Regeneration pattern of natural forest in northern Hokkaido: analysis on the scale of several decades and tens of hectares.
Spatial and temporal patterns of forest regeneration were studied in a mixed forest (main species Abies sachalinensis, Picea jezoensis, Betula ermanii, Acer mono) in northern Hokkaido, Japan, at two scales. Two types of regeneration were common following disturbance (fire, logging, etc.): either tree regeneration, or Sasa sp. grassland regeneration. This study concentrated on tree regeneration, and used aerial photographs and growth ring analysis of stumps to evaluate stand development history. Regeneration patches (10 to 100 m2) occurred continually over a scale of several years. In coniferous forests, regenerated patches were more frequent, and often clumped. Temporal and spatial extent was 10 to 20 years, and 600 to 3000 m2. In broadleaved forest and mixed forests, small regeneration patches did not tend to enlarge. Turnover in broadleaved and mixed forests was between 460 and 770 years, which was a higher value than that of the age distribution of the trees; for coniferous forests the time span was about 200 years, and similar to that of the age distribution. In coniferous forests in this region, the intermittent mosaic spreading of regenerated patches plays a vital role in maintaining natural forest.