Organic matter losses in German Alps forest soils since the 1970s most likely caused by warming

Abstract

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.

Dynamics of deep soil carbon – insights from <sup>14</sup>C time series across a climatic gradient

“…The numerical approach used here builds on previous work concerning turnover modeling of bomb-radiocarbondominated samples (Herold et al, 2014;Solly et al, 2013;Torn et al, 2009) and the approach used in numerous timeseries analyses with box modeling using Excel (Schrumpf and Kaiser, 2015) or Excel Solver (Baisden et al, 2013;Prior et al, 2007). However, certain modifications were made in order to (i) provide objective repeatable estimates, (ii) incorporate longer time-series data, and (iii) identify samples impacted by petrogenic (also called geogenic) carbon.…”

“…Given that the so-called "bomb radiocarbon spike" will continue to diminish in the coming decades, time-series measurements are increasingly a matter of urgency in order to take full advantage of this intrinsic tracer (Graven, 2015). Several case studies have collected time-series 14 C soil datasets and demonstrated the value of this approach (Baisden and Parfitt, 2007;Prior et al, 2007;Fröberg et al, 2010;Mills et al, 2013;Schrumpf and Kaiser, 2015). However, these studies are rare, based on single specific sites, and have been rarely linked to abiotic and biotic parameters.…”

Plant indicators for Folic Histosols in mountain forests of the Calcareous Alps

“…through windfall, the humus is prone to erosion and mineralization (Kohlpaintner & Göttlein, 2009;Mayer, Matthews, Schindlbacher, & Katzensteiner, 2014;Kolb & Kohlpaintner, 2018). Prietzel, Zimmermann, Schubert, and Christophel (2016) showed that since 1970 warming has caused a 14% decline in topsoil organic carbon stocks in the German Alps.…”

Dryland soils in northern China sequester carbon during the early 2000s warming hiatus period

“…Regional comparisons may introduce unintended artefacts due to the lack of well‐matched resampling observations. Compared to the aforementioned two approaches, repeated soil sampling based on a large number of sites has been suggested to be a solution for realistically detecting the signals of soil C dynamics (Bellamy, Loveland, Bradley, Lark, & Kirk, ; Prietzel, Zimmermann, Schubert, & Christophel, ). However, repeated soil sampling is still lacking across arid/semi‐arid regions.…”