2019 Volume 61 Issue 2 Pages 85-94
Spatial distributions of conifer seedlings and ground-surface environmental factors were investigated in an even-aged sub-boreal coniferous forest in Akan region, eastern Hokkaido, Japan. The studied stand was approximately 120 years old and mainly composed of Abies sachalinensis with a small percentage of Picea glehnii and Picea jezoensis. The forest floor of the experimental plot was characterized by the following three features: 1) high dominance of moss vegetation, 2) little in the way of coarse woody debris (CWD) except for pole-size fallen stems, and 3) no dwarf bamboo (Sasa spp.), which has been reported to be common undergrowth in most old-growth sub-boreal forests in Hokkaido. The densities and maximum heights of the seedlings in the plot, with the exception of the current-year seedlings, were 35,859 and 4,902 seedlings/ha, and 23 and 26 cm for A. sachalinensis and Picea spp, respectively. All these seedlings grew on the ground surface. Spatial patterns of seedling distribution were “aggregated distribution" at the smallest grid size of 0.5-2 m for A. sachalinensis and Picea spp, and the seedlings of these two genera showed a sympatric distribution at this spatial scale. Ground-surface environments, such as moss coverage, moss height, soil pH, C, N or C/N ratio varied substantially within the plot (32 m × 32 m) or subplot (4 m × 4 m). Statistical analysis using the conditional autoregressive (CAR) model suggested the potential negative and positive effects of total C content and C/N ratio of the surface soil, respectively, on the local seedling densities of both A. sachalinensis and Picea spp seedlings, and also the negative effect of moss height on the local density of Picea seedlings. These results may suggest that the small-scale spatial heterogeneity of ground-surface environmental conditions in this site may have an influence on the seedling distribution through various abiotic and/or biotic processes, including microbiological interactions.
