Transition of sulfur nutrition from excessive supply to potential deficiency in spruce forest ecosystems in Central Europe

• Applicant: Dr. Dorit Julich
• Subject Area: Forestry ; Plant Cultivation, Plant Nutrition, Agricultural Technology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426668836

Atmospheric sulfur (S) deposition during the 1970-90s caused distinct negative effects in forest ecosystems of North and Central Europe. Therefore, the role of S in forest nutrition was mainly seen as a surplus nutrient, or even pollutant, resulting in the assumption of a long-term sufficient S supply for forest growth. Nonetheless, recent results from European forest monitoring have revealed a considerable decrease of S stocks in forest soils and clearly reduced foliar S contents in different tree species, especially Norway spruce. These effects are related to the marked decrease of atmospheric S deposition and gradual recovery from formerly high S deposition. Consequently, the S nutritional status in forest ecosystems is increasingly relying on internal S cycling (from mineralization) and S supply from mineral sources. In addition, other environmental factors, partly related to climate change (i.e. increased levels of atmospheric CO2 and temperature) may induce changes in forest nutrition, especially with regard to nutrient stoichiometry in plant and soil. Thus, the proposed project focusses on the understanding of the transition of S nutrition in forests from excessive supply to the point of potential deficiency. This will also consider interconnections with other biogeochemical cycles (C, N, P) and potentially emerging nutrient imbalances. We will apply a combination of analytical approaches (classical element analysis, SEM/EDX, IRMS) on various ecosystem compartments (needles, tree ring wood, mineral soil, O-layer) using archived old as well as newly taken samples. The test sites comprise Norway spruce forests in Germany with contrasting S supply in terms of quantity, temporal changes and atmospheric/lithogenic sources. Based on concentrations and elemental ratios ('ecological stoichiometry') changes in S supply over time will be retraced. This will allow to assess ecosystem S nutrition in terms of potentially emerging deficiency and imbalances.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Karl-Heinz Feger; Professor Dr. Stefan Julich