BETA-FOR

Natural forests form a diverse mosaic of different successional stages, with variability in environmental conditions and species compositions both determining the overall ecosystem functions. The recently observed consistent loss of β-diversity across ecosystems indicates increasingly homogeneous communities in patches of landscapes, mainly caused by increasing land-use intensity. Biodiversity is related to numerous ecosystem functions and stability. Therefore, decreasing β-diversity is also expected to reduce multifunctionality. Over centuries, a focus on timber production has on the one hand, considerably homogenized the structure and compositions of temperate forests. On the other hand, forest management constantly creates disturbances on different scales, which may create heterogeneity. Interestingly, these contrasting effects have not been studied in detail, and the impact of forest management practices on β-diversity and β-multifunctionality is still lacking empirical evidence. This is based mainly on the paucity of experimental studies on β-diversity and ecosystem functions at the landscape scale. Recent forest diebacks have rapidly accelerated the need to investigate the role of between-stand heterogeneity on diversity and ecosystem functions as a baseline for long-lasting management strategies.

To assess the impact of homogenization and to develop guidelines to reverse its potentially negative effects, we combine expertise from forest science, ecology, remote sensing, chemical ecology and statistics in a collaborative and experimental β-diversity approach. Specifically, we will address the question whether the Enhancement of Structural Beta Complexity (ESBC) in forests by silviculture or natural disturbances will increase biodiversity and multifunctionality in formerly homogeneously structured production forests. Our approach will identify potential mechanisms behind observed homogenization-diversity-relationships and show how these translate into effects on multifunctionality.

At eleven forest sites throughout Germany, we selected two districts as two types of small ‘forest landscapes’. In one of these two districts, we established ESBC treatments (nine differently treated 50x50 m patches with a focus on canopy cover and deadwood features). In the second, the control district, we will establish nine patches without ESBC. In the Würzburg University Forest Sailershausen, three district pairs are located that serve as intensive study sites with a refined version of ESBC treatments. Here, we will conduct additional sampling of biodiversity, ecosystem functions, and environmental variables, to maximize our mechanistic understanding and to develop a simplified sampling design for long-term monitoring. This will be done at one site per climate region, where the response of trees and associated flora and fauna to ESBC-treatments will be recorded including years with extreme climate conditions. Comprehensive measurements from all eleven sites and repeated rapid assessment in six long-term monitoring sites will allow generalization of our findings for a variety of forests in Germany. By a comprehensive sampling, we will monitor 18 taxonomic groups and measure 21 ecosystem functions, including key functions in temperate forests, on all patches. The statistical framework, will allow a comprehensive biodiversity assessment by quantifying the different aspects of multitrophic biodiversity (taxonomical, functional and phylogenetic diversity) on different levels of biodiversity (α-, β-, γ-diversity). To combine overall diversity, we will apply the concept of multidiversity across the 18 taxa. We will use and develop new approaches for quantification and partitioning of multifunctionality at α- and β- scales.

Overall, our study will herald a new research avenue, namely by experimentally describing the link between β-diversity and multifunctionality. Furthermore, we will help to develop guidelines for improved silvicultural concepts and concepts for management of natural disturbances in temperate forests reversing past homogenization effects.