Abstract
Simple logistic model cannot describe the decrease in the plant biomass after biomass has reached a plateau, i.e., carrying capacity. To alleviate this shortcoming, a practical extension of the logistic model was attempted in this study. Suppose that w is the plant biomass at time t, and r and W are constants designated as growth coefficient and carrying capacity of the plant biomass, respectively. Here, the simple logistic model is represented by the following equation : dw/dt=rw (1-w/W). In the new version, r is replaced by a quadratic polynomial equation of time t as follows : dw/dt=(b_1+b_2t+b_3t^2) w (1-w/W). An example for the analysis of the dynamics of aboveground biomass in the Stipa baicalensis plant community is given in this paper.
