Variation In Age Structure Research Articles

A preliminary study on collembolan populations in a pine forest

Summary A study was made of the populations of Collembola in the pine forest. Among the eight species commonly found, Folsomia octoculataHandschin was numerically dominant. Seasonal population changes of these eight species were described over a year. It was found that many species show two peaks in number. As for F. octoculata, the dominant species, the changes in number was discussed in connection with the variation in age structure. The census data for each species were examined for the distribution pattern by using the regression method. None of these eight species was distributed at random in the soil and they could be classified into three groups based on the differences in the degree of aggregation in terms of coefficient β of the regression. It was suggested that such differences in the distribution pattern are largely due to differences in the response to heterogeneity of the habitat. In the case of F. octoculata, the changes of distribution pattern in the course of post‐embryonic development were examined and it was found that (a) the component of distribution is a single individual rather than a colony, and (b) the degree of aggregation is decreased with the development of individuals. Using the relationship, the relation of the necessary sample size to the population density was derived for a fixed level of presision (D=S.E./m=0.2) and some suggestions were given concerning sampling plans for these insects.