Suitable habitat mathematical model of common reed (Phragmites australis) in shallow lakes with coupling cellular automaton and modified logistic function

Simulating of suitable habitat for the common reed (Phragmites australis) can provide theoretical support for water-resources managing of shallow lakes. Earlier research has focused on statistical models of shallow lakes and process-based dynamic models for coastal wetlands. However, process-based dynamic modeling for shallow lakes remains relatively incomplete, and the loss of biomass in unsuitable situations is seldom considered. This study established an occupied habitat model by coupling a cellular automaton with a modified logistic function. The cellular automaton was used to simulate the spatial diffusion of the reed. The logistic function was used to simulate the accumulation of biomass over time, and modified with the loss of biomass in unsuitable habitats. Both reed distribution and dynamic variations in reed growth can be simulated by this model. Water level was considered the most important factor in reed growth. In Baiyangdian Lake, China, the growing season is from April to October. The suitable habitat area (SHA) and aboveground biomass (AGB) of reeds were simulated using data from actual hydrological processes and hypothetical scenarios. Element contents and water consumption by transpiration were estimated on the basis of the AGB data. The results are as follows. (1) Water-level changes affected the habitat of the common reed. The SHA increased slightly (from 6.0 m) and then decreased with rising water level, reaching its maximum value at 6.7 m of the 90 % guarantee rate water level. SHA declined rapidly when the water level was higher than 7.5 m. (2) When the water level was maintained at 6.3–7.3 m, the water consumption for transpiration per unit AGB was lower than that for other water levels. (3) To maintain a higher water level for a suitable reed habitat area and to reduce water consumption per unit biomass transpiration, a reference value of 6.7 m can be regarded as the lowest ecological water level in Baiyangdian Lake.