Climate warming is expected to induce soil organic carbon losses in mountain soils that result, in turn, in reduced soil fertility, reduced water storage capacity and positive feedback on climate change. Here we combine two independent sets of measurements of soil organic carbon from forest soils in the German Alps-repeated measurements from 1976 to 2010 and from 1987 to 2011-to show that warming has caused a 14% decline in topsoil organic carbon stocks. The decreases in soil carbon occurred over a period of significant increases in six-month summer temperatures, with the most substantial decreases occurring at sites with large changes in mean annual temperature. Organic carbon stock decreases were largest-on average 32%-in forest soils with initial topsoil organic carbon stocks greater than 8 kg C m −2 , which can be found predominantly on calcareous bedrock. However, organic carbon stocks of forest soils with lower initial carbon stocks, as well as soils under pasture or at elevations above 1,150 m, have not changed significantly. We conclude that warming is the most likely reason for the observed losses of soil organic carbon, but that site, land use and elevation may ameliorate the e ects of climate change.

Background and aims For the mountain forests of the Alps, limited comprehensive information is available about soil stocks of important nutrients (N, P, K), stand nutrition, and relationships between soil status and stand nutrition. Methods We investigated total and plant-available soil N, P, and K stocks and the nutritional status of Picea abies concerning these elements on 14 forest soil monitoring sites in the Bavarian Alps. Results Mean soil N, P, and K stocks are 8.0 Mg N ha −1 , thereof 14 % bound in the forest floor, 1.7 Mg P ha −1 (2 % in forest floor), and 42 Mg K ha −1 (0.2 % in forest floor). Citric acid-extractable orthophosphate and exchangeable K contribute to 3 and 0.7 % of total P and K, respectively. Spruce N, P, K, and Mn nutrition differs considerably among sites, with Rendzic Lithosols being most critical, whereas trees on deeply weathered soils are well supplied. Conclusions According to our estimation, the forest is characterized by an insufficient supply with N, P, and/or K at about 30, 20 and 10 % of the forest area in the Bavarian Alps, respectively. A large part of the Bavarian Alps can be judged critical and prone to nutrient shortage in the course of humus degradation and associated SOM losses.

After elevated concentrations of perfluorooctanoate (PFO) were found in river and groundwater in the vicinity of a fluoropolymer manufacturing facility, numerous soils at adjacent sites were sampled in 2007. Within a 5-km northeast-oriented sector around a probable point source, 20 forest sites were investigated and compared to deposition and groundwater data. PFO concentrations up to 600 μg/kg were detected in the soils, and PFO concentrations typically decreased toward deeper soil depths. In mixed or deciduous forests, maximum concentrations of PFO occurred in the topsoil, pointing to the favorable decomposition and incorporation of deciduous litter. PFO concentrations of the organic layer over the 20 sampling sites were interpolated using ordinary kriging. Highest PFO content in the organic layer was located about 500 m away from the point source in the regional wind direction, decreasing asymptotically outwards. Long-term monitoring data pointed to an accumulation of PFO over time in the organic layer. The data suggest that PFO might be released in the course of litter decomposition and transported toward deeper soil regions only gradually. The soils' PFO concentrations reflect the deposition data. The transport link toward groundwater is currently established in lysimeter studies.

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