POPULATION DYNAMICS AND PRODUCTION PROCESSES OF INDIGENOUS AND NATURALIZED DANDELIONS SUBJECTED TO ARTIFICIAL DISTURBANCE BY MOWINGS

Abstract

In Tsugaru district, Aomori Prefecture, the floors of apple orchards are generally covered with vegetations which are subjected to periodical mowings and are dominated by a naturalized species of dandelion, T. officinale, and an indigenous one, T. hondoense. This study describes the population dynamics of these two species of dandelion and their dry matter production processes in an attempt to observe their adaptive strategies to artificial distrubance by mowings. In the sites occupied with small numbers of T. officinale, T. hondoense were frequently more aboundant than T. officinale, whereas with an increase in the density of T. officinale, the density of T. hondoense steadily decreased. The density of the dandelion seedlings linearly decreased with the increase in the total density of adult dandelions. Compared with T. hondoense, T. officinale showed ability to reconstruct rapidly a large quantity of leaves relative to other organs during short periods between each mowing. Individuals of T. offcinale had an average of 2.5 shoots (internodes), ranging from one to six, whereas most individuals of T. hondonse had only one shoot. No statistically significant correlation could be found between the distributional pattern of the dandelion density and the environmental factors including relative light intensity, soil moisture, total carbon and total nitrogen contents of soil and soil pH in their living sites.