Submitted to: Soil Source and Sink of Greenhouse Gases
Publication Type: Proceedings
Publication Acceptance Date: 10/15/1996
Publication Date: N/A
Interpretive Summary: Soil organic matter acts both as a source and a sink in the global carbon cycle in nature. Application of the stable carbon isotope (carbon-13) tracer method can describe the organic matter dynamics in crop rotations, carbon changes, and the humus formation process in soils. The method is reliable and safe to use, and very cost effective as compared to the carbon-14 radioactive tracer technique. Although with obvious benefits, the method is still in the early stages of development. Techniques for various research purposes have yet to be improved. Use is also limited to situations in which long-term studies have been carried out, and periods of crop growth are known. The paper presents data from field and laboratory studies of various types, and covers current trends of research from peer-reviewed journals. This research will provide information which will help us to understand how soil organic matter relates to the 'green- house' effect and 'global warming'.
Technical Abstract: Soil organic matter (SOM) is one of the primary terrestrial carbon pools which provide a sink for atmospheric C02. Quantifying SOM dynamics in relation to agroecosystem management is fundamental to identifying approaches to enhance carbon sequestration in soils. Preliminary evidence has shown that carbon-13 abundance, which can be accurately determined by an automated elemental analyzer/mass spectrometer system, can be used for characterizing organic carbon dynamics in soils. Natural variation in 13C/12C ratios are used to assess the fate of recent organic inputs into SOM. The variations in ratio are induced by plants with either a C4 or C3 photosynthetic pathway. By crop rotation and tillage management interactions, SOM turnover and soil organic fractions can be characterized. The carbon-13 tracer method is sensitive, reproducible, and reliable. The technique has been used in investigating soil respiration, biomass, plant residue decomposition, and long-term field plots with different crop sequence combinations. However, better improved understanding is still needed to account for variations in soil landscapes, seasonal fluctuations of incorporation, and other soil properties, as well as discriminations in the organic matter transformation processes in the soil.