Simulating effects of precipitation and initial planting density on population size of Mongolian pine in the Horqin Sandy Land, China

Sand dunes in China are widely re-vegetated with Mongolian pine (Pinus sylvestris var. mongolica). However, the effects of precipitation and planting density on population dynamics of this tree species are not well known. We established a system dynamics (SD) model for Mongolian pine to explore the effects of precipitation and initial planting density on population dynamics. This study applied the SD model in simulating the dynamics of a plant population with random environmental factors. The results in this study revealed that the SD model performed well in reflecting the dynamics of Mongolian pine population in the Horqin Sandy Land (ARE < 0.13, MARE = 0.048). Population size fluctuated in the range of 1150–1350 individuals ha−1 under mean annual precipitation of 500 mm and planting density of 10,000 individuals ha−1, suggesting that this range was the fittest density of Mongolian pine population at that precipitation level. Population size varied with precipitation, indicating that water supply played an important role in determining the dynamics of Mongolian pine population. Initial plantation density did not influence population size in scenarios with high precipitation but it influenced population size under low precipitation. This suggested that initial plantation density was more important under low than under high water supply used to support the development of Mongolian pine population. These results are important for formulating guiding principles for the management of Mongolian pine populations in the Horqin Sandy Land.