Host: The Japanese Forestry Society
In northern part of Japan, Sakhalin fir and Sakhalin spruce are distributed for typical conifer species. Two species are often distributed on same forest. Large amount of seedlings of Sakhalin fir are distributed on understory of mixed conifer-deciduous forest, however, there are little distribution for seedling of Sakhalin spruce on this region. Therefore, shade tolerance may be lower for Sakhalin spruce than that of Sakhalin fir. However, there is not enough for information of shade tolerance of two species. We examined shade tolerance of seedling of Sakhalin fir and Sakhalin spruce grown on different light environmental region. For growth parameters, photosynthetic capacity, needle morphology, needle longevity, and concentration of chlorophyll and nitrogen were measured. These parameters were compared between seedlings grown on open space (open) and under canopy (shade). Study site was located in mixed conifer-deciduous forest of Uryu experimental forest located in northern part of Hokkaido. Based on these results, specific leaf area (SLA) of Sakhalin fir and spruce on shade region were higher than those on open region. On leaf morphology, there were two lines of palisade tissue on upper part of needles for Sakhalin fir on open region, and one line of them were distributed for that on shade region. In contrast, palisade tissue of Sakhalin spruce was distributed wholly below the epidermal tissue, and arrangement of tissue was similar between open region and shade ones. On photosynthetic capacity, light curve of Sakhalin fir showed large initial slope, and saturated photosynthetic rate at low PPFD. In contrast, light curve of Sakhalin spruce showed small initial slope, and saturated photosynthetic rate at high PPFD. On needle longevity of two species, Sakhalin fir and spruce on shade region were longer needle life span than those on open region. Survivorship of needles for Sakhalin fir and spruce were maintained over 60% until ten-year-old needles. Concentrations of chlorophyll (a+b, b) in needles were higher for Sakhalin fir grown on shade region than that on open region. In contrast, concentration of chlorophyll of in needles of Sakhalin spruces were not significantly difference between open region and shade ones. As a consequence of our results, Sakhalin fir has high shade tolerance compared with Sakhalin spruce. Especially, Sakhalin fir grown on shade region were high concentration of chlorophyll in needles, as a result, photosynthetic rate may be saturated at low PPFD.
