In this post Jan Douda discusses his recent paper ‘Traditional forest management practices stop forest succession and bring back rare plant species‘
The past management practices may continue to influence ecosystem functions and processes for decades, centuries or even longer after they have been abandoned. Until now, few authors have attempted experiments which test the effects of restoring some of these past management practices on long-term forest succession. On the one hand, the restoration of the past management practices may upset a community’s successional trajectory. It may renew characteristics of the target ecosystem. On the other hand, certain irreversible ecosystem changes following the abandonment of traditional management practices (such as the disappearance of some target species and their propagules or ecosystem eutrophication) may constrain ecosystem restoration.
In Europe, lowland forests have long been considered stable, climax habitats and some of these are now conserved in nature reserves without any management interventions. However, strong evidence now indicates that the diversity of various species groups including butterflies, saproxylic beetles and also plants have declined following the abandonment of some traditional forest management practices. These declines very likely correspond to decreasing frequencies of traditional anthropogenic disturbances, such as grass cutting, forest coppicing, litter raking and wood-pasture.
In our paper, we evaluated a five-year field trial in a lowland thermophilous oak forest in the Bohemian Karst (the Czech Republic) to describe the effects of the restoration of litter raking and grass cutting on plant species diversity and presence of rare target species. The central European thermophilous oak forests represent an endangered species-rich vegetation with a large proportion of dry grassland species. From the second half of the 20th century until now, a number of authors have recorded significant declines in species diversity and changes in species composition of this vegetation characterised by the spread of nitrophilous species and mesophilous hornbeam forest species as a consequence of undisturbed forest succession. We asked if restoration of traditional forest management practices stop forest succession and bring back rare plant species.
By introducing traditional forest management practices we were able to reverse the forest succession towards higher richness and cover of target species. Therefore, to maintain plant diversity in European lowland forests, some traditional forms of forest management should be encouraged in contrast to the prevailing strategy which is to attempt to conserve biodiversity by avoiding all interventions. Our study also supports the idea that restoration of traditional forest management practices should carefully distinguish among possible interventions. Litter raking in thermophilous oak forests exposes spaces and encourages recruitment of immigrant plant species, thus maintaining the key understorey vegetation components (i.e. thermophilous forest and dry grassland species). Conversely, grass cutting maintains only the dry grassland species (albeit with more pronounced effect), whereas the forest species were not affected. The restoration of traditional management practices should also consider in which types of forests these might be used to enhance biodiversity. For example, grass cutting makes sense only in rather open forests. In contrast, litter raking was historically applied also in closed mountain beech forests. Future research should also focus on the questions of how the restoration of past management practices interacts with contemporary environmental changes such as climate warming and increasing atmospheric nitrogen deposition.