To evaluate the effects of sika deer (Cervus nippon yesoensis) culling on browsing pressure and height growth of deciduous tree saplings, a ten-year monitoring survey was conducted in Kushiro Wetland National Park, eastern Hokkaido, including a five-year period of active culling. Factors influencing sapling browsing and height growth were analyzed using generalized linear mixed models, in which sapling height, species, snow conditions, site, and culling status (culling vs. post-culling) were included as explanatory variables; browsing occurrence was additionally included as an explanatory variable in the analysis of sapling height growth. Browsing occurred more frequently in shorter saplings and under conditions of deeper snow. Browsing pressure was reduced during the culling period but increased progressively with time after culling ceased, indicating a decline in culling effects. Height growth was significantly reduced in browsed saplings, particularly in taller individuals, and overall growth rates declined during the post-culling period. Recruitment potential strongly depended on initial sapling height. Saplings with greater initial height showed a higher probability of reaching 200 cm, and the probability increased markedly once saplings exceeded 100 cm in height.

In heavy-snow regions, basal bending develops during the juvenile stage under snow pressure, lowering timber quality. This study examined two provenance test sites of Picea glehnii where basal bending was observed, identifying wood quality and growth-trait characteristics in trees showing large versus small bending, and evaluating the potential for breeding individuals with reduced bending. Trees with higher bending-resistance scores at age 20 exhibited significantly lower Pilodyn pin penetration values around age 30 and a significantly larger diameter at breast height (DBH) at age 20. An ordered logit model including site-specific random effects showed a negative influence of Pilodyn pin penetration and a positive influence of DBH, with high resistance scores predicted only when both traits were favorable. When the breeding values for Pilodyn pin penetration and DBH were estimated, a significantly positive regression coefficient was detected between the breeding values of the two traits. Although the selection efficiency for individuals superior in both traits was low, such individuals could still be selected.

To evaluate the combined effects of sika deer browsing and thinning in planted forests on forest floor vegetation, we reanalyzed existing data on the effects of thinning on forest floor vegetation and deer photography frequency, collected at the same sites, focusing on cover degree (indicator for soil conservation function), plant species richness (indicator for species diversity conservation function), and proportion of arboreal cover degree (indicator for diverse functions provided by trees). The degree of cover did not appear to decrease even as increase in the proportion of unpalatable and grazing-tolerant plant cover under the cumulative pressure of deer herbivory, and the degree of herb/vine cover increased following thinning. Woody plant species richness decreased under browsing pressure; conversely, there was no apparent decrease in herb/vine species richness. Both woody plant and herb/vine species richness increased following thinning. The proportion of arboreal cover decreased under browsing pressure and did not increase with thinning. The findings suggest that thinning contributes to an increase in the degree of cover and plant species richness, even under browsing pressure; however, it does not contribute to an increase in the proportion of arboreal cover. Deer management measures should be combined with thinning to increase arboreal coverage.