The Beginning of the 21st Century – a Turning Point in Recent Topsoil Chemistry Changes of Central European Forest Soils?.

During recent decades, forest soils in Central Europe have been subject to considerable anthropogenic influences (acid deposition, N eutrophication, climate warming), which probably have changed their chemical status. However, a direct proof of these changes in many cases is impossible due to the lack of data series from appropriate long-term monitoring plots. We present such data for two mature Scots pine (Pinus sylvestris) forest stands in Germany. For both stands, chemical (pH, SOC, N, exchangeable nutrient cations) as well as physical data (e.g. bulk density) have been obtained in five topsoil (O layer + uppermost 30 cm mineral soil) inventories. The inventories have been conducted in 10-yr intervals during the period 1974/82 to 2014. In each inventory, the soil was sampled in 12 replicates, allowing to test the observed changes for statistical significance.

Both sites have experienced marked topsoil acidification, N eutrophication, and SOC accumulation between 1974/82 and 2004. However, after 2004, the topsoil acidification process was stopped and even partially reverted, and also SOC contents have decreased markedly. Topsoil chemistry developments observed for the two ecosystems are discussed in the context of stand history, recent changes of atmospheric acid deposition, and climate change.