, Volume 52, Issue 3, pp 321-338

Sources of organic and inorganic carbon in a headwater stream: Evidence from carbon isotope studies

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Abstract

A combination of stable isotope studies and 14Cdating were used to identify the main sources andprocesses controlling streamwater DOC and TIC in atemperate non-forested watershed. δ13Cvalues for terrestrial (−24.9 to −29.1‰) and aquatic(−30.5 to −33.5‰) plants were similar to valuesreported in the literature for similar ecosystems.δ13C values for DOC in soil solution andstreamwater were consistent with soil and terrestrialvegetation, indicating that the terrestrial ecosystemis the dominant source of aquatic DOC in thiswatershed. δ13C values of soil atmosphereCO2 (−17.2 to −25.2‰) were slightly lessnegative than would be expected for production viaaerobic soil microbial decomposition and rootrespiration. There was a close correspondence betweenδ13C values (−15.5 to −21.5‰) forstreamwater TIC and soil atmospheric CO2 in thecentral part of the catchment where the stream drainsCO2-rich peats. 14C dating showed thatalthough peat has been accumulating in the watershedfor at least 2700 years, DOC in soil pore water andstreamwater contains carbon of predominantly recentorigin (post-AD 1955).