Direct and Indirect Effects of Management Intensity and Environmental Factors on the Functional Diversity of Lichens in Central European Forests.

Steffen Boch,Markus Fischer,Eric Allan,Hugo Saiz,Laurens B Sparrius,Daniel Prati,Dominik Hessenmöller,Ernst-Detlef Schulze,Peter Schall

doi:10.3390/microorganisms9020463

Abstract

Using 642 forest plots from three regions in Germany, we analyzed the direct and indirect effects of forest management intensity and of environmental variables on lichen functional diversity (FDis). Environmental stand variables were affected by management intensity and acted as an environmental filter: summing direct and indirect effects resulted in a negative total effect of conifer cover on FDis, and a positive total effect of deadwood cover and standing tree biomass. Management intensity had a direct positive effect on FDis, which was compensated by an indirect negative effect via reduced standing tree biomass and lichen species richness, resulting in a negative total effect on FDis and the FDis of adaptation-related traits (FDisAd). This indicates environmental filtering of management and stronger niche partitioning at a lower intensity. In contrast, management intensity had a positive total effect on the FDis of reproduction-, dispersal- and establishment-related traits (FDisRe), mainly because of the direct negative effect of species richness, indicating functional over-redundancy, i.e., most species cluster into a few over-represented functional entities. Our findings have important implications for forest management: high lichen functional diversity can be conserved by promoting old, site-typical deciduous forests with a high richness of woody species and large deadwood quantity.

Highlights

IntroductionLichens are an important component of forest ecosystems
Management intensity (SMId) and conifer cover had a direct positive effect on the woody species richness and deadwood cover, and a direct negative effect on standing tree biomass, rock cover and lichen species richness (Figures 3a, 4a and 5a). They showed contrasting effects on lichen functional diversity, with a direct positive effect of management intensity and a negative direct effect of conifer cover (Figures 3a, 4a and 5a), the significance of these effects depended on the trait considered (Figures 3a, 4a and 5a)
Our results showed that forest management influenced lichen functional diversity through multiple paths, and that indirect effects could be more important than direct ones

Summary

Introduction

Lichens are an important component of forest ecosystems. Lichen communities constitute a substantial part of forest biodiversity [1,2,3,4] and contribute to important ecological functions [5]. Because of lichen sensitivity to environmental changes, human-induced habitat degradation (e.g., by land-use changes) and air pollution have led to strong declines in lichen diversity during the last century [2]. Forest management is proposed to be one of the most important threat factors, responsible for a large number of threatened lichen species [2,6,7].

Methods

Results

Discussion

Conclusion