicting the predisposition of a pine forest to infestation: stand structure, site index, crown closure, stand age, aspect, slope, elevation, maximum temperature, precipitation, and solar radiation. Ten conditioning layers were overlayed separately with a beetle infestation map using geographic information system (GIS) to investigate how the beetle damage changed according to these factors and how much damage it caused. Binary logistic regression analysis was used to determine how combinations of the 10 factors affected beetle infestations and which of the factors were most damaging. It was found that the stand structure, crown closure, site index, stand age, slope, elevation, maximum temperature, precipitation, and solar radiation were definite factors in I. sexdentatus infestation; the aspect was not found to be a strong factor. The crown closure was the most significant factor affecting I. sexdentatus infestation followed by maximum temperature, elevation, slope, precipitation, solar radiation, stand age, site index, and stand structure. The crown closure, stand structure, maximum temperature, solar radiation, and forest stand area variables were significantly included in the logistic regression model.