Abstract
Decomposition of soil organic matter (SOM) plays an important role in the global carbon cycle because the CO2 emitted from soil respiration is an important source of atmospheric CO2. Carbon isotopic fractionation occurs during SOM decomposition, which leads to 12C to enrich in the released CO2 while 13C to enrich in the residual SOM. Understanding the isotope fractionation has been demonstrated to be helpful for studying the global carbon cycle. Soil and litter samples were collected from soil profiles at 27 different sites located along a vertical transect from 1200 to 4500 m above sea level (a.s.l.) in the south-eastern side of the Tibetan Plateau. Their carbon isotope ratios, C and N concentrations were measured. In addition, fiber and lignin in litter samples were also analyzed. Carbon isotope fractionation factor (α) during SOM decomposition was estimated indirectly as the slope of the relationship between carbon isotope ratios of SOM and soil C concentrations. This study shows that litter quality and soil water play a significant role in isotope fractionation during SOM decomposition, and the carbon isotope fractionation factor, α, increases with litter quality and soil water content. However, we found that temperature had no significant impact on the α variance.
Highlights
Soil organic carbon is the largest pool of terrestrial ecosystem and greatly affects global carbon cycling
The CO2 derived from soil organic matter (SOM) decomposition is an important source of atmospheric CO2
Since litters collected in this study were mainly composed of leaves in situ, the C/N ratio of litter depended on the vegetation types and plant species
Summary
Soil organic carbon is the largest pool of terrestrial ecosystem and greatly affects global carbon cycling. Scientists who study global change incorporate carbon isotope data for tropospheric CO2, derived from an international network of stations, into atmospheric circulation models. Current study was undertaken to evaluate the effects of environmental and biotic factors on carbon isotope fractionation during SOM decomposition. In this regard we measured the carbon isotope ratios of soil and litter samples collected from soil profiles along an altitudinal gradient in the south-eastern side of the Tibetan Plateau. Their carbon isotope fractionation (α ) during SOM decomposition was estimated using an indirect method established by Poage and Feng (2004)[13]
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