Counts of herb stems were made with each systematic grid sized 10㎝ by 1300㎝ within six apparently homogeneous herb layers under the open young Japanese red pine, Pinus densiflora, stands. The stands had often been subjected to strong human interferences such as burning, cutting, grazing, and denuding since human settlement until the conservation scheme practiced in these stands for last decade. In addition, amounts of loss of ignition and field capacity were determined to detect soil heterogeneity among and within the stands.
The values of information measure of diversity(H) and Hurlbert´s probability of interspecific encounter(Δ,) obtained here do not show any consistent correlation. The amount of interspecific competetion(Δ_1), the ratio of interspecific to intraspecific competetion(Δ_4), Levin´s niche breadth(Sh), and species evenness(V), increase, while the amount of intraspecific competetion decrease, as the soil factors become favorable. One stand examined does not follow the above trends, which is more young and shows strong within site heterogeneity of the soil factors. The stand includes pioneer species which is not detectable without detailed observation.
It is argued that in stable or favorable environment more intense interspecific competetion and less intraspecific competetion might occur, but this situation does not necessarily always bring smaller niche breadth. In this connection, the results support Hurlbert´s contention that the two components of diversity should be analyzed separately.
|