Abstract
Forest soils play an important role in the active carbon (C) cycle of terrestrial ecosystems as they store one third of the global organic carbon. Therefore, the sequestration of atmospheric carbon in soils as stable organic matter is discussed as a potential contribution to mitigate atmospheric CO2 concentrations. The carbon dynamic in forest ecosystems is expected to be a result of environmental as well as human-induced factors. Germany’s forest soils contained in the organic layer and the mineral soil down to 90 cm on average 117.1 ± 1.7 Mg C ha–1 which has been increased significantly since the NFSI I by 0.75 ± 0.09 Mg C ha–1 year–1 resulting in a total increase of 11.3 Mg C ha–1. Structural equation modelling was performed to analyze direct and indirect factors affecting organic carbon stocks and organic carbon stock changes. The pathway analyses revealed a variation of carbon stocks in the organic layer that was especially controlled by tree species. Organic layers under broadleaf trees stored less carbon than under coniferous trees, while tree species effects on carbon stocks of mineral soil were comparatively less pronounced. Soil carbon stocks were furthermore affected by site conditions. An effective selection of tree species combined with specific site conditions may therefore enhance carbon sequestration potential of soils. We found specific effects of nitrogen deposition and forest liming on carbon stock changes. The additional nitrogen has the potential to increase sequestering carbon by an increase in productivity and accumulation of soil organic matter through increased litter production, while liming may both stimulate and inhibit soil respiration depending on various environmental conditions. Altogether, the results showed that further research is needed to identify the most important factors affecting turnover of soil organic matter in respect to the impact of anthropogenic effects as forest stand management, liming, or atmospheric nitrogen deposition especially on dynamics of microbial communities as well as on recalcitrance and stabilization of soil organic matter.
Highlights
Forests play an important role in the global carbon (C) cycle
Carbon stocks of the organic layer and the mineral soil down to 90 cm totaled to 117.1 Mg ha–1 in 2006, of which 17% of organic C was stored in the organic layer and 58% in the upper 30 cm of the mineral soil
The results showed that the variation of C stocks in the organic layer was especially controlled by tree species as soils under broadleaf trees stored less C in the organic layer than soils under coniferous trees
Summary
Forests play an important role in the global carbon (C) cycle. Through photosynthesis plants convert atmospheric carbon dioxide (CO2) into plant biomass. The mineralization of organic matter is limited by temperature and water availability, and the amount and dynamic of soil C pools are substantially affected by climate (Davidson and Janssens 2006; Lorenz and Lal 2010) It is not yet fully resolved why one part of soil C is decomposed rapidly, while other parts are characterized by turnover times ranging from decades to millennia (Baisden et al 2002). Results of the 1st National Forest Inventory (NFSI) were presented by Wolff and Riek (1996), who showed spatial patterns of C stocks and morphological humus forms and found correlations to bedrock, soil texture, and main soil types They reported effects of a partial decoupling of material cycles on C dynamics due to longlasting acid and N deposits during the last decades. With the repetition of the NFSI, Germany obtained a comprehensive data base to evaluate the status quo of soil organic matter and the C sequestration rate of forested soils over time
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
