A practical technique for estimating deer appearance frequency and cedar sapling damage in young plantations protected by tree shelters in western Japan

We developed simple practical methods to estimate deer appearance frequency and damage risk for cedar saplings protected by tree shelters, by using field signs such as browsed understory plants, debarked trees, and animal trails. The appearance frequency of the sika deer was recorded using camera traps at 29 clear-logged and young plantation sites in the Shikoku Island of western Japan. Field signs such as fecal pellets, footprints, animal trails, and browsed plants were recorded in three transects that were 2 m × 50 m each, located at the margins of the sites. Cubic regression analysis showed that the frequency of deer appearance could be predicted from the number of browsed plant species categorized into three ranks, that is, 0, 1, and ≥2 species. To use this method, plant species are not required for identification, as the user can simply judge whether browsed plants found in 5-m sections are all the same species or not. The damage of sheltered cedar saplings was assessed at 36 sites in the Kyushu and Shikoku Islands of western Japan, and surveys of deer field signs were also conducted. The proportion of heavily damaged saplings could be determined from the indices of binary summarized data of bark stripping and animal trails using a logistic regression model. The indices derived from the field signs will help forest managers to detect relatively low frequency of deer appearances and high risk of cedar sapling damage at a sheltered plantation in the western Japan.

本研究开发了简便实用的方法，通过利用被啃食的林下植被、被剥树皮的树木以及动物活动路径等野外痕迹指标，估算受护林树罩（tree shelters）保护的雪松幼树苗的鹿群出现频次与受损风险。研究人员借助红外相机陷阱（camera traps），在日本西部四国岛的29处皆伐后幼龄人工林样地中记录了梅花鹿（sika deer）的出现频次。在各该样地的边缘设置3条规格为2米×50米的样带，记录了粪便颗粒、足迹、动物活动路径以及被啃食植被等野外痕迹。三次回归分析结果显示，可将被啃食植物物种数量划分为0种、1种、≥2种三个等级，据此即可预测鹿群出现频次。使用该方法时无需识别植物物种，使用者仅需判断在5米分段内发现的被啃食植被是否为同一物种即可。研究人员在日本西部九州岛与四国岛的36处样地中，对受护林树罩保护的雪松幼树苗受损情况开展了评估，并同步进行了鹿类野外痕迹调查。借助逻辑回归模型，可通过剥树皮行为与动物活动路径的二元汇总数据指标，推算出重度受损雪松幼树苗的占比。本研究基于野外痕迹构建的指标，可帮助日本西部人工护林林分的森林管理者，识别出鹿群出现频次相对较低但雪松幼树苗受损风险较高的区域。