Can treeshelter rescue reforestation under deer foraging pressure? Effects on seedling growth, protection, and decision making

Deer browsing damage is a serious problem in woodland ecosystems and forestry in various regions of the world (Gill and Beardall 2001), including Japan (Takatsuki 2009). In Japan, the area of forestry negatively affected by wild animals reached 4,900 ha in 2019, of which deer accounted for more than 70% (Forestry Agency 2021). Although deer exclusion fences have been employed, mainly at plantation sites for conifer timber production, the associated high cost and amount of labor constrained its application in some cases. Deer hunting has already been carried out to the maximum degree possible, and the current cohort of hunters is aging without younger replacements, precluding the possibility of meaningfully increasing the number of deer hunts any further in Japan. This situation may be similar in various parts of the world suffering from deer browsing damage. Therefore, development of alternative options that can be selected according to the forest conditions and deer population density is required to protect seedlings effectively from deer browsing. Treeshelters are single tree protection devices that have been used mainly in Europe and North America (Potter 1991). They have been used in Japan since the 1990s, but their effectiveness has proven to be variable, with many cases of failure. Possible factors included the hot summer conditions in Japan and the species characteristics of major timber trees such as Japanese cedar (Cryptomeria japonica) and hinoki cypress (Chamaecyparis obtusa), but such cases in Japan have never been reported in international journals. In this special feature, we will mainly focus on treeshelters as countermeasures against deer browsing damage, and provide information on their effects and limitations, estimation of deer density, which can be a criterion for decision making about selecting countermeasures, and findings on the latest research including countries other than Japan.