Modeling the dynamics of a spruce forest and dwarf mistletoe population: a coupled system

The parasitic plant dwarf mistletoe (Arceuthobium) is currently one of the most threatening infestations of coniferous forests worldwide, especially in Eurasia and North America, but its population dynamics in relation to one of its hosts (spruce) remain unclear. Here, toward understanding the population dynamics, differential equations were used to construct a life history model for the two populations, and two relatively independent subsystems, host and parasite, were generated from their symbiotic relationships. A suspected-infection model was used to couple them. The resulting models were used to analyze structural changes in the forest. When each infected spruce was assumed to support 1000 parasite shoots, the spruce population first increased rapidly, then slows. When 2000 parasite shoots were assumed, the forest declined dramatically, slipping to zero in the 10th year, and the spruce seedlings were unable to regenerate. Parasite shoot population curves transformed from exponential J-shapes to logistic S-shapes, reaching population limitations as germination rates changed. These results provide important clues to understanding developmental trends of the present parasite population and will assist in reconstructing invasion histories.

Automated summary

The parasitic plant dwarf mistletoe is a major threat to coniferous forests worldwide, especially in Eurasia and North America. By using differential equations to construct a life history model, researchers were able to analyze the population dynamics of both the parasite and its host, spruce. They found that an increase in parasite shoots could lead to a decline in the forest ecosystem, ultimately affecting the regeneration of spruce seedlings. These findings provide important insights into the developmental trends of the parasite population and will help in reconstructing invasion histories.