Geographic and vertical patterns of stable carbon isotopes in tropical rain forest soils of Costa Rica

Jennifer S. Powers, William H. Schlesinger

Research output: Contribution to journalArticlepeer-review

109 Scopus citations

Abstract

Understanding the natural variability in the stable carbon isotope composition of vegetation and soils can aid studies of soil carbon dynamics, and is a prerequisite for using 13C as a natural tracer when vegetation communities change from one photosynthetic pathway to another (e.g. C4 pasture grasses replacing C3 forests). To examine the geographic and vertical patterns of δ13C under mature rain forest vegetation, we measured the isotopic composition of leaf litter, roots, and mineral soil profiles in 35 plots located in a 140,000-ha study region in northeastern Costa Rica. We hypothesized that soil carbon isotopic composition would be closely coupled to the signature of detrital inputs (the average δ13C of forest floor and fine-root biomass) and that the increase in δ13C with depth would be related to abiotic variables that influence soil carbon turnover rates. The correlations between surface soil isotopic composition (0-10 cm) and biophysical factors varied across the landscape. In multiple regression analyses, combinations of soil particle-size distribution and soil C/N ratio explained between 60% and 82% of the variation in surface soil isotopic composition for different regions in the landscape, but the isotopic composition of litter and roots did not explain any additional variation. The isotopic composition of litter, roots, and surface soils (0-20 cm) was fairly similar over large, regional gradients of elevation and edaphic properties (the range of variation was 2.6 ‰), but diverged considerably at depths below 20 cm (up to 5.8 ‰ differences). These large regional differences in the isotopic composition of soil C at depth are attributed to variation in soil carbon turnover rates across the landscape.

Original languageEnglish (US)
Pages (from-to)141-160
Number of pages20
JournalGeoderma
Volume109
Issue number1-2
DOIs
StatePublished - 2002

Bibliographical note

Funding Information:
We would like to thank Dan Richter, Elissa Levine, and Jason McLachlan for helpful reviews of earlier drafts of this manuscript. We especially would like to thank I.C. Grieve and D. Van Dam, who provided excellent suggestions in their reviews of the manuscript. Ed Veldkamp facilitated the isotope analyses and deserves many thanks. This work was made possible by funding from the following sources: NASA Graduate Student Researcher Program Fellowship, NSF Dissertation Improvement Grant (No. 9972569), Andrew W. Mellon Foundation Fellowship for Ecosystem Studies awarded through the Organization for Tropical Studies, National Security Education Program Fellowship, Center for International Studies Travel Grant from Duke University, and a Tinker Field Research Grants from the Duke University Latin American Studies Program.

Keywords

  • Costa Rica
  • Soil carbon
  • Stable carbon isotopes
  • Tropical rain forests

Fingerprint

Dive into the research topics of 'Geographic and vertical patterns of stable carbon isotopes in tropical rain forest soils of Costa Rica'. Together they form a unique fingerprint.

Cite this