Hmodel, a Heterobasidion annosum model for even-aged Norway spruce stands

Heterobasidion annosum (Fr.) Bref. s.l., a group of fungi causing root rot, is a serious threat to Norway spruce (Picea abies (L.) Karst.) stands in northern Europe. A new stochastic spatial model (Hmodel) was developed to simulate H. annosum s.l. infection and spread within a stand. Hmodel was combined with the stand-level decision support system MOTTI, resulting in a platform for estimating H. annosum s.l. development and its effect on tree growth and timber quality. Three H. annosum s.l. scenarios, representing different levels of risk for H. annosum s.l. infections simulated for a typical Norway spruce stand in southern Finland, demonstrated that the mycelial growth rate in the roots of living trees was the most critical parameter influencing the simulation results. In addition, the simulation results indicated that the number of infected trees in the previous stand plays a major role in H. annosum s.l. dynamics within the subsequent tree generation. Hmodel was designed to be a flexible platform for researchers to simulate the effects of H. annosum s.l. on stand dynamics and, vice versa, the effects of different silvicultural methods on H. annosum s.l. dynamics.