FOR 5315:  FOREST FLOOR: Functioning, Dynamics, and Vulnerability in a Changing World

• Subject Area: Agriculture, Forestry and Veterinary Medicine
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 457330647

The forest floor (FF) is the interface between above- and belowground parts of forest ecosystems. It provides habitat for a wide range of organisms, serves a seedbed and growth substrate for vegetation and acts as a central ecosystem hub where organic matter, nutrients, water and gases are stored, absorbed and transformed. As such, FF properties reflect complex interactions between biotic and abiotic ecosystem components, especially those related to microclimate and nutrient supply. An impact of climate warming on FF and associated services is likely especially in temperate regions where small changes in control variables may induce shifts from organic layer-dominated to mineral soil-dominated forests. Our RU focuses on analyzing the causal links between controls, properties, and ecosystem services of FFs. These links will enable (i) the determination of the service fulfillment through the FF in comparison to mineral topsoil, (ii) an assessment of FF vulnerability under climate warming and (iii) the use of FF properties as indicators for service fulfilment under given climatic conditions and properties of the mineral soil. These goals are directed by the overall hypothesis of the RU: Forest Floor properties of European beech forests are shaped by adaptations of organisms to the nutrient status of soils. The influence of climate warming on FF services depends on the interactions with these adaptations. This hypothetical framework will be implemented through specific hypotheses of 11 individual projects in close cooperation by focusing on combined phosphorus (P) and temperature impacts in European beech (Fagus sylvatica) forests admixed with Norway spruce (Picea abies) and sycamore maple (Acer pseudoplatanus). Twelve study sites allow the investigation of the interacting controls air temperature and P level of soils. At these sites, we will conduct 13C, 15N, 2H litter labelling experiments for process tracing and quantification and we will address nutrient, carbon and water dynamics. Our research will be complemented by studies addressing tree seeding experiments, microbial communities, soil fauna food webs, and root- and mycorrhiza-driven processes. Time-series analyses of existing data and ecological modelling will support process understanding, upscaling and scenario estimates.

• DFG Programme: Research Units
• International Connection: Denmark, Switzerland, United Kingdom

Projects

• Carbon fluxes in forest floors (Applicant Hagedorn, Frank )
• Coordination Funds (Applicant Lang, Friederike )
• Driver of microbial nutrient turnover in mineral soil, rhizosphere and forest floors (Applicants Schloter, Michael ;  Schulz, Stefanie )
• Forest floor property controls and consequences for forest soils’ thermal-hydrological functioning (Applicants Puhlmann, Heike ;  Schwärzel, Kai ;  Wellbrock, Nicole )
• Interaction between carbon exudation by tree roots and their mycorrhiza associations and forest floor thickness (Applicant Werner, Christiane )
• Interrelation of biochemical and physicochemical forest floor properties: Effect of SOM-mineral association and interaction (Applicant Prietzel, Jörg )
• Mycorrhizal functions in the forest floor (Applicant Meier, Ina Christin )
• Nutrient dynamics along the litter – mineral soil continuum (Applicants Lang, Friederike ;  Prietzel, Jörg )
• Soil fauna as drivers of the architecture of forest floors (Applicant Scheu, Stefan )
• The architecture of the forest floor and consequences for connectivity (Applicant Schack-Kirchner, Helmer )
• The influence of forest floor changes on the success and composition of tree regeneration (Applicant Bauhus, Jürgen )
• Water storage and redistribution in the forest floor affect percolation, evaporation and DOM loss (Applicant Weiler, Markus )

• Spokesperson: Professorin Dr. Friederike Lang