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

• Final Report Year: 2024

Final Report Abstract

The project investigated the transition of sulfur (S) nutrition in spruce forests from excessive supply by atmospheric deposition during the 1970–90s to the current system with very low S input from external sources. We expected that plant S supply in these forests must increasingly rely on S release by internal nutrient cycling (mineralization). Our multi-compartment approach investigated formerly polluted forests in the Ore Mountains (Saxony/E Germany) for S in microbial and plant biomass, the availability of S in soil, the S-release by mineralization, and the S- export through seepage water. For comparison, we selected plots at a former experimental site in the Black Forest (Schluchsee/SW Germany), where treatments with different S compounds and lime were applied 30 years ago, and a rather undisturbed (“clean-air”) system at Davos (Central Alps/Switzerland). The results for the temporal development of soil S pools confirmed that legacy pools from atmospheric deposition were translocated from upper soil to lower depth over time and consequently, organic S relatively increased. The analysis of stable S isotopes in soil as well strongly indicate a decrease of deposition-derived sulfate-S in the soils. At the same time, the export of sulfate-S with seepage water was observed to decrease significantly over the last three decades and was de-coupled from deposition (currently no relationship detectable). In coherence with the strong decrease in S deposition and S export from soils, S nutrition in spruce needles strongly decreased to a very low level of approximately 0.7–1.0 mg kg-1. Currently, foliar S contents at the former polluted sites no longer differ significantly from “clean-air” and historical lowdeposition sites. Moreover, the element contents of further nutrients, such as phosphorus and magnesium, were on a very low level. The nutrient supply at some of the sites might therefore be critical or already (co-)limited. However, for S release (mineralization) and S availability in soil, we found distinct differences for the sites, indicating that S cycling processes are different. Whereas, internal S cycling with active mobilization of S by microbes seems to be well established at the “clean-air” site, S turnover at the slowly recovering sites still is affected by the former pollution. Liming as countermeasure for soil acidification at these sites has been found to substantially affect S mineralization as well as S uptake by trees and microbes in the longterm. Thus, liming improved conditions for microbial growth considerably and strongly affected the relationships between C, N, and S in soil and microbial biomass.

Publications

• Bindungsformen und Umsätze von Schwefel in Waldböden. BGS/DBG- Jahrestagung, 24.-29. September 2019, Bern, Schweiz
  Feger, K.H., Julich, S. & Julich, D.
  
• Schwefel-Umsätze in Wäldern. DVFFA-Tagung Sektion Waldernährung, 4.-7. Juni 2019, Davos, Schweiz
  Feger, K.H., Julich, S. & Julich, D.
  
• Long-term changes of sulfur supply in forest soils. Eurosoil, 23.- 27. August 2021, Geneva, Switzerland
  Julich, D., Julich, S., Jakob, F. & Feger, K.H.
  
• Nachlieferung von Schwefel und Stickstoff aus der Mineralisierung im Auflagehumus und obersten Mineralboden. DBG-Jahrestagung, 5.–8. September 2022, Trier
  Julich, D., Julich, S., Zethof, H.T.J. & Feger, K.H.
  
• Schwefelverfügbarkeit in Fichtenbeständen 25 Jahre nach Reduktion der Schwefeldeposition im Erzgebirge. Tagung „Stoffflüsse und Vorräte in Waldökosystemen: Messung, Monitoring & Modellierung" 17.-18. März 2022, DBG, DVFFA, DHG (online)
  Zethof, H.T.J., Julich, D., Julich, S. & Feger, K.H.
  
• Sulphur supply from microbial mineralization in Norway spruce stands after former high atmospheric sulphur deposition. World Congress of Soil Science 1.–4. August 2022 (WCSS22), Glasgow, UK
  Zethof, H.T.J., Julich, S., Feger, K.H. & Julich, D.
  
• Sulfur availability in two Norway spruce stands with contrasting atmospheric deposition levels in the past - Evidence from foliar and soil analysis. DBG-Jahrestagung, 02.- 08. September 2023, Halle/Saale
  Zethof, H.T.J, Julich, S., Feger, K.H. & Julich, D.
  
• Effects of Past Sulfur Deposition on the Soil Microbial Biomass at Spruce Forest Sites. Soil Systems, 8(2), 37.
  Julich, Dorit; Julich, Stefan; Feger, Karl-Heinz; Klauder, Tobias & Zethof, Jeroen H. T.