Autor:innen:
Robin Schäfferling | TU Dresden, Institute of Soil Science and Site Ecology | Germany
Lilli Zeh | TU Dresden, Institute of Soil Science and Site Ecology
Patrick Wordell-Dietrich | TU Dresden, Institute of Soil Science and Site Ecology
Kenton P. Stutz | Albert-Ludwigs-Universität Freiburg, Professur für Bodenökologie
Stefan Julich | Hochschule für nachhaltige Entwicklung Eberswalde
Karl-Heinz Feger | TU Dresden, Institute of Soil Science and Site Ecology
Karsten Kalbitz | TU Dresden, Institute of Soil Science and Site Ecology
Deadwood has important functions in forest ecosystems. It is a biodiversity hot spot, serves as a storage of water and stores 8% (73 +- 6 Pg) of the world’s forest carbon. The fate of this carbon (C) is still highly debated particularly concerning its influence on soil organic matter and its contribution to the forest soils C sink. Our research investigates the extend to which downed beech deadwood influences the stable C pool in the soil of temperate beech forests and how that relationship depends on soil moisture.
The research was conducted in a near natural beech forest near Leipzig, Germany (Dübener Heide) and is part of the BENEATH-Project. We sampled three subsites representing a soil moisture gradient, i.e. dry, moist and wet conditions. Undisturbed soil cores were taken from these subsites in three depth (0-10 cm, 10-20 cm and 20-30 cm) beneath coarse woody debris (CWD) at an advanced stage of decay. Reference soils were sampled at a distance of about 2 m. The samples were separated into the free light fraction (F-LF), the occluded light fraction (O-LF) and the heavy fraction (HF) via density fractionation using sodium polytungstate solution (ρ = 1,6 g cm-³). For each fraction, the organic C and N contents were determined.
We expect significantly higher C stocks in the topsoil under CWD compared to the reference sites. These differences should especially occur in the F-LF and in the O-LF fraction because of a high input of particulate organic matter by deadwood (i.e. F-LF) and a high (micro)biological activity promoting aggregation (i.e. O-LF). We also expect higher amounts of C in the HF under deadwood due the high input by dissolved organic matter coming from the deadwood that interacts with the mineral phase of the soil. Carbon in the HF constitutes the mineral-associated organic C that is considered to be stabilized in the soil on the long term. That process should be particularly relevant in the subsoil and under wet conditions.
Our results should sharpen the picture of the deadwood’s role for long term C stabilization in forest soils and how this process is affected by differences in the soil moisture status. They will give implications for climate mitigation through forest management