Isotopic discrimination during long-term decomposition in an arid land ecosystem

TitleIsotopic discrimination during long-term decomposition in an arid land ecosystem
Publication TypeJournal Article
Year of Publication2001
AuthorsConnin S.L, Feng X., Virginia R.A
JournalSoil Biology and Biochemistry
Date Published2001
Accession NumberJRN00337
Keywordsdecomposition, isotopes, isotopes, decomposition, LIDET, long-term decomposition, nitrogen isotope, soil organ matter, SOM

Discrimination in carbon and nitrogen isotopes of decomposing plant litter in the northern Chihuahuan Desert was determined for a 5-year period. Factors influencing isotopic change were assessed from inter-species comparisons of litter chemistry, mass loss patterns, and isotope values of associated soil. Average delta15N litter values of buried roots increased 1.2 and 2.6‰ for Big Blue Stem (Schizachyrium gerardi, grass) and Varital (Drypetes glauca, hardwood) during the study, respectively. Small but inconsistent variations were observed for Slash Pine (Pinus elliotii, conifer) roots. Average delta15N values of wooden dowels from Ramin (Gonystlylus bancanus, hardwood) increased ca. 2.0‰ during years 1–4, and then decreased slightly during year 5. Changes in delta15N litter were independent of N content, and may reflect microbial fractionation or preferential retention of 15N enriched substrates. Surprisingly, there was no clear relationship between litter N dynamics and C/N ratios. There were no discernable changes in delta13C litter values for Gonystlylus bancanus and Pinus elliotii. Average delta13C litter values for Schizachyrium gerardi decreased ~2.0‰ during years 0–2 and then increased slightly. In contrast, average delta13C litter values for Drypetes glauca increased ~0.5‰ from years 0–1 then remained relatively constant until decreasing slightly in year 5. Delta13C litter discrimination may have been masked by interfering delta13C fractionations or feedbacks between decomposers and litter chemistry. Our data indicate that isotopic discrimination is characteristic of early litter decay stages. These results may highlight aspects of isotope discrimination and nutrient cycling unique to arid land environments. Additional studies will be needed to confirm this.

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