Changes in emission regime for nitrogen and sulfur in Germany and its impact on a spruce forest measured over a period of 35 years

Le résumé fourni par la source

Abstract In Germany during several decades, emissions and thus the chemical climate affecting forests have changed significantly. The effects of these changes on the element balance of forests can be documented only by long‐term observations, as has been done at the Höglwald site (Southern Bavaria) since 1985. Since then, structural changes in agriculture have led to a reduction in emissions of reduced nitrogen (NH 3 ). There was also a slight decrease in emissions of oxidized nitrogen (NO x ). Air pollution control measures, especially in the 1980s, led to a particularly drastic reduction of sulfur emissions (SO 2 ). Consequently, inputs to the ecosystem decreased by almost 95% between 1985 and 2020. Dry deposition nowadays plays practically no role for this element. High nitrogen inputs, dominated by reduced nitrogen, have led to a high proton production through N transformations. This has gradually reduced the buffering capacity of the topsoil. Comparing measured fluxes shows that with decreasing sulfur inputs, the sulfur stored in the topsoil from times of high deposition was remobilized. At the Höglwald, this process occurred rather clearly over a period of about 28 years and has resulted in only about 11% of the initial amount of sulfur being still present in the topsoil (humus layer + mineral soil down to 40 cm) in 2020. Forestry should take the changed chemical conditions into account in its nutrient management.

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