P09 Effect of tree nutrient strategies and carbon exudation by root-mycorrhizal associations on forest floor turnover

In this project, we investigate the influence of different tree species on the Forest Floor (FF) with a focus on three specific aspects:

First, the nutrient cycling and tree-internal recycling strategies of the three focal tree species (European beech, Norway spruce, sycamore maple) will be investigated. This includes the sampling of different tissues, analyse their content of carbon (C), nitrogen (N), phosphorus (P) and their isotopic composition (δ¹³C and δ¹⁵N) at different time points throughout the vegetation period.

Second, root exudation plays an important role not only by representing a source of carbon to the FF and the mineral soil, but also by altering the distribution, potentially the composition, and activity of microorganisms, investigated by project P7. The focus in this project will be on the exudation of sugars and organic acids of the above-mentioned species in the FF and the mineral soil across different seasons. This pattern is dependent on the mycorrhizal association of the tree, which is investigated in project P8

Third, the trees’ contribution to lateral displacement of nitrogen (N) and hydrogen (H) will be investigated in a litter dispersal experiment in co-operation with projects P2, P3, P4, P6 and P8. For this purpose, beech and maple litter with traceable ¹⁵N and ²H will be applied at two sites and its displacement over the following years will be studied by sampling roots and branches of the surrounding trees and understory vegetation.

Results gained in this project might help understand the complex forest ecosystem and predict the consequences of forest change.