Earthworms, litter and soil carbon in a northern hardwood forest Timothy J. Fahey • Joseph B. Yavitt • Ruth E. Sherman • John C. Maerz • Peter M. Groffman • Melany C. Fisk • Patrick J. Bohlen Received: 18 June 2012 / Accepted: 22 October 2012 Ó Springer Science+Business Media Dordrecht 2012 Abstract The important role of soil carbon (C) in the global C cycle has stimulated interest in better understanding the mechanisms regulating soil C stor- age and its stabilization. Exotic earthworm invasion of northern forest soils in North America can affect soil C pools, and we examined their effects on these mech- anisms by adding 13 C labeled leaf litter to adjacent northern hardwood forests with and without earth- worms. Two types of labeled litter were produced, one with the 13 C more concentrated in structural (S) com- ponents and the other in non-structural (NS) compo- nents, to evaluate the role of biochemical differences in soil C stabilization. Earthworm invasions have reduced soil C storage in the upper 20 cm of the soil profile by 37 %, mostly by eliminating surface organic horizons. Despite rapid mixing of litter into mineral soil and its incorporation into aggregates, mineral soil C has not increased in the presence of earthworms. Incorporation of litter C into soil and microbial biomass was not affected by biochemical differences between S versus NS labeled litter although NS litter C was assimilated more readily into earthworm biomass and S litter C into fungal hyphae. Apparently, the net effect of earthworm mixing of litter and forest floor C into mineral soil, plus stabilization of that C in aggregates, is counterbalanced by earthworm bioturbation and possible priming effects. Our results support recent arguments that biochemical recalcitrance is not a major contributor to the stabilization of soil C. Keywords Aggregation Á Decomposition Á Fungal hyphae Á Isotope labeling Á Microbial biomass Á Sugar maple Introduction Soil organic matter (SOM) plays a variety of important roles in terrestrial ecosystems, storing carbon (C), maintaining fertility and promoting favorable structure and porosity of soil. Organic C in soils is a major pool in the global C cycle (Post et al. 1982), and potential changes in this pool could serve as either a significant T. J. Fahey (&) Á J. B. Yavitt Á R. E. Sherman Department of Natural Resources, Cornell University, 12 Fernow Hall, Ithaca, NY 14853-3001, USA e-mail: tjf5@cornell.edu J. C. Maerz Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green Street, Athens, GA 30602-2152, USA P. M. Groffman Cary Institute of Ecosystem Studies, Box AB, 2801 Sharon Turnpike, Millbrook, NY 12545, USA M. C. Fisk Department of Zoology, Miami University, 212 Pearson Hall, Oxford, OH 45056, USA P. J. Bohlen Department of Biology, University of Central Florida, P.O. Box 162368, Orlando, FL 32816-2368, USA 123 Biogeochemistry DOI 10.1007/s10533-012-9808-y