IP3: Decomposition Processes in Cryoturbated Soil

People: Andreas Richter (PI), Birgit Wild, Jörg Schnecker

Aims and Objectives

The major aim of IP3 is to elucidate effects of cryoturbation on soil organic matter decomposition processes. Cryoturbation processes may work in two directions: they may lead to burying of carbon-rich top soil material, litter and even living plants into deeper soil layers, thus effectively withdrawing them from the fast carbon cycle by slowing down decomposition processes [1,2] and they may bring soil organic carbon from deeper soil layers (including previously subducted material, which may be rich in labile organic matter [3,4]) back to the top soil and even to the surface, thereby exposing it to more favourable abiotic conditions. In addition, arctic climate change (i.e., warming or changes in soil moisture) may lead to more favourable abiotic conditions for decomposition in deeper soil layers [4,5]. Therefore it is of utmost importance to get a better understanding of the degradability and vulnerability of the deep carbon, which will allow for a refinement of the predictions of future CO2 emissions from arctic regions [3,6,7]. Together with IP2, IP4 and IP5 we will, on the one hand, delineate the mechanisms that are responsible for the delay of decomposition processes and, on the other hand, assess the vulnerability of buried carbon, focussing on the quantification of gross and net processes under field and laboratory conditions.

Our main objectives are:

  • To elucidate the effects of burying organic-rich top soil into deeper soil layers on the time-course and rate of decomposition processes.
  • To assess the quality and vulnerability of soil organic carbon already buried in deeper soil layers to changing environmental conditions and to exposure to upper soil layers or the surface by recent cryoturbation activities.
  • To quantify gross rates of microbial processes (gross N transformation rates, gross CO2 and methane production and consumption) in cryoturbated soils, to facilitate an in-depth understanding of the mechanisms by which soil organic matter decomposition is retarded in buried top soil material or accelerated in subsoil material brought to the surface.

References

[1] Kaiser et al.,2007,J.Geophys.Res. 112:G02017.

[2] Bockheim, 2007, Soil Sci.Soc.Am.J. 71:1335-1342.

[3] Schuur et al.,2008,Bioscience 58:701.

[4] Zimov et al.,2006,Science 312:1612.

[5] Zimov et al, 2009, Geophys.Res.Lett. 36: L02502.

[6] Ping et al.,2008,Nature-Geoscience 1:615.

[7] Beer, 2008, Nature-Geoscience 1:569.