Sblogo499.gif (4312 bytes) 13C IN SOIL ORGANIC MATTER DYNAMICS - PROJECT SUMMARY
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Please note: This research Programme is no longer active

 

 

 


 

OBJECTIVE
To monitor changes in soil organic matter dynamics under different climates and litter inputs.

The soil is the major store of C in terrestrial ecosystems, yet we have very few quantitative assessments of how this store develops under different climates and land uses. A principal feature of land use change is the quality of organic matter which reaches the soil and, in this  project, we investigated how the quality of litter input and climate interact in the formation of soil organic matter. Use was made of the marked differences in the 13C signals in C3 and C4 systems to track soil organic development and trophic pathways in the soil.

THE EXPERIMENTAL CHALLENGE

BASIC CONCEPT
Changes in soil C stores are extremely difficult to detect due to the low signal-to-noise ratio of such changes. Recent FACE experiments in the USA have shown that utilisation of the unusual C stable isotope signal in 'bottled gas' can be used to trace C inputs under elevated CO2 conditions but this signal cannot be used to quantify C input under ambient conditions. This limitation has been circumvented by utilising soils generated under C4 sytems to provide a characteristic C isotope signal, enabling the amount of litter C remaining in soil systems to be quantified (see Plant and Soil, volume 187). This also has the additional, and potentially more useful, advantage of enabling the fate of the carbon to be determined, whilst identifying soil biotic trophic chains.

EXPERIMENTAL DESIGN
The 'C4 soil' was obtained from a natural long-term C4 prairie in North America and contained organic matter with a characteristic 13C signal of permanent C4 input with a mean d13CPDB value of ca. -18. The normal signal d13CPDB value for C3 vegetation is around -26, and this enabled the differentiation between sources of C. Experimental plots are to be established at 3 locations in the UK to assess climatic control of soil C formation under standard litter inputs. One of the sites was Sourhope.

We used the 13C signal introduced into the systems to:

  • Follow trophic interactions in extracted soil fauna
  • Identify where the soil fungal and bacterial biomasses are acquiring their C
  • Partition soil CO2 and dissolved organic C fluxes to old and new organic matter
  • Determine the fate of added C according to climate and litter type

FOR FURTHER INFORMATION PLEASE CONTACT:
Dr. P. Ineson

University of York
Email: pi2@york.ac.uk