Incorporating a model for ground lichens into multi-functional forest planning for boreal forests in Finland

The quantitative assessment of forest management impacts on ecosystem services calls for ecological models to be linked to forest planning systems. In these systems, such models are expected to produce valid and accurate predictions to quantify the effects of alternative forest management strategies on ecosystem services. As an example, we present an evaluation of the model for the percent cover of ground lichens in forests on mineral soils in Finland. First, the performance of the lichen cover model fitted to the data of forest vegetation surveyed in 1985-1986 was comprehensively validated with the data resurveyed on the same plots in 1995. The differences between the observed and predicted values in lichen cover were calculated and analysed. Second, stand-level analyses were conducted to validate the predicted development of lichen cover in accordance with the rotation length development and management of forest stands. Third, the impacts of forest management scenarios on the average lichen cover at regional level were calculated to validate the results over larger areas. Lichen cover was predicted by site fertility, growing stock, forest harvests, soil preparation and geographic location. Our evaluation suggested that the model logically predicted the 10-year change in lichen cover at the stand level. A negative bias was found in predictions especially on xeric sites in northern Finland, although this was not related to stand management, but probably to global greening and reindeer grazing. The model based on the cross-sectional vegetation survey data showed its ability to describe the long-term changes in lichen cover along with the development and management of stands in different site fertility classes. On xeric and barren sites, the analyses showed decreasing trends in the average lichen cover at the regional level during the 30-year simulation period. However, the development of the average lichen cover varied only slightly among the alternative forest management scenarios. This study provides a modelling approach to evaluate the impacts of forest management on ecosystem services, here the cover of ground lichens, as an indicator of forest biodiversity and quality of reindeer pastures.