Forest regeneration inhibition in a mixed broadleaf-conifer forest under sika deer pressure

Abstract

ABSTRACT To examine the tree regeneration and forest structure under sika deer pressure, we established a 1.08 ha plot, including a 0.0176 ha fenced area, and measured DBH (diameter at breast height) and/or height of trees in 2005–2006 and 2015–2016 in a mixed forest in the Ohmine Mountains, Central Japan. Small trees (<10 cm in DBH) were few or none for most species, but for Pieris japonica. Densities of sapling trees (50 cm ≤ height < 130 cm) were not significantly different between fenced and non-fenced areas in 2005, and were significantly different in 2015. Owing to the treefalls of large trees by wind disturbances, the total basal area decreased by 1.6% from 53.3 m2/ha in 2005 to 52.5 m2/ha in 2015. In the non-fenced area, the annual mortality of the other trees (11.7%/year) than P. japonica was significantly greater than that of P. japonica (5.7%/year). The annual recruitment densities of saplings showed a great difference between fenced (1,670.5 stems/ha/year) and non-fenced areas (56.5 stems/ha/year). Although the light condition was improved by wind disturbance, sapling tree survival and growth, except for non-preferred P. japonica, had been inhibited through effects of sika deer pressure, resulting in the decrease in the saplings of preferred tree species and an increase in the saplings of non-preferred P. japonica at this study site.