Short-Term Effects of Selective Cutting on Tree-Related Microhabitats in Cryptomeria japonica Plantations

Tree-related microhabitats (TreMs) are widely recognized in Europe as a strategy to enhance biodiversity in plantation forests. Selective cutting, a common forest management practice, helps maintain forest structure and ecological integrity while balancing economic and ecological needs. This study investigates the short-term effects of selective cutting on TreMs in Cryptomeria japonica plantations. We selected three 0.1 ha square plots within a C. japonica plantation in Xitou, managed by the Experimental Forest of National Taiwan University, and conducted surveys before and six months after selective logging to assess changes in microhabitat availability and heterogeneity. Key TreMs indicators, including cavities, growth deformation, micro-soils, dead branches, bark injuries, and epiphytes, were measured, and a terrestrial LiDAR with a 5-meter grid resolution was used to monitor detailed changes in canopy cover. Modified Hill numbers (q0, q1, q2) were applied to quantify changes in the total types, abundance, and evenness of TreMs. Wilcoxon signed-rank tests were used to compare pre- and post-cutting effects. Results indicated significant increases in Hill numbers (q0, q1, q2), reflecting short-term changes in TreMs. Geometric mean ratios between pre- and post-cutting data showed minimal changes in cavities (0.91, CI: 0.74-1), a moderate increase in growth deformation (1.20, CI: 1-1.41), and no change in micro-soils (1.00, CI: 1-1). In contrast, significant increases were observed in dead branches (1.28, CI: 1.12-1.48), bark injuries (1.11, CI: 1.01-1.22), and epiphytes (1.56, CI: 1.41-1.71), with epiphytes showing the most pronounced change. LiDAR analysis revealed a reduction in canopy cover following logging, which was closely associated with variations in epiphyte abundance, highlighting an interaction between canopy openness and epiphyte colonization. As the first application of the European TreM inventory in Taiwan, this study underscores the importance of further research on microhabitats as indicators of forest ecosystem function and biodiversity at local scales and calls for adaptation of this approach to Taiwan's unique environmental conditions.

Keywords: Cryptomeria japonica Plantation, Tree-related microhabitats (TreMs), Selective cutting, terrestrial LiDAR, Hill numbers, Wilcoxon signed-rank tests.