Abstract
This paper discusses the general control equation of plant community (7), introduced in previous paper (I), under the following conditions; (i) age is neglected (ii) plant community is constructed by one plant species (iii) community is not controlled, but (iv) withering is taken into consideration. In order to study the related problems of plant withering, its mechanism should be given.
In this paper, two models dealing with death phenomenally are introduced. The one, called model III, is based on the idea that withering increases proportionally as the community grow over a certain volume level, and the other, model IV, is the one which is based on the hypothetical death function. Model III is the one based on the following assumption; there is a limit level YLIM that is smaller than maximum community level Y*. The weeker plant in the community dies to maintain the level YLIM, as the community is growing up. This model may be able to describe static characteristics of community, such as mean weight of plant species. However it will not be appropriate to express naturally dynamic one such as distribution change.
Model V is a model based on the death function (6). It is more natural than model III to represent dynamic characteristics such as changes to limit level YLIM and distribution changes. The death function is however, assumed hypothetically and it may be difficult to obtain the actual value.
With regard to the conservation law, which means that community can not grow over a certain volume level in a unit area of field, model III may be ecologically more appropriate.
