Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 15, issue 3
Biogeosciences, 15, 703–719, 2018
https://doi.org/10.5194/bg-15-703-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 15, 703–719, 2018
https://doi.org/10.5194/bg-15-703-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 05 Feb 2018

Research article | 05 Feb 2018

Peat decomposability in managed organic soils in relation to land use, organic matter composition and temperature

Cédric Bader1,2, Moritz Müller3, Rainer Schulin2, and Jens Leifeld1 Cédric Bader et al.
  • 1Agroscope, Climate and Agriculture Group, Zurich 8046, Switzerland
  • 2Inst Terr Ecosyst, ETH Zürich, Zurich 8092, Switzerland
  • 3School of Agricultural, Forest and Food Sciences, Bern University of Applied Sciences, Zollikofen 3052, Switzerland

Abstract. Organic soils comprise a large yet fragile carbon (C) store in the global C cycle. Drainage, necessary for agriculture and forestry, triggers rapid decomposition of soil organic matter (SOM), typically increasing in the order forest < grassland < cropland. However, there is also large variation in decomposition due to differences in hydrological conditions, climate and specific management. Here we studied the role of SOM composition on peat decomposability in a variety of differently managed drained organic soils. We collected a total of 560 samples from 21 organic cropland, grassland and forest soils in Switzerland, monitored their CO2 emission rates in lab incubation experiments over 6 months at two temperatures (10 and 20 °C) and related them to various soil characteristics, including bulk density, pH, soil organic carbon (SOC) content and elemental ratios (C / N, H / C and O / C). CO2 release ranged from 6 to 195 mg CO2-C g−1 SOC at 10 °C and from 12 to 423 mg g−1 at 20 °C. This variation occurring under controlled conditions suggests that besides soil water regime, weather and management, SOM composition may be an underestimated factor that determines CO2 fluxes measured in field experiments. However, correlations between the investigated chemical SOM characteristics and CO2 emissions were weak. The latter also did not show a dependence on land-use type, although peat under forest was decomposed the least. High CO2 emissions in some topsoils were probably related to the accrual of labile crop residues. A comparison with published CO2 rates from incubated mineral soils indicated no difference in SOM decomposability between these soil classes, suggesting that accumulation of recent, labile plant materials that presumably account for most of the evolved CO2 is not systematically different between mineral and organic soils. In our data set, temperature sensitivity of decomposition (Q10 on average 2.57 ± 0.05) was the same for all land uses but lowest below 60 cm in croplands and grasslands. This, in turn, indicates a relative accumulation of recalcitrant peat in topsoils.

Publications Copernicus
Download
Short summary
When drained, peatlands degrade and release large quantities of CO2, thereby contributing to global warming. Do land use or the chemical composition of peat control the rate of that release? We studied 21 sites from the temperate climate zone managed as croplands, grasslands, or forests and found that the CO2 release was high, but only slightly influenced by land use or peat composition. Hence, only keeping peatlands in their natural state prevents them from becoming strong CO2 sources.
When drained, peatlands degrade and release large quantities of CO2, thereby contributing to...
Citation