Food webs in Mongolian grasslands: The analysis of ¹³C and ¹⁵N natural abundances

Abstract

Overgrazing often lowers species richness and productivity of grassland communities. For Mongolian grassland ecosystems, a lack of detailed information about food-web structures makes it difficult to predict the effects of overgrazing on species diversity and community composition. We analysed the δ¹³C and δ¹⁵N signatures of herbaceous plants, arthropods (grouped by feeding habit), wild and domestic mammals, and humans in central Mongolia to understand the predominant food-web pathways in this grassland ecosystem. The δ¹³C and δ¹⁵N values of mammals showed little variation within species, but varied considerably with slope position for arthropods. The apparent isotopic discrimination between body tissue and hair of mammals was estimated as 2.0 ‰ for δ¹³C and 2.1 ‰ for δ¹⁵N, which was large enough to cause overestimation of the trophic level of mammals if not taken into account when using hair samples to measure isotopic enrichment.

Keywords:

• carbon-13
• food selectivity
• grazing food chain
• herbaceous plants
• isotope ecology
• nitrogen-15
• spatial scale
• trophic enrichment

Acknowledgements

This study was supported by a grant-in-aid for Scientific Research (No. 14405037) from the Japan Society for the Promotion of Science and CREST, Japan Science and Technology Agency. The authors thank F. Hyodo, JSTS Research Fellow, and I. Tayasu, Center for Ecological Research, Kyoto University, for their valuable comments and suggestions on improving this article.