Assessing the damage caused by deer on young trees in a Sugi (Cryptomeria japonica) plantation based on field signs

Predicting the level of damage by deer browsing in young plantations is important for considering damage control measures. In this study, we examined a method for assessing the level of deer damage in young Sugi (Cryptomeria japonica) plantations with deer-proof fences by observing field signs of deer. First, a questionnaire survey was conducted to obtain information about the damage by deer browsing on planted trees and the extent of field signs, such as browsing marks and deer fecal pellets around the young plantations. The extent of field signs was recorded as qualitative data (i.e. "None", "A few", and "Many"). A multiple correspondence analysis (MCA) revealed a relationship between the extent of deer damage in young plantations and the presence of five field signs (browsing marks, bark stripping marks, fecal pellets, trails and tracks) around the young plantations. Based on coordinate values of each field sign obtained using the MCA, the extent of each field sign was scored, and the total value was calculated as the deer impact score (DISco). When the relationship between the DISco and the extent of deer damage to planted trees was subjected to a logistic regression analysis (LRA), the DISco was found to be a significant explanatory variable and the LRA was an effective model (AUC of 0.7809 and 0.7048, respectively) for predicting the probability of stand damage and High stand damage. Therefore, the DISco was shown to be an effective tool for assessing the damage risk of deer in young Sugi plantations with deer-proof fences.