Using high resolution mapping of disturbance indicator species to assess the sustainability of silviculture activities

In order to assess environmental degradation in forested ecosystems, we examined the succession of the distribution pattern of four disturbance indicator species (Carex remota, Juncus effusus, Rubus fruticosus and Urtica dioica) after 14 years under various tree species, stand structures and stand diversities. The research was conducted in a 4383 ha-ancient forest in central Belgium. The presence of each of these four key-species was noted according to a grid-map of 6330 cells of 50 m × 50 m. Beech (Fagus sylvatica) stands enhanced all the investigated herbs compared to oak (Quercus robur) stands. Low stand diversity (<3 tree species) also promoted all studied indicator species. Interestingly, different effects were detected within the high forest regime (shelterwood system). Old high forests as well as even-aged high forests enhanced the appearance and the persistence of the studied indicators of disturbance.In our study area, on acidic silt loam soils, some tree species or silvicultural treatments appeared to slow down soil degradation: (1) Q. robur overstories should be preferred to Fagus sylvatica stands; (2) a high stand diversity (preferentially more than three tree species) is highly desirable; (3) a diversification of the stand structure should be encouraged. Within the shelterwood system, uneven-aged stands (irregular shelterwood system) should be promoted compared with even-aged stands (shelterwood uniform system).