This paper aims to clarify the effects of size and intensity (degree of destruction) of disturbance on the forest environments and regeneration processes by a field experiment. Especially, we arranged the experiment in regard to soil disturbance performed by up-rooting.
Four gaps of different size (25 and 100m2) and intensity (A0 layer is flayed or not) were made artificially in a warm-temperate evergreen broadleaved forest in Japan. Gap ratio in the canopy layer was analyzed by fish-eye photographs around the gaps. Soil temperature and soil respiration rates were measured. Seedling recruitment, mortality and growth around these gaps were also surveyed.
The edge effect estimated by analysis of gap ratio was affected by the difference in disturbance size. Soil temperature were affected by the intensity of disturbance. Soil respiration was also affected by thickness of A0 layer. Of major eight species, seedling density of four pioneers (Lindera citriodora, Mallotus japonicus, Rhus succedanea and Fagara mantchurica) were closely related to the gap ratio. Of the four pioneers, Lindera citriodora responded gap formation independently upon the soil disturbance. Mallotus japonicus did not appear in the gaps where soil was disturbed, while Rhus succedanea and Fagara mantchurica only appeared on the disturbed soil. These results are supposed to be due to the differences in gap environments and the differences in the germination mechanism of these species. Effects of size and intensity of disturbance on growth of seedlings were more obvious than on their recruitment.
Key words: disturbance size, disturbance intensity, gap ratio, fish-eye photo.
Correspondence: Miyazaki University Forests, 11300, Otsu, Tano-cho, Miyazaki-gun, Miyazaki, 889-17, Japan
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